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The O/OREOS (Organism/Organic Exposure to Orbital Stresses) is a NASA automated CubeSat nanosatellite laboratory approximately the size of a loaf of bread that contains two separate astrobiology experiments on board. [ 1 ] Developed by the Small Spacecraft Division at NASA Ames Research Center , the spacecraft was successfully launched as a secondary payload on STP-S26 led by the Space Test Program of the United States Air Force on a Minotaur IV launch vehicle from Kodiak Island , Alaska on 20 November 2010, at 01:25:00 UTC .
The O/OREOS satellite is NASA's first CubeSat to demonstrate the capability to have two distinct, completely independent science experiments on an autonomous satellite. One experiment will test how microorganisms survive and adapt to the stresses of space; the other will monitor the stability of organic molecules in space.
The overall goal of the O/OREOS mission is to demonstrate the capability to do low-cost science experiments on autonomous nanosatellites in space in support of the 'Astrobiology Small Payloads' program under the Planetary Science Division of the Science Mission Directorate at NASA's Headquarters. NASA's Ames Small Spacecraft Division manages the O/OREOS mission while all operations will be conducted by staff and students from the Robotic Systems Laboratory at Santa Clara University . [ 2 ] Scientists will apply the knowledge they gain while investigating the space environment and studying how exposure to space changes organisms to help to answer astrobiology 's fundamental questions on the origin , evolution , and distribution of life .
The technology developed in this mission enables a new generation of light-weight, low-cost payloads suitable for future secondary payload opportunities —"piggyback rides"— to the Moon , Mars , and beyond, where they can address evolutionary questions, identify human exploration risks, and study planetary protection concerns. [ 3 ] [ 4 ]
Continuing Ames' development of triple-cube nanosatellite technology and flight systems, which includes the successful GeneSat-1 (launch 16 December 2006) and PharmaSat (launch 19 May 2009) missions, O/OREOS is constructed from off-the-shelf commercial and NASA-designed parts to create a fully self-contained, automated, stable, light-weight space science laboratory with innovative environment and power-control techniques. The spacecraft is equipped with sensors to monitor the levels of internal pressure, temperature, humidity, radiation and acceleration while its communications system regularly transmits data back to Earth for scientific analysis.
The organics payload will house 24 samples in four separate micro-environments to mimic space, lunar, Martian and "wet" planetary conditions. The samples are housed in a rotating carousel and are imaged regularly with UV/VIS spectroscopic instrumentation while being exposed to the space environment. The biological payload is a self-contained pressure vessel which provides life support (air pressure, humidity, growth media, and temperature control) for organisms as they are exposed to the radiation and weightless conditions in space for six months.
In addition to the experiments, the satellite is equipped with a passive magnetic attitude control system, solar panels to generate electric power, a UHF amateur band radio beacon which broadcasts real-time telemetry, battery packs, and NASA's first propellant-less mechanism to ensure that once O/OREOS has completed its mission it will de-orbit and burn up as it re-enters Earth's atmosphere. [ 5 ]
The goals of the O/OREOS mission include: [ 1 ]
The O/OREOS Space Environment Survivability of Live Organisms (SESLO) experiment will characterize the growth, activity, health and ability of microorganisms to adapt to the stresses of the space environment. The experiment is sealed in a vessel at one atmosphere and contains two types of bacteria commonly found in salt ponds and soil: Halorubrum chaoviatoris , which thrives in the sort of briny water that may exist below the surface of Mars or on Jupiter's moon Europa , and Bacillus subtilis , which holds the record for surviving in space for the longest duration (6 years on a NASA satellite). [ 5 ] The bacteria were launched as dried spores and revived at different times during the mission with a nutrient-filled fluid a few days, three months and six months after launch.
Once the satellite is in orbit, the bacteria are constantly being exposed to low Earth orbit radiation while floating in micro-gravity. The SESLO experiment measures the microbes' population density. There was an expected change in color as dyed liquid nutrients were consumed and metabolized by the microorganisms. This color change is used to determine the effects of the combined exposure to space radiation and microgravity on organism growth, health, and survival when compared to a ground-based control experiment.
The SESLO experiment measured the long-term survival, germination, and growth responses, including metabolic activity. [ 6 ]
The O/OREOS Space Environment Viability of Organics (SEVO) experiment will monitor the stability and changes in four classes organic matter as they are exposed to space conditions. Scientists selected the organic samples to represent some building blocks of life and abundant aromatic molecules , they think are distributed throughout the Milky Way galaxy.
The controlled environments in the SEVO reaction cells do not accurately represent natural environments; rather, they are used to establish a set of initial conditions for the chemical reactants involved in photochemical experiments. These reactants were chosen because they can be related to fundamental processes believed to occur in planetary surface environments, comets, and the interstellar medium . As such, each of the different cell types was carefully chosen to simulate important aspects of astrobiologically relevant environments.
Four classes of organic compounds , namely an amino acid , a quinone , a polycyclic aromatic hydrocarbon (PAH) and a metallo- porphyrin are being studied. [ 1 ] The compounds were placed in four different micro-environments that simulate some conditions in interplanetary space , on the Moon , on Mars and in the outer Solar System . The experiment continuously exposes the organic matter to radiation in the form of solar ultraviolet (UV) light, visible light , trapped-particle and cosmic radiation over six months in space. Scientists will determine the stability of the organic matter by studying in-situ the changes in UV, visible and near-infrared light absorption through daily measurements. The survival rate of these molecules will help determine whether some of Earth's biochemistry might have been performed in space and later delivered by meteorites . The data may also help in deciding which molecules are good biomarkers that can signal the existence of past or present life on another world. [ 5 ] [ 7 ]
Spectra from the PAH thin film in a water-vapor-containing microenvironment indicate measurable change due to solar irradiation in orbit, while three other nominally water-free microenvironments show no appreciable change. The quinone anthrarufin showed high photostability and no significant spectroscopically measurable change in any of the four microenvironments during the same period. [ 8 ]
O/OREOS is equipped with an amateur radio beacon which operates at 437.305 MHz . HAM radio operators can decode the satellite's AX.25 packets and submit them to NASA via the beacon processing website. [ 9 ]
In the fall of 2011, nearly 100,000 beacon packets have been submitted by amateurs in 20 countries. About 6 MB of data have been downlinked and processed by the Santa Clara University operation team through S-band (WiFi) bidirectional radio. In addition to the science results from both payloads, these data include measurements of the radiation dose, rotation data, temperature, and health status of the spacecraft. Multiple commands were uplinked successfully to tune operational parameters. [ 10 ]
All three biological experiments using the SESLO payload are complete; they were executed on 3 December 2010, 18 February and 19 May 2011. From the SEVO experiment, the project observed nominal spectrometer function, and so far 24 sets of 24 UV-visible spectra have been recorded and downlinked, amounting to nearly 600 spectra from 4 organic sample types embedded in 4 microenvironments. [ 10 ] | https://en.wikipedia.org/wiki/O/OREOS |
Acetylacetone is an organic compound with the chemical formula CH 3 −C(=O)−CH 2 −C(=O)−CH 3 . It is classified as a 1,3- diketone . It exists in equilibrium with a tautomer CH 3 −C(=O)−CH=C(−OH)−CH 3 . The mixture is a colorless liquid. These tautomers interconvert so rapidly under most conditions that they are treated as a single compound in most applications. [ 2 ] Acetylacetone is a building block for the synthesis of many coordination complexes as well as heterocyclic compounds .
The keto and enol tautomers of acetylacetone coexist in solution. The enol form has C 2v symmetry , meaning the hydrogen atom is shared equally between the two oxygen atoms. [ 4 ] In the gas phase, the equilibrium constant , K keto→enol , is 11.7, favoring the enol form. The two tautomeric forms can be distinguished by NMR spectroscopy , IR spectroscopy and other methods. [ 5 ] [ 6 ]
The equilibrium constant tends to be high in nonpolar solvents; when K keto→enol is equal or greater than 1, the enol form is favoured. The keto form becomes more favourable in polar, hydrogen-bonding solvents, such as water. [ 7 ] The enol form is a vinylogous analogue of a carboxylic acid . [ citation needed ]
Acetylacetone is a weak acid . It forms the acetylacetonate anion C 5 H 7 O − 2 (commonly abbreviated acac − ):
In the acetylacetonate anion, both C − O bonds are equivalent. Both C−C central bonds are equivalent as well, with one hydrogen atom bonded to the central carbon atom (the atom numbered C3 according to the IUPAC nomenclature of organic chemistry ). These equivalencies are because there is a resonance between the four bonds in the O−C2−C3−C4−O linkage in the acetylacetonate anion. Each of the four bonds in the linkage has a bond order of about 1.5, and the two oxygen atoms equally share the negative charge . The acetylacetonate anion is a bidentate ligand .
IUPAC recommended p K a values for this equilibrium in aqueous solution at 25 °C are 8.99 ± 0.04 ( I = 0), 8.83 ± 0.02 ( I = 0.1 M NaClO 4 ) and 9.00 ± 0.03 ( I = 1.0 M NaClO 4 ; I = Ionic strength ). [ 9 ] Values for mixed solvents are available. Very strong bases , such as organolithium compounds, will deprotonate acetylacetone twice. The resulting dilithium species can then be alkylated at the carbon atom at the position 1 .
Acetylacetone is prepared industrially by the thermal rearrangement of isopropenyl acetate . [ 10 ]
Laboratory routes to acetylacetone also begin with acetone . Acetone and acetic anhydride ( (CH 3 C(O)) 2 O ) upon the addition of boron trifluoride ( BF 3 ) catalyst: [ 11 ]
A second synthesis involves the base-catalyzed condensation (e.g., by sodium ethoxide CH 3 CH 2 O − Na + ) of acetone and ethyl acetate , followed by acidification of the sodium acetylacetonate (e.g., by hydrogen chloride HCl): [ 11 ]
Because of the ease of these syntheses, many analogues of acetylacetonates are known. Some examples are benzoylacetone , dibenzoylmethane and tert -butyl analogue 2,2,6,6-tetramethyl-3,5-heptanedione . Trifluoroacetylacetone and hexafluoroacetylacetonate are also used to generate volatile metal complexes .
Acetylacetone is a versatile bifunctional precursor to heterocycles because both keto groups may undergo condensation . For example, condensation with hydrazine produces pyrazoles while condensation with urea provides pyrimidines . Condensation with two aryl- or alkylamines gives NacNacs , wherein the oxygen atoms in acetylacetone are replaced by NR (R = aryl, alkyl).
Sodium acetylacetonate , Na(acac), is the precursor to many acetylacetonate complexes . A general method of synthesis is to treat a metal salt with acetylacetone in the presence of a base : [ 12 ]
Both oxygen atoms bind to the metal to form a six-membered chelate ring. In some cases the chelate effect is so strong that no added base is needed to form the complex.
The enzyme acetylacetone dioxygenase cleaves a central carbon-carbon bond of acetylacetone, producing acetate and 2-oxopropanal . The enzyme is iron(II) -dependent, but it has been proven to bind to zinc as well. Acetylacetone degradation has been characterized in the bacterium Acinetobacter johnsonii . [ 13 ] | https://en.wikipedia.org/wiki/O2C5H7 |
Oxygen fluorides are compounds of elements oxygen and fluorine with the general formula O n F 2 , where n = 1 to 6. Many different oxygen fluorides are known:
Oxygen fluorides are strong oxidizing agents with high energy and can release their energy either instantaneously or at a controlled rate. Thus, these compounds attracted much attention as potential oxidizers in jet propulsion systems . [ 5 ]
A common preparative method involves fluorination of sodium hydroxide :
OF 2 is a colorless gas at room temperature and a yellow liquid below 128 K. Oxygen difluoride has an irritating odor and is poisonous. [ 3 ] It reacts quantitatively with aqueous haloacids to give free halogens :
It can also displace halogens from their salts. [ 3 ] It is both an effective fluorinating agent and a strong oxidizing agent . When reacted with unsaturated nitrogen fluorides with electrical discharge, it results in the formation of nitrogen trifluoride , oxide fluorides and other oxides. [ 6 ] [ 7 ]
O 2 F 2 precipitates as a brown solid upon the UV irradiation of a mixture of liquid O 2 and F 2 at −196 °C. [ 8 ] It also only appears to be stable below −160 °C. [ 9 ] The general method of preparation of many oxygen fluorides is a gas-phase electric discharge in cold containers including O 2 F 2 . [ 10 ]
It is typically an orange-yellow solid which rapidly decomposes to O 2 and F 2 close to its normal boiling point of about 216 K. [ 3 ]
O 2 F 2 reacts violently with red phosphorus , even at −196 °C. Explosions can also occur if Freon-13 is used to moderate the reaction. [ 9 ]
O 3 F 2 is a viscous, blood-red liquid. It remains liquid at 90 K and so can be differentiated from O 2 F 2 which has a melting point of about 109 K. [ 11 ] [ 3 ]
Like the other oxygen fluorides, O 3 F 2 is endothermic and decomposes at about 115 K with the evolution of heat, which is given by the following reaction:
O 3 F 2 is safer to work with than ozone , and can be evaporated, or thermally decomposed, or exposed to electric sparks, without any explosions. But on contact with organic matter or oxidizable compounds, it can detonate or explode. Thus, the addition of even one drop of ozone difluoride to solid anhydrous ammonia will result in a mild explosion, when they are both at 90 K each. [ 3 ]
Fluoroperoxyl is a molecule such as O–O–F, whose chemical formula is O 2 F and is stable only at low temperature. It has been reported to be produced from atomic fluorine and dioxygen. [ 12 ]
Oxygen- and fluorine-containing radicals like O 2 F and OF occur in the atmosphere. These along with other halogen radicals have been implicated in the destruction of ozone in the atmosphere. However, the oxygen monofluoride radicals are assumed to not play as big a role in the ozone depletion because free fluorine atoms in the atmosphere are believed to react with methane to produce hydrofluoric acid which precipitates in rain. This decreases the availability of free fluorine atoms for oxygen atoms to react with and destroy ozone molecules. [ 13 ]
Net reaction:
Despite the low solubility of O 3 F 2 in liquid oxygen, it has been shown to be hypergolic with most rocket propellant fuels. The mechanism involves the boiling off oxygen from the solution containing O 3 F 2 , making it more reactive to have a spontaneous reaction with the rocket fuel. The degree of reactivity is also dependent on the type of fuel used. [ 3 ] | https://en.wikipedia.org/wiki/O2F |
Dioxygen difluoride is a compound of fluorine and oxygen with the molecular formula O 2 F 2 . It can exist as an orange-red colored solid which melts into a red liquid at −163 °C (110 K). It is an extremely strong oxidant and decomposes into oxygen and fluorine even at −160 °C (113 K) at a rate of 4% per day — its lifetime at room temperature is thus extremely short. [ 1 ] Dioxygen difluoride reacts vigorously with nearly every chemical it encounters (including ordinary ice ) leading to its onomatopoeic nickname FOOF (a play on its chemical structure and its explosive tendencies). [ 2 ]
Dioxygen difluoride can be obtained by subjecting a 1:1 mixture of gaseous fluorine and oxygen at low pressure (7–17 mmHg (0.9–2.3 kPa ) is optimal) to an electric discharge of 25–30 mA at 2.1–2.4 kV . [ 3 ]
A similar method was used for the first synthesis by Otto Ruff in 1933. [ 4 ] Another synthesis involves mixing O 2 and F 2 in a stainless steel vessel cooled to −196 °C (77.1 K), followed by exposing the elements to 3 MeV bremsstrahlung for several hours. A third method requires heating a mix of fluorine and oxygen to 700 °C (1,292 °F), and then rapidly cooling it using liquid oxygen . [ 5 ] All of these methods involve synthesis according to the equation
It also arises from the thermal decomposition of ozone difluoride : [ 6 ]
In O 2 F 2 , oxygen is assigned the unusual oxidation state of +1. In most of its other compounds, oxygen has an oxidation state of −2.
The structure of dioxygen difluoride resembles that of hydrogen peroxide , H 2 O 2 , in its large dihedral angle , which approaches 90° and C 2 symmetry . This geometry conforms with the predictions of VSEPR theory .
The bonding within dioxygen difluoride has been the subject of considerable speculation, particularly because of the very short O−O distance and the long O−F distances. The O−O bond length is within 2 pm of the 120.7 pm distance for the O=O double bond in the dioxygen molecule, O 2 . Several bonding systems have been proposed to explain this, including an O−O triple bond with O−F single bonds destabilised and lengthened by repulsion between the lone pairs on the fluorine atoms and the π orbitals of the O−O bond. [ 7 ] Repulsion involving the fluorine lone pairs is also responsible for the long and weak covalent bonding in the fluorine molecule .
Computational chemistry indicates that dioxygen difluoride has an exceedingly high barrier to rotation of 81.17 kJ/mol around the O−O bond (in hydrogen peroxide the barrier is 29.45 kJ/mol); this is close to the O−F bond disassociation energy of 81.59 kJ/mol. [ 8 ]
The 19 F NMR chemical shift of dioxygen difluoride is 865 ppm, which is by far the highest chemical shift recorded for a fluorine nucleus, thus underlining the extraordinary electronic properties of this compound. Despite its instability, thermochemical data for O 2 F 2 have been compiled. [ 9 ]
The compound readily decomposes into oxygen and fluorine. Even at a temperature of −160 °C (113 K), 4% decomposes each day [ 1 ] by this process:
The other main property of this unstable compound is its oxidizing power, although most experimental reactions have been conducted near −100 °C (173 K). [ 10 ] Several experiments with the compound resulted in a series of fires and explosions. Some of the compounds that produced violent reactions with O 2 F 2 include ethyl alcohol , methane , ammonia , and even water ice . [ 10 ]
With BF 3 and PF 5 , it gives the corresponding dioxygenyl salts: [ 1 ] [ 11 ]
The compound currently has no practical applications, but has been of theoretical interest. Los Alamos National Laboratory used it to synthesize plutonium hexafluoride at unprecedentedly low temperatures, which was significant because previous methods for preparation needed temperatures so high that the plutonium hexafluoride created would decompose rapidly. [ 12 ] | https://en.wikipedia.org/wiki/O2F2 |
Dioxidanylium, which is protonated molecular oxygen, or just protonated oxygen, is an ion with formula HO + 2 .
It is formed when hydrogen containing substances combust , and exists in the ionosphere , and in plasmas that contain oxygen and hydrogen . [ 2 ] Oxidation by O 2 in superacids could be by way of the production of protonated molecular oxygen.
It is the conjugate acid of dioxygen . The proton affinity of dioxygen (O 2 ) is 4.4 eV. [ 3 ]
Protonated molecular oxygen is of interest in trying to detect dioxygen in space. Because Earth's atmosphere is full of O 2 , its spectrum from a space object is impossible to observe from the ground. However HO + 2 should be much more detectable. [ 4 ]
Reaction of dioxygenyl O + 2 with hydrogen: [ 5 ]
The reaction of the trihydrogen cation with dioxygen is approximately thermoneutral: [ 3 ]
When atomic hydrogen, created in an electric discharge is rapidly cooled with oxygen and condensed in solid neon, several reactive ions and molecules are produced. These include HO 2 ( hydroperoxyl ), HOHOH − , H 2 O(HO), HOHO − as well as HO + 2 . [ 6 ] This reaction also forms hydrogen peroxide (H 2 O 2 ) and hydrogen tetroxide (H 2 O 4 ). [ 7 ]
In the infrared spectrum HO + 2 the v 1 band due to vibrating O–H has a band head at 3016.73 cm −1 . [ 8 ]
A helium complex (He–O 2 H + ) also is known. [ 8 ]
HO + 2 appears to react rapidly with hydrogen: [ 9 ]
HO + 2 also reacts with dinitrogen and water: [ 9 ]
The protonated molecular oxygen dimer HO + 4 has a lower energy than that of protonated molecular oxygen. [ 3 ] | https://en.wikipedia.org/wiki/O2H+ |
Dinitrogen tetroxide , commonly referred to as nitrogen tetroxide ( NTO ), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl , is the chemical compound N 2 O 4 . It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide . Its molar mass is 92.011 g/mol.
Dinitrogen tetroxide is a powerful oxidizer that is hypergolic (spontaneously reacts) upon contact with various forms of hydrazine , which has made the pair a common bipropellant for rockets.
Dinitrogen tetroxide could be regarded as two nitro groups (-NO 2 ) bonded together. It forms an equilibrium mixture with nitrogen dioxide . [ 5 ] The molecule is planar with an N-N bond distance of 1.78 Å and N-O distances of 1.19 Å. The N-N distance corresponds to a weak bond, since it is significantly longer than the average N-N single bond length of 1.45 Å. [ 6 ] This exceptionally weak σ bond (amounting to overlapping of the sp 2 hybrid orbitals of the two NO 2 units [ 7 ] ) results from the simultaneous delocalization of the bonding electron pair across the whole N 2 O 4 molecule, and the considerable electrostatic repulsion of the doubly occupied molecular orbitals of each NO 2 unit. [ 8 ]
Unlike NO 2 , N 2 O 4 is diamagnetic since it has no unpaired electrons. [ 9 ] The liquid is also colorless but can appear as a brownish yellow liquid due to the presence of NO 2 according to the following equilibrium: [ 9 ]
Higher temperatures push the equilibrium towards nitrogen dioxide. Inevitably, some dinitrogen tetroxide is a component of smog containing nitrogen dioxide.
Solid N 2 O 4 is white, and melts at −11.2 °C. [ 9 ]
Nitrogen tetroxide is made by the catalytic oxidation of ammonia (the Ostwald process ): steam is used as a diluent to reduce the combustion temperature. In the first step, the ammonia is oxidized into nitric oxide :
Most of the water is condensed out, and the gases are further cooled; the nitric oxide that was produced is oxidized to nitrogen dioxide, which is then dimerized into nitrogen tetroxide:
and the remainder of the water is removed as nitric acid . The gas is essentially pure nitrogen dioxide, which is condensed into dinitrogen tetroxide in a brine-cooled liquefier. [ 10 ]
Dinitrogen tetroxide can also be made through the reaction of concentrated nitric acid and metallic copper. This synthesis is practical in a laboratory setting. Dinitrogen tetroxide can also be produced by heating metal nitrates. [ 11 ] The oxidation of copper by nitric acid is a complex reaction forming various nitrogen oxides of varying stability which depends on the concentration of the nitric acid, presence of oxygen, and other factors. The unstable species further react to form nitrogen dioxide which is then purified and condensed to form dinitrogen tetroxide.
Nitrogen tetroxide is used as an oxidizing agent in one of the most important rocket propellant systems because it can be stored as a liquid at room temperature. Pedro Paulet , a Peruvian polymath , reported in 1927 that he had experimented in the 1890s with a rocket engine that used spring-loaded nozzles that periodically introduced vaporized nitrogen tetroxide and a petroleum benzine to a spark plug for ignition, with the engine putting out 300 pulsating explosions per minute. [ 12 ] [ 13 ] Paulet would go on to visit the German rocket association Verein für Raumschiffahrt (VfR) and on March 15, 1928, Valier applauded Paulet's liquid-propelled rocket design in the VfR publication Die Rakete , saying the engine had "amazing power". [ 14 ] Paulet would soon be approached by Nazi Germany to help develop rocket technology, though he refused to assist and never shared the formula for his propellant. [ 15 ]
In early 1944, research on the usability of dinitrogen tetroxide as an oxidizing agent for rocket fuel was conducted by German scientists, although the Germans only used it to a very limited extent as an additive for S-Stoff (fuming nitric acid). It became the storable oxidizer of choice for many rockets in both the United States and USSR by the late 1950s. It is a hypergolic propellant in combination with a hydrazine -based rocket fuel . One of the earliest uses of this combination was on the Titan family of rockets used originally as ICBMs and then as launch vehicles for many spacecraft. Used on the U.S. Gemini and Apollo spacecraft and also on the Space Shuttle , it continues to be used as station-keeping propellant on most geo-stationary satellites, and many deep-space probes. It is also the primary oxidizer for Russia's Proton rocket .
When used as a propellant, dinitrogen tetroxide is usually referred to simply as nitrogen tetroxide and the abbreviation NTO is extensively used. Additionally, NTO is often used with the addition of a small percentage of nitric oxide that reacts to form dinitrogen trioxide , which inhibits stress-corrosion cracking of titanium alloys, and in this form, propellant-grade NTO is referred to as mixed oxides of nitrogen ( MON ) and can be distinguished by its green-blue color. Larger additions of nitric oxide, up to 25-30%, also lower the freezing point of NTO, improving storability in space conditions. [ 16 ] Most spacecraft now use MON instead of NTO; for example, the Space Shuttle reaction control system used MON3 (NTO containing 3% NO by weight). [ 17 ]
On 24 July 1975, NTO poisoning affected three U.S. astronauts on the final descent to Earth after the Apollo-Soyuz Test Project flight. This was due to a switch accidentally left in the wrong position, which allowed the attitude control thrusters to fire after the cabin fresh air intake was opened, allowing NTO fumes to enter the cabin. One crew member lost consciousness during descent. Upon landing, the crew was hospitalized for five days for chemical-induced pneumonia and pulmonary edema . [ 18 ] [ 19 ]
The tendency of N 2 O 4 to reversibly break into NO 2 has led to research into its use in advanced power generation systems as a so-called dissociating gas. [ 20 ] "Cool" dinitrogen tetroxide is compressed and heated, causing it to dissociate into nitrogen dioxide at half the molecular weight. This hot nitrogen dioxide is expanded through a turbine, cooling it and lowering the pressure, and then cooled further in a heat sink, causing it to recombine into nitrogen tetroxide at the original molecular weight. It is then much easier to compress to start the entire cycle again. Such dissociative gas Brayton cycles have the potential to considerably increase efficiencies of power conversion equipment. [ 21 ]
The high molecular weight and smaller volumetric expansion ratio of nitrogen dioxide compared to steam allows the turbines to be more compact. [ 22 ]
N 2 O 4 was the main component of the "nitrin" working fluid in the decommissioned Pamir-630D portable nuclear reactor which operated from 1985 to 1987. [ 23 ]
Nitric acid is manufactured on a large scale via N 2 O 4 . This species reacts with water to give both nitrous acid and nitric acid :
The coproduct HNO 2 upon heating disproportionates to NO and more nitric acid. When exposed to oxygen, NO is converted back into nitrogen dioxide:
The resulting NO 2 and N 2 O 4 can be returned to the cycle to give the mixture of nitrous and nitric acids again.
N 2 O 4 undergoes molecular autoionization to give [NO + ] [NO 3 − ], with the former nitrosonium ion being a strong oxidant. Various anhydrous transition metal nitrate complexes can be prepared from N 2 O 4 and base metal. [ 24 ]
where M = Cu , Zn , or Sn .
If metal nitrates are prepared from N 2 O 4 in completely anhydrous conditions, a range of covalent metal nitrates can be formed with many transition metals. This is because there is a thermodynamic preference for the nitrate ion to bond covalently with such metals rather than form an ionic structure. Such compounds must be prepared in anhydrous conditions, since the nitrate ion is a much weaker ligand than water, and if water is present the simple nitrate of the hydrated metal ion will form. The anhydrous nitrates concerned are themselves covalent, and many, e.g. anhydrous copper nitrate , are volatile at room temperature. Anhydrous titanium nitrate sublimes in vacuum at only 40 °C. Many of the anhydrous transition metal nitrates have striking colours. This branch of chemistry was developed by Cliff Addison and Norman Logan at the University of Nottingham in the UK during the 1960s and 1970s when highly efficient desiccants and dry boxes started to become available.
In even slightly basic solvents, N 2 O 4 adds to alkenes radically, giving mixtures of nitro compounds and nitrite esters . Pure or in entirely nonbasic solvents, the compounds autoionizes as above, to give nitroso compounds and nitrate esters . [ 25 ] | https://en.wikipedia.org/wiki/O2N-NO2 |
Lead(IV) oxide , commonly known as lead dioxide , is an inorganic compound with the chemical formula PbO 2 . It is an oxide where lead is in an oxidation state of +4. [ 1 ] It is a dark-brown solid which is insoluble in water. [ 2 ] It exists in two crystalline forms. It has several important applications in electrochemistry , in particular as the positive plate of lead acid batteries .
Lead dioxide has two major polymorphs, alpha and beta, which occur naturally as rare minerals scrutinyite and plattnerite , respectively. Whereas the beta form had been identified in 1845, [ 3 ] α- PbO 2 was first identified in 1946 and found as a naturally occurring mineral 1988. [ 4 ]
The alpha form has orthorhombic symmetry, space group Pbcn (No. 60), Pearson symbol oP 12, lattice constants a = 0.497 nm, b = 0.596 nm, c = 0.544 nm, Z = 4 (four formula units per unit cell). [ 4 ] The lead atoms are six-coordinate.
The symmetry of the beta form is tetragonal , space group P4 2 /mnm (No. 136), Pearson symbol tP 6, lattice constants a = 0.491 nm, c = 0.3385 nm, Z = 2 [ 5 ] and related to the rutile structure and can be envisaged as containing columns of octahedra sharing opposite edges and joined to other chains by corners. This contrasts with the alpha form where the octahedra are linked by adjacent edges to give zigzag chains. [ 4 ]
Lead dioxide decomposes upon heating in air as follows:
The stoichiometry of the end product can be controlled by changing the temperature – for example, in the above reaction, the first step occurs at 290 °C, second at 350 °C, third at 375 °C and fourth at 600 °C. In addition, Pb 2 O 3 can be obtained by decomposing PbO 2 at 580–620 °C under an oxygen pressure of 1,400 atm (140 MPa). Therefore, thermal decomposition of lead dioxide is a common way of producing various lead oxides. [ 6 ]
Lead dioxide is an amphoteric compound with prevalent acidic properties. It dissolves in strong bases to form the hydroxy plumbate ion, [Pb(OH) 6 ] 2− : [ 2 ]
It also reacts with basic oxides in the melt, yielding orthoplumbates M 4 [PbO 4 ] .
Because of the instability of its Pb 4+ cation, lead dioxide reacts with hot acids, converting to the more stable Pb 2+ state and liberating oxygen: [ 6 ]
However these reactions are slow.
Lead dioxide is well known for being a good oxidizing agent , with an example reactions listed below: [ 7 ]
Although the formula of lead dioxide is nominally given as PbO 2 , the actual oxygen to lead ratio varies between 1.90 and 1.98 depending on the preparation method. Deficiency of oxygen (or excess of lead) results in the characteristic metallic conductivity of lead dioxide, with a resistivity as low as 10 −4 Ω·cm and which is exploited in various electrochemical applications. Like metals, lead dioxide has a characteristic electrode potential , and in electrolytes it can be polarized both anodically and cathodically . Lead dioxide electrodes have a dual action, that is both the lead and oxygen ions take part in the electrochemical reactions. [ 8 ]
Lead dioxide is produced commercially by several methods, which include oxidation of red lead ( Pb 3 O 4 ) in alkaline slurry in a chlorine atmosphere, [ 6 ] reaction of lead(II) acetate with "chloride of lime" ( calcium hypochlorite ), [ 9 ] [ 10 ] The reaction of Pb 3 O 4 with nitric acid also affords the dioxide: [ 2 ] [ 11 ]
PbO 2 reacts with sodium hydroxide to form the hexahydroxoplumbate(IV) ion [Pb(OH) 6 ] 2− , soluble in water.
An alternative synthesis method is electrochemical : lead dioxide forms on pure lead, in dilute sulfuric acid , when polarized anodically at electrode potential about +1.5 V at room temperature. This procedure is used for large-scale industrial production of PbO 2 anodes. Lead and copper electrodes are immersed in sulfuric acid flowing at a rate of 5–10 L/min. The electrodeposition is carried out galvanostatically , by applying a current of about 100 A/m 2 for about 30 minutes.
The drawback of this method for the production of lead dioxide anodes is its softness, especially compared to the hard and brittle PbO 2 which has a Mohs hardness of 5.5. [ 12 ] This mismatch in mechanical properties results in peeling of the coating which is preferred for bulk PbO 2 production. Therefore, an alternative method is to use harder substrates, such as titanium , niobium , tantalum or graphite and deposit PbO 2 onto them from lead(II) nitrate in static or flowing nitric acid. The substrate is usually sand-blasted before the deposition to remove surface oxide and contamination and to increase the surface roughness and adhesion of the coating. [ 13 ]
Lead dioxide is used in the production of matches , pyrotechnics , dyes and the curing of sulfide polymers . It is also used in the construction of high-voltage lightning arresters . [ 6 ]
Lead dioxide is used as an anode material in electrochemistry. β- PbO 2 is more attractive for this purpose than the α form because it has relatively low resistivity , good corrosion resistance even in low- pH medium, and a high overvoltage for the evolution of oxygen in sulfuric- and nitric-acid-based electrolytes. Lead dioxide can also withstand chlorine evolution in hydrochloric acid . Lead dioxide anodes are inexpensive and were once used instead of conventional platinum and graphite electrodes for regenerating potassium dichromate . They were also applied as oxygen anodes for electroplating copper and zinc in sulfate baths. In organic synthesis, lead dioxide anodes were applied for the production of glyoxylic acid from oxalic acid in a sulfuric acid electrolyte. [ 13 ]
The most important use of lead dioxide is as the cathode of lead acid batteries . Its utility arises from the anomalous metallic conductivity of PbO 2 . The lead acid battery stores and releases energy by shifting the equilibrium (a comproportionation) between metallic lead, lead dioxide, and lead(II) salts in sulfuric acid .
Lead compounds are poisons . Chronic contact with the skin can potentially cause lead poisoning through absorption, or redness and irritation in the short term. [ 14 ]
PbO 2 is not combustible, but it enhances flammability of other substances and the intensity of the fire. In case of a fire it gives off irritating and toxic fumes. [ 15 ] [ better source needed ]
Lead dioxide is poisonous to aquatic life, but because of its insolubility it usually settles out of water. [ 16 ] [ 15 ] | https://en.wikipedia.org/wiki/O2Pb |
Dioxygenyl hexafluoroplatinate is a compound with formula O 2 PtF 6 . It is a hexafluoroplatinate of the unusual dioxygenyl cation, O 2 + , and is the first known compound containing this cation. [ 1 ] It can be produced by the reaction of dioxygen with platinum hexafluoride . The fact that PtF 6 is strong enough to oxidise O 2 , whose first ionization potential is 12.2 eV , led Neil Bartlett to correctly surmise that it might be able to oxidise xenon (first ionization potential 12.13 eV). This led to the discovery of xenon hexafluoroplatinate , [ 2 ] which proved that the noble gases , previously thought to be inert, are able to form chemical compounds.
Dioxygenyl hexafluoroplatinate can be synthesized from the elements by the action of a mixture of oxygen and fluorine gas on platinum sponge at 450 °C. [ 1 ] It can also be prepared by the reaction of oxygen difluoride ( OF 2 ) with platinum sponge . At 350 °C, platinum tetrafluoride is produced; above 400 °C, dioxygenyl hexafluoroplatinate is formed. [ 1 ]
Bartlett demonstrated that it can be synthesized at room temperature by the reaction of oxygen gas with PtF 6 . [ 1 ]
Dioxygenyl hexafluoroplatinate(V) has a rhombohedral crystal structure at low temperatures, and a cubic structure at high temperatures, [ 3 ] isomorphous to potassium hexafluoroplatinate(V) , KPtF 6 . Its ionic lattice is indicated by its insolubility in carbon tetrafluoride . In its cubic form, the PtF − 6 octahedra are slightly compressed along the three-fold rotational axis, along which the long axis of the [O 2 ] + cations also lies. Each O + 2 cation is surrounded by 12 fluorine atoms, 6 of which surround it in a puckered six-membered ring, and of the remaining 3 each belong to the two PtF − 6 octahedra lying along the long axis of the cation. [ 1 ]
Dioxygenyl hexafluoroplatinate(V) is a convenient route to prepare other platinum(V) compounds, such as potassium hexafluoroplatinate(V) via reaction with potassium fluoride in iodine pentafluoride ( IF 5 ) solution [ 3 ] in which iodine heptafluoride is produced: | https://en.wikipedia.org/wiki/O2PtF6 |
Plutonium(IV) oxide , or plutonia , is a chemical compound with the formula Pu O 2 . This high melting-point solid is a principal compound of plutonium . It can vary in color from yellow to olive green, depending on the particle size, temperature and method of production. [ 2 ]
PuO 2 crystallizes in the fluorite motif, with the Pu 4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes. [ 3 ] PuO 2 owes its utility as a nuclear fuel to the fact that vacancies in the octahedral holes allows room for fission products. In nuclear fission, one atom of plutonium splits into two. The vacancy of the octahedral holes provides room for the new product and allows the PuO 2 monolith to retain its structural integrity. [ citation needed ]
At high temperatures PuO 2 tends to lose oxygen, becoming sub-stoichiometric PuO 2−x , with the introduction of lower valence Pu 3+ . This continues into the molten liquid state where the local Pu-O coordination number drops to predominantly 6-fold, compared to 8-fold in the stoichiometric fluorite structure. [ 4 ]
Plutonium dioxide is a stable ceramic material with an extremely low solubility in water and with a high melting point (2,744 °C). The melting point was revised upwards in 2011 by several hundred degrees, based on evidence from rapid laser melting studies which avoid contamination by any container material. [ 5 ]
As with all plutonium compounds, it is subject to control under the Nuclear Non-Proliferation Treaty .
Plutonium spontaneously oxidizes to PuO 2 in an atmosphere of oxygen. Plutonium dioxide is mainly produced by calcination of plutonium(IV) oxalate, Pu(C 2 O 4 ) 2 ·6H 2 O, at 300 °C. Plutonium oxalate is obtained during the reprocessing of nuclear fuel as plutonium is dissolved in a solution of nitric and hydrofluoric acid . [ 6 ] Plutonium dioxide can also be recovered from molten-salt breeder reactors by adding sodium carbonate to the fuel salt after any remaining uranium is removed from the salt as its hexafluoride.
PuO 2 , along with UO 2 , is used in MOX fuels for nuclear reactors . Plutonium-238 dioxide is used as fuel for several deep-space spacecraft such as the Cassini , Voyager , Galileo and New Horizons probes as well as in the Curiosity and Perseverance rovers on Mars . The isotope decays by emitting α-particles, which then generate heat (see radioisotope thermoelectric generator ). There have been concerns that an accidental re-entry into Earth's atmosphere from orbit might lead to the break-up and/or burn-up of a spacecraft, resulting in the dispersal of the plutonium, either over a large tract of the planetary surface or within the upper atmosphere. However, although at least two spacecraft carrying PuO 2 RTGs have reentered the Earth's atmosphere and burned up ( Nimbus B-1 in May 1968 and the Apollo 13 Lunar Module in April 1970), [ 7 ] [ 8 ] the RTGs from both spacecraft survived reentry and impact intact, and no environmental contamination was noted in either instance; in fact, the Nimbus RTG was recovered intact from the Pacific Ocean seafloor and launched aboard Nimbus 3 one year later. In any case, RTGs since the mid-1960s have been designed to remain intact in the event of reentry and impact, following the 1964 launch failure of Transit 5-BN-3 (the early-generation plutonium RTG on board disintegrated upon reentry and dispersed radioactive material into the atmosphere north of Madagascar , prompting a redesign of all U.S. RTGs then in use or under development). [ 9 ]
Physicist Peter Zimmerman, following up a suggestion by Ted Taylor , calculated that a low-yield (1- kiloton ) nuclear weapon could be made relatively easily from plutonium dioxide. [ 10 ] Such bomb would require a considerably larger critical mass than one made from elemental plutonium (almost three times larger, even with the dioxide at maximum crystal density; if the dioxide were in powder form, as is often encountered, the critical mass would be much higher still), due both to the lower density of plutonium in dioxide compared with elemental plutonium and to the added inert mass of the oxygen contained. [ 11 ]
The behavior of plutonium dioxide in the body varies with the way in which it is taken. When ingested, most of it will be eliminated from the body quite rapidly in body wastes, [ 12 ] but a small part will dissolve into ions in acidic gastric juice and cross the blood barrier, depositing itself in other chemical forms in other organs such as in phagocytic cells of lung, bone marrow and liver. [ 13 ]
In particulate form, plutonium dioxide at a particle size less than 10 μm [ 14 ] is radiotoxic if inhaled due to its strong alpha-emission . [ 15 ] | https://en.wikipedia.org/wiki/O2Pu |
Selenium dioxide is the chemical compound with the formula SeO 2 . This colorless solid is one of the most frequently encountered compounds of selenium . It is used in making specialized glasses as well as a reagent in organic chemistry. [ 4 ]
Solid SeO 2 is a one-dimensional polymer , the chain consisting of alternating selenium and oxygen atoms. Each Se atom is pyramidal and bears a terminal oxide group. The bridging Se-O bond lengths are 179 pm and the terminal Se-O distance is 162 pm. [ 5 ] The relative stereochemistry at Se alternates along the polymer chain ( syndiotactic ).
In the gas phase selenium dioxide is present as dimers and other oligomeric species, at higher temperatures it is monomeric. [ 6 ] The monomeric form adopts a bent structure very similar to that of sulfur dioxide with a bond length of 161 pm. [ 6 ] The dimeric form has been isolated in a low temperature argon matrix and vibrational spectra indicate that it has a centrosymmetric chair form. [ 5 ] Dissolution of SeO 2 in selenium oxydichloride give the trimer [Se(O)O] 3 . [ 6 ] Monomeric SeO 2 is a polar molecule, with the dipole moment of 2.62 D [ 7 ] pointed from the midpoint of the two oxygen atoms to the selenium atom.
The solid sublimes readily. At very low concentrations the vapour has a revolting odour, resembling decayed horseradishes. At higher concentrations the vapour has an odour resembling horseradish sauce and can burn the nose and throat on inhalation. Whereas SO 2 tends to be molecular and SeO 2 is a one-dimensional chain, TeO 2 is a cross-linked polymer. [ 5 ]
SeO 2 is considered an acidic oxide : it dissolves in water to form selenous acid . [ 6 ] Often the terms selenous acid and selenium dioxide are used interchangeably. It reacts with base to form selenite salts containing the SeO 2− 3 anion. For example, reaction with sodium hydroxide produces sodium selenite :
Selenium dioxide is prepared by oxidation of selenium by burning in air or by reaction with nitric acid or hydrogen peroxide , but perhaps the most convenient preparation is by the dehydration of selenous acid .
The natural form of selenium dioxide, downeyite, is a very rare mineral. It is only found at a small number of burning coal banks , where it forms around vents created from escaping gasses. [ 8 ]
SeO 2 is an important reagent in organic synthesis . Oxidation of paraldehyde (acetaldehyde trimer) with SeO 2 gives glyoxal [ 9 ] and the oxidation of cyclohexanone gives 1,2-cyclohexanedione . [ 10 ] The selenium starting material is reduced to selenium, and precipitates as a red amorphous solid which can easily be filtered off. [ 10 ] This type of reaction is called a Riley oxidation . It is also renowned as a reagent for allylic oxidation , [ 11 ] a reaction that entails the following conversion
This can be described more generally as;
where R, R', R" may be alkyl or aryl substituents.
Selenium dioxide can also be used to synthesize 1,2,3-selenadiazoles from acylated hydrazone derivatives. [ 12 ]
Selenium dioxide imparts a red colour to glass . It is used in small quantities to counteract the colour due to iron impurities and so to create (apparently) colourless glass. In larger quantities, it gives a deep ruby red colour.
Selenium dioxide is the active ingredient in some cold-bluing solutions.
It was also used as a toner in photographic developing .
Selenium is an essential element , but ingestion of more than 5 mg/day leads to nonspecific symptoms . [ 13 ] | https://en.wikipedia.org/wiki/O2Se |
Silicon dioxide , also known as silica , is an oxide of silicon with the chemical formula SiO 2 , commonly found in nature as quartz . [ 5 ] [ 6 ] In many parts of the world, silica is the major constituent of sand . Silica is one of the most complex and abundant families of materials , existing as a compound of several minerals and as a synthetic product. Examples include fused quartz , fumed silica , opal , and aerogels . It is used in structural materials , microelectronics , and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored.
Silicon dioxide is a common fundamental constituent of glass .
In the majority of silicon dioxides, the silicon atom shows tetrahedral coordination , with four oxygen atoms surrounding a central Si atom ( see 3-D Unit Cell ). Thus, SiO 2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. [ 8 ] [ 9 ] In contrast, CO 2 is a linear molecule. The starkly different structures of the dioxides of carbon and silicon are a manifestation of the double bond rule . [ 10 ]
Based on the crystal structural differences, silicon dioxide can be divided into two categories: crystalline and non-crystalline (amorphous). In crystalline form, this substance can be found naturally occurring as quartz , tridymite (high-temperature form), cristobalite (high-temperature form), stishovite (high-pressure form), and coesite (high-pressure form). On the other hand, amorphous silica can be found in nature as opal and diatomaceous earth . Quartz glass is a form of intermediate state between these structures. [ 11 ]
All of these distinct crystalline forms always have the same local structure around Si and O. In α-quartz the Si–O bond length is 161 pm, whereas in α-tridymite it is in the range 154–171 pm. The Si–O–Si angle also varies between a low value of 140° in α-tridymite, up to 180° in β-tridymite. In α-quartz, the Si–O–Si angle is 144°. [ 12 ]
Alpha quartz is the most stable form of solid SiO 2 at room temperature. The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction than quartz. The transformation from α-quartz to beta-quartz takes place abruptly at 573 °C. Since the transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature limit. [ 13 ] The high-pressure minerals, seifertite , stishovite, and coesite, though, have higher densities and indices of refraction than quartz. [ 14 ] Stishovite has a rutile -like structure where silicon is 6-coordinate. The density of stishovite is 4.287 g/cm 3 , which compares to α-quartz, the densest of the low-pressure forms, which has a density of 2.648 g/cm 3 . [ 15 ] The difference in density can be ascribed to the increase in coordination as the six shortest Si–O bond lengths in stishovite (four Si–O bond lengths of 176 pm and two others of 181 pm) are greater than the Si–O bond length (161 pm) in α-quartz. [ 16 ] The change in the coordination increases the ionicity of the Si–O bond. [ 17 ]
Faujasite silica, another polymorph, is obtained by the dealumination of a low-sodium, ultra-stable Y zeolite with combined acid and thermal treatment. The resulting product contains over 99% silica, and has high crystallinity and specific surface area (over 800 m 2 /g). Faujasite-silica has very high thermal and acid stability. For example, it maintains a high degree of long-range molecular order or crystallinity even after boiling in concentrated hydrochloric acid . [ 18 ]
Molten silica exhibits several peculiar physical characteristics that are similar to those observed in liquid water : negative temperature expansion, density maximum at temperatures ~5000 °C, and a heat capacity minimum. [ 19 ] Its density decreases from 2.08 g/cm 3 at 1950 °C to 2.03 g/cm 3 at 2200 °C. [ 20 ]
The molecular SiO 2 has a linear structure like CO 2 . It has been produced by combining silicon monoxide (SiO) with oxygen in an argon matrix.
The dimeric silicon dioxide, (SiO 2 ) 2 has been obtained by reacting O 2 with matrix isolated dimeric silicon monoxide, (Si 2 O 2 ). In dimeric silicon dioxide there are two oxygen atoms bridging between the silicon atoms with an Si–O–Si angle of 94° and bond length of 164.6 pm and the terminal Si–O bond length is 150.2 pm. The Si–O bond length is 148.3 pm, which compares with the length of 161 pm in α-quartz. The bond energy is estimated at 621.7 kJ/mol. [ 21 ]
SiO 2 is most commonly encountered in nature as quartz , which comprises more than 10% by mass of the Earth's crust. [ 22 ] Quartz is the only polymorph of silica stable at the Earth's surface. Metastable occurrences of the high-pressure forms coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism . The high-temperature forms of tridymite and cristobalite are known from silica-rich volcanic rocks . In many parts of the world, silica is the major constituent of sand . [ 23 ]
Even though it is poorly soluble, silica occurs in many plants such as rice . Plant materials with high silica phytolith content appear to be of importance to grazing animals, from chewing insects to ungulates . Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by insects may have developed as a defense mechanism against predation. [ 24 ] [ 25 ]
Silica is also the primary component of rice husk ash , which is used, for example, in filtration and as supplementary cementitious material (SCM) in cement and concrete manufacturing. [ 26 ]
Silicification in and by cells has been common in the biological world and it occurs in bacteria, protists, plants, and animals (invertebrates and vertebrates). [ 27 ]
Prominent examples include:
About 95% of the commercial use of silicon dioxide (sand) is in the construction industry, e.g. in the production of concrete ( Portland cement concrete ). [ 22 ]
Certain deposits of silica sand, with desirable particle size and shape and desirable clay and other mineral content, were important for sand casting of metallic products. [ 33 ] The high melting point of silica enables it to be used in such applications such as iron casting; modern sand casting sometimes uses other minerals for other reasons.
Crystalline silica is used in hydraulic fracturing of formations which contain tight oil and shale gas . [ 34 ]
Silica is the primary ingredient in the production of most glass . As other minerals are melted with silica, the principle of freezing point depression lowers the melting point of the mixture and increases fluidity. The glass transition temperature of pure SiO 2 is about 1475 K. [ 35 ] When molten silicon dioxide SiO 2 is rapidly cooled, it does not crystallize, but solidifies as a glass. [ 36 ] Because of this, most ceramic glazes have silica as the main ingredient. [ 37 ]
The structural geometry of silicon and oxygen in glass is similar to that in quartz and most other crystalline forms of silicon and oxygen, with silicon surrounded by regular tetrahedra of oxygen centres. The difference between the glass and crystalline forms arises from the connectivity of the tetrahedral units: Although there is no long-range periodicity in the glassy network, ordering remains at length scales well beyond the SiO bond length. One example of this ordering is the preference to form rings of 6-tetrahedra. [ 38 ]
The majority of optical fibers for telecommunications are also made from silica. It is a primary raw material for many ceramics such as earthenware , stoneware , and porcelain .
Silicon dioxide is used to produce elemental silicon . The process involves carbothermic reduction in an electric arc furnace : [ 39 ]
Fumed silica , also known as pyrogenic silica, is prepared by burning SiCl 4 in an oxygen-rich hydrogen flame to produce a "smoke" of SiO 2 . [ 15 ]
It can also be produced by vaporizing quartz sand in a 3000 °C electric arc. Both processes result in microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles, a white powder with extremely low bulk density (0.03-0.15 g/cm 3 ) and thus high surface area. [ 40 ] The particles act as a thixotropic thickening agent, or as an anti-caking agent, and can be treated to make them hydrophilic or hydrophobic for either water or organic liquid applications.
Silica fume is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production. It consists of amorphous (non-crystalline) spherical particles with an average particle diameter of 150 nm, without the branching of the pyrogenic product. The main use is as pozzolanic material for high performance concrete. Fumed silica nanoparticles can be successfully used as an anti-aging agent in asphalt binders. [ 41 ]
Silica, either colloidal, precipitated, or pyrogenic fumed, is a common additive in food production. It is used primarily as a flow or anti- caking agent in powdered foods such as spices and non-dairy coffee creamer, or powders to be formed into pharmaceutical tablets. [ 40 ] It can adsorb water in hygroscopic applications. Colloidal silica is used as a fining agent for wine, beer, and juice, with the E number reference E551 . [ 22 ]
In cosmetics, silica is useful for its light-diffusing properties [ 42 ] and natural absorbency. [ 43 ]
Diatomaceous earth , a mined product, has been used in food and cosmetics for centuries. It consists of the silica shells of microscopic diatoms ; in a less processed form it was sold as tooth powder . [ 44 ] [ 45 ] Manufactured or mined hydrated silica is used as the hard abrasive in toothpaste .
Silicon dioxide is widely used in the semiconductor technology:
Because silicon dioxide is a native oxide of silicon it is more widely used compared to other semiconductors like gallium arsenide or indium phosphide .
Silicon dioxide could be grown on a silicon semiconductor surface. [ 46 ] Silicon oxide layers could protect silicon surfaces during diffusion processes , and could be used for diffusion masking. [ 47 ] [ 48 ]
Surface passivation is the process by which a semiconductor surface is rendered inert, and does not change semiconductor properties as a result of interaction with air or other materials in contact with the surface or edge of the crystal. [ 49 ] [ 50 ] The formation of a thermally grown silicon dioxide layer greatly reduces the concentration of electronic states at the silicon surface . [ 50 ] SiO 2 films preserve the electrical characteristics of p–n junctions and prevent these electrical characteristics from deteriorating by the gaseous ambient environment. [ 48 ] Silicon oxide layers could be used to electrically stabilize silicon surfaces. [ 47 ] The surface passivation process is an important method of semiconductor device fabrication that involves coating a silicon wafer with an insulating layer of silicon oxide so that electricity could reliably penetrate to the conducting silicon below. Growing a layer of silicon dioxide on top of a silicon wafer enables it to overcome the surface states that otherwise prevent electricity from reaching the semiconducting layer. [ 49 ] [ 51 ]
The process of silicon surface passivation by thermal oxidation (silicon dioxide) is critical to the semiconductor industry . It is commonly used to manufacture metal–oxide–semiconductor field-effect transistors (MOSFETs) and silicon integrated circuit chips (with the planar process ). [ 49 ] [ 51 ]
Hydrophobic silica is used as a defoamer component .
In its capacity as a refractory , it is useful in fiber form as a high-temperature thermal protection fabric. [ 52 ]
Silica is used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes . [ 53 ]
Silica aerogel was used in the Stardust spacecraft to collect extraterrestrial particles. [ 54 ]
Pure silica (silicon dioxide), when cooled as fused quartz into a glass with no true melting point, can be used as a glass fibre for fibreglass.
Silicon dioxide is mostly obtained by mining, including sand mining and purification of quartz .
Quartz is suitable for many purposes, while chemical processing is required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product. [ 55 ] [ 56 ]
Precipitated silica or amorphous silica is produced by the acidification of solutions of sodium silicate . The gelatinous precipitate or silica gel , is first washed and then dehydrated to produce colorless microporous silica. [ 15 ] The idealized equation involving a trisilicate and sulfuric acid is:
Approximately one billion kilograms/year (1999) of silica were produced in this manner, mainly for use for polymer composites – tires and shoe soles. [ 22 ]
Thin films of silica grow spontaneously on silicon wafers via thermal oxidation , producing a very shallow layer of about 1 nm or 10 Å of so-called native oxide. [ 57 ] Higher temperatures and alternative environments are used to grow well-controlled layers of silicon dioxide on silicon, for example at temperatures between 600 and 1200 °C, using so-called dry oxidation with O 2
or wet oxidation with H 2 O. [ 58 ] [ 59 ]
The native oxide layer is beneficial in microelectronics , where it acts as electric insulator with high chemical stability. It can protect the silicon, store charge, block current, and even act as a controlled pathway to limit current flow. [ 60 ]
Many routes to silicon dioxide start with an organosilicon compound, e.g., HMDSO, [ 61 ] TEOS. Synthesis of silica is illustrated below using tetraethyl orthosilicate (TEOS). [ 62 ] Simply heating TEOS at 680–730 °C results in the oxide:
Similarly TEOS combusts around 400 °C:
TEOS undergoes hydrolysis via the so-called sol-gel process . The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is: [ 63 ]
Being highly stable, silicon dioxide arises from many methods. Conceptually simple, but of little practical value, combustion of silane gives silicon dioxide. This reaction is analogous to the combustion of methane:
However the chemical vapor deposition of silicon dioxide onto crystal surface from silane had been used using nitrogen as a carrier gas at 200–500 °C. [ 64 ]
Silicon dioxide is a relatively inert material (hence its widespread occurrence as a mineral). Silica is often used as inert containers for chemical reactions. At high temperatures, it is converted to silicon by reduction with carbon.
Fluorine reacts with silicon dioxide to form SiF 4 and O 2 whereas the other halogen gases (Cl 2 , Br 2 , I 2 ) are unreactive. [ 15 ]
Most forms of silicon dioxide are attacked ("etched") by hydrofluoric acid (HF) to produce hexafluorosilicic acid : [ 12 ]
Stishovite does not react to HF to any significant degree. [ 65 ] HF is used to remove or pattern silicon dioxide in the semiconductor industry.
Silicon dioxide acts as a Lux–Flood acid , being able to react with bases under certain conditions. As it does not contain any hydrogen, non-hydrated silica cannot directly act as a Brønsted–Lowry acid . While silicon dioxide is only poorly soluble in water at low or neutral pH (typically, 2 × 10 −4 M for quartz up to 10 −3 M for cryptocrystalline chalcedony ), strong bases react with glass and easily dissolve it. Therefore, strong bases have to be stored in plastic bottles to avoid jamming the bottle cap, to preserve the integrity of the recipient, and to avoid undesirable contamination by silicate anions. [ 66 ]
Silicon dioxide dissolves in hot concentrated alkali or fused hydroxide, as described in this idealized equation: [ 15 ]
Silicon dioxide will neutralise basic metal oxides (e.g. sodium oxide , potassium oxide , lead(II) oxide , zinc oxide , or mixtures of oxides, forming silicates and glasses as the Si-O-Si bonds in silica are broken successively). [ 12 ] As an example the reaction of sodium oxide and SiO 2 can produce sodium orthosilicate , sodium silicate, and glasses, dependent on the proportions of reactants: [ 15 ]
Examples of such glasses have commercial significance, e.g. soda–lime glass , borosilicate glass , lead glass . In these glasses, silica is termed the network former or lattice former. [ 12 ] The reaction is also used in blast furnaces to remove sand impurities in the ore by neutralisation with calcium oxide , forming calcium silicate slag .
Silicon dioxide reacts in heated reflux under dinitrogen with ethylene glycol and an alkali metal base to produce highly reactive, pentacoordinate silicates which provide access to a wide variety of new silicon compounds. [ 67 ] The silicates are essentially insoluble in all polar solvent except methanol .
Silicon dioxide reacts with elemental silicon at high temperatures to produce SiO: [ 12 ]
The solubility of silicon dioxide in water strongly depends on its crystalline form and is three to four times higher for amorphous silica than quartz; as a function of temperature, it peaks around 340 °C (644 °F). [ 68 ] This property is used to grow single crystals of quartz in a hydrothermal process where natural quartz is dissolved in superheated water in a pressure vessel that is cooler at the top. Crystals of 0.5–1 kg can be grown for 1–2 months. [ 12 ] These crystals are a source of very pure quartz for use in electronic applications. [ 15 ] Above the critical temperature of water 647.096 K (373.946 °C; 705.103 °F) and a pressure of 22.064 megapascals (3,200.1 psi) or higher, water is a supercritical fluid and solubility is once again higher than at lower temperatures. [ 69 ]
Silica ingested orally is essentially nontoxic, with an LD 50 of 5000 mg/kg (5 g/kg). [ 22 ] A 2008 study following subjects for 15 years found that higher levels of silica in water appeared to decrease the risk of dementia . An increase of 10 mg/day of silica in drinking water was associated with a reduced risk of dementia of 11%. [ 70 ]
Inhaling finely divided crystalline silica dust can lead to silicosis , bronchitis , or lung cancer , as the dust becomes lodged in the lungs and continuously irritates the tissue, reducing lung capacities. [ 71 ] When fine silica particles are inhaled in large enough quantities (such as through occupational exposure), it increases the risk of systemic autoimmune diseases such as lupus [ 72 ] and rheumatoid arthritis compared to expected rates in the general population. [ 73 ]
Silica is an occupational hazard for people who do sandblasting or work with powdered crystalline silica products. Amorphous silica, such as fumed silica, may cause irreversible lung damage in some cases but is not associated with the development of silicosis. Children, asthmatics of any age, those with allergies , and the elderly (all of whom have reduced lung capacity ) can be affected in less time. [ 74 ]
Crystalline silica is an occupational hazard for those working with stone countertops because the process of cutting and installing the countertops creates large amounts of airborne silica. [ 75 ] Crystalline silica used in hydraulic fracturing presents a health hazard to workers. [ 34 ]
In the body, crystalline silica particles do not dissolve over clinically relevant periods. Silica crystals inside the lungs can activate the NLRP3 inflammasome inside macrophages and dendritic cells and thereby result in production of interleukin , a highly pro-inflammatory cytokine in the immune system. [ 76 ] [ 77 ] [ 78 ]
Regulations restricting silica exposure 'with respect to the silicosis hazard' specify that they are concerned only with silica, which is both crystalline and dust-forming. [ 79 ] [ 80 ] [ 81 ] [ 82 ] [ 83 ] [ 84 ]
In 2013, the U.S. Occupational Safety and Health Administration reduced the exposure limit to 50 μg /m 3 of air. Prior to 2013, it had allowed 100 μg/m 3 and in construction workers even 250 μg/m 3 . [ 34 ] In 2013, OSHA also required the "green completion" of fracked wells to reduce exposure to crystalline silica and restrict the exposure limit. [ 34 ]
SiO 2 , more so than almost any material, exists in many crystalline forms. These forms are called polymorphs .
Inhaling finely divided crystalline silica can lead to severe inflammation of the lung tissue, silicosis , bronchitis , lung cancer , and systemic autoimmune diseases , such as lupus and rheumatoid arthritis . Inhalation of amorphous silicon dioxide, in high doses, leads to non-permanent short-term inflammation, where all effects heal. [ 100 ]
This extended list enumerates synonyms for silicon dioxide; all of these values are from a single source; values in the source were presented capitalized. [ 101 ] | https://en.wikipedia.org/wiki/O2Si |
Tellurium dioxide (TeO 2 ) is a solid oxide of tellurium . It is encountered in two different forms, the yellow orthorhombic mineral tellurite , β-TeO 2 , and the synthetic, colourless tetragonal (paratellurite), α-TeO 2 . [ 2 ] Most of the information regarding reaction chemistry has been obtained in studies involving paratellurite, α-TeO 2 . [ 3 ]
Paratellurite, α-TeO 2 , is produced by reacting tellurium with O 2 : [ 2 ]
An alternative preparation is to dehydrate tellurous acid, H 2 TeO 3 , or to thermally decompose basic tellurium nitrate , Te 2 O 4 ·HNO 3 , above 400 °C. [ 2 ]
The longitudinal speed of sound in Tellurium dioxide is 4,260 metres per second (14,000 ft/s) at around room temperature. [ 4 ]
TeO 2 is barely soluble in water and soluble in strong acids and alkali metal hydroxides . [ 5 ] It is an amphoteric substance and therefore can act both as an acid or as a base depending on the solution it is in. [ 6 ] It reacts with acids to make tellurium salts and bases to make tellurites . It can be oxidized to telluric acid or tellurates .
The tellurite ion is kinetically inert, but TeO 2 equivalents will oxidize thioates in acid to the diacyl disulfide. [ 7 ]
Paratellurite, α-TeO 2 , converts at high pressure into the β-, tellurite form. [ 8 ] Both the α-, (paratellurite) and β- (tellurite forms) contain four coordinate Te with the oxygen atoms at four of the corners of a trigonal bipyramid. In paratellurite all vertices are shared to give a rutile -like structure, where the O-Te-O bond angle are 140°. α-TeO 2 In tellurite pairs of trigonal pyramidal, TeO 4 units, sharing an edge, share vertices to then form a layer. [ 8 ] The shortest Te-Te distance in tellurite is 317 pm, compared to 374 pm in paratellurite. [ 8 ] Similar Te 2 O 6 units are found in the mineral denningite . [ 8 ]
TeO 2 melts at 732.6 °C, forming a red liquid. [ 9 ] The structure of the liquid, as well as the glass which can be formed from it with sufficiently rapid cooling, are also based on approximately four coordinate Te. However, compared to the crystalline forms, the liquid and glass appear to incorporate short-range disorder (a variety of coordination geometries) which marks TeO 2 glass as distinct from the canonical single-oxide glass-formers such as SiO 2 , which share the same short-range order with their parent liquids. [ 10 ]
It is used as an acousto-optic material. [ 4 ]
Tellurium dioxide is also a reluctant glass former, it will form a glass under suitable cooling conditions, [ 11 ] or with additions of a small molar fraction of a second compound such as an oxide or halide. TeO 2 glasses have high refractive indices and transmit into the mid- infrared part of the electromagnetic spectrum , therefore they are of technological interest for optical waveguides . Tellurite glasses have also been shown to exhibit Raman gain up to 30 times that of silica , useful in optical fibre amplification. [ 12 ]
TeO 2 is a possible teratogen . [ 13 ]
Exposure to tellurium compounds produces a garlic -like odour on the breath, caused by the formation of diethyl telluride . [ 14 ] | https://en.wikipedia.org/wiki/O2Te |
Thorium dioxide (ThO 2 ), also called thorium(IV) oxide , is a crystalline solid, often white or yellow in colour. Also known as thoria , it is mainly a by-product of lanthanide and uranium production. [ 4 ] Thorianite is the name of the mineralogical form of thorium dioxide. It is moderately rare and crystallizes in an isometric system. The melting point of thorium oxide is 3300 °C – the highest of all known oxides. Only a few elements (including tungsten and carbon ) and a few compounds (including tantalum carbide ) have higher melting points. [ 6 ] All thorium compounds, including the dioxide, are radioactive because there are no stable isotopes of thorium .
Thoria exists as two polymorphs. One has a fluorite crystal structure. This is uncommon among binary dioxides. (Other binary oxides with fluorite structure include cerium dioxide , uranium dioxide and plutonium dioxide .) [ clarification needed ] The band gap of thoria is about 6 eV . A tetragonal form of thoria is also known.
Thorium dioxide is more stable than thorium monoxide (ThO). [ 7 ] Only with careful control of reaction conditions can oxidation of thorium metal give the monoxide rather than the dioxide. At extremely high temperatures, the dioxide can convert to the monoxide either by a disproportionation reaction (equilibrium with liquid thorium metal) above 1,850 K (1,580 °C; 2,870 °F) or by simple dissociation (evolution of oxygen) above 2,500 K (2,230 °C; 4,040 °F). [ 8 ]
Thorium dioxide (thoria) can be used in nuclear reactors as ceramic fuel pellets, typically contained in nuclear fuel rods clad with zirconium alloys. Thorium is not fissile (but is "fertile", breeding fissile uranium-233 under neutron bombardment); hence, it must be used as a nuclear reactor fuel in conjunction with fissile isotopes of either uranium or plutonium. This can be achieved by blending thorium with uranium or plutonium, or using it in its pure form in conjunction with separate fuel rods containing uranium or plutonium. Thorium dioxide offers advantages over conventional uranium dioxide fuel pellets, because of its higher thermal conductivity (lower operating temperature), considerably higher melting point, and chemical stability (does not oxidize in the presence of water/oxygen, unlike uranium dioxide).
Thorium dioxide can be turned into a nuclear fuel by breeding it into uranium-233 (see below and refer to the article on thorium for more information on this). The high thermal stability of thorium dioxide allows applications in flame spraying and high-temperature ceramics.
Thorium dioxide is used as a stabilizer in tungsten electrodes in TIG welding , electron tubes, and aircraft gas turbine engines. As an alloy, thoriated tungsten metal is not easily deformed because the high-fusion material thoria augments the high-temperature mechanical properties, and thorium helps stimulate the emission of electrons ( thermions ). It is the most popular oxide additive because of its low cost, but is being phased out in favor of non-radioactive elements such as cerium , lanthanum and zirconium .
Thoria-dispersed nickel finds its applications in various high-temperature operations like combustion engines because it is a good creep-resistant material. It can also be used for hydrogen trapping. [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ]
Thorium dioxide has almost no value as a commercial catalyst, but such applications have been well investigated. It is a catalyst in the Ruzicka large ring synthesis . Other applications that have been explored include petroleum cracking , conversion of ammonia to nitric acid and preparation of sulfuric acid . [ 14 ]
Thorium dioxide was the primary ingredient in Thorotrast , a once-common radiocontrast agent used for cerebral angiography , however, it causes a rare form of cancer (hepatic angiosarcoma ) many years after administration. [ 15 ] This use was replaced with injectable iodine or ingestable barium sulfate suspension as standard X-ray contrast agents.
Another major use in the past was in gas mantle of lanterns developed by Carl Auer von Welsbach in 1890, which are composed of 99% ThO 2 and 1% cerium(IV) oxide . Even as late as the 1980s it was estimated that about half of all ThO 2 produced (several hundred tonnes per year) was used for this purpose. [ 16 ] Some mantles still use thorium, but yttrium oxide (or sometimes zirconium oxide ) is used increasingly as a replacement.
When added to glass , thorium dioxide helps increase its refractive index and decrease dispersion . Such glass finds application in high-quality lenses for cameras and scientific instruments. [ 17 ] The radiation from these lenses can darken them and turn them yellow over a period of years and degrade film, but the health risks are minimal. [ 18 ] Yellowed lenses may be restored to their original colourless state by lengthy exposure to intense ultraviolet radiation. Thorium dioxide has since been replaced by rare-earth oxides such as lanthanum oxide in almost all modern high-index glasses, as they provide similar effects and are not radioactive. [ 19 ] | https://en.wikipedia.org/wiki/O2Th |
Oxygen fluorides are compounds of elements oxygen and fluorine with the general formula O n F 2 , where n = 1 to 6. Many different oxygen fluorides are known:
Oxygen fluorides are strong oxidizing agents with high energy and can release their energy either instantaneously or at a controlled rate. Thus, these compounds attracted much attention as potential oxidizers in jet propulsion systems . [ 5 ]
A common preparative method involves fluorination of sodium hydroxide :
OF 2 is a colorless gas at room temperature and a yellow liquid below 128 K. Oxygen difluoride has an irritating odor and is poisonous. [ 3 ] It reacts quantitatively with aqueous haloacids to give free halogens :
It can also displace halogens from their salts. [ 3 ] It is both an effective fluorinating agent and a strong oxidizing agent . When reacted with unsaturated nitrogen fluorides with electrical discharge, it results in the formation of nitrogen trifluoride , oxide fluorides and other oxides. [ 6 ] [ 7 ]
O 2 F 2 precipitates as a brown solid upon the UV irradiation of a mixture of liquid O 2 and F 2 at −196 °C. [ 8 ] It also only appears to be stable below −160 °C. [ 9 ] The general method of preparation of many oxygen fluorides is a gas-phase electric discharge in cold containers including O 2 F 2 . [ 10 ]
It is typically an orange-yellow solid which rapidly decomposes to O 2 and F 2 close to its normal boiling point of about 216 K. [ 3 ]
O 2 F 2 reacts violently with red phosphorus , even at −196 °C. Explosions can also occur if Freon-13 is used to moderate the reaction. [ 9 ]
O 3 F 2 is a viscous, blood-red liquid. It remains liquid at 90 K and so can be differentiated from O 2 F 2 which has a melting point of about 109 K. [ 11 ] [ 3 ]
Like the other oxygen fluorides, O 3 F 2 is endothermic and decomposes at about 115 K with the evolution of heat, which is given by the following reaction:
O 3 F 2 is safer to work with than ozone , and can be evaporated, or thermally decomposed, or exposed to electric sparks, without any explosions. But on contact with organic matter or oxidizable compounds, it can detonate or explode. Thus, the addition of even one drop of ozone difluoride to solid anhydrous ammonia will result in a mild explosion, when they are both at 90 K each. [ 3 ]
Fluoroperoxyl is a molecule such as O–O–F, whose chemical formula is O 2 F and is stable only at low temperature. It has been reported to be produced from atomic fluorine and dioxygen. [ 12 ]
Oxygen- and fluorine-containing radicals like O 2 F and OF occur in the atmosphere. These along with other halogen radicals have been implicated in the destruction of ozone in the atmosphere. However, the oxygen monofluoride radicals are assumed to not play as big a role in the ozone depletion because free fluorine atoms in the atmosphere are believed to react with methane to produce hydrofluoric acid which precipitates in rain. This decreases the availability of free fluorine atoms for oxygen atoms to react with and destroy ozone molecules. [ 13 ]
Net reaction:
Despite the low solubility of O 3 F 2 in liquid oxygen, it has been shown to be hypergolic with most rocket propellant fuels. The mechanism involves the boiling off oxygen from the solution containing O 3 F 2 , making it more reactive to have a spontaneous reaction with the rocket fuel. The degree of reactivity is also dependent on the type of fuel used. [ 3 ] | https://en.wikipedia.org/wiki/O3F2 |
Antimony(III) oxide is the inorganic compound with the formula Sb 2 O 3 . It is the most important commercial compound of antimony . It is found in nature as the minerals valentinite and senarmontite. [ 3 ] Like most polymeric oxides , Sb 2 O 3 dissolves in aqueous solutions with hydrolysis . A mixed arsenic-antimony oxide occurs in nature as the very rare mineral stibioclaudetite. [ 4 ] [ 5 ]
Global production of antimony(III) oxide in 2012 was 130,000 tonnes, an increase from 112,600 tonnes in 2002. China produces the largest share followed by US/Mexico, Europe, Japan and South Africa and other countries (2%). [ 6 ]
As of 2010, antimony(III) oxide was produced at four sites in the EU. It is produced via two routes, re-volatilizing of crude antimony(III) oxide and by oxidation of antimony metal.
Oxidation of antimony metal dominates in Europe. Several processes for the production of crude antimony(III) oxide or metallic antimony from virgin material. The choice of process depends on the composition of the ore and other factors. Typical steps include mining, crushing and grinding of ore, sometimes followed by froth flotation and separation of the metal using pyrometallurgical processes (smelting or roasting) or in a few cases (e.g. when the ore is rich in precious metals) by hydrometallurgical processes. These steps do not take place in the EU but closer to the mining location.
Step 1) Crude stibnite is oxidized to crude antimony(III) oxide using furnaces operating at approximately 500 to 1,000 °C. The reaction is the following:
Step 2) The crude antimony(III) oxide is purified by sublimation .
Antimony metal is oxidized to antimony(III) oxide in furnaces. The reaction is exothermic. Antimony(III) oxide is formed through sublimation and recovered in bag filters. The size of the formed particles is controlled by process conditions in furnace and gas flow. The reaction can be schematically described by:
Antimony(III) oxide is an amphoteric oxide . It dissolves in aqueous sodium hydroxide solution to give the meta-antimonite NaSbO 2 , which can be isolated as the trihydrate. Antimony(III) oxide also dissolves in concentrated mineral acids to give the corresponding salts, which hydrolyzes upon dilution with water. [ 7 ] With nitric acid , the trioxide is oxidized to antimony(V) oxide . [ 8 ]
When heated with carbon , the oxide is reduced to antimony metal. With other reducing agents such as sodium borohydride or lithium aluminium hydride , the unstable and very toxic gas stibine is produced. [ 9 ] When heated with potassium bitartrate , a complex salt potassium antimony tartrate , KSb(OH) 2 ·C 4 H 2 O 6 , is formed. [ 8 ]
The structure of Sb 2 O 3 depends on the temperature of the sample. Dimeric Sb 4 O 6 is the high temperature (1560 °C) gas. [ 10 ] Sb 4 O 6 molecules are bicyclic cages, similar to the related oxide of phosphorus(III), phosphorus trioxide . [ 11 ] The cage structure is retained in a solid that crystallizes in a cubic habit. The Sb–O distance is 197.7 pm and the O–Sb–O angle of 95.6°. [ 12 ] This form exists in nature as the mineral senarmontite . [ 11 ] Above 606 °C, the more stable form is orthorhombic , consisting of pairs of -Sb-O-Sb-O- chains that are linked by oxide bridges between the Sb centers. This form exists in nature as the mineral valentinite . [ 11 ]
The annual consumption of antimony(III) oxide in the United States and Europe is approximately 10,000 and 25,000 tonnes , respectively. The main application is as flame retardant synergist in combination with halogenated materials. The combination of the halides and the antimony is key to the flame-retardant action for polymers, helping to form less flammable chars. Such flame retardants are found in electrical apparatuses, textiles, leather, and coatings. [ 13 ]
Other applications:
Antimony(III) oxide has suspected carcinogenic potential for humans. [ 13 ] Its TLV is 0.5 mg/m 3 , as for most antimony compounds. [ 14 ] Before 2021, no other human health hazards were identified for antimony(III) oxide, and no risks to human health and the environment were identified from the production and use of antimony trioxide in daily life. However, the 15th Report on Carcinogens released on December 21, 2021, by the US Department of Health and Human Services categorised antimony(III) oxide as carcinogenic. [ 15 ] | https://en.wikipedia.org/wiki/O3Sb2 |
Scandium(III) oxide or scandia is a inorganic compound with formula Sc 2 O 3 . It is one of several oxides of rare earth elements with a high melting point . It is used in the preparation of other scandium compounds as well as in high-temperature systems (for its resistance to heat and thermal shock ), electronic ceramics , and glass composition (as a helper material).
Scandium(III) oxide adopts a cubic crystal structure ( point group : tetrahedral (T h ), space group : Ia 3 ) containing 6-coordinate metal centres. [ 2 ] Powder diffraction analysis shows Sc−O bond distances of 2.159–2.071 Å. [ 1 ]
Scandium oxide is an insulator with a band gap of 6.0 eV. [ 3 ]
Scandium oxide is the primary form of refined scandium produced by the mining industry. Scandium-rich ores, such as thortveitite (Sc,Y) 2 (Si 2 O 7 ) and kolbeckite ScPO 4 ·2H 2 O are rare, however trace amounts of scandium are present in many other minerals. Scandium oxide is therefore predominantly produced as a by-product from the extraction of other elements.
Scandium oxide is the primary form of refined scandium produced by the mining industry, making it the start point for all scandium chemistry.
Scandium oxide reacts with most acids upon heating, to produce the expected hydrated product. For example, heating in excess aqueous HCl produces hydrated ScCl 3 · n H 2 O . This can be rendered anhydrous by evaporation to dryness in the presence of NH 4 Cl , with the mixture then being purified by removal of NH 4 Cl by sublimation at 300-500 °C. [ 4 ] The presence of NH 4 Cl is required, as the hydrated ScCl 3 · n H 2 O would otherwise form a mixed oxychloride upon drying.
Likewise, it is converted into hydrated scandium(III) triflate (Sc(OTf) 3 · n H 2 O) by a reaction with triflic acid . [ 5 ]
Metallic scandium is produced industrially by the reduction of scandium oxide; this proceeds via conversion to scandium fluoride followed by a reduction with metallic calcium . This process is in some ways similar to the Kroll process for the production of metallic titanium .
Scandium oxide forms scandate salts with alkalis, unlike its higher homologues yttrium oxide and lanthanum oxide (but like lutetium oxide ), for example forming K 3 Sc(OH) 6 with KOH. In this, scandium oxide shows more similarity with aluminium oxide .
Natural scandia, although impure, occurs as mineral kangite . [ 6 ] | https://en.wikipedia.org/wiki/O3Sc2 |
Selenium trioxide is the inorganic compound with the formula Se O 3 . It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid . It is of academic interest as a precursor to Se(VI) compounds. [ 4 ]
Selenium trioxide is difficult to prepare because it is unstable with respect to the dioxide :
It has been generated in a number of ways despite the fact that the dioxide does not combust under normal conditions. [ 4 ] One method entails dehydration of anhydrous selenic acid with phosphorus pentoxide at 150–160 °C. Another method is the reaction of liquid sulfur trioxide with potassium selenate .
In its chemistry SeO 3 generally resembles sulfur trioxide , SO 3 , rather than tellurium trioxide , TeO 3 . [ 4 ] The substance reacts explosively with oxidizable organic compounds . [ 5 ]
At 120 °C SeO 3 reacts with selenium dioxide to form the Se(VI)-Se(IV) compound diselenium pentaoxide: [ 6 ]
It reacts with selenium tetrafluoride to form selenoyl fluoride , the selenium analogue of sulfuryl fluoride
As with SO 3 adducts are formed with Lewis bases such as pyridine , dioxane and ether . [ 4 ]
With lithium oxide and sodium oxide it reacts to form salts of Se VI O 5 4− and Se VI O 6 6− : [ 7 ] With Li 2 O, it gives Li 4 SeO 5 , containing the trigonal pyramidal anion Se VI O 5 4− with equatorial bonds, 170.6–171.9 pm; and longer axial Se−O bonds of 179.5 pm. With Na 2 O it gives Na 4 SeO 5 , containing the square pyramidal Se VI O 5 4− , with Se−O bond lengths ranging from range 172.9 → 181.5 pm, and Na 12 (SeO 4 ) 3 (SeO 6 ), containing octahedral Se VI O 6 6− . Se VI O 6 6− is the conjugate base of the unknown orthoselenic acid (Se(OH) 6 ).
In the solid phase SeO 3 consists of cyclic tetramers, with an 8 membered (Se−O) 4 ring. Selenium atoms are 4-coordinate, bond lengths being Se−O bridging are 175 pm and 181 pm, non-bridging 156 and 154 pm. [ 7 ]
SeO 3 in the gas phase consists of tetramers and monomeric SeO 3 which is trigonal planar with an Se−O bond length of 168.78 pm. [ 8 ] | https://en.wikipedia.org/wiki/O3Se |
Tausonite
Strontium titanate is an oxide of strontium and titanium with the chemical formula Sr Ti O 3 . At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure. At low temperatures it approaches a ferroelectric phase transition with a very large dielectric constant ~10 4 but remains paraelectric down to the lowest temperatures measured as a result of quantum fluctuations , making it a quantum paraelectric. [ 1 ] It was long thought to be a wholly artificial material, until 1982 when its natural counterpart—discovered in Siberia and named tausonite —was recognised by the IMA . Tausonite remains an extremely rare mineral in nature, occurring as very tiny crystals . Its most important application has been in its synthesized form wherein it is occasionally encountered as a diamond simulant , in precision optics , in varistors , and in advanced ceramics .
The name tausonite was given in honour of Lev Vladimirovich Tauson (1917–1989), a Russian geochemist . Disused trade names for the synthetic product include strontium mesotitanate , Diagem , and Marvelite . This product is currently being marketed for its use in jewelry under the name Fabulite . [ 2 ] Other than its type locality of the Murun Massif in the Sakha Republic , natural tausonite is also found in Cerro Sarambi , Concepción department , Paraguay ; and along the Kotaki River of Honshū , Japan . [ 3 ] [ 4 ]
SrTiO 3 has an indirect band gap of 3.25 eV and a direct gap of 3.75 eV [ 5 ] in the typical range of semiconductors .
Synthetic strontium titanate has a very large dielectric constant (300) at room temperature and low electric field. It has a specific resistivity of over 10 9 Ω-cm for very pure crystals. [ 6 ] It is also used in high-voltage capacitors.
Introducing mobile charge carriers by doping leads to Fermi-liquid metallic behavior already at very low charge carrier densities. [ 7 ] At high electron densities strontium titanate becomes superconducting below 0.35 K and was the first insulator and oxide discovered to be superconductive. [ 8 ]
Strontium titanate is both much denser ( specific gravity 4.88 for natural, 5.13 for synthetic) and much softer ( Mohs hardness 5.5 for synthetic, 6–6.5 for natural) than diamond . Its crystal system is cubic and its refractive index (2.410—as measured by sodium light, 589.3 nm) is nearly identical to that of diamond (at 2.417), but the dispersion (the optical property responsible for the "fire" of the cut gemstones) of strontium titanate is 4.3× that of diamond, at 0.190 (B–G interval). This results in a shocking display of fire compared to diamond and diamond simulants such as YAG , GAG , GGG , Cubic Zirconia , and Moissanite . [ 3 ] [ 4 ]
Synthetics are usually transparent and colourless, but can be doped with certain rare earth or transition metals to give reds, yellows, browns, and blues. Natural tausonite is usually translucent to opaque, in shades of reddish brown, dark red, or grey. Both have an adamantine (diamond-like) lustre . Strontium titanate is considered extremely brittle with a conchoidal fracture ; natural material is cubic or octahedral in habit and streaks brown. Through a hand-held (direct vision) spectroscope , doped synthetics will exhibit a rich absorption spectrum typical of doped stones. Synthetic material has a melting point of ca. 2080 °C (3776 °F) and is readily attacked by hydrofluoric acid . [ 3 ] [ 4 ] Under extremely low oxygen partial pressure, strontium titanate decomposes via incongruent sublimation of strontium well below the melting temperature. [ 9 ]
At temperatures lower than 105 K, its cubic structure transforms to tetragonal . [ 10 ] Its monocrystals can be used as optical windows and high-quality sputter deposition targets.
SrTiO 3 is an excellent substrate for epitaxial growth of high-temperature superconductors and many oxide-based thin films . It is particularly well known as the substrate for the growth of the lanthanum aluminate-strontium titanate interface . Doping strontium titanate with niobium makes it electrically conductive, being one of the only conductive commercially available single crystal substrates for the growth of perovskite oxides. Its bulk lattice parameter of 3.905Å makes it suitable as the substrate for the growth of many other oxides, including the rare-earth manganites, titanates, lanthanum aluminate (LaAlO 3 ), strontium ruthenate (SrRuO 3 ) and many others. Oxygen vacancies are fairly common in SrTiO 3 crystals and thin films. Oxygen vacancies induce free electrons in the conduction band of the material, making it more conductive and opaque. These vacancies can be caused by exposure to reducing conditions, such as high vacuum at elevated temperatures.
High-quality, epitaxial SrTiO 3 layers can also be grown on silicon without forming silicon dioxide , thereby making SrTiO 3 an alternative gate dielectric material. This also enables the integration of other thin film perovskite oxides onto silicon. [ 11 ]
SrTiO 3 can change its properties when it is exposed to light. [ 12 ] [ 13 ] These changes depend on the temperature and the defects in the material. [ 13 ] [ 12 ] SrTiO 3 has been shown to possess persistent photoconductivity where exposing the crystal to light will increase its electrical conductivity by over 2 orders of magnitude. After the light is turned off, the enhanced conductivity persists for several days, with negligible decay. [ 14 ] [ 15 ] At low temperatures, the main effects of light are electronic, meaning that they involve the creation, movement, and recombination of electrons and holes (positive charges) in the material. [ 13 ] [ 12 ] These effects include photoconductivity, photoluminescence, photovoltage, and photochromism. They are influenced by the defect chemistry of SrTiO 3 , which determines the energy levels, band gap, carrier concentration, and mobility of the material. At high temperatures (>200 °C), the main effects of light are photoionic, meaning that they involve the migration of oxygen vacancies (negative ions) in the material. These vacancies are the main ionic defects in SrTiO 3 , and they can alter the electronic structure, defect chemistry, and surface properties of the material. These effects include photoinduced phase transitions, photoinduced oxygen exchange, and photoinduced surface reconstruction. They are influenced by the oxygen pressure, the crystal structure, and the doping level of SrTiO 3 . [ 13 ] [ 12 ]
Due to the significant ionic and electronic conduction of SrTiO 3 , it is potent to be used as the mixed conductor . [ 16 ]
Synthetic strontium titanate was one of several titanates patented during the late 1940s and early 1950s; other titanates included barium titanate and calcium titanate . Research was conducted primarily at the National Lead Company (later renamed NL Industries ) in the United States , by Leon Merker and Langtry E. Lynd . Merker and Lynd first patented the growth process on February 10, 1953; a number of refinements were subsequently patented over the next four years, such as modifications to the feed powder and additions of colouring dopants.
A modification to the basic Verneuil process (also known as flame-fusion) is the favoured method of growth. An inverted oxy-hydrogen blowpipe is used, with feed powder mixed with oxygen carefully fed through the blowpipe in the typical fashion, but with the addition of a third pipe to deliver oxygen—creating a tricone burner. The extra oxygen is required for successful formation of strontium titanate, which would otherwise fail to oxidize completely due to the titanium component. The ratio is ca. 1.5 volumes of hydrogen for each volume of oxygen. The highly purified feed powder is derived by first producing titanyl double oxalate salt (SrTiO( C 2 O 4 ) 2 · 2 H 2 O ) by reacting strontium chloride (Sr Cl 2 ) and oxalic acid ((COO H ) 2 · 2 H 2 O ) with titanium tetrachloride (TiCl 4 ). The salt is washed to eliminate chloride , heated to 1000 °C in order to produce a free-flowing granular
powder of the required composition, and is then ground and sieved to ensure all particles are between 0.2 and 0.5 micrometres in size. [ 17 ]
The feed powder falls through the oxyhydrogen flame , melts, and lands on a rotating and slowly descending pedestal below. The height of the pedestal is constantly adjusted to keep its top at the optimal position below the flame, and over a number of hours the molten powder cools and crystallises to form a single pedunculated pear or boule crystal. This boule is usually no larger than 2.5 centimetres in diameter and 10 centimetres long; it is an opaque black to begin with, requiring further annealing in an oxidizing atmosphere in order to make the crystal colourless and to relieve strain . This is done at over 1000 °C for 12 hours. [ 17 ]
Thin films of SrTiO 3 can be grown epitaxially by various methods, including pulsed laser deposition , molecular beam epitaxy , RF sputtering and atomic layer deposition . As in most thin films, different growth methods can result in significantly different defect and impurity densities and crystalline quality, resulting in a large variation of the electronic and optical properties.
Its cubic structure and high dispersion once made synthetic strontium titanate a prime candidate for simulating diamond . Beginning c. 1955 , large quantities of strontium titanate were manufactured for this sole purpose. Strontium titanate was in competition with synthetic rutile ("titania") at the time, and had the advantage of lacking the unfortunate yellow tinge and strong birefringence inherent to the latter material. While it was softer, it was significantly closer to diamond in likeness. Eventually, however, both would fall into disuse, being eclipsed by the creation of "better" simulants: first by yttrium aluminium garnet (YAG) and followed shortly after by gadolinium gallium garnet (GGG); and finally by the (to date) ultimate simulant in terms of diamond-likeness and cost-effectiveness, cubic zirconia . [ 18 ]
Despite being outmoded, strontium titanate is still manufactured and periodically encountered in jewellery. It is one of the most costly of diamond simulants, and due to its rarity collectors may pay a premium for large i.e. >2 carat (400 mg) specimens. As a diamond simulant, strontium titanate is most deceptive when mingled with melée i.e. <0.20 carat (40 mg) stones and when it is used as the base material for a composite or doublet stone (with, e.g., synthetic corundum as the crown or top of the stone). Under the microscope , gemmologists distinguish strontium titanate from diamond by the former's softness—manifested by surface abrasions—and excess dispersion (to the trained eye), and occasional gas bubbles which are remnants of synthesis. Doublets can be detected by a join line at the girdle ("waist" of the stone) and flattened air bubbles or glue visible within the stone at the point of bonding. [ 19 ] [ 20 ] [ 21 ]
Due to its high melting point and insolubility in water, strontium titanate has been used as a strontium-90 -containing material in radioisotope thermoelectric generators (RTGs), such as the US Sentinel and Soviet Beta-M series. [ 22 ] [ 23 ] As strontium-90 has a high fission product yield and is easily extracted from spent nuclear fuel , Sr-90 based RTGs can in principle be produced cheaper than those based on plutonium-238 or other radionuclides which have to be produced in dedicated facilities. However, due to the lower power density (~0.45W thermal per gram of Strontium-90-Titanate) and half life, space based applications, which put a particular premium on low weight, high reliability and longevity prefer Plutonium-238 . Terrestrial off-grid applications of RTGs meanwhile have been largely phased out due to concern over orphan sources and the decreasing price and increasing availability of solar panels, small wind turbines, chemical battery storage and other off-grid power solutions.
Strontium titanate's mixed conductivity has attracted attention for use in solid oxide fuel cells (SOFCs). It demonstrates both electronic and ionic conductivity which is useful for SOFC electrodes because there is an exchange of gas and oxygen ions in the material and electrons on both sides of the cell.
Strontium titanate is doped with different materials for use on different sides of a fuel cell. On the fuel side (anode), where the first reaction occurs, it is often doped with lanthanum to form lanthanum-doped strontium titanate (LST). In this case, the A-site, or position in the unit cell where strontium usually sits, is sometimes filled by lanthanum instead, this causes the material to exhibit n-type semiconductor properties, including electronic conductivity. It also shows oxygen ion conduction due to the perovskite structure tolerance for oxygen vacancies. This material has a thermal coefficient of expansion similar to that of the common electrolyte yttria-stabilized zirconia (YSZ), chemical stability during the reactions which occur at fuel cell electrodes, and electronic conductivity of up to 360 S/cm under SOFC operating conditions. [ 24 ] Another key advantage of these LST is that it shows a resistance to sulfur poisoning, which is an issue with the currently used nickel - ceramic ( cermet ) anodes. [ 25 ]
Another related compound is strontium titanium ferrite (STF) which is used as a cathode (oxygen-side) material in SOFCs. This material also shows mixed ionic and electronic conductivity which is important as it means the reduction reaction which happens at the cathode can occur over a wider area. [ 26 ] Building on this material by adding cobalt on the B-site (replacing titanium) as well as iron, we have the material STFC, or cobalt-substituted STF, which shows remarkable stability as a cathode material as well as lower polarization resistance than other common cathode materials such as lanthanum strontium cobalt ferrite . These cathodes also have the advantage of not containing rare earth metals which make them cheaper than many of the alternatives. [ 27 ] | https://en.wikipedia.org/wiki/O3SrTi |
Thallium(III) oxide , also known as thallic oxide , is a chemical compound of thallium and oxygen . It occurs in nature as the rare mineral avicennite . [ 4 ] Its structure is related to that of Mn 2 O 3 which has a bixbyite like structure. Tl 2 O 3 is metallic with high conductivity and is a degenerate n-type semiconductor which may have potential use in solar cells . [ 5 ] A method of producing Tl 2 O 3 by MOCVD is known. [ 6 ] Any practical use of thallium(III) oxide will always have to take account of thallium's poisonous nature. Contact with moisture and acids may form poisonous thallium compounds.
It is produced by the reaction of thallium with oxygen or hydrogen peroxide in an alkaline thallium(I) solution. Alternatively, it can be created by the oxidation of thallium(I) nitrate by chlorine in an aqueous potassium hydroxide solution. [ 7 ] | https://en.wikipedia.org/wiki/O3Tl2 |
Vanadium(III) oxide is the inorganic compound with the formula V 2 O 3 . It is a black solid prepared by reduction of V 2 O 5 with hydrogen or carbon monoxide . [ 3 ] [ 4 ] It is a basic oxide dissolving in acids to give solutions of vanadium (III) complexes. [ 4 ] V 2 O 3 has the corundum structure. [ 4 ] It is antiferromagnetic with a critical temperature of 160 K, below which there is an abrupt change in conductivity from metallic to insulating. [ 5 ] This also distorts the crystal structure to a monoclinic space group: C2/c. [ 1 ]
Upon exposure to air it gradually converts into indigo-blue V 2 O 4 . [ 5 ]
In nature it occurs as the rare mineral karelianite . [ 6 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/O3V2 |
Yttrium oxide , also known as yttria , is Y 2 O 3 . It is an air-stable, white solid substance .
The thermal conductivity of yttrium oxide is 27 W/(m·K). [ 5 ]
Yttrium oxide is widely used to make Eu:YVO 4 and Eu:Y 2 O 3 phosphors that give the red color in color TV picture tubes.
Y 2 O 3 is a prospective solid-state laser material. In particular, lasers with ytterbium as dopant allow the efficient operation both in continuous operation [ 6 ] and in pulsed regimes. [ 7 ] At high concentration of excitations (of order of 1%) and poor cooling, the quenching of emission at laser frequency and avalanche broadband emission takes place. [ 8 ] (Yttria-based lasers are not to be confused with YAG lasers using yttrium aluminium garnet , a widely used crystal host for rare earth laser dopants).
The original use of the mineral yttria and the purpose of its extraction from mineral sources was as part of the process of making gas mantles and other products for turning the flames of artificially-produced gases (initially hydrogen, later coal gas, paraffin, or other products) into human-visible light. This use is almost obsolete - thorium and cerium oxides are larger components of such products these days.
Yttrium oxide is used to stabilize the Zirconia in late-generation porcelain-free metal-free dental ceramics. This is a very hard ceramic used as a strong base material in some full ceramic restorations. [ 9 ] The zirconia used in dentistry is zirconium oxide which has been stabilized with the addition of yttrium oxide . The full name of zirconia used in dentistry is "yttria-stabilized zirconia" or YSZ.
Yttrium oxide is also used to make yttrium iron garnets , which are very effective microwave filters. [ 10 ]
Y 2 O 3 is used to make the high temperature superconductor YBa 2 Cu 3 O 7 , known as "1-2-3" to indicate the ratio of the metal constituents:
This synthesis is typically conducted at 800 °C.
Yttrium oxide is an important starting point for inorganic compounds. For organometallic chemistry it is converted to YCl 3 in a reaction with concentrated hydrochloric acid and ammonium chloride .
Y 2 O 3 is used in specialty coatings and pastes that can withstand high temperatures and act as a barrier for reactive metals such as uranium. [ 11 ]
NASA developed a material it dubbed Solar White that it is exploring for use as a radiator in deep space, where it is expected to reflect more than 99.9% of the sun’s energy (low solar radiation absorption and high infrared emittance). [ 12 ] A sphere covered with a 10 mm coating sited far from the Earth and 1 astronomical unit from the sun could keep temperatures below 50 K. One use is long-term cryogenic storage. [ 13 ]
It's also used to create red phosphors for LED screens and TV tubes, as well as in anti-reflective coatings to enhance light transmission. [ 14 ]
Yttriaite-(Y) , approved as a new mineral species in 2010, is the natural form of yttria. It is exceedingly rare, occurring as inclusions in native tungsten particles in a placer deposit of the Bol’shaja Pol’ja ( Russian : Большая Полья ) river, Prepolar Ural , Siberia . As a chemical component of other minerals, the oxide yttria was first isolated in 1789 by Johan Gadolin , from rare-earth minerals in a mine at the Swedish town of Ytterby , near Stockholm . [ 15 ] | https://en.wikipedia.org/wiki/O3Y2 |
Ytterbium(III) oxide is the chemical compound with the formula Yb 2 O 3 . It is one of the more commonly encountered compounds of ytterbium . It occurs naturally in trace amounts in the mineral gadolinite . It was first isolated from this in 1878 by Jean Charles Galissard de Marignac . [ 3 ]
Ytterbium(III) oxide can be obtained by directly reacting ytterbium with oxygen : [ 4 ]
It can also be obtained by the thermal decomposition of ytterbium carbonate or ytterbium oxalate at temperatures around 700 °C: [ 5 ]
Ytterbium(III) oxide is a white powder. [ 2 ] It reacts with carbon tetrachloride [ 6 ] or hot hydrochloric acid to form ytterbium(III) chloride : [ 7 ]
Like the other trivalent oxides of the heavier lanthanides, ytterbium(III) oxide has the "rare-earth C-type sesquioxide" structure which is related to the fluorite structure with one quarter of the anions removed, leading to ytterbium atoms in two different six coordinate (non-octahedral) environments. [ 8 ] | https://en.wikipedia.org/wiki/O3Yb2 |
Tetraoxygen difluoride is an inorganic chemical compound of oxygen, belonging to the family of oxygen fluorides . It consists of two O 2 F units bound together with a weak O-O bond, and is the dimer of the O 2 F radical. [ 1 ]
Tetraoxygen difluoride can be prepared in two steps. In the first step, a photochemically generated fluorine atom reacts with oxygen to form the dioxygen fluoride radical. [ 1 ]
This radical subsequently undergoes dimerization, entering an equilibrium with tetraoxygen difluoride at temperatures under −175 °C: [ 1 ]
At the same time, the dioxygen fluoride radicals decompose into dioxygen difluoride and oxygen gas, which shifts the above equilibrium with O 4 F 2 to the left. [ 2 ]
Tetraoxygen difluoride is dark red-brown as a solid and has a melting point around −191 °C. [ 1 ]
It is a strong fluorinating and oxidizing agent, even stronger than dioxygen difluoride , so that it can, for example, oxidize Ag(II) to Ag(III) or Au(III) to Au(V). This process creates the corresponding anions AgF - 4 and AuF - 6 . With non-noble substances this oxidation can lead to explosions even at low temperatures. As an example, elemental sulfur reacts explosively to form sulfur hexafluoride even at −180 °C. [ 1 ]
Similar to [O 2 F] • or O 2 F 2 , tetraoxygen difluoride tends to form salts with the dioxygenyl cation O + 2 when it reacts with fluoride acceptors such as boron trifluoride (BF 3 ). In the case of BF 3 , this leads to the formation of O 2 + •BF 4 − : [ 1 ]
Similarly, for arsenic pentafluoride it reacts to create O 2 + AsF 6 − . [ 1 ] | https://en.wikipedia.org/wiki/O4F2 |
soluble in ammonium acetate (≥ 6 mol/L)
soluble in ammonium tartrate in presence of ammonium chloride and ammonia
Lead(II) sulfate (PbSO 4 ) is a white solid, which appears white in microcrystalline form. It is also known as fast white , milk white , sulfuric acid lead salt or anglesite .
It is often seen in the plates/electrodes of car batteries , as it is formed when the battery is discharged (when the battery is recharged, then the lead sulfate is transformed back to metallic lead and sulfuric acid on the negative terminal or lead dioxide and sulfuric acid on the positive terminal). Lead sulfate is poorly soluble in water.
Anglesite (lead(II) sulfate, PbSO 4 ) adopts the same orthorhombic crystal structure as celestite ( strontium sulfate , SrSO 4 ) and barite ( barium sulfate , BaSO 4 ). All three minerals' structures are in the space group Pbnm (number 62) . [ 6 ] Each lead(II) ion is surrounded by 12 oxygen atoms from 7 sulfate ions, forming a PbO 12 polyhedron. [ 7 ] The lead–oxygen distances range from 2.612 Å to 3.267 Å and the average distance is 2.865 Å. [ 6 ]
Lead(II) sulfate is prepared by treating lead oxide, hydroxide or carbonate with warm sulfuric acid or by treating a soluble lead salt with sulfuric acid.
Alternatively, it can be made by the interaction of solutions of lead nitrate and sodium sulfate.
Lead sulfate is toxic by inhalation, ingestion and skin contact. It is a cumulative poison , and repeated exposure may lead to anemia, kidney damage, eyesight damage or damage to the central nervous system (especially in children). It is also corrosive - contact with the eyes can lead to severe irritation or burns. Typical threshold limit value is 0.15 mg/m 3 .
The naturally occurring mineral anglesite , PbSO 4 , occurs as an oxidation product of primary lead sulfide ore,
A number of lead basic sulfates are known: PbSO 4 ·PbO; PbSO 4 ·2PbO; PbSO 4 ·3PbO; PbSO 4 ·4PbO. They are used in manufacturing of active paste for lead–acid batteries. A related mineral is leadhillite , 2PbCO 3 ·PbSO 4 ·Pb(OH) 2 .
At high concentration of sulfuric acid (>80%), lead hydrogensulfate, Pb(HSO 4 ) 2 , forms. [ 8 ]
Lead(II) sulfate can be dissolved in concentrated HNO 3 , HCl, H 2 SO 4 producing acidic salts or complex compounds, and in concentrated alkali giving soluble tetrahydroxidoplumbate(II) [Pb(OH) 4 ] 2− complexes.
Lead(II) sulfate decomposes when heated above 1000 °C: | https://en.wikipedia.org/wiki/O4PbS |
Ruthenium tetroxide is the inorganic compound with the formula RuO 4 . It is a yellow volatile solid that melts near room temperature. [ 3 ] It has the odor of ozone. [ 4 ] Samples are typically black due to impurities. The analogous OsO 4 is more widely used and better known. It is also the anhydride of hyperruthenic acid (H 2 RuO 5 ). One of the few solvents in which RuO 4 forms stable solutions is CCl 4 . [ 5 ]
RuO 4 is prepared by oxidation of ruthenium(III) chloride with NaIO 4 . [ 3 ] The reaction initially produces sodium diperiododihydroxoruthenate(VI), which then decomposes in acid solution to the tetroxide: [ 6 ]
Due to its challenging reactivity, RuO 4 is always generated in situ and used in catalytic quantities, at least in organic reactions. [ 5 ]
RuO 4 forms two crystal structures, one with cubic symmetry and another with monoclinic symmetry, isotypic to OsO 4 . The molecule adopts a tetrahedral geometry, with the Ru–O distances ranging from 169 to 170 pm. [ 8 ]
The main commercial value of RuO 4 is as an intermediate in the production of ruthenium compounds and metal from ores. Like other platinum group metals (PGMs), ruthenium occurs at low concentrations and often mixed with other PGMs. Together with OsO 4 , it is separated from other PGMs by distillation of a chlorine-oxidized extract. Ruthenium is separated from OsO 4 by reducing RuO 4 with hydrochloric acid , a process that exploits the highly positive reduction potential for the [RuO 4 ] 0/- couple. [ 9 ] [ 10 ]
RuO 4 is of specialized value in organic chemistry because it oxidizes virtually any hydrocarbon. [ 11 ] For example, it will oxidize adamantane to 1-adamantanol. Because it is such an aggressive oxidant, reaction conditions must be mild, generally room temperature. Although a strong oxidant, RuO 4 oxidations do not perturb stereocenters that are not oxidized. Illustrative is the oxidation of the following diol to a carboxylic acid :
Oxidation of epoxy alcohols also occurs without degradation of the epoxide ring:
Under milder conditions, oxidative reaction yields aldehydes instead. RuO 4 readily converts secondary alcohols into ketones . Although similar results can be achieved with other cheaper oxidants such as PCC - or DMSO -based oxidants, RuO 4 is ideal when a very vigorous oxidant is needed, but mild conditions must be maintained. It is used in organic synthesis to oxidize internal alkynes to 1,2- diketones , and terminal alkynes along with primary alcohols to carboxylic acids . When used in this fashion, the ruthenium(VIII) oxide is used in catalytic amounts and regenerated by the addition of sodium periodate to ruthenium(III) chloride and a solvent mixture of acetonitrile , water and carbon tetrachloride . RuO 4 readily cleaves double bonds to yield carbonyl products, in a manner similar to ozonolysis . OsO 4 , a more familiar oxidant that is structurally similar to RuO 4 , does not cleave double bonds, instead producing vicinal diol products. However, with short reaction times and carefully controlled conditions, RuO 4 can also be used for dihydroxylation. [ 12 ]
Because RuO 4 degrades the "double bonds" of arenes (especially electron-rich ones) by dihydroxylation and cleavage of the C-C bond in a way few other reagents can, it is useful as a "deprotection" reagent for carboxylic acids that are masked as aryl groups (typically phenyl or p -methoxyphenyl). Because the fragments formed are themselves readily oxidizable by RuO 4 , a substantial fraction of the arene carbon atoms undergo exhaustive oxidation to form carbon dioxide. Consequently, multiple equivalents of the terminal oxidant (often in excess of 10 equivalents per aryl ring) are required to achieve complete conversion to the carboxylic acid, limiting the practicality of the transformation. [ 13 ] [ 14 ] [ 15 ]
Although used as a direct oxidant , due to the relatively high cost of RuO 4 it is also used catalytically with a cooxidant. For an oxidation of cyclic alcohols with RuO 4 as a catalyst and bromate as oxidant under basic conditions, RuO 4 is first activated by hydroxide, turning into the hyperruthenate anion: [ 16 ]
The reaction proceeds via a glycolate complex.
Ruthenium tetroxide is a potential staining agent. It is used to expose latent fingerprints by turning to the brown/black ruthenium dioxide when in contact with fatty oils or fats contained in sebaceous contaminants of the print. [ 17 ]
Because of the very high volatility of ruthenium tetroxide ( RuO 4 ) ruthenium radioactive isotopes with their relative short half-life are considered as the second most hazardous gaseous isotopes after iodine-131 in case of release by a nuclear accident. [ 18 ] [ 4 ] [ 19 ] The two most important radioactive isotopes of ruthenium are 103 Ru and 106 Ru. They have half-lives of 39.6 days and 373.6 days, respectively. [ 4 ] | https://en.wikipedia.org/wiki/O4Ru |
Zinc sulfate is an inorganic compound with the formula ZnSO 4 . It forms hydrates ZnSO 4 · n H 2 O, where n can range from 0 to 7. All are colorless solids. The most common form includes water of crystallization as the heptahydrate, [ 4 ] with the formula Zn SO 4 ·7H 2 O . As early as the 16th century it was prepared on a large scale, and was historically known as "white vitriol " [ 5 ] (the name was used, for example, in 1620s by the collective writing under the pseudonym of Basil Valentine ). [ citation needed ] Zinc sulfate and its hydrates are colourless solids.
The main application of the heptahydrate is as a coagulant in the production of rayon . It is also a precursor to the pigment lithopone . It is also used as an electrolyte for zinc electroplating , as a mordant in dyeing, and as a preservative for skins and leather.
Zinc sulfate is used to supply zinc in animal feeds, fertilizers, toothpaste, and agricultural sprays. Zinc sulfate, [ 6 ] like many zinc compounds, can be used to control moss growth on roofs. [ 7 ]
Zinc sulfate can be used to supplement zinc in the brewing process. Zinc is a necessary nutrient for optimal yeast health and performance, although it is not a necessary supplement for low-gravity beers, as the grains commonly used in brewing already provide adequate zinc. It is a more common practice when pushing yeast to their limit by increasing alcohol content beyond their comfort zone. Before modern stainless steel, brew Kettles, fermenting vessels and after wood, zinc was slowly leached by the use of copper kettles. A modern copper immersion chiller is speculated to provide trace amounts of zinc; thus care must be taken when adding supplemental zinc so as not to cause excess. Side effects include "...increased acetaldehyde and fusel alcohol production due to high yeast growth when zinc concentrations exceed 5 ppm. Excess zinc can also cause soapy or goaty flavors." [ 8 ] [ 9 ] [ 10 ]
Zinc sulfate is a potent inhibitor of sweetness perception for most sweet-tasting substances. [ 11 ]
It is used as a dietary supplement to treat zinc deficiency and to prevent the condition in those at high risk. [ 12 ] Side effects of excess supplementation may include abdominal pain , vomiting , headache , and tiredness . [ 13 ] it is also used together with oral rehydration therapy (ORT) and an astringent . [ 4 ]
Zinc sulfate is produced by treating virtually any zinc-containing material (metal, minerals, oxides) with sulfuric acid. [ 4 ]
Specific reactions include the reaction of the metal with aqueous sulfuric acid :
Pharmaceutical-grade zinc sulfate is produced by treating high-purity zinc oxide with sulfuric acid:
In aqueous solution, all forms of zinc sulfate behave identically. These aqueous solutions consist of the metal aquo complex [Zn(H 2 O) 6 ] 2+ and SO 2− 4 ions. Barium sulfate forms when these solutions are treated with solutions of barium ions:
With a reduction potential of −0.76 V, zinc(II) reduces only with difficulty.
When heated above 680 °C, zinc sulfate decomposes into sulfur dioxide gas and zinc oxide fume, both of which are hazardous. [ 14 ]
The heptahydrate is isostructural with ferrous sulfate heptahydrate. The solid consists of [Zn(H 2 O) 6 ] 2+ ions interacting with sulfate and one water of crystallization by hydrogen bonds. Anhydrous zinc sulfate is isomorphous with anhydrous copper(II) sulfate . It exists as the mineral zincosite . [ 15 ] A monohydrate is known. [ 16 ] The hexahydrate is also recognized. [ 17 ]
As a mineral, ZnSO 4 ·7H 2 O is known as goslarite . Zinc sulfate occurs as several other minor minerals, such as zincmelanterite , (Zn,Cu,Fe)SO 4 ·7H 2 O (structurally different from goslarite). Lower hydrates of zinc sulfate are rarely found in nature: (Zn,Fe)SO 4 ·6H 2 O (bianchite), (Zn,Mg)SO 4 ·4H 2 O (boyleite), and (Zn,Mn)SO 4 ·H 2 O ( gunningite ).
Zinc sulfate powder is an eye irritant. Ingestion of trace amounts is considered safe, and zinc sulfate is added to animal feed as a source of essential zinc, at rates of up to several hundred milligrams per kilogram of feed. Excess ingestion results in acute stomach distress, with nausea and vomiting appearing at 2–8 mg/kg of body weight. [ 18 ] Nasal irrigation with a solution of zinc sulfate has been found to be able to damage the olfactory sense nerves and induce anosmia in a number of different species, including humans. [ 19 ] | https://en.wikipedia.org/wiki/O4SZn |
Xenon tetroxide is a chemical compound of xenon and oxygen with molecular formula XeO 4 , remarkable for being a relatively stable compound of a noble gas . It is a yellow crystalline solid that is stable below −35.9 ° C ; above that temperature it is very prone to exploding and decomposing into elemental xenon and oxygen (O 2 ). [ 4 ] [ 5 ]
All eight valence electrons of xenon are involved in the bonds with the oxygen, and the oxidation state of the xenon atom is +8. Oxygen is the only element that can bring xenon up to its highest oxidation state; even fluorine can only give XeF 6 (+6).
Two other short-lived xenon compounds with an oxidation state of +8, XeO 3 F 2 and XeO 2 F 4 , are accessible by the reaction of xenon tetroxide with xenon hexafluoride . XeO 3 F 2 and XeO 2 F 4 can be detected with mass spectrometry . The perxenates are also compounds where xenon has the +8 oxidation state.
At temperatures above −35.9 °C, xenon tetroxide is very prone to explosion, decomposing into xenon and oxygen gases with Δ H = −643 kJ/mol:
Xenon tetroxide dissolves in water to form perxenic acid and in alkalis to form perxenate salts:
Xenon tetroxide can also react with xenon hexafluoride to give xenon oxyfluorides:
All syntheses start from the perxenates , which are accessible from the xenates through two methods. One is the disproportionation of xenates to perxenates and xenon:
The other is oxidation of the xenates with ozone in basic solution:
Barium perxenate is reacted with sulfuric acid and the unstable perxenic acid is dehydrated to give xenon tetroxide: [ 6 ]
Any excess perxenic acid slowly undergoes a decomposition reaction to xenic acid and oxygen: | https://en.wikipedia.org/wiki/O4Xe |
Phosphorus pentoxide is a chemical compound with molecular formula P 4 O 10 (with its common name derived from its empirical formula , P 2 O 5 ). This white crystalline solid is the anhydride of phosphoric acid . It is a powerful desiccant and dehydrating agent .
Phosphorus pentoxide crystallizes in at least four forms or polymorphs . The most familiar one, a metastable form [ 1 ] (shown in the figure), comprises molecules of P 4 O 10 . Weak van der Waals forces hold these molecules together in a hexagonal lattice (However, in spite of the high symmetry of the molecules, the crystal packing is not a close packing [ 2 ] ). The structure of the P 4 O 10 cage is reminiscent of adamantane with T d symmetry point group . [ 3 ] It is closely related to the corresponding anhydride of phosphorous acid , P 4 O 6 . The latter lacks terminal oxo groups. Its density is 2.30 g/cm 3 . It boils at 423 °C under atmospheric pressure; if heated more rapidly it can sublimate. This form can be made by condensing the vapor of phosphorus pentoxide rapidly, and the result is an extremely hygroscopic solid. [ 4 ]
The other polymorphs are polymeric, but in each case the phosphorus atoms are bound by a tetrahedron of oxygen atoms, one of which forms a terminal P=O bond involving the donation of the terminal oxygen p-orbital electrons to the antibonding phosphorus-oxygen single bonds. The macromolecular form can be made by heating the compound in a sealed tube for several hours, and maintaining the melt at a high temperature before cooling the melt to the solid. [ 4 ] The metastable orthorhombic "O"-form (density 2.72 g/cm 3 , melting point 562 °C) adopts a layered structure consisting of interconnected P 6 O 6 rings, not unlike the structure adopted by certain poly silicates . The stable form is a higher density phase, also orthorhombic, the so-called O' form. It consists of a 3-dimensional framework, density 3.5 g/cm 3 . [ 1 ] [ 5 ] The remaining polymorph is a glass or amorphous form; it can be made by fusing any of the others.
P 4 O 10 is prepared by burning white phosphorus with a sufficient supply of oxygen: [ 6 ]
The dehydration of phosphoric acid to give phosphorus pentoxide is not possible, as on heating it forms various polyphosphates but will not dehydrate sufficiently to form P 4 O 10 .
Phosphorus pentoxide is a potent dehydrating agent as indicated by the exothermic nature of its hydrolysis producing phosphoric acid :
However, its utility for drying is limited somewhat by its tendency to form a protective viscous coating that inhibits further dehydration by unspent material. A granular form of P 4 O 10 is used in desiccators .
Consistent with its strong desiccating power, P 4 O 10 is used in organic synthesis for dehydration. The most important application is for the conversion of primary amides into nitriles : [ 7 ]
The indicated coproduct P 4 O 9 (OH) 2 is an idealized formula for undefined products resulting from the hydration of P 4 O 10 .
Alternatively, when combined with a carboxylic acid , the result is the corresponding anhydride : [ 8 ]
The "Onodera reagent", a solution of P 4 O 10 in DMSO , is employed for the oxidation of alcohols . [ 9 ] This reaction is reminiscent of the Swern oxidation .
The desiccating power of P 4 O 10 is strong enough to convert many mineral acids to their anhydrides. Examples: HNO 3 is converted to N 2 O 5 ; H 2 SO 4 is converted to SO 3 ; HClO 4 is converted to Cl 2 O 7 ; CF 3 SO 3 H is converted to (CF 3 ) 2 S 2 O 5 .
P 2 O 5 content is often used by industry as proxy value for all the phosphorus oxides in a material. For example, fertilizer grade phosphoric acid can also contain various related phosphorous compounds which are also of use. All these compounds are described collectively in terms of ' P 2 O 5 content' to allow convenient comparison of the phosphorous content of different products. Despite this, phosphorus pentoxide is not actually present in most samples as it is not stable in aqueous solutions.
Phosphorus pentoxide itself is not flammable. Just like sulfur trioxide , it reacts vigorously with water and water-containing substances like wood or cotton, liberates much heat and may even cause fire due to the highly exothermic nature of such reactions. It is corrosive to metal and is very irritating – it may cause severe burns to the eye, skin, mucous membrane , and respiratory tract even at concentrations as low as 1 mg/m 3 . [ 10 ] | https://en.wikipedia.org/wiki/O5P2 |
Vanadyl(IV) sulfate describes a collection of inorganic compounds of vanadium with the formula, VOSO 4 (H 2 O) x where 0 ≤ x ≤ 6. The pentahydrate is common. This hygroscopic blue solid is one of the most common sources of vanadium in the laboratory, reflecting its high stability. It features the vanadyl ion, VO 2+ , which has been called the "most stable diatomic ion". [ 1 ]
Vanadyl sulfate is an intermediate in the extraction of vanadium from petroleum residues, one commercial source of vanadium. [ 2 ]
Vanadyl sulfate is most commonly obtained by reduction of vanadium pentoxide with sulfur dioxide :
From aqueous solution, the salt crystallizes as the pentahydrate , the fifth water is not bound to the metal in the solid. Viewed as a coordination complex , the ion is octahedral , with oxo, four equatorial water ligands, and a monodentate sulfate. [ 1 ] [ 3 ] The trihydrate has also been examined by crystallography. [ 4 ] A hexahydrate exists below 13.6 °C (286.8 K). [ 5 ] Two polymorphs of anhydrous VOSO 4 are known. [ 6 ]
The V=O bond distance is 160 pm , about 50 pm shorter than the V–OH 2 bonds. In solution, the sulfate ion dissociates rapidly.
Being widely available, vanadyl sulfate is a common precursor to other vanadyl derivatives, such as vanadyl acetylacetonate : [ 7 ]
In acidic solution, oxidation of vanadyl sulfate gives yellow-coloured vanadyl(V) derivatives. Reduction, e.g. by zinc , gives vanadium(III) and vanadium(II) derivatives, which are characteristically green and violet, respectively.
Like most water-soluble sulfates, vanadyl sulfate is only rarely found in nature. Anhydrous form is pauflerite, [ 8 ] a mineral of fumarolic origin. Hydrated forms, also rare, include hexahydrate (stanleyite), pentahydrates (minasragrite, orthominasragrite, [ 9 ] and anorthominasragrite) and trihydrate - bobjonesite. [ 10 ]
Vanadyl sulfate is a component of food supplements and experimental drugs. Vanadyl sulfate exhibits insulin-like effects. [ 11 ]
Vanadyl sulfate has been extensively studied in the field of diabetes research as a potential means of increasing insulin sensitivity. No evidence indicates that oral vanadium supplementation improves glycaemic control. [ 12 ] [ 13 ] Treatment with vanadium often results in gastrointestinal side-effects, primarily diarrhea .
Vanadyl sulfate is also marketed as a health supplement, often for bodybuilding . Deficiencies in vanadium result in reduced growth in rats. [ 14 ] Its effectiveness for bodybuilding has not been proven; some evidence suggests that athletes who take it are merely experiencing a placebo effect . [ 15 ] | https://en.wikipedia.org/wiki/O5SV |
Tantalum pentoxide , also known as tantalum (V) oxide, is the inorganic compound with the formula Ta 2 O 5 . It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid . Ta 2 O 5 is an inert material with a high refractive index and low absorption (i.e. colourless), which makes it useful for coatings. [ 2 ] It is also extensively used in the production of capacitors , due to its high dielectric constant .
Tantalum occurs in the minerals tantalite and columbite (columbium being an archaic name for niobium), which occur in pegmatites , an igneous rock formation. Mixtures of columbite and tantalite are called coltan . Tantalum was discovered in Tantalite in 1802 by Anders Gustaf Ekeberg at Ytterby , Sweden, and Kimoto, Finland. The minerals microlite and pyrochlore contain approximately 70% and 10% Ta, respectively.
Tantalum ores often contain significant amounts of niobium , which is itself a valuable metal. As such, both metals are extracted so that they may be sold. The overall process is one of hydrometallurgy and begins with a leaching step; in which the ore is treated with hydrofluoric acid and sulfuric acid to produce water-soluble hydrogen fluorides , such as the heptafluorotantalate . This allows the metals to be separated from the various non-metallic impurities in the rock.
The tantalum and niobium hydrogenfluorides are then removed from the aqueous solution by liquid-liquid extraction using organic solvents , such as cyclohexanone or methyl isobutyl ketone . This step allows the simple removal of various metal impurities (e.g. iron and manganese) which remain in the aqueous phase in the form of fluorides . Separation of the tantalum and niobium is then achieved by pH adjustment. Niobium requires a higher level of acidity to remain soluble in the organic phase and can hence be selectively removed by extraction into less acidic water.
The pure tantalum hydrogen fluoride solution is then neutralised with aqueous ammonia to give hydrated tantalum oxide (Ta 2 O 5 (H 2 O) x ), which is calcinated to tantalum pentoxide (Ta 2 O 5 ) as described in these idealized equations: [ 3 ]
Natural pure tantalum oxide is known as the mineral tantite , although it is exceedingly rare. [ 4 ]
Tantalum oxide is frequently used in electronics, often in the form of thin films . For these applications it can be produced by MOCVD (or related techniques), which involves the hydrolysis of its volatile halides or alkoxides :
The crystal structure of tantalum pentoxide has been the matter of some debate. The bulk material is disordered , [ 5 ] being either amorphous or polycrystalline ; with single crystals being difficult to grow. As such Xray crystallography has largely been limited to powder diffraction , which provides less structural information.
At least 2 polymorphs are known to exist. A low temperature form, known as L- or β-Ta 2 O 5 , and the high temperature form known as H- or α-Ta 2 O 5 . The transition between these two forms is slow and reversible; taking place between 1000 and 1360 °C, with a mixture of structures existing at intermediate temperatures. [ 5 ] The structures of both polymorphs consist of chains built from octahedral TaO 6 and pentagonal bipyramidal TaO 7 polyhedra sharing opposite vertices; which are further joined by edge-sharing. [ 6 ] [ 7 ] The overall crystal system is orthorhombic in both cases, with the space group of β-Ta 2 O 5 being identified as Pna2 by single crystal X-ray diffraction. [ 8 ] [ 9 ]
A high pressure form ( Z -Ta 2 O 5 ) has also been reported, in which the Ta atoms adopt a 7 coordinate geometry to give a monoclinic structure (space group C2). [ 10 ]
Purely amorphous tantalum pentoxide has a similar local structure to the crystalline polymorphs, built from TaO 6 and TaO 7 polyhedra, while the molten liquid phase has a distinct structure based on lower coordination polyhedra, mainly TaO 5 and TaO 6 . [ 11 ]
The difficulty in forming material with a uniform structure has led to variations in its reported properties. Like many metal oxides Ta 2 O 5 is an insulator and its band gap has variously been reported as being between 3.8 and 5.3 eV, depending on the method of manufacture. [ 12 ] [ 13 ] [ 14 ] In general the more amorphous the material the greater its observed band gap.
These observed values are significantly higher than those predicted by computational chemistry (2.3 - 3.8 eV). [ 15 ] [ 16 ] [ 17 ]
Its dielectric constant is typically about 25 [ 18 ] although values of over 50 have been reported. [ 19 ] In general tantalum pentoxide is considered to be a high-k dielectric material.
Ta 2 O 5 does not react appreciably with either HCl or HBr, however it will dissolve in hydrofluoric acid , and reacts with potassium bifluoride and HF according to the following equation: [ 20 ] [ 21 ]
Ta 2 O 5 can be reduced to metallic Ta via the use of metallic reductants such as calcium and aluminium.
Owing to its high band gap and dielectric constant , tantalum pentoxide has found a variety of uses in electronics, particularly in tantalum capacitors . These are used in automotive electronics , cell phones, and pagers, electronic circuitry; thin-film components; and high-speed tools. In the 1990s, interest grew in the use of tantalum oxide as a high-k dielectric for DRAM capacitor applications. [ 22 ] [ 23 ]
It is used in on-chip metal-insulator-metal capacitors for high frequency CMOS integrated circuits. Tantalum oxide may have applications as the charge trapping layer for non-volatile memories . [ 24 ] [ 25 ] There are applications of tantalum oxide in resistive switching memories . [ 26 ]
Due to its high refractive index , Ta 2 O 5 has been utilized in the fabrication of the glass of photographic lenses . [ 2 ] [ 27 ] It can also be deposited as an optical coating with typical applications being antireflection and multilayer filter coatings in near UV to near infrared . [ 28 ]
Ta 2 O 5 has also been found to have a high nonlinear refractive index , [ 29 ] [ 30 ] on the order of three times that of silicon nitiride , which has led to interest in the utilization of Ta 2 O 5 in photonic integrated circuits . Ta 2 O 5 has been recently utilized as the material platform for the generation of supercontinuum [ 31 ] [ 32 ] and Kerr frequency combs [ 30 ] in waveguides and optical ring resonators . Through the addition of rare-earth dopants in the deposition process, Ta 2 O 5 waveguide lasers have been presented for a variety of applications, such as remote sensing and LiDAR . [ 33 ] [ 34 ] [ 35 ] | https://en.wikipedia.org/wiki/O5Ta2 |
C 0.1 mg V 2 O 5 /m 3 (fume) [ 6 ]
Vanadium(V) oxide ( vanadia ) is the inorganic compound with the formula V 2 O 5 . Commonly known as vanadium pentoxide , it is a dark yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high oxidation state , it is both an amphoteric oxide and an oxidizing agent . From the industrial perspective, it is the most important compound of vanadium , being the principal precursor to alloys of vanadium and is a widely used industrial catalyst . [ 8 ]
The mineral form of this compound, shcherbinaite, is extremely rare, almost always found among fumaroles . A mineral trihydrate , V 2 O 5 ·3H 2 O, is also known under the name of navajoite.
Upon heating a mixture of vanadium(V) oxide and vanadium(III) oxide , comproportionation occurs to give vanadium(IV) oxide , as a deep-blue solid: [ 9 ]
The reduction can also be effected by oxalic acid , carbon monoxide , and sulfur dioxide . Further reduction using hydrogen or excess CO can lead to complex mixtures of oxides such as V 4 O 7 and V 5 O 9 before black V 2 O 3 is reached.
V 2 O 5 is an amphoteric oxide, and unlike most transition metal oxides, it is slightly water soluble , giving a pale yellow, acidic solution. Thus V 2 O 5 reacts with strong non-reducing acids to form solutions containing the pale yellow salts containing dioxovanadium(V) centers:
It also reacts with strong alkali to form polyoxovanadates , which have a complex structure that depends on pH . [ 10 ] If excess aqueous sodium hydroxide is used, the product is a colourless salt , sodium orthovanadate , Na 3 VO 4 . If acid is slowly added to a solution of Na 3 VO 4 , the colour gradually deepens through orange to red before brown hydrated V 2 O 5 precipitates around pH 2. These solutions contain mainly the ions HVO 4 2− and V 2 O 7 4− between pH 9 and pH 13, but below pH 9 more exotic species such as V 4 O 12 4− and HV 10 O 28 5− ( decavanadate ) predominate.
Upon treatment with thionyl chloride , it converts to the volatile liquid vanadium oxychloride , VOCl 3 : [ 11 ]
Hydrochloric acid and hydrobromic acid are oxidised to the corresponding halogen , e.g.,
Vanadates or vanadyl compounds in acid solution are reduced by zinc amalgam through the colourful pathway:
The ions are all hydrated to varying degrees.
Technical grade V 2 O 5 is produced as a black powder used for the production of vanadium metal and ferrovanadium . [ 10 ] A vanadium ore or vanadium-rich residue is treated with sodium carbonate and an ammonium salt to produce sodium metavanadate , NaVO 3 . This material is then acidified to pH 2–3 using H 2 SO 4 to yield a precipitate of "red cake" (see above ). The red cake is then melted at 690 °C to produce the crude V 2 O 5 .
Vanadium(V) oxide is produced when vanadium metal is heated with excess oxygen , but this product is contaminated with other, lower oxides. A more satisfactory laboratory preparation involves the decomposition of ammonium metavanadate at 500–550 °C: [ 13 ]
In terms of quantity, the dominant use for vanadium(V) oxide is in the production of ferrovanadium (see above ). The oxide is heated with scrap iron and ferrosilicon , with lime added to form a calcium silicate slag . Aluminium may also be used, producing the iron-vanadium alloy along with alumina as a byproduct.
Another important use of vanadium(V) oxide is in the manufacture of sulfuric acid , an important industrial chemical with an annual worldwide production of 165 million tonnes in 2001, with an approximate value of US$8 billion. Vanadium(V) oxide serves the crucial purpose of catalysing the mildly exothermic oxidation of sulfur dioxide to sulfur trioxide by air in the contact process :
The discovery of this simple reaction, for which V 2 O 5 is the most effective catalyst, allowed sulfuric acid to become the cheap commodity chemical it is today. The reaction is performed between 400 and 620 °C; below 400 °C the V 2 O 5 is inactive as a catalyst, and above 620 °C it begins to break down. Since it is known that V 2 O 5 can be reduced to VO 2 by SO 2 , one likely catalytic cycle is as follows:
followed by
It is also used as catalyst in the selective catalytic reduction (SCR) of NO x emissions in some power plants and diesel engines. Due to its effectiveness in converting sulfur dioxide into sulfur trioxide, and thereby sulfuric acid, special care must be taken with the operating temperatures and placement of a power plant's SCR unit when firing sulfur-containing fuels.
Maleic anhydride is produced by the V 2 O 5 -catalysed oxidation of butane with air:
Maleic anhydride is used for the production of polyester resins and alkyd resins . [ 15 ]
Phthalic anhydride is produced similarly by V 2 O 5 -catalysed oxidation of ortho -xylene or naphthalene at 350–400 °C. The equation for the vanadium oxide-catalysed oxidation of o -xylene to phthalic anhydride:
The equation for the vanadium oxide-catalysed oxidation of naphthalene to phthalic anhydride: [ 16 ]
Phthalic anhydride is a precursor to plasticisers , used for conferring pliability to polymers.
A variety of other industrial compounds are produced similarly, including adipic acid , acrylic acid , oxalic acid , and anthraquinone . [ 8 ]
Due to its high coefficient of thermal resistance , vanadium(V) oxide finds use as a detector material in bolometers and microbolometer arrays for thermal imaging . It also finds application as an ethanol sensor in ppm levels (up to 0.1 ppm).
Vanadium redox batteries are a type of flow battery used for energy storage , including large power facilities such as wind farms . [ 17 ] Vanadium oxide is also used as a cathode in lithium-ion batteries . [ 18 ]
Vanadium(V) oxide exhibits very modest acute toxicity to humans, with an LD 50 of about 470 mg/kg. The greater hazard is with inhalation of the dust, where the LD 50 ranges from 4–11 mg/kg for a 14-day exposure. [ 8 ] Vanadate ( VO 3− 4 ), formed by hydrolysis of V 2 O 5 at high pH, appears to inhibit enzymes that process phosphate (PO 4 3− ). However the mode of action remains elusive. [ 10 ] [ better source needed ] | https://en.wikipedia.org/wiki/O5V2 |
Dichlorine heptoxide is the chemical compound with the formula Cl 2 O 7 . This chlorine oxide is the anhydride of perchloric acid . It is produced by the careful distillation of perchloric acid in the presence of the dehydrating agent phosphorus pentoxide : [ 1 ]
Cl 2 O 7 can be distilled off from the mixture.
It may also be formed by illumination of mixtures of chlorine and ozone with blue light. [ 2 ] It slowly hydrolyzes back to perchloric acid .
Cl 2 O 7 is an endergonic molecule, meaning it is intrinsically unstable, decomposing to its constituent elements with release of energy: [ 3 ]
Dichlorine heptoxide is a covalent compound consisting of two ClO 3 groups linked by an oxygen atom. It has an overall bent molecular geometry (C 2 symmetry ), with a Cl−O−Cl angle of 118.6°. The chlorine–oxygen bond lengths are 1.709 Å in the central region and 1.405 Å within each ClO 3 cluster. [ 1 ] In this compound, chlorine exists in its highest formal oxidation state of +7.
Dichlorine heptoxide reacts with primary and secondary amines in carbon tetrachloride solution to yield perchloric amides: [ 4 ]
It also reacts with alkenes to give alkyl perchlorates. For example, it reacts with propene in carbon tetrachloride solution to yield isopropyl perchlorate and 1-chloro-2-propyl perchlorate. [ 5 ]
Dichlorine heptoxide reacts with alcohols to form alkyl perchlorates. [ 6 ]
Dichlorine heptoxide is a strongly acidic oxide, and in solution it forms an equilibrium with perchloric acid.
Although it is the most stable chlorine oxide, Cl 2 O 7 is a strong oxidizer as well as an explosive that can be set off with flame or mechanical shock, or by contact with iodine . [ 7 ] Nevertheless, it is less strongly oxidising than the other chlorine oxides, and does not attack sulfur , phosphorus , or paper when cold. [ 1 ] It has the same effects on the human body as elemental chlorine , and requires the same precautions. [ 8 ] | https://en.wikipedia.org/wiki/O7Cl2 |
Triuranium octoxide (U 3 O 8 ) [ 4 ] is a compound of uranium . It is present as an olive green to black, odorless solid. It is one of the more popular forms of yellowcake and is shipped between mills and refineries in this form.
U 3 O 8 has potential long-term stability in a geologic environment . [ 5 ] In the presence of oxygen (O 2 ), uranium dioxide (UO 2 ) is oxidized to U 3 O 8 , whereas uranium trioxide (UO 3 ) loses oxygen at temperatures above 500 °C and is reduced to U 3 O 8 . [ 6 ] [ 7 ] [ 8 ] The compound can be produced by the calcination of ammonium diuranate or ammonium uranyl carbonate . [ 9 ] Due to its high stability, it can be used for the disposal of depleted uranium . [ 10 ] Its particle density is 8.38 g cm −3 .
Triuranium octoxide is converted to uranium hexafluoride for the purpose of uranium enrichment .
Triuranium octoxide can be formed by the multi-step oxidation of uranium dioxide by oxygen gas at around 250°C: [ 7 ]
It can also be formed from the reduction of compounds like ammonium uranyl carbonate, ammonium diuranate, and uranium trioxide through calcination at high temperatures (~600°C for (NH 4 ) 2 U 2 O 7 , 700°C for UO 3 ): [ 8 ] [ 9 ] [ 11 ] [ 12 ]
Calcination of ammonium uranyl carbonate and ammonium diuranate is the main method for the production of U 3 O 8 . [ 9 ]
Uranium trioxide can be reduced by other methods, such as reaction with reducing agents like hydrogen gas at around 500°C−700°C: [ 11 ] [ 12 ]
This process can produce other uranium oxides, such as U 4 O 9 and UO 2 . [ 12 ]
While many studies have shown contradicting results on the oxidation state of uranium in U 3 O 8 , a study on its absorption spectrum determined that each formula unit of U 3 O 8 contains 2 U V atoms and 1 U VI atom, without any atoms of U IV . The study used the compounds uranium dioxide and uranyl acetylacetonate as references for the spectra of U IV and U VI , respectively. [ 13 ]
The analysis that U 3 O 8 contains 2 U V and 1 U VI is supported by other studies. [ 14 ]
Triuranium octoxide can be reduced to uranium dioxide through reduction with hydrogen: [ 11 ] [ 12 ]
Triuranium octoxide also loses oxygen to form a non-stoichiometric compound (U 3 O 8- z ) at high temperatures (>800°C), but recovers it when reverted to normal temperatures. [ 15 ]
Triuranium octoxide is slowly oxidized to uranium trioxide under high pressures of oxygen: [ 15 ]
Triuranium octoxide is attacked by hydrofluoric acid at 250 °C to form uranyl fluoride : [ 16 ]
Triuranium octoxide can also be attacked by a solution of hydrochloric acid and hydrogen peroxide to form uranyl chloride . [ 17 ]
Triuranium octoxide has multiple polymorphs , including α -U 3 O 8 , β -U 3 O 8 , γ -U 3 O 8 , and a non-stoichiometric high-pressure phase with the fluorite structure . [ 6 ] [ 15 ] [ 18 ]
α -U 3 O 8 is the most commonly encountered polymorph of triuranium octoxide, being the most stable under standard conditions. At room temperature, it has an orthorhombic pseudo- hexagonal structure , with lattice constants a =6.72Å, b =11.97Å, c =4.15Å and space group Amm2 . At higher temperatures (~350 °C), it transitions into a true hexagonal structure, with space group P 6 2m . [ 6 ] [ 15 ] [ 18 ]
α -U 3 O 8 is made up of layers of uranium and oxygen atoms. Each layer has the same U-O structure, and oxygen bridges connect corresponding uranium atoms in different layers. Within each layer, the U sites are surrounded by five oxygen atoms. This means that each U atom is bonded to seven oxygen atoms total, giving U a molecular geometry of pentagonal bipyramidal . [ 6 ]
β -U 3 O 8 can be formed by heating α -U 3 O 8 to 1350 °C and slowly cooling. The structure of β -U 3 O 8 is similar to that of α -U 3 O 8 , having a similar sheet-like arrangement and similar lattice constants ( a =7.07Å, b =11.45Å, c =8.30Å [ c/2 =4.15Å]). It also has an orthorhombic cell, with space group Cmcm . [ 6 ]
Like α -U 3 O 8 , β -U 3 O 8 has a layered structure containing uranium and oxygen atoms, but unlike α -U 3 O 8 , adjacent layers have a different structure- instead, every other layer has the same arrangement of U and O atoms. It also features oxygen bridges between U and O atoms in adjacent layers, though instead of all U atoms having a geometry of pentagonal bipyramidal, 2 U atoms per formula unit have distinct pentagonal bipyramidal molecular geometries, and the other U atom has a molecular geometry of tetragonal bipyramidal . [ 6 ]
γ -U 3 O 8 is formed at around 200-300 °C and at 16,000 atmospheres of pressure. [ 15 ] Very little information on it is available.
A high-pressure phase of U 3 O 8 with a hyperstoichiometric fluorite-type structure is formed at pressures greater than 8.1 GPa. During the phase transition, the volume of the solid decreases by more than 20%. The high-pressure phase is stable under ambient conditions, in which it is 28% denser than α -U 3 O 8 . [ 18 ]
This phase has a cubic structure with a high amount of defects . Its formula is UO 2+ x , where x ≈ 0.8. [ 18 ]
Triuranium octoxide can be found in small quantities (~0.01-0.05%) in the mineral pitchblende . [ 19 ]
Triuranium octoxide can be used to produce uranium hexafluoride , which is used for the enrichment of uranium in the nuclear fuel cycle . In the so-called 'dry' process, common in the United States, triuranium octoxide is purified through calcination, then crushed. Another process, called the 'wet' process, common outside the U.S., involves dissolving U 3 O 8 in nitric acid to form uranyl nitrate , followed by calcining to uranium trioxide in a fluidized bed reactor . [ 20 ] [ 21 ]
No matter which method is used, the uranium oxide is then reduced using hydrogen gas to form uranium dioxide, which is then reacted with hydrofluoric acid to form uranium tetrafluoride and then with fluorine gas to produce uranium hexafluoride. This can then be separated into uranium-235 and uranium-238 hexafluoride. [ 20 ] [ 21 ]
Triuranium octoxide is a certified reference material and can be used to determine the impurity of a sample of uranium. [ 2 ] [ 22 ]
Triuranium octoxide is a carcinogen and is toxic by inhalation and ingestion with repeated exposure. If consumed, it targets the kidney, liver, lungs, and brain, and causes irritation upon contact with the skin and eyes. It should only be handled with adequate ventilation. In addition, it is also radioactive , being an alpha emitter. [ 2 ] | https://en.wikipedia.org/wiki/O8U3 |
Formic acid (from Latin formica ' ant ' ), systematically named methanoic acid , is the simplest carboxylic acid . It has the chemical formula HCOOH and structure H−C(=O)−O−H . This acid is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Esters , salts , and the anion derived from formic acid are called formates . Industrially, formic acid is produced from methanol . [ 5 ]
Formic acid, which has a pungent, penetrating odor, is found naturally in insects, weeds, fruits and vegetables, and forest emissions. It appears in most ants and in stingless bees of the genus Oxytrigona . [ 6 ] [ 7 ] Wood ants from the genus Formica can spray formic acid on their prey or to defend the nest. The puss moth caterpillar ( Cerura vinula ) will spray it as well when threatened by predators. It is also found in the trichomes of stinging nettle ( Urtica dioica ). Apart from that, this acid is incorporated in many fruits such as pineapple (0.21 mg per 100 g), apple (2 mg per 100 g) and kiwi (1 mg per 100 g), as well as in many vegetables, namely onion (45 mg per 100 g), eggplant (1.34 mg per 100 g) and, in extremely low concentrations, cucumber (0.11 mg per 100 g). [ 8 ] Formic acid is a naturally occurring component of the atmosphere primarily due to forest emissions. [ 9 ]
As early as the 15th century, some alchemists and naturalists were aware that ant hills give off an acidic vapor. The first person to describe the isolation of this substance (by the distillation of large numbers of ants) was the English naturalist John Ray , in 1671. [ 10 ] [ 11 ] Ants secrete the formic acid for attack and defense purposes. Formic acid was first synthesized from hydrocyanic acid by the French chemist Joseph Gay-Lussac . In 1855, another French chemist, Marcellin Berthelot , developed a synthesis from carbon monoxide similar to the process used today. [ 12 ]
Formic acid was long considered a chemical compound of only minor interest in the chemical industry. In the late 1960s, significant quantities became available as a byproduct of acetic acid production. It now finds increasing use as a preservative and antibacterial in livestock feed. [ 12 ]
Formic acid is a colorless liquid having a pungent, penetrating odor [ 13 ] at room temperature, comparable to the related acetic acid . Formic acid is about ten times stronger than acetic acid having a (logarithmic) dissociation constant of 3.745 compared to 4.756 for acetic acid. [ 3 ]
It is miscible with water and most polar organic solvents , and is somewhat soluble in hydrocarbons . In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules. [ 14 ] [ 15 ] Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law . [ 15 ] Solid formic acid, which can exist in either of two polymorphs , consists of an effectively endless network of hydrogen-bonded formic acid molecules. Formic acid forms a high-boiling azeotrope with water (107.3 °C; 77.5% formic acid). Liquid formic acid tends to supercool .
Formic acid readily decomposes by dehydration in the presence of concentrated sulfuric acid to form carbon monoxide and water:
Treatment of formic acid with sulfuric acid is a convenient laboratory source of CO. [ 16 ] [ 17 ]
In the presence of platinum , it decomposes with a release of hydrogen and carbon dioxide .
Soluble ruthenium catalysts are also effective for producing carbon monoxide-free hydrogen. [ 18 ]
Formic acid shares most of the chemical properties of other carboxylic acids . Because of its high acidity, solutions in alcohols form esters spontaneously; in Fischer esterifications of formic acid, it self-catalyzes the reaction and no additional acid catalyst is needed. [ 19 ] Formic acid shares some of the reducing properties of aldehydes , reducing solutions of metal oxides to their respective metal. [ 20 ]
Formic acid is a source for a formyl group for example in the formylation of N -methylaniline to N -methylformanilide in toluene . [ 21 ]
In synthetic organic chemistry , formic acid is often used as a source of hydride ion, as in the Eschweiler–Clarke reaction :
It is used as a source of hydrogen in transfer hydrogenation , as in the Leuckart reaction to make amines , and (in aqueous solution or in its azeotrope with triethylamine ) for hydrogenation of ketones . [ 22 ]
Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with alkenes . Formic acids and alkenes readily react to form formate esters . In the presence of certain acids, including sulfuric and hydrofluoric acids , however, a variant of the Koch reaction occurs instead, and formic acid adds to the alkene to produce a larger carboxylic acid. [ 23 ]
An unstable formic anhydride , H(C=O)−O−(C=O)H, can be obtained by dehydration of formic acid with N , N ′ -dicyclohexylcarbodiimide in ether at low temperature. [ 24 ]
In 2009, the worldwide capacity for producing formic acid was 720 thousand tonnes (1.6 billion pounds) per year, roughly equally divided between Europe (350 thousand tonnes or 770 million pounds, mainly in Germany) and Asia (370 thousand tonnes or 820 million pounds, mainly in China) while production was below 1 thousand tonnes or 2.2 million pounds per year in all other continents. [ 25 ] It is commercially available in solutions of various concentrations between 85 and 99 w/w %. [ 14 ] As of 2009 [update] , the largest producers are BASF , Eastman Chemical Company , LC Industrial , and Feicheng Acid Chemicals , with the largest production facilities in Ludwigshafen (200 thousand tonnes or 440 million pounds per year, BASF, Germany), Oulu (105 thousand tonnes or 230 million pounds, Eastman, Finland), Nakhon Pathom (n/a, LC Industrial), and Feicheng (100 thousand tonnes or 220 million pounds, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States. [ 25 ]
Regenerating CO 2 to make useful products, that displace incumbent fossil fuel based pathways is a more impactful process than CO 2 sequestration.
Both formic acid and CO (carbon monoxide) are C1 (one carbon molecules). Formic is a hydrogen-rich liquid which can be transported and easily donates its hydrogen to enable a variety of condensation and esterification reactions to make a wide variety of derivative molecules. CO, while more difficult to transport as a gas, is also one of the primary constituents of syngas useful in synthesizing a wide variety of molecules.
CO 2 electrolysis is distinct from photosynthesis and offers a promising alternative to accelerate decarbonization. By converting CO 2 into products using clean electricity, we reduce CO 2 emissions in two ways: first and most simply by the amount of CO 2 that is regenerated, but the second way is less obvious but even more consequential by avoiding the CO 2 emissions otherwise generated by making these same products from fossil fuels. This is known as carbon displacement or abatement.
CO 2 electrolysis holds promise for reducing atmospheric CO 2 levels and providing a sustainable method for producing chemicals, materials, and fuels. Its efficiency and scalability are active areas of research, but now also commercialization, aiming to make it a viable commercial technology for both carbon management and molecule production. [ 26 ]
When methanol and carbon monoxide are combined in the presence of a strong base , the result is methyl formate , according to the chemical equation : [ 14 ]
In industry, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80 °C and 40 atm. The most widely used base is sodium methoxide . Hydrolysis of the methyl formate produces formic acid:
Efficient hydrolysis of methyl formate requires a large excess of water. Some routes proceed indirectly by first treating the methyl formate with ammonia to give formamide , which is then hydrolyzed with sulfuric acid :
A disadvantage of this approach is the need to dispose of the ammonium sulfate byproduct. This problem has led some manufacturers to develop energy-efficient methods of separating formic acid from the excess water used in direct hydrolysis. In one of these processes, used by BASF , the formic acid is removed from the water by liquid-liquid extraction with an organic base. [ citation needed ]
A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals. At one time, acetic acid was produced on a large scale by oxidation of alkanes , by a process that cogenerates significant formic acid. [ 14 ] This oxidative route to acetic acid has declined in importance so that the aforementioned dedicated routes to formic acid have become more important. [ citation needed ]
The catalytic hydrogenation of CO 2 to formic acid has long been studied. This reaction can be conducted homogeneously. [ 27 ] [ 28 ] [ 29 ]
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process . [ 30 ] [ 31 ] A Keggin-type polyoxometalate (H 5 PV 2 Mo 10 O 40 ) is used as the homogeneous catalyst to convert sugars, wood, waste paper, or cyanobacteria to formic acid and CO 2 as the sole byproduct. Yields of up to 53% formic acid can be achieved. [ citation needed ]
In the laboratory, formic acid can be obtained by heating oxalic acid in glycerol followed by steam distillation. [ 32 ] Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. If the reaction mixture is heated to higher temperatures, allyl alcohol results. The net reaction is thus:
Another illustrative method involves the reaction between lead formate and hydrogen sulfide , driven by the formation of lead sulfide . [ 33 ]
Formate is formed by the electrochemical reduction of CO 2 (in the form of bicarbonate ) at a lead cathode at pH 8.6: [ 34 ]
or
If the feed is CO 2 and oxygen is evolved at the anode, the total reaction is:
Formic acid is named after ants which have high concentrations of the compound in their venom, derived from serine through a 5,10-methenyltetrahydrofolate intermediate. [ 35 ] The conjugate base of formic acid, formate, also occurs widely in nature. An assay for formic acid in body fluids, designed for determination of formate after methanol poisoning, is based on the reaction of formate with bacterial formate dehydrogenase . [ 36 ]
A major use of formic acid is as a preservative and antibacterial agent in livestock feed. It arrests certain decay processes and causes the feed to retain its nutritive value longer,
In Europe, it is applied on silage , including fresh hay, to promote the fermentation of lactic acid and to suppress the formation of butyric acid ; it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value. [ 14 ] It is widely used to preserve winter feed for cattle , [ 37 ] and is sometimes added to poultry feed to kill E. coli bacteria. [ 38 ] [ 39 ] Use as a preservative for silage and other animal feed constituted 30% of the global consumption in 2009. [ 25 ]
Beekeepers use formic acid as a miticide against the tracheal mite ( Acarapis woodi ) and the Varroa destructor mite and Varroa jacobsoni mite . [ 40 ]
Formic acid can be used directly in formic acid fuel cells or indirectly in hydrogen fuel cells . [ 41 ] [ 42 ]
Electrolytic conversion of electrical energy to chemical fuel has been proposed as a large-scale source of formate by various groups. [ 43 ] The formate could be used as feed to modified E. coli bacteria for producing biomass . [ 44 ] [ 45 ] Natural methylotroph microbes can feed on formic acid or formate.
Formic acid has been considered as a means of hydrogen storage . [ 46 ] The co-product of this decomposition, carbon dioxide, can be rehydrogenated back to formic acid in a second step. Formic acid contains 53 g/L hydrogen at room temperature and atmospheric pressure, which is three and a half times as much as compressed hydrogen gas can attain at 350 bar pressure (14.7 g/L). Pure formic acid is a liquid with a flash point of 69 °C, much higher than that of gasoline (−40 °C) or ethanol (13 °C). [ citation needed ]
It is possible to use formic acid as an intermediary to produce isobutanol from CO 2 using microbes. [ 47 ] [ 48 ]
Formic acid has a potential application in soldering . Due to its capacity to reduce oxide layers, formic acid gas can be blasted at an oxide surface to increase solder wettability . [ citation needed ]
Formic acid is used as a volatile pH modifier in HPLC and capillary electrophoresis . Formic acid is often used as a component of mobile phase in reversed-phase high-performance liquid chromatography (RP-HPLC) analysis and separation techniques for the separation of hydrophobic macromolecules, such as peptides, proteins and more complex structures including intact viruses. Especially when paired with mass spectrometry detection, formic acid offers several advantages over the more traditionally used phosphoric acid . [ 49 ] [ 50 ]
Formic acid is also significantly used in the production of leather, including tanning (23% of the global consumption in 2009 [ 25 ] ), and in dyeing and finishing textiles (9% of the global consumption in 2009 [ 25 ] ) because of its acidic nature. Use as a coagulant in the production of rubber [ 14 ] consumed 6% of the global production in 2009. [ 25 ]
Formic acid is also used in place of mineral acids for various cleaning products, [ 14 ] such as limescale remover and toilet bowl cleaner . Some formate esters are artificial flavorings and perfumes.
Formic acid application has been reported to be an effective treatment for warts . [ 51 ]
Formic acid has low toxicity (hence its use as a food additive), with an LD 50 of 1.8 g/kg (tested orally on mice). The concentrated acid is corrosive to the skin. [ 14 ]
Formic acid is readily metabolized and eliminated by the body. Nonetheless, it has specific toxic effects; the formic acid and formaldehyde produced as metabolites of methanol are responsible for the optic nerve damage, causing blindness, seen in methanol poisoning . [ 52 ] Some chronic effects of formic acid exposure have been documented. Some experiments on bacterial species have demonstrated it to be a mutagen . [ 53 ] Chronic exposure in humans may cause kidney damage. [ 53 ] Another possible effect of chronic exposure is development of a skin allergy that manifests upon re-exposure to the chemical.
Concentrated formic acid slowly decomposes to carbon monoxide and water, leading to pressure buildup in the containing vessel. For this reason, 98% formic acid is shipped in plastic bottles with self-venting caps. [ citation needed ]
The hazards of solutions of formic acid depend on the concentration. The following table lists the Globally Harmonized System of Classification and Labelling of Chemicals for formic acid solutions: [ citation needed ]
Formic acid in 85% concentration is flammable, and diluted formic acid is on the U.S. Food and Drug Administration list of food additives. [ 54 ] The principal danger from formic acid is from skin or eye contact with the concentrated liquid or vapors. The U.S. OSHA Permissible Exposure Level ( PEL ) of formic acid vapor in the work environment is 5 parts per million (ppm) of air. [ 55 ] | https://en.wikipedia.org/wiki/O=CH-O-H |
Formic acid (from Latin formica ' ant ' ), systematically named methanoic acid , is the simplest carboxylic acid . It has the chemical formula HCOOH and structure H−C(=O)−O−H . This acid is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Esters , salts , and the anion derived from formic acid are called formates . Industrially, formic acid is produced from methanol . [ 5 ]
Formic acid, which has a pungent, penetrating odor, is found naturally in insects, weeds, fruits and vegetables, and forest emissions. It appears in most ants and in stingless bees of the genus Oxytrigona . [ 6 ] [ 7 ] Wood ants from the genus Formica can spray formic acid on their prey or to defend the nest. The puss moth caterpillar ( Cerura vinula ) will spray it as well when threatened by predators. It is also found in the trichomes of stinging nettle ( Urtica dioica ). Apart from that, this acid is incorporated in many fruits such as pineapple (0.21 mg per 100 g), apple (2 mg per 100 g) and kiwi (1 mg per 100 g), as well as in many vegetables, namely onion (45 mg per 100 g), eggplant (1.34 mg per 100 g) and, in extremely low concentrations, cucumber (0.11 mg per 100 g). [ 8 ] Formic acid is a naturally occurring component of the atmosphere primarily due to forest emissions. [ 9 ]
As early as the 15th century, some alchemists and naturalists were aware that ant hills give off an acidic vapor. The first person to describe the isolation of this substance (by the distillation of large numbers of ants) was the English naturalist John Ray , in 1671. [ 10 ] [ 11 ] Ants secrete the formic acid for attack and defense purposes. Formic acid was first synthesized from hydrocyanic acid by the French chemist Joseph Gay-Lussac . In 1855, another French chemist, Marcellin Berthelot , developed a synthesis from carbon monoxide similar to the process used today. [ 12 ]
Formic acid was long considered a chemical compound of only minor interest in the chemical industry. In the late 1960s, significant quantities became available as a byproduct of acetic acid production. It now finds increasing use as a preservative and antibacterial in livestock feed. [ 12 ]
Formic acid is a colorless liquid having a pungent, penetrating odor [ 13 ] at room temperature, comparable to the related acetic acid . Formic acid is about ten times stronger than acetic acid having a (logarithmic) dissociation constant of 3.745 compared to 4.756 for acetic acid. [ 3 ]
It is miscible with water and most polar organic solvents , and is somewhat soluble in hydrocarbons . In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules. [ 14 ] [ 15 ] Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law . [ 15 ] Solid formic acid, which can exist in either of two polymorphs , consists of an effectively endless network of hydrogen-bonded formic acid molecules. Formic acid forms a high-boiling azeotrope with water (107.3 °C; 77.5% formic acid). Liquid formic acid tends to supercool .
Formic acid readily decomposes by dehydration in the presence of concentrated sulfuric acid to form carbon monoxide and water:
Treatment of formic acid with sulfuric acid is a convenient laboratory source of CO. [ 16 ] [ 17 ]
In the presence of platinum , it decomposes with a release of hydrogen and carbon dioxide .
Soluble ruthenium catalysts are also effective for producing carbon monoxide-free hydrogen. [ 18 ]
Formic acid shares most of the chemical properties of other carboxylic acids . Because of its high acidity, solutions in alcohols form esters spontaneously; in Fischer esterifications of formic acid, it self-catalyzes the reaction and no additional acid catalyst is needed. [ 19 ] Formic acid shares some of the reducing properties of aldehydes , reducing solutions of metal oxides to their respective metal. [ 20 ]
Formic acid is a source for a formyl group for example in the formylation of N -methylaniline to N -methylformanilide in toluene . [ 21 ]
In synthetic organic chemistry , formic acid is often used as a source of hydride ion, as in the Eschweiler–Clarke reaction :
It is used as a source of hydrogen in transfer hydrogenation , as in the Leuckart reaction to make amines , and (in aqueous solution or in its azeotrope with triethylamine ) for hydrogenation of ketones . [ 22 ]
Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with alkenes . Formic acids and alkenes readily react to form formate esters . In the presence of certain acids, including sulfuric and hydrofluoric acids , however, a variant of the Koch reaction occurs instead, and formic acid adds to the alkene to produce a larger carboxylic acid. [ 23 ]
An unstable formic anhydride , H(C=O)−O−(C=O)H, can be obtained by dehydration of formic acid with N , N ′ -dicyclohexylcarbodiimide in ether at low temperature. [ 24 ]
In 2009, the worldwide capacity for producing formic acid was 720 thousand tonnes (1.6 billion pounds) per year, roughly equally divided between Europe (350 thousand tonnes or 770 million pounds, mainly in Germany) and Asia (370 thousand tonnes or 820 million pounds, mainly in China) while production was below 1 thousand tonnes or 2.2 million pounds per year in all other continents. [ 25 ] It is commercially available in solutions of various concentrations between 85 and 99 w/w %. [ 14 ] As of 2009 [update] , the largest producers are BASF , Eastman Chemical Company , LC Industrial , and Feicheng Acid Chemicals , with the largest production facilities in Ludwigshafen (200 thousand tonnes or 440 million pounds per year, BASF, Germany), Oulu (105 thousand tonnes or 230 million pounds, Eastman, Finland), Nakhon Pathom (n/a, LC Industrial), and Feicheng (100 thousand tonnes or 220 million pounds, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States. [ 25 ]
Regenerating CO 2 to make useful products, that displace incumbent fossil fuel based pathways is a more impactful process than CO 2 sequestration.
Both formic acid and CO (carbon monoxide) are C1 (one carbon molecules). Formic is a hydrogen-rich liquid which can be transported and easily donates its hydrogen to enable a variety of condensation and esterification reactions to make a wide variety of derivative molecules. CO, while more difficult to transport as a gas, is also one of the primary constituents of syngas useful in synthesizing a wide variety of molecules.
CO 2 electrolysis is distinct from photosynthesis and offers a promising alternative to accelerate decarbonization. By converting CO 2 into products using clean electricity, we reduce CO 2 emissions in two ways: first and most simply by the amount of CO 2 that is regenerated, but the second way is less obvious but even more consequential by avoiding the CO 2 emissions otherwise generated by making these same products from fossil fuels. This is known as carbon displacement or abatement.
CO 2 electrolysis holds promise for reducing atmospheric CO 2 levels and providing a sustainable method for producing chemicals, materials, and fuels. Its efficiency and scalability are active areas of research, but now also commercialization, aiming to make it a viable commercial technology for both carbon management and molecule production. [ 26 ]
When methanol and carbon monoxide are combined in the presence of a strong base , the result is methyl formate , according to the chemical equation : [ 14 ]
In industry, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80 °C and 40 atm. The most widely used base is sodium methoxide . Hydrolysis of the methyl formate produces formic acid:
Efficient hydrolysis of methyl formate requires a large excess of water. Some routes proceed indirectly by first treating the methyl formate with ammonia to give formamide , which is then hydrolyzed with sulfuric acid :
A disadvantage of this approach is the need to dispose of the ammonium sulfate byproduct. This problem has led some manufacturers to develop energy-efficient methods of separating formic acid from the excess water used in direct hydrolysis. In one of these processes, used by BASF , the formic acid is removed from the water by liquid-liquid extraction with an organic base. [ citation needed ]
A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals. At one time, acetic acid was produced on a large scale by oxidation of alkanes , by a process that cogenerates significant formic acid. [ 14 ] This oxidative route to acetic acid has declined in importance so that the aforementioned dedicated routes to formic acid have become more important. [ citation needed ]
The catalytic hydrogenation of CO 2 to formic acid has long been studied. This reaction can be conducted homogeneously. [ 27 ] [ 28 ] [ 29 ]
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process . [ 30 ] [ 31 ] A Keggin-type polyoxometalate (H 5 PV 2 Mo 10 O 40 ) is used as the homogeneous catalyst to convert sugars, wood, waste paper, or cyanobacteria to formic acid and CO 2 as the sole byproduct. Yields of up to 53% formic acid can be achieved. [ citation needed ]
In the laboratory, formic acid can be obtained by heating oxalic acid in glycerol followed by steam distillation. [ 32 ] Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. If the reaction mixture is heated to higher temperatures, allyl alcohol results. The net reaction is thus:
Another illustrative method involves the reaction between lead formate and hydrogen sulfide , driven by the formation of lead sulfide . [ 33 ]
Formate is formed by the electrochemical reduction of CO 2 (in the form of bicarbonate ) at a lead cathode at pH 8.6: [ 34 ]
or
If the feed is CO 2 and oxygen is evolved at the anode, the total reaction is:
Formic acid is named after ants which have high concentrations of the compound in their venom, derived from serine through a 5,10-methenyltetrahydrofolate intermediate. [ 35 ] The conjugate base of formic acid, formate, also occurs widely in nature. An assay for formic acid in body fluids, designed for determination of formate after methanol poisoning, is based on the reaction of formate with bacterial formate dehydrogenase . [ 36 ]
A major use of formic acid is as a preservative and antibacterial agent in livestock feed. It arrests certain decay processes and causes the feed to retain its nutritive value longer,
In Europe, it is applied on silage , including fresh hay, to promote the fermentation of lactic acid and to suppress the formation of butyric acid ; it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value. [ 14 ] It is widely used to preserve winter feed for cattle , [ 37 ] and is sometimes added to poultry feed to kill E. coli bacteria. [ 38 ] [ 39 ] Use as a preservative for silage and other animal feed constituted 30% of the global consumption in 2009. [ 25 ]
Beekeepers use formic acid as a miticide against the tracheal mite ( Acarapis woodi ) and the Varroa destructor mite and Varroa jacobsoni mite . [ 40 ]
Formic acid can be used directly in formic acid fuel cells or indirectly in hydrogen fuel cells . [ 41 ] [ 42 ]
Electrolytic conversion of electrical energy to chemical fuel has been proposed as a large-scale source of formate by various groups. [ 43 ] The formate could be used as feed to modified E. coli bacteria for producing biomass . [ 44 ] [ 45 ] Natural methylotroph microbes can feed on formic acid or formate.
Formic acid has been considered as a means of hydrogen storage . [ 46 ] The co-product of this decomposition, carbon dioxide, can be rehydrogenated back to formic acid in a second step. Formic acid contains 53 g/L hydrogen at room temperature and atmospheric pressure, which is three and a half times as much as compressed hydrogen gas can attain at 350 bar pressure (14.7 g/L). Pure formic acid is a liquid with a flash point of 69 °C, much higher than that of gasoline (−40 °C) or ethanol (13 °C). [ citation needed ]
It is possible to use formic acid as an intermediary to produce isobutanol from CO 2 using microbes. [ 47 ] [ 48 ]
Formic acid has a potential application in soldering . Due to its capacity to reduce oxide layers, formic acid gas can be blasted at an oxide surface to increase solder wettability . [ citation needed ]
Formic acid is used as a volatile pH modifier in HPLC and capillary electrophoresis . Formic acid is often used as a component of mobile phase in reversed-phase high-performance liquid chromatography (RP-HPLC) analysis and separation techniques for the separation of hydrophobic macromolecules, such as peptides, proteins and more complex structures including intact viruses. Especially when paired with mass spectrometry detection, formic acid offers several advantages over the more traditionally used phosphoric acid . [ 49 ] [ 50 ]
Formic acid is also significantly used in the production of leather, including tanning (23% of the global consumption in 2009 [ 25 ] ), and in dyeing and finishing textiles (9% of the global consumption in 2009 [ 25 ] ) because of its acidic nature. Use as a coagulant in the production of rubber [ 14 ] consumed 6% of the global production in 2009. [ 25 ]
Formic acid is also used in place of mineral acids for various cleaning products, [ 14 ] such as limescale remover and toilet bowl cleaner . Some formate esters are artificial flavorings and perfumes.
Formic acid application has been reported to be an effective treatment for warts . [ 51 ]
Formic acid has low toxicity (hence its use as a food additive), with an LD 50 of 1.8 g/kg (tested orally on mice). The concentrated acid is corrosive to the skin. [ 14 ]
Formic acid is readily metabolized and eliminated by the body. Nonetheless, it has specific toxic effects; the formic acid and formaldehyde produced as metabolites of methanol are responsible for the optic nerve damage, causing blindness, seen in methanol poisoning . [ 52 ] Some chronic effects of formic acid exposure have been documented. Some experiments on bacterial species have demonstrated it to be a mutagen . [ 53 ] Chronic exposure in humans may cause kidney damage. [ 53 ] Another possible effect of chronic exposure is development of a skin allergy that manifests upon re-exposure to the chemical.
Concentrated formic acid slowly decomposes to carbon monoxide and water, leading to pressure buildup in the containing vessel. For this reason, 98% formic acid is shipped in plastic bottles with self-venting caps. [ citation needed ]
The hazards of solutions of formic acid depend on the concentration. The following table lists the Globally Harmonized System of Classification and Labelling of Chemicals for formic acid solutions: [ citation needed ]
Formic acid in 85% concentration is flammable, and diluted formic acid is on the U.S. Food and Drug Administration list of food additives. [ 54 ] The principal danger from formic acid is from skin or eye contact with the concentrated liquid or vapors. The U.S. OSHA Permissible Exposure Level ( PEL ) of formic acid vapor in the work environment is 5 parts per million (ppm) of air. [ 55 ] | https://en.wikipedia.org/wiki/O=CH-OH |
Formaldehyde ( / f ɔːr ˈ m æ l d ɪ h aɪ d / ⓘ for- MAL -di-hide , US also / f ə r -/ ⓘ fər- ) ( systematic name methanal ) is an organic compound with the chemical formula CH 2 O and structure H−CHO , more precisely H 2 C=O . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde . It is stored as aqueous solutions ( formalin ), which consists mainly of the hydrate CH 2 (OH) 2 . It is the simplest of the aldehydes ( R−CHO ). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. [ 14 ] It is mainly used in the production of industrial resins , e.g., for particle board and coatings .
Formaldehyde also occurs naturally. It is derived from the degradation of serine , dimethylglycine , and lipids . Demethylases act by converting N-methyl groups to formaldehyde. [ 15 ]
Formaldehyde is classified as a group 1 carcinogen [ note 1 ] [ 17 ] and can cause respiratory and skin irritation upon exposure. [ 16 ]
Formaldehyde is more complicated than many simple carbon compounds in that it adopts several diverse forms. These compounds can often be used interchangeably and can be interconverted. [ citation needed ]
A small amount of stabilizer , such as methanol , is usually added to suppress oxidation and polymerization . A typical commercial-grade formalin may contain 10–12% methanol in addition to various metallic impurities.
"Formaldehyde" was first used as a generic trademark in 1893 following a previous trade name, "formalin". [ 18 ]
Molecular formaldehyde contains a central carbon atom with a double bond to the oxygen atom and a single bond to each hydrogen atom . This structure is summarised by the condensed formula H 2 C=O. [ 19 ] The molecule is planar, Y-shaped and its molecular symmetry belongs to the C 2v point group . [ 20 ] The precise molecular geometry of gaseous formaldehyde has been determined by gas electron diffraction [ 19 ] [ 21 ] and microwave spectroscopy . [ 22 ] [ 23 ] The bond lengths are 1.21 Å for the carbon–oxygen bond [ 19 ] [ 21 ] [ 22 ] [ 23 ] [ 24 ] and around 1.11 Å for the carbon–hydrogen bond , [ 19 ] [ 21 ] [ 22 ] [ 23 ] while the H–C–H bond angle is 117°, [ 22 ] [ 23 ] close to the 120° angle found in an ideal trigonal planar molecule . [ 19 ] Some excited electronic states of formaldehyde are pyramidal rather than planar as in the ground state . [ 24 ]
Processes in the upper atmosphere contribute more than 80% of the total formaldehyde in the environment. [ 25 ] Formaldehyde is an intermediate in the oxidation (or combustion ) of methane , as well as of other carbon compounds, e.g. in forest fires , automobile exhaust, and tobacco smoke . When produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons , it becomes part of smog . Formaldehyde has also been detected in outer space.
Formaldehyde and its adducts are ubiquitous in nature. Food may contain formaldehyde at levels 1–100 mg/kg. [ 26 ] Formaldehyde, formed in the metabolism of the amino acids serine and threonine , is found in the bloodstream of humans and other primates at concentrations of approximately 50 micromolar . [ 27 ] Experiments in which animals are exposed to an atmosphere containing isotopically labeled formaldehyde have demonstrated that even in deliberately exposed animals, the majority of formaldehyde-DNA adducts found in non-respiratory tissues are derived from endogenously produced formaldehyde. [ 28 ]
Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to formic acid . [ 29 ] [ 30 ] It nonetheless presents significant health concerns , as a contaminant .
Formaldehyde appears to be a useful probe in astrochemistry due to prominence of the 1 10 ←1 11 and 2 11 ←2 12 K -doublet transitions. It was the first polyatomic organic molecule detected in the interstellar medium . [ 31 ] Since its initial detection in 1969, it has been observed in many regions of the galaxy . Because of the widespread interest in interstellar formaldehyde, it has been extensively studied, yielding new extragalactic sources. [ 32 ] A proposed mechanism for the formation is the hydrogenation of CO ice: [ 33 ]
HCN , HNC , H 2 CO, and dust have also been observed inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) . [ 34 ] [ 35 ]
Formaldehyde was discovered in 1859 by the Russian chemist Aleksandr Butlerov (1828–1886) when he attempted to synthesize methanediol ("methylene glycol") from iodomethane and silver oxalate . [ 36 ] In his paper, Butlerov referred to formaldehyde as "dioxymethylen" (methylene dioxide) because his empirical formula for it was incorrect, as atomic weights were not precisely determined until the Karlsruhe Congress .
The compound was identified as an aldehyde by August Wilhelm von Hofmann , who first announced its production by passing methanol vapor in air over hot platinum wire. [ 37 ] [ 38 ] With modifications, Hofmann's method remains the basis of the present day industrial route.
Solution routes to formaldehyde also entail oxidation of methanol or iodomethane . [ 39 ]
Formaldehyde is produced industrially by the catalytic oxidation of methanol . The most common catalysts are silver metal (i.e. the FASIL process ), iron(III) oxide , [ 40 ] iron molybdenum oxides (e.g. iron(III) molybdate ) with a molybdenum -enriched surface, [ 41 ] or vanadium oxides . In the commonly used formox process , methanol and oxygen react at c. 250–400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation : [ 42 ]
The silver-based catalyst usually operates at a higher temperature, about 650 °C. Two chemical reactions on it simultaneously produce formaldehyde: that shown above and the dehydrogenation reaction:
In principle, formaldehyde could be generated by oxidation of methane , but this route is not industrially viable because the methanol is more easily oxidized than methane. [ 42 ]
Formaldehyde is produced via several enzyme-catalyzed routes. [ 43 ] Living beings, including humans, produce formaldehyde as part of their metabolism. Formaldehyde is key to several bodily functions (e.g. epigenetics [ 27 ] ), but its amount must also be tightly controlled to avoid self-poisoning. [ 44 ]
Formaldehyde is catabolized by alcohol dehydrogenase ADH5 and aldehyde dehydrogenase ALDH2 . [ 45 ]
Formaldehyde is a building block in the synthesis of many other compounds of specialised and industrial significance. It exhibits most of the chemical properties of other aldehydes but is more reactive. [ 46 ]
Monomeric CH 2 O is a gas and is rarely encountered in the laboratory. Aqueous formaldehyde, unlike some other small aldehydes (which need specific conditions to oligomerize through aldol condensation ) oligomerizes spontaneously at a common state. The trimer 1,3,5-trioxane, (CH 2 O) 3 , is a typical oligomer. Many cyclic oligomers of other sizes have been isolated. Similarly, formaldehyde hydrates to give the geminal diol methanediol , which condenses further to form hydroxy-terminated oligomers HO(CH 2 O) n H. The polymer is called paraformaldehyde . The higher concentration of formaldehyde—the more equilibrium shifts towards polymerization. Diluting with water or increasing the solution temperature, as well as adding alcohols (such as methanol or ethanol) lowers that tendency.
Gaseous formaldehyde polymerizes at active sites on vessel walls, but the mechanism of the reaction is unknown. [ 47 ] Small amounts of hydrogen chloride , boron trifluoride , or stannic chloride present in gaseous formaldehyde provide the catalytic effect and make the polymerization rapid. [ 48 ]
Formaldehyde forms cross-links by first combining with a protein to form methylol , which loses a water molecule to form a Schiff base . [ 49 ] The Schiff base can then react with DNA or protein to create a cross-linked product. [ 49 ] This reaction is the basis for the most common process of chemical fixation .
Formaldehyde is readily oxidized by atmospheric oxygen into formic acid . For this reason, commercial formaldehyde is typically contaminated with formic acid. Formaldehyde can be hydrogenated into methanol .
In the Cannizzaro reaction , formaldehyde and base react to produce formic acid and methanol, a disproportionation reaction .
Formaldehyde reacts with many compounds, resulting in hydroxymethylation :
The resulting hydroxymethyl derivatives typically react further. Thus, amines give hexahydro-1,3,5-triazines :
Similarly, when combined with hydrogen sulfide , it forms trithiane : [ 50 ]
In the presence of acids, it participates in electrophilic aromatic substitution reactions with aromatic compounds resulting in hydroxymethylated derivatives:
When conducted in the presence of hydrogen chloride, the product is the chloromethyl compound, as described in the Blanc chloromethylation . If the arene is electron-rich, as in phenols, elaborate condensations ensue. With 4-substituted phenols one obtains calixarenes . [ 51 ] Phenol results in polymers.
Many amino acids react with formaldehyde. [ 43 ] Cysteine converts to thioproline .
Formaldehyde is a common precursor to more complex compounds and materials. In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin , melamine resin , phenol formaldehyde resin , polyoxymethylene plastics , 1,4-butanediol , and methylene diphenyl diisocyanate . [ 42 ] The textile industry uses formaldehyde-based resins as finishers to make fabrics crease-resistant. [ 52 ]
When condensed with phenol , urea , or melamine , formaldehyde produces, respectively, hard thermoset phenol formaldehyde resin, urea formaldehyde resin, and melamine resin. These polymers are permanent adhesives used in plywood and carpeting . They are also foamed to make insulation , or cast into moulded products. Production of formaldehyde resins accounts for more than half of formaldehyde consumption.
Formaldehyde is also a precursor to polyfunctional alcohols such as pentaerythritol , which is used to make paints and explosives . Other formaldehyde derivatives include methylene diphenyl diisocyanate, an important component in polyurethane paints and foams, and hexamine , which is used in phenol-formaldehyde resins as well as the explosive RDX .
Condensation with acetaldehyde affords pentaerythritol , a chemical necessary in synthesizing PETN , a high explosive: [ 53 ]
An aqueous solution of formaldehyde can be useful as a disinfectant as it kills most bacteria and fungi (including their spores). It is used as an additive in vaccine manufacturing to inactivate toxins and pathogens. [ 54 ] Formaldehyde releasers are used as biocides in personal care products such as cosmetics. Although present at levels not normally considered harmful, they are known to cause allergic contact dermatitis in certain sensitised individuals. [ 55 ]
Aquarists use formaldehyde as a treatment for the parasites Ichthyophthirius multifiliis and Cryptocaryon irritans . [ 56 ] Formaldehyde is one of the main disinfectants recommended for destroying anthrax . [ 57 ]
Formaldehyde is also approved for use in the manufacture of animal feeds in the US. It is an antimicrobial agent used to maintain complete animal feeds or feed ingredients Salmonella negative for up to 21 days. [ 58 ]
Formaldehyde preserves or fixes tissue or cells. The process involves cross-linking of primary amino groups . The European Union has banned the use of formaldehyde as a biocide (including embalming ) under the Biocidal Products Directive (98/8/EC) due to its carcinogenic properties. [ 59 ] [ 60 ] Countries with a strong tradition of embalming corpses, such as Ireland and other colder-weather countries, have raised concerns. Despite reports to the contrary, [ 61 ] no decision on the inclusion of formaldehyde on Annex I of the Biocidal Products Directive for product-type 22 (embalming and taxidermist fluids) had been made as of September 2009 [update] . [ 62 ]
Formaldehyde-based crosslinking is exploited in ChIP-on-chip or ChIP-sequencing genomics experiments, where DNA-binding proteins are cross-linked to their cognate binding sites on the chromosome and analyzed to determine what genes are regulated by the proteins. Formaldehyde is also used as a denaturing agent in RNA gel electrophoresis , preventing RNA from forming secondary structures. A solution of 4% formaldehyde fixes pathology tissue specimens at about one mm per hour at room temperature.
Formaldehyde and 18 M (concentrated) sulfuric acid makes Marquis reagent —which can identify alkaloids and other compounds.
In photography, formaldehyde is used in low concentrations for the process C-41 (color negative film) stabilizer in the final wash step, [ 63 ] as well as in the process E-6 pre-bleach step, to make it unnecessary in the final wash. Due to improvements in dye coupler chemistry, more modern (2006 or later) E-6 and C-41 films do not need formaldehyde, as their dyes are already stable.
In view of its widespread use, toxicity, and volatility, formaldehyde poses a significant danger to human health. [ 64 ] [ 65 ] In 2011, the US National Toxicology Program described formaldehyde as "known to be a human carcinogen". [ 66 ] [ 67 ] [ 68 ]
Concerns are associated with chronic (long-term) exposure by inhalation as may happen from thermal or chemical decomposition of formaldehyde-based resins and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). As formaldehyde resins are used in many construction materials , it is one of the more common indoor air pollutants . [ 69 ] [ 70 ] At concentrations above 0.1 ppm in air, formaldehyde can irritate the eyes and mucous membranes . [ 71 ] Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, and can trigger or aggravate asthma symptoms. [ 72 ] [ 73 ]
The CDC considers formaldehyde as a systemic poison. Formaldehyde poisoning can cause permanent changes in the nervous system 's functions. [ 74 ]
A 1988 Canadian study of houses with urea-formaldehyde foam insulation found that formaldehyde levels as low as 0.046 ppm were positively correlated with eye and nasal irritation. [ 75 ] A 2009 review of studies has shown a strong association between exposure to formaldehyde and the development of childhood asthma . [ 76 ]
A theory was proposed for the carcinogenesis of formaldehyde in 1978. [ 77 ] In 1987 the United States Environmental Protection Agency (EPA) classified it as a probable human carcinogen , and after more studies the WHO International Agency for Research on Cancer (IARC) in 1995 also classified it as a probable human carcinogen . Further information and evaluation of all known data led the IARC to reclassify formaldehyde as a known human carcinogen [ 78 ] associated with nasal sinus cancer and nasopharyngeal cancer . [ 79 ] Studies in 2009 and 2010 have also shown a positive correlation between exposure to formaldehyde and the development of leukemia , particularly myeloid leukemia . [ 80 ] [ 81 ] Nasopharyngeal and sinonasal cancers are relatively rare, with a combined annual incidence in the United States of < 4,000 cases. [ 82 ] [ 83 ] About 30,000 cases of myeloid leukemia occur in the United States each year. [ 84 ] [ 85 ] Some evidence suggests that workplace exposure to formaldehyde contributes to sinonasal cancers. [ 86 ] Professionals exposed to formaldehyde in their occupation, such as funeral industry workers and embalmers , showed an increased risk of leukemia and brain cancer compared with the general population. [ 87 ] Other factors are important in determining individual risk for the development of leukemia or nasopharyngeal cancer. [ 86 ] [ 88 ] [ 89 ] In yeast, formaldehyde is found to perturb pathways for DNA repair and cell cycle. [ 90 ]
In the residential environment, formaldehyde exposure comes from a number of routes; formaldehyde can be emitted by treated wood products, such as plywood or particle board , but it is produced by paints, varnishes , floor finishes, and cigarette smoking as well. [ 91 ] In July 2016, the U.S. EPA released a prepublication version of its final rule on Formaldehyde Emission Standards for Composite Wood Products. [ 92 ] These new rules impact manufacturers, importers, distributors, and retailers of products containing composite wood, including fiberboard, particleboard, and various laminated products, who must comply with more stringent record-keeping and labeling requirements. [ 93 ]
The U.S. EPA allows no more than 0.016 ppm formaldehyde in the air in new buildings constructed for that agency. [ 94 ] [ failed verification ] A U.S. EPA study found a new home measured 0.076 ppm when brand new and 0.045 ppm after 30 days. [ 95 ] The Federal Emergency Management Agency (FEMA) has also announced limits on the formaldehyde levels in trailers purchased by that agency. [ 96 ] The EPA recommends the use of "exterior-grade" pressed-wood products with phenol instead of urea resin to limit formaldehyde exposure, since pressed-wood products containing formaldehyde resins are often a significant source of formaldehyde in homes. [ 79 ]
The eyes are most sensitive to formaldehyde exposure: The lowest level at which many people can begin to smell formaldehyde ranges between 0.05 and 1 ppm. The maximum concentration value at the workplace is 0.3 ppm. [ 97 ] [ need quotation to verify ] In controlled chamber studies, individuals begin to sense eye irritation at about 0.5 ppm; 5 to 20 percent report eye irritation at 0.5 to 1 ppm; and greater certainty for sensory irritation occurred at 1 ppm and above. While some agencies have used a level as low as 0.1 ppm as a threshold for irritation, the expert panel found that a level of 0.3 ppm would protect against nearly all irritation. In fact, the expert panel found that a level of 1.0 ppm would avoid eye irritation—the most sensitive endpoint—in 75–95% of all people exposed. [ 98 ]
Formaldehyde levels in building environments are affected by a number of factors. These include the potency of formaldehyde-emitting products present, the ratio of the surface area of emitting materials to volume of space, environmental factors, product age, interactions with other materials, and ventilation conditions. Formaldehyde emits from a variety of construction materials, furnishings, and consumer products. The three products that emit the highest concentrations are medium density fiberboard , hardwood plywood, and particle board. Environmental factors such as temperature and relative humidity can elevate levels because formaldehyde has a high vapor pressure . Formaldehyde levels from building materials are the highest when a building first opens because materials would have less time to off-gas. Formaldehyde levels decrease over time as the sources suppress.
In operating rooms , formaldehyde is produced as a byproduct of electrosurgery and is present in surgical smoke, exposing surgeons and healthcare workers to potentially unsafe concentrations. [ 99 ]
Formaldehyde levels in air can be sampled and tested in several ways, including impinger, treated sorbent, and passive monitors. [ 100 ] The National Institute for Occupational Safety and Health (NIOSH) has measurement methods numbered 2016, 2541, 3500, and 3800. [ 101 ]
In June 2011, the twelfth edition of the National Toxicology Program (NTP) Report on Carcinogens (RoC) changed the listing status of formaldehyde from "reasonably anticipated to be a human carcinogen" to "known to be a human carcinogen." [ 66 ] [ 67 ] [ 68 ] Concurrently, a National Academy of Sciences (NAS) committee was convened and issued an independent review of the draft U.S. EPA IRIS assessment of formaldehyde, providing a comprehensive health effects assessment and quantitative estimates of human risks of adverse effects. [ 102 ]
For most people, irritation from formaldehyde is temporary and reversible, although formaldehyde can cause allergies and is part of the standard patch test series. In 2005–06, it was the seventh-most-prevalent allergen in patch tests (9.0%). [ 103 ] People with formaldehyde allergy are advised to avoid formaldehyde releasers as well (e.g., Quaternium-15 , imidazolidinyl urea , and diazolidinyl urea ). [ 104 ] People who suffer allergic reactions to formaldehyde tend to display lesions on the skin in the areas that have had direct contact with the substance, such as the neck or thighs (often due to formaldehyde released from permanent press finished clothing) or dermatitis on the face (typically from cosmetics). [ 55 ] Formaldehyde has been banned in cosmetics in both Sweden [ 105 ] and Japan . [ 106 ]
In humans, ingestion of as little as 30 millilitres (1.0 US fl oz) of 37% formaldehyde solution can cause death. Other symptoms associated with ingesting such a solution include gastrointestinal damage (vomiting, abdominal pain), and systematic damage (dizziness). [ 74 ] Testing for formaldehyde is by blood and/or urine by gas chromatography–mass spectrometry . Other methods to detect formaldehyde include infrared detection, gas detector tubes, gas detectors using electrochemical sensors, and high-performance liquid chromatography (HPLC). HPLC is the most sensitive. [ 107 ]
The fifteenth edition (2021) of the U.S. National Toxicology Program Report on Carcinogens notes that currently in the U.S. “The general population can be exposed to formaldehyde primarily from breathing indoor or outdoor air, from tobacco smoke, from use of cosmetic products containing formaldehyde, and, to a more limited extent, from ingestion of food and water.” Affected water includes groundwater, surface water, and bottled water. It also notes that occupational exposure can be significant. [ 108 ]
Formaldehyde in food can be present naturally, added as an inadvertent contaminant, or intentionally added as a preservative, disinfectant, or bacteriostatic agent . Cooking and smoking food can also result in formaldehyde being produced in food. Foods that the U.S. National Toxicology Program has reported to have higher levels compared to other foods are fish, seafood, and smoked ham. It also notes formaldehyde in food generally occurs in a bound form and that formaldehyde is unstable in an aqueous solution . [ 109 ]
Scandals have broken in both the 2005 Indonesia food scare and 2007 Vietnam food scare regarding the addition of formaldehyde to foods to extend shelf life. In 2011, after a four-year absence, Indonesian authorities found foods with formaldehyde being sold in markets in a number of regions across the country. [ 110 ] In August 2011, at least at two Carrefour supermarkets, the Central Jakarta Livestock and Fishery Sub-Department found cendol containing 10 parts per million of formaldehyde. [ 111 ] In 2014, the owner of two noodle factories in Bogor , Indonesia, was arrested for using formaldehyde in noodles. [ 112 ] Foods known to be contaminated included noodles, salted fish, and tofu. Chicken and beer were also rumored to be contaminated. In some places, such as China, manufacturers still use formaldehyde illegally as a preservative in foods, which exposes people to formaldehyde ingestion. [ 113 ]
In 2011 in Nakhon Ratchasima , Thailand, truckloads of rotten chicken were treated with formaldehyde for sale in which "a large network", including 11 slaughterhouses run by a criminal gang, were implicated. [ 114 ] In 2012, 1 billion rupiah (almost US$100,000) of fish imported from Pakistan to Batam , Indonesia, were found laced with formaldehyde. [ 115 ]
Formalin contamination of foods has been reported in Bangladesh , with stores and supermarkets selling fruits, fishes, and vegetables that have been treated with formalin to keep them fresh. [ 116 ] However, in 2015, a Formalin Control Bill was passed in the Parliament of Bangladesh with a provision of life-term imprisonment as the maximum punishment as well as a maximum fine of 2,000,000 BDT but not less than 500,000 BDT for importing, producing, or hoarding formalin without a license. [ 117 ]
In the early 1900s, formaldehyde was frequently added by US milk plants to milk bottles as a method of pasteurization due to the lack of knowledge and concern [ 118 ] regarding formaldehyde's toxicity. [ 119 ] [ 120 ]
Formaldehyde was one of the chemicals used in 19th century industrialised food production that was investigated by Dr. Harvey W. Wiley with his famous 'Poison Squad' as part of the US Department of Agriculture . This led to the 1906 Pure Food and Drug Act , a landmark event in the early history of food regulation in the United States . [ 121 ]
Formaldehyde is banned from use in certain applications (preservatives for liquid-cooling and processing systems, slimicides , metalworking-fluid preservatives, and antifouling products) under the Biocidal Products Directive. [ 122 ] [ 123 ] In the EU, the maximum allowed concentration of formaldehyde in finished products is 0.2%, and any product that exceeds 0.05% has to include a warning that the product contains formaldehyde. [ 55 ]
In the United States, Congress passed a bill July 7, 2010, regarding the use of formaldehyde in hardwood plywood , particle board , and medium density fiberboard . The bill limited the allowable amount of formaldehyde emissions from these wood products to 0.09 ppm, and required companies to meet this standard by January 2013. [ 124 ] The final U.S. EPA rule specified maximum emissions of "0.05 ppm formaldehyde for hardwood plywood, 0.09 ppm formaldehyde for particleboard, 0.11 ppm formaldehyde for medium-density fiberboard, and 0.13 ppm formaldehyde for thin medium-density fiberboard." [ 125 ]
Formaldehyde was declared a toxic substance by the 1999 Canadian Environmental Protection Act . [ 126 ]
The FDA is proposing a ban on hair relaxers with formaldehyde due to cancer concerns. [ 127 ] | https://en.wikipedia.org/wiki/O=CH2 |
The nitrite ion has the chemical formula NO − 2 . Nitrite (mostly sodium nitrite ) is widely used throughout chemical and pharmaceutical industries. [ 1 ] The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also refers to organic compounds having the –ONO group, which are esters of nitrous acid .
Sodium nitrite is made industrially by passing a mixture of nitrogen oxides into aqueous sodium hydroxide or sodium carbonate solution: [ 2 ] [ 1 ]
The product is purified by recrystallization. Alkali metal nitrites are thermally stable up to and beyond their melting point (441 °C for KNO 2 ). Ammonium nitrite can be made from dinitrogen trioxide , N 2 O 3 , which is formally the anhydride of nitrous acid:
The nitrite ion has a symmetrical structure (C 2v symmetry ), with both N–O bonds having equal length and a bond angle of about 115°. In valence bond theory , it is described as a resonance hybrid with equal contributions from two canonical forms that are mirror images of each other. In molecular orbital theory , there is a sigma bond between each oxygen atom and the nitrogen atom, and a delocalized pi bond made from the p orbitals on nitrogen and oxygen atoms which is perpendicular to the plane of the molecule. The negative charge of the ion is equally distributed on the two oxygen atoms. Both nitrogen and oxygen atoms carry a lone pair of electrons. Therefore, the nitrite ion is a Lewis base .
In the gas phase it exists predominantly as a trans -planar molecule.
Nitrite is the conjugate base of the weak acid nitrous acid :
Nitrous acid is also highly unstable, tending to disproportionate :
This reaction is slow at 0 °C. [ 2 ] Addition of acid to a solution of a nitrite in the presence of a reducing agent , such as iron(II), is a way to make nitric oxide (NO) in the laboratory.
The formal oxidation state of the nitrogen atom in nitrite is +3. This means that it can be either oxidized to oxidation states +4 and +5, or reduced to oxidation states as low as −3. Standard reduction potentials for reactions directly involving nitrous acid are shown in the table below: [ 4 ]
The data can be extended to include products in lower oxidation states. For example:
Oxidation reactions usually result in the formation of the nitrate ion, with nitrogen in oxidation state +5. For example, oxidation with permanganate ion can be used for quantitative analysis of nitrite (by titration ):
The product of reduction reactions with nitrite ion are varied, depending on the reducing agent used and its strength. With sulfur dioxide , the products are NO and N 2 O; with tin(II) (Sn 2+ ) the product is hyponitrous acid (H 2 N 2 O 2 ); reduction all the way to ammonia (NH 3 ) occurs with hydrogen sulfide . With the hydrazinium cation ( N 2 H + 5 ) the product of nitrite reduction is hydrazoic acid (HN 3 ), an unstable and explosive compound:
which can also further react with nitrite:
This reaction is unusual in that it involves compounds with nitrogen in four different oxidation states. [ 2 ]
Nitrite is detected and analyzed by the Griess Reaction , involving the formation of a deep red-colored azo dye upon treatment of a NO − 2 -containing sample with sulfanilic acid and naphthyl-1-amine in the presence of acid. [ 5 ]
Nitrite is an ambidentate ligand and can form a wide variety of coordination complexes by binding to metal ions in several ways. [ 2 ] Two examples are the red nitrito complex [Co(NH 3 ) 5 (ONO)] 2+ is metastable , isomerizing to the yellow nitro complex [Co(NH 3 ) 5 (NO 2 )] 2+ . Nitrite is processed by several enzymes, all of which utilize coordination complexes.
In nitrification , ammonium is converted to nitrite. Important species include Nitrosomonas . Other bacterial species such as Nitrobacter , are responsible for the oxidation of the nitrite into nitrate.
Nitrite can be reduced to nitric oxide or ammonia by many species of bacteria. Under hypoxic conditions, nitrite may release nitric oxide, which causes potent vasodilation . Several mechanisms for nitrite conversion to NO have been described, including enzymatic reduction by xanthine oxidoreductase , nitrite reductase , and NO synthase (NOS), as well as nonenzymatic acidic disproportionation reactions.
Azo dyes and other colorants are prepared by the process called diazotization , which requires nitrite. [ 1 ]
The addition of nitrites and nitrates to processed meats such as ham, bacon, and sausages speeds up the curing of meat and also impart an attractive colour. [ 8 ]
The academic and industrial consensus is that nitrites also reduces growth and toxin production of Clostridium botulinum . [ 9 ] [ 10 ] [ 11 ] On the other hand, a 2018 study (full text not available) by the British Meat Producers Association determined that legally permitted levels of nitrite do not affect the growth of C. botulinum . [ 12 ] In the U.S., meat cannot be labeled as "cured" without the addition of nitrite. [ 13 ] [ 14 ] [ 15 ] In some countries, cured-meat products are manufactured without nitrate or nitrite, and without nitrite from vegetable sources. Parma ham , produced without nitrite since 1993, was reported in 2018 to have caused no cases of botulism. This is because the interior of the muscle is sterile and the surface is exposed to oxygen. [ 8 ] Other manufacture processes do not assure these conditions, and reduction of nitrite results in toxin production. [ 16 ]
In mice, food rich in nitrites together with unsaturated fats can prevent hypertension by forming nitro fatty acids that inhibit soluble epoxide hydrolase , which is one explanation for the apparent health effect of the Mediterranean diet . [ 17 ] Adding nitrites to meat has been shown to generate known carcinogens ; the World Health Organization (WHO) advises that eating 50 g (1.8 oz) of nitrite processed meat a day would raise the risk of getting bowel cancer by 18% over a lifetime. [ 8 ]
The recommended maximum limits by the World Health Organization in drinking water are 3 mg L −1 and 50 mg L −1 for nitrite and nitrate ions, respectively. [ 18 ] Ingesting too much nitrite and/or nitrate through well water is suspected to cause methemoglobinemia . [ 19 ]
95% of the nitrite ingested in modern diets comes from bacterial conversion of nitrates naturally found in vegetables. [ 20 ] However, potentially cancer-causing nitroso compounds are not made in the pH-neutral colon. They are mostly made in the acidic stomach. [ 21 ] [ 22 ]
Nitrite reacts with the meat's myoglobin by attaching to the heme iron atom, forming reddish-brown nitrosomyoglobin and the characteristic pink "fresh" color of nitrosohemochrome or nitrosyl-heme upon cooking. [ 23 ] In the US, nitrite has been formally used since 1925. According to scientists working for the industry group American Meat Institute , this use of nitrite started in the Middle Ages . [ 24 ] Historians and epidemiologists argue that the widespread use of nitrite in meat-curing is closely linked to the development of industrial meat-processing. [ 25 ] [ 26 ] French investigative journalist Guillaume Coudray [ fr ] asserts that the meat industry chooses to cure its meats with nitrite even though it is established that this chemical gives rise to cancer-causing nitroso -compounds. [ 27 ] Some traditional and artisanal producers avoid nitrites.
Addition of ascorbic acid , erythorbic acid , or one of their salts enhance the binding of nitrite to the iron atom in myoglobin. [ 23 ] These chemicals also reduce the formation of nitrosamine in the stomach, but only when the fat content of a meal is less than 10%, beyond which they instead increase the formation of nitrosamine. [ 28 ] [ 29 ]
Nitrites in the form of sodium nitrite and amyl nitrite are components of many cyanide antidote kits. [ 30 ] Both of these compounds bind to hemoglobin and oxidize the Fe 2+ ions to Fe 3+ ions forming methemoglobin . Methemoglobin, in turn, binds to cyanide (CN), creating cyanmethemoglobin, effectively removing cyanide from the complex IV of the electron transport chain (ETC) in mitochondria , which is the primary site of disruption caused by cyanide. Another mechanism by which nitrites help treat cyanide toxicity is the generation of nitric oxide (NO). NO displaces the CN from the cytochrome c oxidase (ETC complex IV), making it available for methemoglobin to bind. [ 31 ]
In organic chemistry , alkyl nitrites are esters of nitrous acid and contain the nitrosoxy functional group. Nitro compounds contain the C–NO 2 group. Nitrites have the general formula RONO, where R is an aryl or alkyl group. Amyl nitrite and other alkyl nitrites have a vasodilating action and must be handled in the laboratory with caution. They are sometimes used in medicine for the treatment of heart diseases. A classic named reaction for the synthesis of alkyl nitrites is the Meyer synthesis [ 32 ] [ 33 ] in which alkyl halides react with metallic nitrites to a mixture to nitroalkanes and nitrites.
Nitrite salts can react with secondary amines to produce N -nitrosamines , which are suspected of causing stomach cancer . The World Health Organization (WHO) advises that each 50 g (1.8 oz) of processed meat eaten a day would raise the risk of getting bowel cancer by 18% over a lifetime; processed meat refers to meat that has been transformed through fermentation, nitrite curing, salting, smoking, or other processes to enhance flavor or improve preservation. The World Health Organization's review of more than 400 studies concluded in 2015 that there was sufficient evidence that processed meats caused cancer, particularly colon cancer; the WHO's International Agency for Research on Cancer (IARC) classified processed meats as carcinogenic to humans ( Group 1 ). [ 8 ] [ 34 ]
Nitrite (ingested) under conditions that result in endogenous nitrosation , specifically the production of nitrosamine , has been classified as Probably carcinogenic to humans ( Group 2A ) by the IARC. [ 35 ] | https://en.wikipedia.org/wiki/O=N-O |
The nitrite ion has the chemical formula NO − 2 . Nitrite (mostly sodium nitrite ) is widely used throughout chemical and pharmaceutical industries. [ 1 ] The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also refers to organic compounds having the –ONO group, which are esters of nitrous acid .
Sodium nitrite is made industrially by passing a mixture of nitrogen oxides into aqueous sodium hydroxide or sodium carbonate solution: [ 2 ] [ 1 ]
The product is purified by recrystallization. Alkali metal nitrites are thermally stable up to and beyond their melting point (441 °C for KNO 2 ). Ammonium nitrite can be made from dinitrogen trioxide , N 2 O 3 , which is formally the anhydride of nitrous acid:
The nitrite ion has a symmetrical structure (C 2v symmetry ), with both N–O bonds having equal length and a bond angle of about 115°. In valence bond theory , it is described as a resonance hybrid with equal contributions from two canonical forms that are mirror images of each other. In molecular orbital theory , there is a sigma bond between each oxygen atom and the nitrogen atom, and a delocalized pi bond made from the p orbitals on nitrogen and oxygen atoms which is perpendicular to the plane of the molecule. The negative charge of the ion is equally distributed on the two oxygen atoms. Both nitrogen and oxygen atoms carry a lone pair of electrons. Therefore, the nitrite ion is a Lewis base .
In the gas phase it exists predominantly as a trans -planar molecule.
Nitrite is the conjugate base of the weak acid nitrous acid :
Nitrous acid is also highly unstable, tending to disproportionate :
This reaction is slow at 0 °C. [ 2 ] Addition of acid to a solution of a nitrite in the presence of a reducing agent , such as iron(II), is a way to make nitric oxide (NO) in the laboratory.
The formal oxidation state of the nitrogen atom in nitrite is +3. This means that it can be either oxidized to oxidation states +4 and +5, or reduced to oxidation states as low as −3. Standard reduction potentials for reactions directly involving nitrous acid are shown in the table below: [ 4 ]
The data can be extended to include products in lower oxidation states. For example:
Oxidation reactions usually result in the formation of the nitrate ion, with nitrogen in oxidation state +5. For example, oxidation with permanganate ion can be used for quantitative analysis of nitrite (by titration ):
The product of reduction reactions with nitrite ion are varied, depending on the reducing agent used and its strength. With sulfur dioxide , the products are NO and N 2 O; with tin(II) (Sn 2+ ) the product is hyponitrous acid (H 2 N 2 O 2 ); reduction all the way to ammonia (NH 3 ) occurs with hydrogen sulfide . With the hydrazinium cation ( N 2 H + 5 ) the product of nitrite reduction is hydrazoic acid (HN 3 ), an unstable and explosive compound:
which can also further react with nitrite:
This reaction is unusual in that it involves compounds with nitrogen in four different oxidation states. [ 2 ]
Nitrite is detected and analyzed by the Griess Reaction , involving the formation of a deep red-colored azo dye upon treatment of a NO − 2 -containing sample with sulfanilic acid and naphthyl-1-amine in the presence of acid. [ 5 ]
Nitrite is an ambidentate ligand and can form a wide variety of coordination complexes by binding to metal ions in several ways. [ 2 ] Two examples are the red nitrito complex [Co(NH 3 ) 5 (ONO)] 2+ is metastable , isomerizing to the yellow nitro complex [Co(NH 3 ) 5 (NO 2 )] 2+ . Nitrite is processed by several enzymes, all of which utilize coordination complexes.
In nitrification , ammonium is converted to nitrite. Important species include Nitrosomonas . Other bacterial species such as Nitrobacter , are responsible for the oxidation of the nitrite into nitrate.
Nitrite can be reduced to nitric oxide or ammonia by many species of bacteria. Under hypoxic conditions, nitrite may release nitric oxide, which causes potent vasodilation . Several mechanisms for nitrite conversion to NO have been described, including enzymatic reduction by xanthine oxidoreductase , nitrite reductase , and NO synthase (NOS), as well as nonenzymatic acidic disproportionation reactions.
Azo dyes and other colorants are prepared by the process called diazotization , which requires nitrite. [ 1 ]
The addition of nitrites and nitrates to processed meats such as ham, bacon, and sausages speeds up the curing of meat and also impart an attractive colour. [ 8 ]
The academic and industrial consensus is that nitrites also reduces growth and toxin production of Clostridium botulinum . [ 9 ] [ 10 ] [ 11 ] On the other hand, a 2018 study (full text not available) by the British Meat Producers Association determined that legally permitted levels of nitrite do not affect the growth of C. botulinum . [ 12 ] In the U.S., meat cannot be labeled as "cured" without the addition of nitrite. [ 13 ] [ 14 ] [ 15 ] In some countries, cured-meat products are manufactured without nitrate or nitrite, and without nitrite from vegetable sources. Parma ham , produced without nitrite since 1993, was reported in 2018 to have caused no cases of botulism. This is because the interior of the muscle is sterile and the surface is exposed to oxygen. [ 8 ] Other manufacture processes do not assure these conditions, and reduction of nitrite results in toxin production. [ 16 ]
In mice, food rich in nitrites together with unsaturated fats can prevent hypertension by forming nitro fatty acids that inhibit soluble epoxide hydrolase , which is one explanation for the apparent health effect of the Mediterranean diet . [ 17 ] Adding nitrites to meat has been shown to generate known carcinogens ; the World Health Organization (WHO) advises that eating 50 g (1.8 oz) of nitrite processed meat a day would raise the risk of getting bowel cancer by 18% over a lifetime. [ 8 ]
The recommended maximum limits by the World Health Organization in drinking water are 3 mg L −1 and 50 mg L −1 for nitrite and nitrate ions, respectively. [ 18 ] Ingesting too much nitrite and/or nitrate through well water is suspected to cause methemoglobinemia . [ 19 ]
95% of the nitrite ingested in modern diets comes from bacterial conversion of nitrates naturally found in vegetables. [ 20 ] However, potentially cancer-causing nitroso compounds are not made in the pH-neutral colon. They are mostly made in the acidic stomach. [ 21 ] [ 22 ]
Nitrite reacts with the meat's myoglobin by attaching to the heme iron atom, forming reddish-brown nitrosomyoglobin and the characteristic pink "fresh" color of nitrosohemochrome or nitrosyl-heme upon cooking. [ 23 ] In the US, nitrite has been formally used since 1925. According to scientists working for the industry group American Meat Institute , this use of nitrite started in the Middle Ages . [ 24 ] Historians and epidemiologists argue that the widespread use of nitrite in meat-curing is closely linked to the development of industrial meat-processing. [ 25 ] [ 26 ] French investigative journalist Guillaume Coudray [ fr ] asserts that the meat industry chooses to cure its meats with nitrite even though it is established that this chemical gives rise to cancer-causing nitroso -compounds. [ 27 ] Some traditional and artisanal producers avoid nitrites.
Addition of ascorbic acid , erythorbic acid , or one of their salts enhance the binding of nitrite to the iron atom in myoglobin. [ 23 ] These chemicals also reduce the formation of nitrosamine in the stomach, but only when the fat content of a meal is less than 10%, beyond which they instead increase the formation of nitrosamine. [ 28 ] [ 29 ]
Nitrites in the form of sodium nitrite and amyl nitrite are components of many cyanide antidote kits. [ 30 ] Both of these compounds bind to hemoglobin and oxidize the Fe 2+ ions to Fe 3+ ions forming methemoglobin . Methemoglobin, in turn, binds to cyanide (CN), creating cyanmethemoglobin, effectively removing cyanide from the complex IV of the electron transport chain (ETC) in mitochondria , which is the primary site of disruption caused by cyanide. Another mechanism by which nitrites help treat cyanide toxicity is the generation of nitric oxide (NO). NO displaces the CN from the cytochrome c oxidase (ETC complex IV), making it available for methemoglobin to bind. [ 31 ]
In organic chemistry , alkyl nitrites are esters of nitrous acid and contain the nitrosoxy functional group. Nitro compounds contain the C–NO 2 group. Nitrites have the general formula RONO, where R is an aryl or alkyl group. Amyl nitrite and other alkyl nitrites have a vasodilating action and must be handled in the laboratory with caution. They are sometimes used in medicine for the treatment of heart diseases. A classic named reaction for the synthesis of alkyl nitrites is the Meyer synthesis [ 32 ] [ 33 ] in which alkyl halides react with metallic nitrites to a mixture to nitroalkanes and nitrites.
Nitrite salts can react with secondary amines to produce N -nitrosamines , which are suspected of causing stomach cancer . The World Health Organization (WHO) advises that each 50 g (1.8 oz) of processed meat eaten a day would raise the risk of getting bowel cancer by 18% over a lifetime; processed meat refers to meat that has been transformed through fermentation, nitrite curing, salting, smoking, or other processes to enhance flavor or improve preservation. The World Health Organization's review of more than 400 studies concluded in 2015 that there was sufficient evidence that processed meats caused cancer, particularly colon cancer; the WHO's International Agency for Research on Cancer (IARC) classified processed meats as carcinogenic to humans ( Group 1 ). [ 8 ] [ 34 ]
Nitrite (ingested) under conditions that result in endogenous nitrosation , specifically the production of nitrosamine , has been classified as Probably carcinogenic to humans ( Group 2A ) by the IARC. [ 35 ] | https://en.wikipedia.org/wiki/O=N−O− |
Ozone ( / ˈ oʊ z oʊ n / ) (or trioxygen ) is an inorganic molecule with the chemical formula O 3 . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O 2 , breaking down in the lower atmosphere to O 2 ( dioxygen ). Ozone is formed from dioxygen by the action of ultraviolet (UV) light and electrical discharges within the Earth's atmosphere . It is present in very low concentrations throughout the atmosphere, with its highest concentration high in the ozone layer of the stratosphere , which absorbs most of the Sun 's ultraviolet (UV) radiation.
Ozone's odor is reminiscent of chlorine , and detectable by many people at concentrations of as little as 0.1 ppm in air. Ozone's O 3 structure was determined in 1865. The molecule was later proven to have a bent structure and to be weakly diamagnetic . At standard temperature and pressure , ozone is a pale blue gas that condenses at cryogenic temperatures to a dark blue liquid and finally a violet-black solid . Ozone's instability with regard to more common dioxygen is such that both concentrated gas and liquid ozone may decompose explosively at elevated temperatures, physical shock, or fast warming to the boiling point. [ 5 ] [ 6 ] It is therefore used commercially only in low concentrations.
Ozone is a powerful oxidizing agent (far more so than dioxygen) and has many industrial and consumer applications related to oxidation. This same high oxidizing potential, however, causes ozone to damage mucous and respiratory tissues in animals, and also tissues in plants, above concentrations of about 0.1 ppm . While this makes ozone a potent respiratory hazard and pollutant near ground level , a higher concentration in the ozone layer (from two to eight ppm) is beneficial, preventing damaging UV light from reaching the Earth's surface.
The trivial name ozone is the most commonly used and preferred IUPAC name . The systematic names 2λ 4 -trioxidiene [ dubious – discuss ] and catena-trioxygen , valid IUPAC names, are constructed according to the substitutive and additive nomenclatures , respectively. The name ozone derives from ozein (ὄζειν), the Greek neuter present participle for smell, [ 7 ] referring to ozone's distinctive smell.
In appropriate contexts, ozone can be viewed as trioxidane with two hydrogen atoms removed, and as such, trioxidanylidene may be used as a systematic name, according to substitutive nomenclature. By default, these names pay no regard to the radicality of the ozone molecule. In an even more specific context, this can also name the non-radical singlet ground state, whereas the diradical state is named trioxidanediyl .
Trioxidanediyl (or ozonide ) is used, non-systematically, to refer to the substituent group (-OOO-). Care should be taken to avoid confusing the name of the group for the context-specific name for the ozone given above.
In 1785, Dutch chemist Martinus van Marum was conducting experiments involving electrical sparking above water when he noticed an unusual smell, which he attributed to the electrical reactions, failing to realize that he had in fact produced ozone. [ 8 ] [ 9 ]
A half century later, Christian Friedrich Schönbein noticed the same pungent odour and recognized it as the smell often following a bolt of lightning . In 1839, he succeeded in isolating the gaseous chemical and named it "ozone", from the Greek word ozein ( ὄζειν ) meaning "to smell". [ 10 ] [ 11 ] For this reason, Schönbein is generally credited with the discovery of ozone. [ 12 ] [ 13 ] [ 14 ] [ 8 ] He also noted the similarity of ozone smell to the smell of phosphorus, and in 1844 proved that the product of reaction of white phosphorus with air is identical. [ 10 ] A subsequent effort to call ozone "electrified oxygen" he ridiculed by proposing to call the ozone from white phosphorus "phosphorized oxygen". [ 10 ] The chemical formula for ozone, O 3 , was not determined until 1865 by Jacques-Louis Soret [ 15 ] and confirmed by Schönbein in 1867. [ 10 ] [ 16 ]
For much of the second half of the 19th century and well into the 20th, ozone was considered a healthy component of the environment by naturalists and health-seekers. Beaumont, California , had as its official slogan "Beaumont: Zone of Ozone", as evidenced on postcards and Chamber of Commerce letterhead. [ 17 ] Naturalists working outdoors often considered the higher elevations beneficial because of their ozone content which was readily monitored. [ 18 ] "There is quite a different atmosphere [at higher elevation] with enough ozone to sustain the necessary energy [to work]", wrote naturalist Henry Henshaw , working in Hawaii. [ 19 ] Seaside air was considered to be healthy because of its believed ozone content. The smell giving rise to this belief is in fact that of halogenated seaweed metabolites [ 20 ] and dimethyl sulfide . [ 21 ]
Much of ozone's appeal seems to have resulted from its "fresh" smell, which evoked associations with purifying properties. Scientists noted its harmful effects. In 1873 James Dewar and John Gray McKendrick documented that frogs grew sluggish, birds gasped for breath, and rabbits' blood showed decreased levels of oxygen after exposure to "ozonized air", which "exercised a destructive action". [ 22 ] [ 12 ] Schönbein himself reported that chest pains, irritation of the mucous membranes , and difficulty breathing occurred as a result of inhaling ozone, and small mammals died. [ 23 ] In 1911, Leonard Hill and Martin Flack stated in the Proceedings of the Royal Society B that ozone's healthful effects "have, by mere iteration, become part and parcel of common belief; and yet exact physiological evidence in favour of its good effects has been hitherto almost entirely wanting ... The only thoroughly well-ascertained knowledge concerning the physiological effect of ozone, so far attained, is that it causes irritation and œdema of the lungs, and death if inhaled in relatively strong concentration for any time." [ 12 ] [ 24 ]
During World War I , ozone was tested at Queen Alexandra Military Hospital in London as a possible disinfectant for wounds. The gas was applied directly to wounds for as long as 15 minutes. This resulted in damage to both bacterial cells and human tissue. Other sanitizing techniques, such as irrigation with antiseptics , were found preferable. [ 12 ] [ 25 ]
Until the 1920s, it was not certain whether small amounts of oxozone , O 4 , were also present in ozone samples due to the difficulty of applying analytical chemistry techniques to the explosive concentrated chemical. [ 26 ] [ 27 ] In 1923, Georg-Maria Schwab (working for his doctoral thesis under Ernst Hermann Riesenfeld ) was the first to successfully solidify ozone and perform accurate analysis which conclusively refuted the oxozone hypothesis. [ 26 ] [ 27 ] Further hitherto unmeasured physical properties of pure concentrated ozone were determined by the Riesenfeld group in the 1920s. [ 26 ]
Ozone is a colourless or pale blue gas, slightly soluble in water, and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, in which it forms a blue solution. At 161 K (−112 °C; −170 °F), it condenses to form a dark blue liquid . It is dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below 80 K (−193.2 °C; −315.7 °F), it forms a violet-black solid . [ 28 ]
Ozone has a very specific sharp odour somewhat resembling chlorine bleach . Most people can detect it at the 0.01 μmol/mol level in air. Exposure of 0.1 to 1 μmol/mol produces headaches and burning eyes and irritates the respiratory passages. [ 29 ] Even low concentrations of ozone in air are very destructive to organic materials such as latex, plastics, and animal lung tissue.
The ozone molecule is weakly diamagnetic . [ 30 ]
According to experimental evidence from microwave spectroscopy , ozone is a bent molecule, with C 2v symmetry (similar to the water molecule). [ 31 ] The O–O distances are 127.2 pm (1.272 Å ). The O–O–O angle is 116.78°. [ 32 ] The central atom is sp ² hybridized with one lone pair. Ozone is a polar molecule with a dipole moment of 0.53 D . [ 33 ] The molecule can be represented as a resonance hybrid with two contributing structures, each with a single bond on one side and double bond on the other. The arrangement possesses an overall bond order of 1.5 for both sides. It is isoelectronic with the nitrite anion . Naturally occurring ozone can be composed of substituted isotopes ( 16 O, 17 O, 18 O). A cyclic form has been predicted but not observed.
Ozone is among the most powerful oxidizing agents known, far stronger than O 2 . It is also unstable at high concentrations, decaying into ordinary diatomic oxygen. Its half-life varies with atmospheric conditions such as temperature, humidity, and air movement. Under laboratory conditions, the half-life will average ~1500 minutes (25 hours) in still air at room temperature (24 °C), zero humidity with zero air changes per hour. [ 34 ]
This reaction proceeds more rapidly with increasing temperature. Deflagration of ozone can be triggered by a spark and can occur in ozone concentrations of 10 wt% or higher. [ 35 ]
Ozone can also be produced from oxygen at the anode of an electrochemical cell. This reaction can create smaller quantities of ozone for research purposes. [ 36 ]
This can be observed as an unwanted reaction in a Hoffman apparatus during the electrolysis of water when the voltage is set above the necessary voltage.
Ozone oxidizes most metals (except gold , platinum , and iridium ) into oxides of the metals in their highest oxidation state . For example:
Ozone oxidizes nitric oxide to nitrogen dioxide :
This reaction is accompanied by chemiluminescence .
The NO 2 can be further oxidized to nitrate radical :
The NO 3 formed can react with NO 2 to form dinitrogen pentoxide ( N 2 O 5 ).
Solid nitronium perchlorate can be made from NO 2 , ClO 2 , and O 3 gases:
Ozone does not react with ammonium salts , but it oxidizes ammonia to ammonium nitrate :
Ozone reacts with carbon to form carbon dioxide , even at room temperature:
Ozone oxidizes sulfides to sulfates . For example, lead(II) sulfide is oxidized to lead(II) sulfate :
Sulfuric acid can be produced from ozone, water and either elemental sulfur or sulfur dioxide :
In the gas phase , ozone reacts with hydrogen sulfide to form sulfur dioxide:
In an aqueous solution, however, two competing simultaneous reactions occur, one to produce elemental sulfur, and one to produce sulfuric acid :
Alkenes can be oxidatively cleaved by ozone, in a process called ozonolysis , giving alcohols, aldehydes, ketones, and carboxylic acids, depending on the second step of the workup.
Ozone can also cleave alkynes to form an acid anhydride or diketone product. [ 38 ] If the reaction is performed in the presence of water, the anhydride hydrolyzes to give two carboxylic acids .
Usually ozonolysis is carried out in a solution of dichloromethane , at a temperature of −78 °C. After a sequence of cleavage and rearrangement, an organic ozonide is formed. With reductive workup (e.g. zinc in acetic acid or dimethyl sulfide ), ketones and aldehydes will be formed, with oxidative workup (e.g. aqueous or alcoholic hydrogen peroxide ), carboxylic acids will be formed. [ 39 ]
All three atoms of ozone may also react, as in the reaction of tin(II) chloride with hydrochloric acid and ozone:
Iodine perchlorate can be made by treating iodine dissolved in cold anhydrous perchloric acid with ozone:
Ozone could also react with potassium iodide to give oxygen and iodine gas that can be titrated for quantitative determination: [ 40 ]
Ozone can be used for combustion reactions and combustible gases; ozone provides higher temperatures than burning in dioxygen ( O 2 ). The following is a reaction for the combustion of carbon subnitride which can also cause higher temperatures:
Ozone can react at cryogenic temperatures. At 77 K (−196.2 °C; −321.1 °F), atomic hydrogen reacts with liquid ozone to form a hydrogen superoxide radical , which dimerizes : [ 41 ]
Ozone is a toxic substance, [ 42 ] [ 43 ] commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers, ...).
The catalytic decomposition of ozone is very important to reduce pollution. This type of decomposition is the most widely used, especially with solid catalysts, and it has many advantages such as a higher conversion with a lower temperature. Furthermore, the product and the catalyst can be instantaneously separated, and this way the catalyst can be easily recovered without using any separation operation. The most-used materials in the catalytic decomposition of ozone in the gas phase are manganese dioxide , transition metals such as Mn, Co, Cu, Fe, Ni, or Ag, and noble metals such as Pt, Rh, or Pd.
Free radicals of chlorine (Cl · ), formed by the action of ultraviolet radiation on chlorofluorocarbons (CFCs) and sea salt, are known to catalyze the breakdown of ozone in the atmosphere.
There are two other possibilities for decomposing ozone in the gas phase:
The uncatalyzed process of ozone decomposition in the gas phase is a complex reaction involving two elementary reactions that finally lead to molecular oxygen, [ 45 ] and this means that the reaction order and the rate law cannot be determined by the stoichiometry of the overall reaction.
Overall reaction: 2 O 3 ⟶ 3 O 2 {\displaystyle {\ce {2 O3 -> 3 O2}}}
Rate law (observed): V = K o b s ⋅ [ O 3 ] 2 [ O 2 ] {\displaystyle V={\frac {K_{obs}\cdot [{\ce {O3}}]^{2}}{[{\ce {O2}}]}}}
where K o b s {\displaystyle K_{obs}} is the observed rate constant and V {\displaystyle V} is the reaction rate. From the rate law above it can be determined that the partial order respect to molecular oxygen is −1 and respect to ozone is 2; therefore, the global reaction order is 1.
The first step is a unimolecular reaction wherein one molecule of ozone decomposes into two products (molecular oxygen and oxygen). The oxygen atom from the first step is a reactive intermediate because it participates as a reactant in the second step, which is a bimolecular reaction because there are two different reactants (ozone and oxygen) that give rise to molecular oxygen.
Step 1: Unimolecular reaction O 3 ⟶ O 2 + O {\displaystyle {\ce {O3 -> O2 + O}}}
Step 2: Bimolecular reaction O 3 + O ⟶ 2 O 2 {\displaystyle {\ce {O3 + O -> 2 O2}}}
These two steps have different reaction rates and rate constants. The reaction rate laws for each of these steps are shown below:
The following mechanism allows to explain the rate law of the ozone decomposition observed experimentally, and also it allows to determine the reaction orders with respect to ozone and oxygen, with which the overall reaction order will be determined.
The first step is assumed reversible and faster than the second reaction, which means that the slower rate determining step is the second reaction. This step determines the rate of product formation, and so V = V 2 {\displaystyle V=V_{2}} . However, this equation depends on the concentration of oxygen (intermediate), which does not appear in the observed rate law. Since the first step is a rapid equilibrium, the concentration of the intermediate can be determined as follows:
Then using these equations, the formation rate of molecular oxygen is as shown below:
The mechanism is consistent with the rate law observed experimentally if the rate constant ( K obs ) is given in terms of the individual mechanistic steps' rate constants as follows: [ 46 ]
where K obs = K 2 ⋅ K 1 K − 1 {\displaystyle K_{\text{obs}}={K_{2}\cdot K_{1} \over K_{-1}}}
Reduction of ozone gives the ozonide anion, O − 3 . Derivatives of this anion are explosive and must be stored at cryogenic temperatures. Ozonides for all the alkali metals are known. KO 3 , RbO 3 , and CsO 3 can be prepared from their respective superoxides:
Although KO 3 can be formed as above, it can also be formed from potassium hydroxide and ozone: [ 47 ]
NaO 3 and LiO 3 must be prepared by action of CsO 3 in liquid NH 3 on an ion-exchange resin containing Na + or Li + ions: [ 48 ]
A solution of calcium in ammonia reacts with ozone to give ammonium ozonide and not calcium ozonide: [ 41 ]
Ozone can be used to remove iron and manganese from water , forming a precipitate which can be filtered:
Ozone oxidizes dissolved hydrogen sulfide in water to sulfurous acid :
These three reactions are central in the use of ozone-based well water treatment.
Ozone detoxifies cyanides by converting them to cyanates .
Ozone completely decomposes urea : [ 49 ]
Ozone is a bent triatomic molecule with three vibrational modes: the symmetric stretch (1103.157 cm −1 ), bend (701.42 cm −1 ) and antisymmetric stretch (1042.096 cm −1 ). [ 50 ] The symmetric stretch and bend are weak absorbers, but the antisymmetric stretch is strong and responsible for ozone being an important minor greenhouse gas . This IR band is also used to detect ambient and atmospheric ozone although UV-based measurements are more common. [ 51 ]
The electromagnetic spectrum of ozone is quite complex. An overview can be seen at the MPI Mainz UV/VIS Spectral Atlas of Gaseous Molecules of Atmospheric Interest. [ 52 ]
All of the bands are dissociative, meaning that the molecule falls apart to O + O 2 after absorbing a photon. The most important absorption is the Hartley band, extending from slightly above 300 nm down to slightly above 200 nm. It is this band that is responsible for absorbing UV C in the stratosphere.
On the high wavelength side, the Hartley band transitions to the so-called Huggins band, which falls off rapidly until disappearing by ~360 nm. Above 400 nm, extending well out into the NIR, are the Chappius and Wulf bands. There, unstructured absorption bands are useful for detecting high ambient concentrations of ozone, but are so weak that they do not have much practical effect.
There are additional absorption bands in the far UV, which increase slowly from 200 nm down to reaching a maximum at ~120 nm.
The standard way to express total ozone levels (the amount of ozone in a given vertical column) in the atmosphere is by using Dobson units . Point measurements are reported as mole fractions in nmol/mol (parts per billion, ppb) or as concentrations in μg/m 3 . The study of ozone concentration in the atmosphere started in the 1920s. [ 53 ]
The highest levels of ozone in the atmosphere are in the stratosphere , in a region also known as the ozone layer between about 10 and 50 km above the surface (or between about 6 and 31 miles). However, even in this "layer", the ozone concentrations are only two to eight parts per million, so most of the oxygen there is dioxygen, O 2 , at about 210,000 parts per million by volume. [ 54 ]
Ozone in the stratosphere is mostly produced from short-wave ultraviolet rays between 240 and 160 nm. Oxygen starts to absorb weakly at 240 nm in the Herzberg bands, but most of the oxygen is dissociated by absorption in the strong Schumann–Runge bands between 200 and 160 nm where ozone does not absorb. While shorter wavelength light, extending to even the X-Ray limit, is energetic enough to dissociate molecular oxygen, there is relatively little of it, and, the strong solar emission at Lyman-alpha, 121 nm, falls at a point where molecular oxygen absorption is a minimum. [ 55 ]
The process of ozone creation and destruction is called the Chapman cycle and starts with the photolysis of molecular oxygen
followed by reaction of the oxygen atom with another molecule of oxygen to form ozone.
where "M" denotes the third body that carries off the excess energy of the reaction. The ozone molecule can then absorb a UV-C photon and dissociate
The excess kinetic energy heats the stratosphere when the O atoms and the molecular oxygen fly apart and collide with other molecules. This conversion of UV light into kinetic energy warms the stratosphere. The oxygen atoms produced in the photolysis of ozone then react back with other oxygen molecule as in the previous step to form more ozone. In the clear atmosphere, with only nitrogen and oxygen, ozone can react with the atomic oxygen to form two molecules of O 2 :
An estimate of the rate of this termination step to the cycling of atomic oxygen back to ozone can be found simply by taking the ratios of the concentration of O 2 to O 3 . The termination reaction is catalysed by the presence of certain free radicals, of which the most important are hydroxyl (OH), nitric oxide (NO) and atomic chlorine (Cl) and bromine (Br). In the second half of the 20th century, the amount of ozone in the stratosphere was discovered to be declining , mostly because of increasing concentrations of chlorofluorocarbons (CFC) and similar chlorinated and brominated organic molecules . The concern over the health effects of the decline led to the 1987 Montreal Protocol , the ban on the production of many ozone-depleting chemicals and in the first and second decade of the 21st century the beginning of the recovery of stratospheric ozone concentrations.
Ozone in the ozone layer filters out sunlight wavelengths from about 200 nm UV rays to 315 nm, with ozone peak absorption at about 250 nm. [ 56 ] This ozone UV absorption is important to life, since it extends the absorption of UV by ordinary oxygen and nitrogen in air (which absorb all wavelengths < 200 nm) through the lower UV-C (200–280 nm) and the entire UV-B band (280–315 nm). The small unabsorbed part that remains of UV-B after passage through ozone causes sunburn in humans, and direct DNA damage in living tissues in both plants and animals. Ozone's effect on mid-range UV-B rays is illustrated by its effect on UV-B at 290 nm, which has a radiation intensity 350 million times as powerful at the top of the atmosphere as at the surface. Nevertheless, enough of UV-B radiation at similar frequency reaches the ground to cause some sunburn, and these same wavelengths are also among those responsible for the production of vitamin D in humans.
The ozone layer has little effect on the longer UV wavelengths called UV-A (315–400 nm), but this radiation does not cause sunburn or direct DNA damage. While UV-A probably does cause long-term skin damage in certain humans, it is not as dangerous to plants and to the health of surface-dwelling organisms on Earth in general (see ultraviolet for more information on near ultraviolet).
Ground-level ozone (or tropospheric ozone) is an atmospheric pollutant. [ 57 ] It is not emitted directly by car engines or by industrial operations, but formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers downwind.
Ozone reacts directly with some hydrocarbons such as aldehydes and thus begins their removal from the air, but the products are themselves key components of smog . Ozone photolysis by UV light leads to production of the hydroxyl radical HO• and this plays a part in the removal of hydrocarbons from the air, but is also the first step in the creation of components of smog such as peroxyacyl nitrates , which can be powerful eye irritants. The atmospheric lifetime of tropospheric ozone is about 22 days; its main removal mechanisms are being deposited to the ground, the above-mentioned reaction giving HO•, and by reactions with OH and the peroxy radical HO 2 •. [ 58 ]
There is evidence of significant reduction in agricultural yields because of increased ground-level ozone and pollution which interferes with photosynthesis and stunts overall growth of some plant species. [ 59 ] [ 60 ] The United States Environmental Protection Agency (EPA) has proposed a secondary regulation to reduce crop damage, in addition to the primary regulation designed for the protection of human health.
Certain examples of cities with elevated ozone readings are Denver, Colorado ; Houston, Texas ; and Mexico City , Mexico . Houston has a reading of around 41 nmol/mol, while Mexico City is far more hazardous, with a reading of about 125 nmol/mol. [ 60 ]
Ground-level ozone, or tropospheric ozone, is the most concerning type of ozone pollution in urban areas and is increasing in general. [ 61 ] Ozone pollution in urban areas affects denser populations, and is worsened by high populations of vehicles, which emit pollutants NO 2 and VOCs , the main contributors to problematic ozone levels. [ 62 ] Ozone pollution in urban areas is especially concerning with increasing temperatures, raising heat-related mortality during heat waves . [ 63 ] During heat waves in urban areas, ground level ozone pollution can be 20% higher than usual. [ 64 ] Ozone pollution in urban areas reaches higher levels of exceedance in the summer and autumn, which may be explained by weather patterns and traffic patterns. [ 62 ] People experiencing poverty are more affected by pollution in general, even though these populations are less likely to be contributing to pollution levels. [ 65 ]
As mentioned above, Denver, Colorado, is one of the many cities in the U.S. that have high amounts of ozone. According to the American Lung Association , the Denver–Aurora area is the 14th most ozone-polluted area in the U.S. [ 66 ] The problem of high ozone levels is not new to this area. In 2004, the EPA allotted the Denver Metro /North Front Range [ b ] as non-attainment areas per 1997's 8-hour ozone standard, [ 67 ] but later deferred this status until 2007. The non-attainment standard indicates that an area does not meet the EPA's air quality standards. The Colorado Ozone Action Plan was created in response, and numerous changes were implemented from this plan. The first major change was that car emission testing was expanded across the state to more counties that did not previously mandate emissions testing, like areas of Larimer and Weld County. There have also been changes made to decrease Nitrogen Oxides (NOx) and Volatile Organic Compound (VOC) emissions, which should help lower ozone levels.
One large contributor to high ozone levels in the area is the oil and natural gas industry situated in the Denver-Julesburg Basin (DJB) which overlaps with a majority of Colorado's metropolitan areas. Ozone is produced naturally in the Earth's stratosphere, but is also produced in the troposphere from human efforts. Briefly mentioned above, NOx and VOCs react with sunlight to create ozone through a process called photochemistry. One hour elevated ozone events (<75 ppb) "occur during June–August indicating that elevated ozone levels are driven by regional photochemistry". [ 68 ] According to an article from the University of Colorado-Boulder, "Oil and natural gas VOC emission have a major role in ozone production and bear the potential to contribute to elevated O 3 levels in the Northern Colorado Front Range (NCFR)". [ 68 ] Using complex analyses to research wind patterns and emissions from large oil and natural gas operations, the authors concluded that "elevated O 3 levels in the NCFR are predominantly correlated with air transport from N– ESE, which are the upwind sectors where the O&NG operations in the Wattenberg Field area of the DJB are located". [ 68 ]
Contained in the Colorado Ozone Action Plan, created in 2008, plans exist to evaluate "emission controls for large industrial sources of NOx" and "statewide control requirements for new oil and gas condensate tanks and pneumatic valves". [ 69 ] In 2011, the Regional Haze Plan was released that included a more specific plan to help decrease NOx emissions. These efforts are increasingly difficult to implement and take many years to come to pass. Of course there are also other reasons that ozone levels remain high. These include: a growing population meaning more car emissions, and the mountains along the NCFR that can trap emissions. If interested, daily air quality readings can be found at the Colorado Department of Public Health and Environment's website. [ 70 ] As noted earlier, Denver continues to experience high levels of ozone to this day. It will take many years and a systems-thinking approach to combat this issue of high ozone levels in the Front Range of Colorado.
Ozone gas attacks any polymer possessing olefinic or double bonds within its chain structure, such as natural rubber , nitrile rubber , and styrene-butadiene rubber. Products made using these polymers are especially susceptible to attack, which causes cracks to grow longer and deeper with time, the rate of crack growth depending on the load carried by the rubber component and the concentration of ozone in the atmosphere. Such materials can be protected by adding antiozonants , such as waxes, which bond to the surface to create a protective film or blend with the material and provide long term protection. Ozone cracking used to be a serious problem in car tires, [ 71 ] for example, but it is not an issue with modern tires. On the other hand, many critical products, like gaskets and O-rings , may be attacked by ozone produced within compressed air systems. Fuel lines made of reinforced rubber are also susceptible to attack, especially within the engine compartment, where some ozone is produced by electrical components. Storing rubber products in close proximity to a DC electric motor can accelerate ozone cracking. The commutator of the motor generates sparks which in turn produce ozone.
Although ozone was present at ground level before the Industrial Revolution , peak concentrations are now far higher than the pre-industrial levels, and even background concentrations well away from sources of pollution are substantially higher. [ 73 ] [ 74 ] Ozone acts as a greenhouse gas , absorbing some of the infrared energy emitted by the earth. Quantifying the greenhouse gas potency of ozone is difficult because it is not present in uniform concentrations across the globe. However, the most widely accepted scientific assessments relating to climate change (e.g. the Intergovernmental Panel on Climate Change Third Assessment Report ) [ 75 ] suggest that the radiative forcing of tropospheric ozone is about 25% that of carbon dioxide .
The annual global warming potential of tropospheric ozone is between 918 and 1022 tons carbon dioxide equivalent /tons tropospheric ozone. This means on a per-molecule basis, ozone in the troposphere has a radiative forcing effect roughly 1,000 times as strong as carbon dioxide . However, tropospheric ozone is a short-lived greenhouse gas, which decays in the atmosphere much more quickly than carbon dioxide . This means that over a 20-year span, the global warming potential of tropospheric ozone is much less, roughly 62 to 69 tons carbon dioxide equivalent / ton tropospheric ozone. [ 76 ]
Because of its short-lived nature, tropospheric ozone does not have strong global effects, but has very strong radiative forcing effects on regional scales. In fact, there are regions of the world where tropospheric ozone has a radiative forcing up to 150% of carbon dioxide . [ 77 ] For example, ozone increase in the troposphere is shown to be responsible for ~30% of upper Southern Ocean interior warming between 1955 and 2000. [ 78 ]
Filters containing an adsorbent or catalyst such as charcoal (carbon) may be used to remove odors and gaseous pollutants such as volatile organic compounds or ozone. [ 79 ]
For the last few decades, scientists studied the effects of acute and chronic ozone exposure on human health. Hundreds of studies suggest that ozone is harmful to people at levels currently found in urban areas. [ 80 ] [ 81 ] Ozone has been shown to affect the respiratory, cardiovascular and central nervous system. Early death and problems in reproductive health and development are also shown to be associated with ozone exposure. [ 82 ]
The American Lung Association has identified five populations who are especially vulnerable to the effects of breathing ozone: [ 83 ]
Additional evidence suggests that women, those with obesity and low-income populations may also face higher risk from ozone, although more research is needed. [ 83 ]
Acute ozone exposure ranges from hours to a few days. Because ozone is a gas, it directly affects the lungs and the entire respiratory system. Inhaled ozone causes inflammation and acute—but reversible—changes in lung function, as well as airway hyperresponsiveness. [ 84 ] These changes lead to shortness of breath, wheezing, and coughing which may exacerbate lung diseases, like asthma or chronic obstructive pulmonary disease (COPD) resulting in the need to receive medical treatment. [ 85 ] [ 86 ] Acute and chronic exposure to ozone has been shown to cause an increased risk of respiratory infections, due to the following mechanism. [ 87 ]
Multiple studies have been conducted to determine the mechanism behind ozone's harmful effects, particularly in the lungs. These studies have shown that exposure to ozone causes changes in the immune response within the lung tissue, resulting in disruption of both the innate and adaptive immune response, as well as altering the protective function of lung epithelial cells. [ 88 ] It is thought that these changes in immune response and the related inflammatory response are factors that likely contribute to the increased risk of lung infections, and worsening or triggering of asthma and reactive airways after exposure to ground-level ozone pollution. [ 88 ] [ 89 ]
The innate (cellular) immune system consists of various chemical signals and cell types that work broadly and against multiple pathogen types, typically bacteria or foreign bodies/substances in the host. [ 89 ] [ 90 ] The cells of the innate system include phagocytes, neutrophils, [ 90 ] both thought to contribute to the mechanism of ozone pathology in the lungs, as the functioning of these cell types have been shown to change after exposure to ozone. [ 89 ] Macrophages, cells that serve the purpose of eliminating pathogens or foreign material through the process of "phagocytosis", [ 90 ] have been shown to change the level of inflammatory signals they release in response to ozone, either up-regulating and resulting in an inflammatory response in the lung, or down-regulating and reducing immune protection. [ 88 ] Neutrophils, another important cell type of the innate immune system that primarily targets bacterial pathogens, [ 90 ] are found to be present in the airways within 6 hours of exposure to high ozone levels. Despite high levels in the lung tissues, however, their ability to clear bacteria appears impaired by exposure to ozone. [ 88 ]
The adaptive immune system is the branch of immunity that provides long-term protection via the development of antibodies targeting specific pathogens and is also impacted by high ozone exposure. [ 89 ] [ 90 ] Lymphocytes, a cellular component of the adaptive immune response, produce an increased amount of inflammatory chemicals called "cytokines" after exposure to ozone, which may contribute to airway hyperreactivity and worsening asthma symptoms. [ 88 ]
The airway epithelial cells also play an important role in protecting individuals from pathogens. In normal tissue, the epithelial layer forms a protective barrier, and also contains specialized ciliary structures that work to clear foreign bodies, mucus and pathogens from the lungs. When exposed to ozone, the cilia become damaged and mucociliary clearance of pathogens is reduced. Furthermore, the epithelial barrier becomes weakened, allowing pathogens to cross the barrier, proliferate and spread into deeper tissues. Together, these changes in the epithelial barrier help make individuals more susceptible to pulmonary infections. [ 88 ]
Inhaling ozone not only affects the immune system and lungs, but it may also affect the heart as well. Ozone causes short-term autonomic imbalance leading to changes in heart rate and reduction in heart rate variability; [ 91 ] and high levels exposure for as little as one-hour results in a supraventricular arrhythmia in the elderly, [ 92 ] both increase the risk of premature death and stroke. Ozone may also lead to vasoconstriction resulting in increased systemic arterial pressure contributing to increased risk of cardiac morbidity and mortality in patients with pre-existing cardiac diseases. [ 93 ] [ 94 ]
Breathing ozone for periods longer than eight hours at a time for weeks, months or years defines chronic exposure. Numerous studies suggest a serious impact on the health of various populations from this exposure.
One study finds significant positive associations between chronic ozone and all-cause, circulatory, and respiratory mortality with 2%, 3%, and 12% increases in risk per 10 ppb [ 95 ] and report an association (95% CI) of annual ozone and all-cause mortality with a hazard ratio of 1.02 (1.01–1.04), and with cardiovascular mortality of 1.03 (1.01–1.05). A similar study finds similar associations with all-cause mortality and even larger effects for cardiovascular mortality. [ 96 ] An increased risk of mortality from respiratory causes is associated with long-term chronic exposure to ozone. [ 97 ]
Chronic ozone has detrimental effects on children, especially those with asthma. The risk for hospitalization in children with asthma increases with chronic exposure to ozone; younger children and those with low-income status are even at greater risk. [ 98 ]
Adults suffering from respiratory diseases (asthma, [ 99 ] COPD, [ 100 ] lung cancer [ 101 ] ) are at a higher risk of mortality and morbidity and critically ill patients have an increased risk of developing acute respiratory distress syndrome with chronic ozone exposure as well. [ 102 ]
Ozone generators sold as air cleaners intentionally produce the gas ozone. [ 43 ] These are often marketed to control indoor air pollution , and use misleading terms to describe ozone. Some examples are describing it as "energized oxygen" or "pure air", suggesting that ozone is a healthy or "better" kind of oxygen. [ 43 ] However, according to the EPA , "There is evidence to show that at concentrations that do not exceed public health standards, ozone is not effective at removing many odor-causing chemicals", and "If used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants.". [ 43 ] Furthermore, another report states that "results of some controlled studies show that concentrations of ozone considerably higher than these [human safety] standards are possible even when a user follows the manufacturer's operating instructions". [ 103 ]
The California Air Resources Board has a page listing air cleaners (many with ionizers ) meeting their indoor ozone limit of 0.050 parts per million. [ 104 ] From that article:
All portable indoor air cleaning devices sold in California must be certified by the California Air Resources Board (CARB). To be certified, air cleaners must be tested for electrical safety and ozone emissions, and meet an ozone emission concentration limit of 0.050 parts per million. For more information about the regulation, visit the air cleaner regulation .
Ozone precursors are a group of pollutants, predominantly those emitted during the combustion of fossil fuels . Ground-level ozone pollution (tropospheric ozone) is produced near the Earth's surface by the action of daylight UV rays on these precursors. The ozone at ground level is primarily from fossil fuel precursors, but methane is a natural precursor, and the very low natural background level of ozone at ground level is considered safe. This section examines the health impacts of fossil fuel burning, which raises ground level ozone far above background levels.
There is a great deal of evidence to show that ground-level ozone can harm lung function and irritate the respiratory system . [ 57 ] [ 106 ] Exposure to ozone (and the pollutants that produce it) is linked to premature death , asthma , bronchitis , heart attack , and other cardiopulmonary problems. [ 107 ] [ 108 ]
Long-term exposure to ozone has been shown to increase risk of death from respiratory illness . [ 43 ] A study of 450,000 people living in U.S. cities saw a significant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people living in cities with high ozone levels, such as Houston or Los Angeles, had an over 30% increased risk of dying from lung disease. [ 109 ] [ 110 ]
Air quality guidelines such as those from the World Health Organization , the U.S. Environmental Protection Agency (EPA), and the European Union are based on detailed studies designed to identify the levels that can cause measurable ill health effects .
According to scientists with the EPA, susceptible people can be adversely affected by ozone levels as low as 40 nmol/mol. [ 108 ] [ 111 ] [ 112 ] In the EU, the current target value for ozone concentrations is 120 μg/m 3 which is about 60 nmol/mol. This target applies to all member states in accordance with Directive 2008/50/EC. [ 113 ] Ozone concentration is measured as a maximum daily mean of 8 hour averages and the target should not be exceeded on more than 25 calendar days per year, starting from January 2010. While the directive requires in the future a strict compliance with 120 μg/m 3 limit (i.e. mean ozone concentration not to be exceeded on any day of the year), there is no date set for this requirement and this is treated as a long-term objective. [ 114 ]
In the US, the Clean Air Act directs the EPA to set National Ambient Air Quality Standards for several pollutants, including ground-level ozone, and counties out of compliance with these standards are required to take steps to reduce their levels. In May 2008, under a court order, the EPA lowered its ozone standard from 80 nmol/mol to 75 nmol/mol. The move proved controversial, since the Agency's own scientists and advisory board had recommended lowering the standard to 60 nmol/mol. [ 108 ] Many public health and environmental groups also supported the 60 nmol/mol standard, [ 115 ] and the World Health Organization recommends 100 μg/m 3 (51 nmol/mol). [ 116 ]
On January 7, 2010, the U.S. Environmental Protection Agency (EPA) announced proposed revisions to the National Ambient Air Quality Standard (NAAQS) for the pollutant ozone, the principal component of smog:
... EPA proposes that the level of the 8-hour primary standard, which was set at 0.075 μmol/mol in the 2008 final rule, should instead be set at a lower level within the range of 0.060 to 0.070 μmol/mol, to provide increased protection for children and other at risk populations against an array of O 3 – related adverse health effects that range from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes, and possibly cardiovascular-related morbidity as well as total non- accidental and cardiopulmonary mortality ... [ 117 ]
On October 26, 2015, the EPA published a final rule with an effective date of December 28, 2015, that revised the 8-hour primary NAAQS from 0.075 ppm to 0.070 ppm. [ 118 ]
The EPA has developed an air quality index (AQI) to help explain air pollution levels to the general public. Under the current standards, eight-hour average ozone mole fractions of 85 to 104 nmol/mol are described as "unhealthy for sensitive groups", 105 nmol/mol to 124 nmol/mol as "unhealthy", and 125 nmol/mol to 404 nmol/mol as "very unhealthy". [ 119 ]
Ozone can also be present in indoor air pollution , partly as a result of electronic equipment such as photocopiers. A connection has also been known to exist between the increased pollen, fungal spores, and ozone caused by thunderstorms and hospital admissions of asthma sufferers. [ 120 ]
In the Victorian era , one British folk myth held that the smell of the sea was caused by ozone. In fact, the characteristic "smell of the sea" is caused by dimethyl sulfide , a chemical generated by phytoplankton . Victorian Britons considered the resulting smell "bracing". [ 121 ]
An investigation to assess the joint mortality effects of ozone and heat during the European heat waves in 2003, concluded that these appear to be additive. [ 122 ]
Ozone, along with reactive forms of oxygen such as superoxide , singlet oxygen , hydrogen peroxide , and hypochlorite ions, is produced by white blood cells and other biological systems (such as the roots of marigolds ) as a means of destroying foreign bodies. Ozone reacts directly with organic double bonds. Also, when ozone breaks down to dioxygen it gives rise to oxygen free radicals , which are highly reactive and capable of damaging many organic molecules . Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation . The cause-and-effect relationship of how the ozone is created in the body and what it does is still under consideration and still subject to various interpretations, since other body chemical processes can trigger some of the same reactions. There is evidence linking the antibody-catalyzed water-oxidation pathway of the human immune response to the production of ozone. In this system, ozone is produced by antibody-catalyzed production of trioxidane from water and neutrophil-produced singlet oxygen. [ 123 ]
When inhaled, ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques (a form of heart disease ). These metabolites have been confirmed as naturally occurring in human atherosclerotic arteries and are categorized into a class of secosterols termed atheronals , generated by ozonolysis of cholesterol's double bond to form a 5,6 secosterol [ 124 ] as well as a secondary condensation product via aldolization. [ 125 ]
Ozone has been implicated to have an adverse effect on plant growth: "... ozone reduced total chlorophylls, carotenoid and carbohydrate concentration, and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production. In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and solute leakage were significantly higher than in ozone-free controls. The data indicated that ozone triggered protective mechanisms against oxidative stress in citrus." [ 126 ] Studies that have used pepper plants as a model have shown that ozone decreased fruit yield and changed fruit quality. [ 127 ] [ 128 ] Furthermore, it was also observed a decrease in chlorophylls levels and antioxidant defences on the leaves, as well as increased the reactive oxygen species (ROS) levels and lipid and protein damages. [ 127 ] [ 128 ]
A 2022 study concludes that East Asia loses 63 billion dollars in crops per year due to ozone pollution, a byproduct of fossil fuel combustion. China loses about one-third of its potential wheat production and one-fourth of its rice production. [ 129 ] [ 130 ]
Because of the strongly oxidizing properties of ozone, ozone is a primary irritant, affecting especially the eyes and respiratory systems and can be hazardous at even low concentrations. The Canadian Centre for Occupation Safety and Health reports that:
Even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs. The severity of injury depends on both the concentration of ozone and the duration of exposure. Severe and permanent lung injury or death could result from even a very short-term exposure to relatively low concentrations." [ 131 ]
To protect workers potentially exposed to ozone, U.S. Occupational Safety and Health Administration has established a permissible exposure limit (PEL) of 0.1 μmol/mol (29 CFR 1910.1000 table Z-1), calculated as an 8-hour time weighted average. Higher concentrations are especially hazardous and NIOSH has established an Immediately Dangerous to Life and Health Limit (IDLH) of 5 μmol/mol. [ 132 ] Work environments where ozone is used or where it is likely to be produced should have adequate ventilation and it is prudent to have a monitor for ozone that will alarm if the concentration exceeds the OSHA PEL. Continuous monitors for ozone are available from several suppliers.
Elevated ozone exposure can occur on passenger aircraft , with levels depending on altitude and atmospheric turbulence. [ 133 ] U.S. Federal Aviation Administration regulations set a limit of 250 nmol/mol with a maximum four-hour average of 100 nmol/mol. [ 134 ] Some planes are equipped with ozone converters in the ventilation system to reduce passenger exposure. [ 133 ]
Ozone generators , or ozonators , [ 135 ] are used to produce ozone for cleaning air or removing smoke odours in unoccupied rooms. These ozone generators can produce over 3 g of ozone per hour. Ozone often forms in nature under conditions where O 2 will not react. [ 29 ] Ozone used in industry is measured in μmol/mol (ppm, parts per million), nmol/mol (ppb, parts per billion), μg/m 3 , mg/h (milligrams per hour) or weight percent. The regime of applied concentrations ranges from 1% to 5% (in air) and from 6% to 14% (in oxygen) for older generation methods. New electrolytic methods can achieve up 20% to 30% dissolved ozone concentrations in output water.
Temperature and humidity play a large role in how much ozone is being produced using traditional generation methods (such as corona discharge and ultraviolet light). Old generation methods will produce less than 50% of nominal capacity if operated with humid ambient air, as opposed to very dry air. New generators, using electrolytic methods, can achieve higher purity and dissolution through using water molecules as the source of ozone production.
This is the most common type of ozone generator for most industrial and personal uses. While variations of the "hot spark" coronal discharge method of ozone production exist, including medical grade and industrial grade ozone generators, these units usually work by means of a corona discharge tube or ozone plate. [ 136 ] [ 137 ] They are typically cost-effective and do not require an oxygen source other than the ambient air to produce ozone concentrations of 3–6%. Fluctuations in ambient air, due to weather or other environmental conditions, cause variability in ozone production. However, they also produce nitrogen oxides as a by-product. Use of an air dryer can reduce or eliminate nitric acid formation by removing water vapor and increase ozone production. At room temperature, nitric acid will form into a vapour that is hazardous if inhaled. Symptoms can include chest pain, shortness of breath, headaches and a dry nose and throat causing a burning sensation. Use of an oxygen concentrator can further increase the ozone production and further reduce the risk of nitric acid formation by removing not only the water vapor, but also the bulk of the nitrogen.
UV ozone generators, or vacuum-ultraviolet (VUV) ozone generators, employ a light source that generates a narrow-band ultraviolet light, a subset of that produced by the Sun. The Sun's UV sustains the ozone layer in the stratosphere of Earth. [ 138 ]
UV ozone generators use ambient air for ozone production, no air prep systems are used (air dryer or oxygen concentrator), therefore these generators tend to be less expensive. However, UV ozone generators usually produce ozone with a concentration of about 0.5% or lower which limits the potential ozone production rate. Another disadvantage of this method is that it requires the ambient air (oxygen) to be exposed to the UV source for a longer amount of time, and any gas that is not exposed to the UV source will not be treated. This makes UV generators impractical for use in situations that deal with rapidly moving air or water streams (in-duct air sterilization , for example). Production of ozone is one of the potential dangers of ultraviolet germicidal irradiation . VUV ozone generators are used in swimming pools and spa applications ranging to millions of gallons of water. VUV ozone generators, unlike corona discharge generators, do not produce harmful nitrogen by-products and also unlike corona discharge systems, VUV ozone generators work extremely well in humid air environments. There is also not normally a need for expensive off-gas mechanisms, and no need for air driers or oxygen concentrators which require extra costs and maintenance.
In the cold plasma method, pure oxygen gas is exposed to a plasma created by DBD . The diatomic oxygen is split into single atoms, which then recombine in triplets to form ozone.
It is common in the industry to mislabel some DBD ozone generators as CD Corona Discharge generators. Typically all solid flat metal electrode ozone generators produce ozone using the dielectric barrier discharge method. Cold plasma machines use pure oxygen as the input source and produce a maximum concentration of about 24% ozone. They produce far greater quantities of ozone in a given time compared to ultraviolet production that has about 2% efficiency. The discharges manifest as filamentary transfer of electrons (micro discharges) in a gap between two electrodes. In order to evenly distribute the micro discharges, a dielectric insulator must be used to separate the metallic electrodes and to prevent arcing.
Electrolytic ozone generation (EOG) splits water molecules into H 2 , O 2 , and O 3 .
In most EOG methods, the hydrogen gas will be removed to leave oxygen and ozone as the only reaction products. Therefore, EOG can achieve higher dissolution in water without other competing gases found in corona discharge method, such as nitrogen gases present in ambient air. This method of generation can achieve concentrations of 20–30% and is independent of air quality because water is used as the source material. Production of ozone electrolytically is typically unfavorable because of the high overpotential required to produce ozone as compared to oxygen. This is why ozone is not produced during typical water electrolysis. However, it is possible to increase the overpotential of oxygen by careful catalyst selection such that ozone is preferentially produced under electrolysis. Catalysts typically chosen for this approach are lead dioxide [ 139 ] or boron-doped diamond. [ 140 ]
The ozone-to-oxygen ratio is improved by increasing current density at the anode, cooling the electrolyte around the anode close to 0 °C, using an acidic electrolyte (such as dilute sulfuric acid) instead of a basic solution, and by applying pulsed current instead of DC. [ 141 ]
Ozone cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site. Available ozone generators vary in the arrangement and design of the high-voltage electrodes. At production capacities higher than 20 kg per hour, a gas/water tube heat-exchanger may be utilized as ground electrode and assembled with tubular high-voltage electrodes on the gas-side. The regime of typical gas pressures is around 2 bars (200 kPa ) absolute in oxygen and 3 bars (300 kPa) absolute in air. Several megawatts of electrical power may be installed in large facilities, applied as single phase AC current at 50 to 8000 Hz and peak voltages between 3,000 and 20,000 volts. Applied voltage is usually inversely related to the applied frequency.
The dominating parameter influencing ozone generation efficiency is the gas temperature, which is controlled by cooling water temperature and/or gas velocity. The cooler the water, the better the ozone synthesis. The lower the gas velocity, the higher the concentration (but the lower the net ozone produced). At typical industrial conditions, almost 90% of the effective power is dissipated as heat and needs to be removed by a sufficient cooling water flow.
Because of the high reactivity of ozone, only a few materials may be used like stainless steel (quality 316L), titanium , aluminium (as long as no moisture is present), glass , polytetrafluorethylene , or polyvinylidene fluoride . Viton may be used with the restriction of constant mechanical forces and absence of humidity (humidity limitations apply depending on the formulation). Hypalon may be used with the restriction that no water comes in contact with it, except for normal atmospheric levels. Embrittlement or shrinkage is the common mode of failure of elastomers with exposure to ozone. Ozone cracking is the common mode of failure of elastomer seals like O-rings .
Silicone rubbers are usually adequate for use as gaskets in ozone concentrations below 1 wt%, such as in equipment for accelerated aging of rubber samples.
Ozone may be formed from O 2 by electrical discharges and by action of high energy electromagnetic radiation . Unsuppressed arcing in electrical contacts, motor brushes, or mechanical switches breaks down the chemical bonds of the atmospheric oxygen surrounding the contacts [ O 2 -> 2O]. Free radicals of oxygen in and around the arc recombine to create ozone [ O 3 ]. [ 142 ] Certain electrical equipment generate significant levels of ozone. This is especially true of devices using high voltages , such as ionic air purifiers , laser printers , photocopiers , tasers , and arc welders . Electric motors using brushes can generate ozone from repeated sparking inside the unit. Large motors that use brushes, such as those used by elevators or hydraulic pumps, will generate more ozone than smaller motors.
Ozone is similarly formed in the Catatumbo lightning storms phenomenon on the Catatumbo River in Venezuela , though ozone's instability makes it dubious that it has any effect on the ozonosphere. [ 143 ] It is the world's largest single natural generator of ozone, lending calls for it to be designated a UNESCO World Heritage Site . [ 144 ]
In the laboratory, ozone can be produced by electrolysis using a 9 volt battery , a pencil graphite rod cathode , a platinum wire anode , and a 3 molar sulfuric acid electrolyte . [ 145 ] The half cell reactions taking place are:
where E° represents the standard electrode potential .
In the net reaction, three equivalents of water are converted into one equivalent of ozone and three equivalents of hydrogen . Oxygen formation is a competing reaction.
It can also be generated by a high voltage arc . In its simplest form, high voltage AC, such as the output of a neon-sign transformer is connected to two metal rods with the ends placed sufficiently close to each other to allow an arc. The resulting arc will convert atmospheric oxygen to ozone.
It is often desirable to contain the ozone. This can be done with an apparatus consisting of two concentric glass tubes sealed together at the top with gas ports at the top and bottom of the outer tube. The inner core should have a length of metal foil inserted into it connected to one side of the power source. The other side of the power source should be connected to another piece of foil wrapped around the outer tube. A source of dry O 2 is applied to the bottom port. When high voltage is applied to the foil leads, electricity will discharge between the dry dioxygen in the middle and form O 3 and O 2 which will flow out the top port. This is called a Siemen's ozoniser. The reaction can be summarized as follows: [ 29 ]
The largest use of ozone is in the preparation of pharmaceuticals , synthetic lubricants , and many other commercially useful organic compounds , where it is used to sever carbon -carbon bonds. [ 29 ] It can also be used for bleaching substances and for killing microorganisms in air and water sources. [ 146 ] Many municipal drinking water systems kill bacteria with ozone instead of the more common chlorine . [ 147 ] Ozone has a very high oxidation potential . [ 148 ] Ozone does not form organochlorine compounds, nor does it remain in the water after treatment. Ozone can form the suspected carcinogen bromate in source water with high bromide concentrations. The U.S. Safe Drinking Water Act mandates that these systems introduce an amount of chlorine to maintain a minimum of 0.2 μmol/mol residual free chlorine in the pipes, based on results of regular testing. Where electrical power is abundant, ozone is a cost-effective method of treating water, since it is produced on demand and does not require transportation and storage of hazardous chemicals. Once it has decayed, it leaves no taste or odour in drinking water.
Although low levels of ozone have been advertised to be of some disinfectant use in residential homes, the concentration of ozone in dry air required to have a rapid, substantial effect on airborne pathogens exceeds safe levels recommended by the U.S. Occupational Safety and Health Administration and Environmental Protection Agency . Humidity control can vastly improve both the killing power of the ozone and the rate at which it decays back to oxygen (more humidity allows more effectiveness). Spore forms of most pathogens are very tolerant of atmospheric ozone in concentrations at which asthma patients start to have issues.
In 1908 artificial ozonisation of the Central Line of the London Underground was introduced for aerial disinfection. The process was found to be worthwhile, but was phased out by 1956. However the beneficial effect was maintained by the ozone created incidentally from the electrical discharges of the train motors (see above: Incidental production ). [ 149 ]
Ozone generators were made available to schools and universities in Wales for the Autumn term 2021, to disinfect classrooms after COVID-19 outbreaks. [ 150 ]
Industrially, ozone is used to:
Ozone is a reagent in many organic reactions in the laboratory and in industry. Ozonolysis is the cleavage of an alkene to carbonyl compounds.
Many hospitals around the world use large ozone generators to decontaminate operating rooms between surgeries. The rooms are cleaned and then sealed airtight before being filled with ozone which effectively kills or neutralizes all remaining bacteria. [ 156 ]
Ozone is used as an alternative to chlorine or chlorine dioxide in the bleaching of wood pulp . [ 157 ] It is often used in conjunction with oxygen and hydrogen peroxide to eliminate the need for chlorine-containing compounds in the manufacture of high-quality, white paper . [ 158 ]
Ozone can be used to detoxify cyanide wastes (for example from gold and silver mining ) by oxidizing cyanide to cyanate and eventually to carbon dioxide . [ 159 ]
Since the invention of dielectric barrier discharge (DBD) plasma reactors, it has been employed for water treatment with ozone. [ 160 ] However, with cheaper alternative disinfectants like chlorine, such applications of DBD ozone water decontamination have been limited by high power consumption and bulky equipment. [ 161 ] [ 162 ] Despite this, with research revealing the negative impacts of common disinfectants like chlorine with respect to toxic residuals and ineffectiveness in killing certain micro-organisms, [ 163 ] DBD plasma-based ozone decontamination is of interest in current available technologies. Although ozonation of water with a high concentration of bromide does lead to the formation of undesirable brominated disinfection byproducts, unless drinking water is produced by desalination, ozonation can generally be applied without concern for these byproducts. [ 162 ] [ 164 ] [ 165 ] [ 166 ] Advantages of ozone include high thermodynamic oxidation potential, less sensitivity to organic material and better tolerance for pH variations while retaining the ability to kill bacteria, fungi, viruses, as well as spores and cysts. [ 167 ] [ 168 ] [ 169 ] Although, ozone has been widely accepted in Europe for decades, it is sparingly used for decontamination in the U.S. due to limitations of high-power consumption, bulky installation and stigma attached with ozone toxicity. [ 161 ] [ 170 ] Considering this, recent research efforts have been directed toward the study of effective ozone water treatment systems. [ 171 ] Researchers have looked into lightweight and compact low power surface DBD reactors, [ 172 ] [ 173 ] energy efficient volume DBD reactors [ 174 ] and low power micro-scale DBD reactors. [ 175 ] [ 176 ] Such studies can help pave the path to re-acceptance of DBD plasma-based ozone decontamination of water, especially in the U.S.
Ozone levels which are safe for people are ineffective at killing fungi and bacteria. [ 177 ] Some consumer disinfection and cosmetic products emit ozone at levels harmful to human health. [ 177 ]
Devices generating high levels of ozone, some of which use ionization, are used to sanitize and deodorize uninhabited buildings, rooms, ductwork, woodsheds, boats, and other vehicles.
Ozonated water is used to launder clothes and to sanitize food, drinking water, and surfaces in the home. According to the U.S. Food and Drug Administration (FDA), it is "amending the food additive regulations to provide for the safe use of ozone in gaseous and aqueous phases as an antimicrobial agent on food, including meat and poultry." Studies at California Polytechnic University demonstrated that 0.3 μmol/mol levels of ozone dissolved in filtered tapwater can produce a reduction of more than 99.99% in such food-borne microorganisms as salmonella, E. coli 0157:H7 and Campylobacter . This quantity is 20,000 times the WHO -recommended limits stated above. [ 152 ] [ 178 ]
Ozone can be used to remove pesticide residues from fruits and vegetables . [ 179 ] [ 180 ]
Ozone is used in homes and hot tubs to kill bacteria in the water and to reduce the amount of chlorine or bromine required by reactivating them to their free state. Since ozone does not remain in the water long enough, ozone by itself is ineffective at preventing cross-contamination among bathers and must be used in conjunction with halogens . Gaseous ozone created by ultraviolet light or by corona discharge is injected into the water. [ 181 ]
Ozone is also widely used in the treatment of water in aquariums and fishponds. Its use can minimize bacterial growth, control parasites, eliminate transmission of some diseases, and reduce or eliminate "yellowing" of the water. Ozone must not come in contact with fishes' gill structures. Natural saltwater (with life forms) provides enough "instantaneous demand" that controlled amounts of ozone activate bromide ions to hypobromous acid , and the ozone entirely decays in a few seconds to minutes. If oxygen-fed ozone is used, the water will be higher in dissolved oxygen and fishes' gill structures will atrophy, making them dependent on oxygen-enriched water.
Ozonation – a process of infusing water with ozone – can be used in aquaculture to facilitate organic breakdown. Ozone is also added to recirculating systems to reduce nitrite levels [ 182 ] through conversion into nitrate . If nitrite levels in the water are high, nitrites will also accumulate in the blood and tissues of fish, where it interferes with oxygen transport (it causes oxidation of the heme-group of haemoglobin from ferrous ( Fe 2+ ) to ferric ( Fe 3+ ), making haemoglobin unable to bind O 2 ). [ 183 ] Despite these apparent positive effects, ozone use in recirculation systems has been linked to reducing the level of bioavailable iodine in salt water systems, resulting in iodine deficiency symptoms such as goitre and decreased growth in Senegalese sole ( Solea senegalensis ) larvae. [ 184 ]
Ozonate seawater is used for surface disinfection of haddock and Atlantic halibut eggs against nodavirus. Nodavirus is a lethal and vertically transmitted virus which causes severe mortality in fish. Haddock eggs should not be treated with high ozone level as eggs so treated did not hatch and died after 3–4 days. [ 185 ]
Ozone application on freshly cut pineapple and banana shows increase in flavonoids and total phenol contents when exposure is up to 20 minutes. Decrease in ascorbic acid (one form of vitamin C ) content is observed but the positive effect on total phenol content and flavonoids can overcome the negative effect. [ 186 ] Tomatoes upon treatment with ozone show an increase in β-carotene, lutein and lycopene. [ 187 ] However, ozone application on strawberries in pre-harvest period shows decrease in ascorbic acid content. [ 188 ]
Ozone facilitates the extraction of some heavy metals from soil using EDTA . EDTA forms strong, water-soluble coordination compounds with some heavy metals ( Pb and Zn ) thereby making it possible to dissolve them out from contaminated soil. If contaminated soil is pre-treated with ozone, the extraction efficacy of Pb , Am , and Pu increases by 11.0–28.9%, [ 189 ] 43.5% [ 190 ] and 50.7% [ 190 ] respectively.
Crop pollination is an essential part of an ecosystem. Ozone can have detrimental effects on plant-pollinator interactions. [ 191 ] Pollinators carry pollen from one plant to another. This is an essential cycle inside of an ecosystem. Causing changes in certain atmospheric conditions around pollination sites or with xenobiotics could cause unknown changes to the natural cycles of pollinators and flowering plants. In a study conducted in North-Western Europe, crop pollinators were negatively affected more when ozone levels were higher. [ 192 ]
The use of ozone for the treatment of medical conditions is not supported by high quality evidence, and is generally considered alternative medicine . [ 193 ]
Footnotes
Citations
Nascent oxygen O
Dioxygen ( singlet and triplet ) O 2
Trioxygen ( ozone and cyclic ozone ) O 3
Tetraoxygen O 4
Octaoxygen O 8 | https://en.wikipedia.org/wiki/O=O-O |
The Open Biological and Biomedical Ontologies ( OBO ) Foundry is a group of people who build and maintain ontologies related to the life sciences . [ 1 ] The OBO Foundry establishes a set of principles for ontology development for creating a suite of interoperable reference ontologies in the biomedical domain. Currently, there are more than a hundred ontologies that follow the OBO Foundry principles .
The OBO Foundry effort makes it easier to integrate biomedical results and carry out analysis in bioinformatics . It does so by offering a structured reference for terms of different research fields and their interconnections (ex: a phenotype in a mouse model and its related phenotype in zebrafish ). [ 2 ]
The Foundry initiative aims at improving the integration of data in the life sciences. One approach to integration is the annotation of data from different sources using controlled vocabularies . Ideally, such controlled vocabularies take the form of ontologies , which support logical reasoning over the data annotated using the terms in the vocabulary.
The formalization of concepts in the biomedical domain is especially known via the work of the Gene Ontology Consortium, a part of the OBO Foundry. This has led to the development of certain proposed principles of good practice in ontology development, which are now being put into practice within the framework of the Open Biomedical Ontologies consortium through its OBO Foundry initiative. OBO ontologies form part of the resources of the National Center for Biomedical Ontology , where they form a central component of the NCBO's BioPortal.
The Open Biological and Biomedical Ontologies (OBO; formerly Open Biomedical Ontologies) is an effort to create ontologies ( controlled vocabularies ) for use across biological and medical domains.
A subset of the original OBO ontologies has started the OBO Foundry, which leads the OBO efforts since 2007. [ 1 ]
The creation of OBO in 2001 was largely inspired by the efforts of the Gene Ontology project. [ 3 ] OBO forms part of the resources of the U.S. National Center for Biomedical Ontology (NCBIO) and a central element of the NCBO's BioPortal. It is an initiative led by the OBO Foundry.
The OBO Foundry is open to participations of any interested individuals. Ontologies that intend to be officially part of the OBO Foundry have to adhere to the OBO principles and pass a series of reviews done by the members, when "the Foundry coordinators serve as analogs of journal editors". [ 1 ] There are ontologies that follow OBO principles but are not officially part of OBO, such as eagle-i 's Reagent Application Ontology. [ 4 ] and the Animals in Context Ontology. [ 5 ]
An integration into OBO of the OntoClean's theory of rigidity has been proposed as a step to standardize candidate ontologies. This integration would make it easier to develop software to automatically check candidates. [ 6 ]
The OBO Foundry community is also dedicated to developing tools to facilitate creating and maintaining ontologies. Most ontology developers in OBO use the Protégé ontology editor and the Web Ontology Language (OWL) for building ontologies. To facilitate command line management of ontologies in a Protégé- and OWL-compatible format, the OBO Foundry has developed the tool ROBOT (ROBOT is an OBO Tool). ROBOT aggregates functions for routine tasks in ontology development, is open source , and can be used either via the command line or as a library for any language on the Java Virtual Machine . [ 7 ]
Other tool related to the OBO effort is OBO-Edit , [ 8 ] an ontology editor and reasoner funded by the Gene Ontology Consortium . There are also plugins for OBO-Edit which facilitate the development of ontologies, such as the semi-automatic ontology generator DOG4DAG. [ 9 ]
The OBO file format is a biology-oriented language for building ontologies. It is based on the principles of Web Ontology Language (OWL) .
As a community effort, standard common mappings have been created for lossless roundtrip transformations between Open Biomedical Ontologies (OBO) format and OWL. [ 10 ] [ 11 ] The research contains methodical examination of each of the constructs of OBO and a layer cake for OBO, similar to the Semantic Web stack. [ 12 ]
The initial set of OBO Foundry ontologies was composed by mature ontologies (such as the Gene Ontology , GO, and the Foundational Model of Anatomy , FMAO), by mergers of previously existing ontologies (ex: the Cell Ontology, [ 13 ] CL, formed from different dedicated ontologies, [ 14 ] [ 15 ] and related parts on GO and FMAO) and by development of new ontologies based on its principles. [ 16 ]
The original set of ontologies also included the Zebrafish Anatomical Ontology [ 17 ] (a part of the Zebrafish Information Network ), the CheBI ontology, the Disease Ontology , the Plant Ontology , the Sequence Ontology , the Ontology for Biomedical Investigations and the Protein Ontology . [ 16 ]
The number of ontologies in OBO has grown to the order of hundreds, and they are gathered in the list of OBO Foundry ontologies .
A number of different OBO Foundry ontologies have also been integrated to the Wikidata knowledge graph. [ 18 ] [ 19 ] This has led to the integration of OBO structured ontologies to data from other, non-OBO databases . For example, the integration of the Human Disease Ontology [ 20 ] to Wikidata has enabled its link to the description of cell-lines from the resource Cellosaurus . [ 21 ] One of the goals of the integration of OBO Foundry to Wikidata has been to lower the barriers for non-ontologists to contribute to and use ontologies. Wikidata is arguably easier to understand and use than the traditional ontology models (which require a high degree of specific expertise). [ 22 ]
Summary of OBO Foundry Principles [ 23 ] for development of an OBO-compatible life sciences ontology :
The ontologies are openly available and have to be released under either the license CC BY 3.0 or under the public domain ( CC0 ). [ 24 ] The openness of the ontologies has enabled, for example, the import of terms from the Gene Ontology (one of the ontologies that follow OBO Principles) to the Wikidata project. [ 25 ]
The ontologies have to be available in a common formal language . In practice, that means that ontologies that are part of the OBO foundry need to describe items unsing the formats OWL/ OWL2 or OBO using a RDF/XML syntax to maximize interoperability. [ 26 ]
Terms should be unique in the OBO space, meaning that each item has a unique ontology prefix (such as CHEBI , GO , PRO ) and a local numeric identifier within the ontology. [ 27 ] The choice of a numerical ID was made in order to improve maintenance and evolution of the resources. [ 28 ] In order to participate in OBO Foundry, ontologies have to be orthogonal and the concepts it models must be unique within OBO, so each concept has a single Uniform Resource Identifier (URI). New ontologies have, then, to reuse work done in other efforts. [ 28 ]
Despite the ideal of uniqueness of terms and interoperability, in practice, this is difficult to enforce, leading to the occurrence of term duplication. Furthermore, some ontologies do not reuse terms or even reuse terms inappropriately. [ 29 ]
Ontologies evolve in time, refining concepts and descriptions according to advances in the knowledge of their specific domains. [ 30 ] In order to ensure that new versions are updated, but tools that use older version of the ontologies are still function, OBO enforces a system of versioning systems , with each ontology version receiving a unique identifier, either in the format of a date or a numbering system, and metadata dags. [ 31 ]
The ontologies should have a clearly specified scope (the domain it intends to cover). [ 32 ]
The ontologies should have textual definitions for each item, in a human-readable way. That means that beside the alphanumeric identification for each item, they should be described in natural language by logical affirmations following the Aristotelian logic in a way that is unique within the ontology. [ 33 ]
The ontologies should use relations between items from the Relations Ontology (RO) . This ensures that different ontologies can integrated seamlessly, which is specially important for logical inference . [ 34 ]
The Relation Ontology (RO) is an ontology designed to represent the relationships between different biomedical concepts. [ 35 ] It describes rigorously relations like "part_of", "located_in" and "preceded_by" that are reused by many OBO Foundry ontologies.
OBO ontologies need to be thoroughly documented. Frequently this is done via GitHub repositories for each specific ontologies (see List of OBO Foundry ontologies ). [ 36 ]
The ontologies should be useful for multiple different people, and ontology developers should document the evidence of use. This criterion is important for the review process. Examples of use include linking to terms by other ontologies, use in semantic web projects, use in annotations or other research applications. [ 37 ]
The ontologies should be developed in a way that allows collaborations with other OBO Foundry members. [ 38 ]
The ontologies should have one person responsible for the ontology who mediates interaction with the community. [ 39 ]
Naming conventions for OBO ontologies aim at making primary labels unambiguous and unique inside the ontology (and preferably, inside OBO). Labels and synonyms should be written in English, avoiding the use of underscores and camel case . [ 40 ] OBO lacks a mechanism for multilingual support, in contrast to Wikidata , which allows labels in different systems. The naming system in OBO is based on a series of surveys at cataloguing naming conventions of current ontologies, as well as discover issues relating to these conventions. [ 41 ]
The ontologies should be updated with regards to changes in scientific consensus . The OBO Foundry defines scientific consensus as "multiple publications by independent labs over a year come to the same conclusion, and there is no or limited (<10%) dissenting opinions published in the same time frame." [ 42 ] | https://en.wikipedia.org/wiki/OBO_Foundry |
Carbonic acid is a chemical compound with the chemical formula H 2 C O 3 . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature . [ 5 ] [ 6 ] The interconversion of carbon dioxide and carbonic acid is related to the breathing cycle of animals and the acidification of natural waters . [ 4 ]
In biochemistry and physiology, the name "carbonic acid" is sometimes applied to aqueous solutions of carbon dioxide . These chemical species play an important role in the bicarbonate buffer system , used to maintain acid–base homeostasis . [ 7 ]
In chemistry , the term "carbonic acid" strictly refers to the chemical compound with the formula H 2 CO 3 . Some biochemistry literature effaces the distinction between carbonic acid and carbon dioxide dissolved in extracellular fluid.
In physiology , carbon dioxide excreted by the lungs may be called volatile acid or respiratory acid .
At ambient temperatures, pure carbonic acid is a stable gas. [ 6 ] There are two main methods to produce anhydrous carbonic acid: reaction of hydrogen chloride and potassium bicarbonate at 100 K in methanol and proton irradiation of pure solid carbon dioxide . [ 3 ] Chemically, it behaves as a diprotic Brønsted acid . [ 8 ] [ 9 ]
Carbonic acid monomers exhibit three conformational isomers : cis–cis, cis–trans, and trans–trans. [ 10 ]
At low temperatures and atmospheric pressure , solid carbonic acid is amorphous and lacks Bragg peaks in X-ray diffraction . [ 11 ] But at high pressure, carbonic acid crystallizes, and modern analytical spectroscopy can measure its geometry.
According to neutron diffraction of dideuterated carbonic acid ( D 2 CO 3 ) in a hybrid clamped cell ( Russian alloy / copper-beryllium ) at 1.85 GPa, the molecules are planar and form dimers joined by pairs of hydrogen bonds . All three C-O bonds are nearly equidistant at 1.34 Å , intermediate between typical C-O and C=O distances (respectively 1.43 and 1.23 Å). The unusual C-O bond lengths are attributed to delocalized π bonding in the molecule's center and extraordinarily strong hydrogen bonds. The same effects also induce a very short O—O separation (2.13 Å), through the 136° O-H-O angle imposed by the doubly hydrogen-bonded 8-membered rings. [ 4 ] Longer O—O distances are observed in strong intramolecular hydrogen bonds, e.g. in oxalic acid , where the distances exceed 2.4 Å. [ 11 ]
In even a slight presence of water, carbonic acid dehydrates to carbon dioxide and water , which then catalyzes further decomposition. [ 6 ] For this reason, carbon dioxide can be considered the carbonic acid anhydride .
The hydration equilibrium constant at 25 °C is [ H 2 CO 3 ]/[CO 2 ] ≈ 1.7×10 −3 in pure water [ 12 ] and ≈ 1.2×10 −3 in seawater . [ 13 ] Hence the majority of carbon dioxide at geophysical or biological air-water interfaces does not convert to carbonic acid, remaining dissolved CO 2 gas. However, the uncatalyzed equilibrium is reached quite slowly: the rate constants are 0.039 s −1 for hydration and 23 s −1 for dehydration.
In the presence of the enzyme carbonic anhydrase , equilibrium is instead reached rapidly, and the following reaction takes precedence: [ 14 ] HCO 3 − + H + ↽ − − ⇀ CO 2 + H 2 O {\displaystyle {\ce {HCO3^- {+}H^+ <=> CO2 {+}H2O}}}
When the created carbon dioxide exceeds its solubility, gas evolves and a third equilibrium CO 2 ( soln ) ↽ − − ⇀ CO 2 ( g ) {\displaystyle {\ce {CO_2 (soln) <=> CO_2 (g)}}} must also be taken into consideration. The equilibrium constant for this reaction is defined by Henry's law .
The two reactions can be combined for the equilibrium in solution: HCO 3 − + H + ↽ − − ⇀ CO 2 ( soln ) + H 2 O K 3 = [ H + ] [ HCO 3 − ] [ CO 2 ( soln ) ] {\displaystyle {\begin{aligned}{\ce {HCO3^{-}{}+ H+{}<=> CO2(soln){}+ H2O}}&&K_{3}={\frac {[{\ce {H+}}][{\ce {HCO3^-}}]}{[{\ce {CO2(soln)}}]}}\end{aligned}}} When Henry's law is used to calculate the denominator care is needed with regard to units since Henry's law constant can be commonly expressed with 8 different dimensionalities. [ 15 ]
In wastewater treatment and agriculture irrigation, carbonic acid is used to acidify the water similar to sulfuric acid and sulfurous acid produced by sulfur burners. [ 16 ]
In the beverage industry , sparkling or "fizzy water" is usually referred to as carbonated water . It is made by dissolving carbon dioxide under a small positive pressure in water. Many soft drinks treated the same way effervesce .
Significant amounts of molecular H 2 CO 3 exist in aqueous solutions subjected to pressures of multiple gigapascals (tens of thousands of atmospheres) in planetary interiors. [ 17 ] [ 18 ] Pressures of 0.6–1.6 GPa at 100 K , and 0.75–1.75 GPa at 300 K are attained in the cores of large icy satellites such as Ganymede , Callisto , and Titan , where water and carbon dioxide are present. Pure carbonic acid, being denser, is expected to have sunk under the ice layers and separate them from the rocky cores of these moons. [ 19 ]
Carbonic acid is the formal Brønsted–Lowry conjugate acid of the bicarbonate anion, stable in alkaline solution . The protonation constants have been measured to great precision, but depend on overall ionic strength I . The two equilibria most easily measured are as follows: CO 3 2 − + H + ↽ − − ⇀ HCO 3 − β 1 = [ HCO 3 − ] [ H + ] [ CO 3 2 − ] CO 3 2 − + 2 H + ↽ − − ⇀ H 2 CO 3 β 2 = [ H 2 CO 3 ] [ H + ] 2 [ CO 3 2 − ] {\displaystyle {\begin{aligned}{\ce {CO3^{2-}{}+ H+{}<=> HCO3^-}}&&\beta _{1}={\frac {[{\ce {HCO3^-}}]}{[{\ce {H+}}][{\ce {CO3^{2-}}}]}}\\{\ce {CO3^{2-}{}+ 2H+{}<=> H2CO3}}&&\beta _{2}={\frac {[{\ce {H2CO3}}]}{[{\ce {H+}}]^{2}[{\ce {CO3^{2-}}}]}}\end{aligned}}} where brackets indicate the concentration of species . At 25 °C, these equilibria empirically satisfy [ 20 ] log ( β 1 ) = 0 .54 I 2 − 0 .96 I + 9 .93 log ( β 2 ) = − 2 .5 I 2 − 0 .043 I + 16 .07 {\displaystyle {\begin{alignedat}{6}\log(\beta _{1})=&&0&.54&I^{2}-0&.96&I+&&9&.93\\\log(\beta _{2})=&&-2&.5&I^{2}-0&.043&I+&&16&.07\end{alignedat}}} log( β 1 ) decreases with increasing I , as does log( β 2 ) . In a solution absent other ions (e.g. I = 0 ), these curves imply the following stepwise dissociation constants : p K 1 = log ( β 2 ) − log ( β 1 ) = 6.77 p K 2 = log ( β 1 ) = 9.93 {\displaystyle {\begin{alignedat}{3}p{\text{K}}_{1}&=\log(\beta _{2})-\log(\beta _{1})&=6.77\\p{\text{K}}_{2}&=\log(\beta _{1})&=9.93\end{alignedat}}} Direct values for these constants in the literature include p K 1 = 6.35 and p K 2 - p K 1 = 3.49 . [ 21 ]
To interpret these numbers, note that two chemical species in an acid equilibrium are equiconcentrated when p K = p H . In particular, the extracellular fluid ( cytosol ) in biological systems exhibits p H ≈ 7.2 , so that carbonic acid will be almost 50%-dissociated at equilibrium.
The Bjerrum plot shows typical equilibrium concentrations, in solution, in seawater , of carbon dioxide and the various species derived from it, as a function of pH . [ 8 ] [ 9 ] As human industrialization has increased the proportion of carbon dioxide in Earth's atmosphere , the proportion of carbon dioxide dissolved in sea- and freshwater as carbonic acid is also expected to increase. This rise in dissolved acid is also expected to acidify those waters, generating a decrease in pH. [ 22 ] [ 23 ] It has been estimated that the increase in dissolved carbon dioxide has already caused the ocean's average surface pH to decrease by about 0.1 from pre-industrial levels. | https://en.wikipedia.org/wiki/OC(OH)2 |
Formaldehyde ( / f ɔːr ˈ m æ l d ɪ h aɪ d / ⓘ for- MAL -di-hide , US also / f ə r -/ ⓘ fər- ) ( systematic name methanal ) is an organic compound with the chemical formula CH 2 O and structure H−CHO , more precisely H 2 C=O . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde . It is stored as aqueous solutions ( formalin ), which consists mainly of the hydrate CH 2 (OH) 2 . It is the simplest of the aldehydes ( R−CHO ). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. [ 14 ] It is mainly used in the production of industrial resins , e.g., for particle board and coatings .
Formaldehyde also occurs naturally. It is derived from the degradation of serine , dimethylglycine , and lipids . Demethylases act by converting N-methyl groups to formaldehyde. [ 15 ]
Formaldehyde is classified as a group 1 carcinogen [ note 1 ] [ 17 ] and can cause respiratory and skin irritation upon exposure. [ 16 ]
Formaldehyde is more complicated than many simple carbon compounds in that it adopts several diverse forms. These compounds can often be used interchangeably and can be interconverted. [ citation needed ]
A small amount of stabilizer , such as methanol , is usually added to suppress oxidation and polymerization . A typical commercial-grade formalin may contain 10–12% methanol in addition to various metallic impurities.
"Formaldehyde" was first used as a generic trademark in 1893 following a previous trade name, "formalin". [ 18 ]
Molecular formaldehyde contains a central carbon atom with a double bond to the oxygen atom and a single bond to each hydrogen atom . This structure is summarised by the condensed formula H 2 C=O. [ 19 ] The molecule is planar, Y-shaped and its molecular symmetry belongs to the C 2v point group . [ 20 ] The precise molecular geometry of gaseous formaldehyde has been determined by gas electron diffraction [ 19 ] [ 21 ] and microwave spectroscopy . [ 22 ] [ 23 ] The bond lengths are 1.21 Å for the carbon–oxygen bond [ 19 ] [ 21 ] [ 22 ] [ 23 ] [ 24 ] and around 1.11 Å for the carbon–hydrogen bond , [ 19 ] [ 21 ] [ 22 ] [ 23 ] while the H–C–H bond angle is 117°, [ 22 ] [ 23 ] close to the 120° angle found in an ideal trigonal planar molecule . [ 19 ] Some excited electronic states of formaldehyde are pyramidal rather than planar as in the ground state . [ 24 ]
Processes in the upper atmosphere contribute more than 80% of the total formaldehyde in the environment. [ 25 ] Formaldehyde is an intermediate in the oxidation (or combustion ) of methane , as well as of other carbon compounds, e.g. in forest fires , automobile exhaust, and tobacco smoke . When produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons , it becomes part of smog . Formaldehyde has also been detected in outer space.
Formaldehyde and its adducts are ubiquitous in nature. Food may contain formaldehyde at levels 1–100 mg/kg. [ 26 ] Formaldehyde, formed in the metabolism of the amino acids serine and threonine , is found in the bloodstream of humans and other primates at concentrations of approximately 50 micromolar . [ 27 ] Experiments in which animals are exposed to an atmosphere containing isotopically labeled formaldehyde have demonstrated that even in deliberately exposed animals, the majority of formaldehyde-DNA adducts found in non-respiratory tissues are derived from endogenously produced formaldehyde. [ 28 ]
Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to formic acid . [ 29 ] [ 30 ] It nonetheless presents significant health concerns , as a contaminant .
Formaldehyde appears to be a useful probe in astrochemistry due to prominence of the 1 10 ←1 11 and 2 11 ←2 12 K -doublet transitions. It was the first polyatomic organic molecule detected in the interstellar medium . [ 31 ] Since its initial detection in 1969, it has been observed in many regions of the galaxy . Because of the widespread interest in interstellar formaldehyde, it has been extensively studied, yielding new extragalactic sources. [ 32 ] A proposed mechanism for the formation is the hydrogenation of CO ice: [ 33 ]
HCN , HNC , H 2 CO, and dust have also been observed inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) . [ 34 ] [ 35 ]
Formaldehyde was discovered in 1859 by the Russian chemist Aleksandr Butlerov (1828–1886) when he attempted to synthesize methanediol ("methylene glycol") from iodomethane and silver oxalate . [ 36 ] In his paper, Butlerov referred to formaldehyde as "dioxymethylen" (methylene dioxide) because his empirical formula for it was incorrect, as atomic weights were not precisely determined until the Karlsruhe Congress .
The compound was identified as an aldehyde by August Wilhelm von Hofmann , who first announced its production by passing methanol vapor in air over hot platinum wire. [ 37 ] [ 38 ] With modifications, Hofmann's method remains the basis of the present day industrial route.
Solution routes to formaldehyde also entail oxidation of methanol or iodomethane . [ 39 ]
Formaldehyde is produced industrially by the catalytic oxidation of methanol . The most common catalysts are silver metal (i.e. the FASIL process ), iron(III) oxide , [ 40 ] iron molybdenum oxides (e.g. iron(III) molybdate ) with a molybdenum -enriched surface, [ 41 ] or vanadium oxides . In the commonly used formox process , methanol and oxygen react at c. 250–400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation : [ 42 ]
The silver-based catalyst usually operates at a higher temperature, about 650 °C. Two chemical reactions on it simultaneously produce formaldehyde: that shown above and the dehydrogenation reaction:
In principle, formaldehyde could be generated by oxidation of methane , but this route is not industrially viable because the methanol is more easily oxidized than methane. [ 42 ]
Formaldehyde is produced via several enzyme-catalyzed routes. [ 43 ] Living beings, including humans, produce formaldehyde as part of their metabolism. Formaldehyde is key to several bodily functions (e.g. epigenetics [ 27 ] ), but its amount must also be tightly controlled to avoid self-poisoning. [ 44 ]
Formaldehyde is catabolized by alcohol dehydrogenase ADH5 and aldehyde dehydrogenase ALDH2 . [ 45 ]
Formaldehyde is a building block in the synthesis of many other compounds of specialised and industrial significance. It exhibits most of the chemical properties of other aldehydes but is more reactive. [ 46 ]
Monomeric CH 2 O is a gas and is rarely encountered in the laboratory. Aqueous formaldehyde, unlike some other small aldehydes (which need specific conditions to oligomerize through aldol condensation ) oligomerizes spontaneously at a common state. The trimer 1,3,5-trioxane, (CH 2 O) 3 , is a typical oligomer. Many cyclic oligomers of other sizes have been isolated. Similarly, formaldehyde hydrates to give the geminal diol methanediol , which condenses further to form hydroxy-terminated oligomers HO(CH 2 O) n H. The polymer is called paraformaldehyde . The higher concentration of formaldehyde—the more equilibrium shifts towards polymerization. Diluting with water or increasing the solution temperature, as well as adding alcohols (such as methanol or ethanol) lowers that tendency.
Gaseous formaldehyde polymerizes at active sites on vessel walls, but the mechanism of the reaction is unknown. [ 47 ] Small amounts of hydrogen chloride , boron trifluoride , or stannic chloride present in gaseous formaldehyde provide the catalytic effect and make the polymerization rapid. [ 48 ]
Formaldehyde forms cross-links by first combining with a protein to form methylol , which loses a water molecule to form a Schiff base . [ 49 ] The Schiff base can then react with DNA or protein to create a cross-linked product. [ 49 ] This reaction is the basis for the most common process of chemical fixation .
Formaldehyde is readily oxidized by atmospheric oxygen into formic acid . For this reason, commercial formaldehyde is typically contaminated with formic acid. Formaldehyde can be hydrogenated into methanol .
In the Cannizzaro reaction , formaldehyde and base react to produce formic acid and methanol, a disproportionation reaction .
Formaldehyde reacts with many compounds, resulting in hydroxymethylation :
The resulting hydroxymethyl derivatives typically react further. Thus, amines give hexahydro-1,3,5-triazines :
Similarly, when combined with hydrogen sulfide , it forms trithiane : [ 50 ]
In the presence of acids, it participates in electrophilic aromatic substitution reactions with aromatic compounds resulting in hydroxymethylated derivatives:
When conducted in the presence of hydrogen chloride, the product is the chloromethyl compound, as described in the Blanc chloromethylation . If the arene is electron-rich, as in phenols, elaborate condensations ensue. With 4-substituted phenols one obtains calixarenes . [ 51 ] Phenol results in polymers.
Many amino acids react with formaldehyde. [ 43 ] Cysteine converts to thioproline .
Formaldehyde is a common precursor to more complex compounds and materials. In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin , melamine resin , phenol formaldehyde resin , polyoxymethylene plastics , 1,4-butanediol , and methylene diphenyl diisocyanate . [ 42 ] The textile industry uses formaldehyde-based resins as finishers to make fabrics crease-resistant. [ 52 ]
When condensed with phenol , urea , or melamine , formaldehyde produces, respectively, hard thermoset phenol formaldehyde resin, urea formaldehyde resin, and melamine resin. These polymers are permanent adhesives used in plywood and carpeting . They are also foamed to make insulation , or cast into moulded products. Production of formaldehyde resins accounts for more than half of formaldehyde consumption.
Formaldehyde is also a precursor to polyfunctional alcohols such as pentaerythritol , which is used to make paints and explosives . Other formaldehyde derivatives include methylene diphenyl diisocyanate, an important component in polyurethane paints and foams, and hexamine , which is used in phenol-formaldehyde resins as well as the explosive RDX .
Condensation with acetaldehyde affords pentaerythritol , a chemical necessary in synthesizing PETN , a high explosive: [ 53 ]
An aqueous solution of formaldehyde can be useful as a disinfectant as it kills most bacteria and fungi (including their spores). It is used as an additive in vaccine manufacturing to inactivate toxins and pathogens. [ 54 ] Formaldehyde releasers are used as biocides in personal care products such as cosmetics. Although present at levels not normally considered harmful, they are known to cause allergic contact dermatitis in certain sensitised individuals. [ 55 ]
Aquarists use formaldehyde as a treatment for the parasites Ichthyophthirius multifiliis and Cryptocaryon irritans . [ 56 ] Formaldehyde is one of the main disinfectants recommended for destroying anthrax . [ 57 ]
Formaldehyde is also approved for use in the manufacture of animal feeds in the US. It is an antimicrobial agent used to maintain complete animal feeds or feed ingredients Salmonella negative for up to 21 days. [ 58 ]
Formaldehyde preserves or fixes tissue or cells. The process involves cross-linking of primary amino groups . The European Union has banned the use of formaldehyde as a biocide (including embalming ) under the Biocidal Products Directive (98/8/EC) due to its carcinogenic properties. [ 59 ] [ 60 ] Countries with a strong tradition of embalming corpses, such as Ireland and other colder-weather countries, have raised concerns. Despite reports to the contrary, [ 61 ] no decision on the inclusion of formaldehyde on Annex I of the Biocidal Products Directive for product-type 22 (embalming and taxidermist fluids) had been made as of September 2009 [update] . [ 62 ]
Formaldehyde-based crosslinking is exploited in ChIP-on-chip or ChIP-sequencing genomics experiments, where DNA-binding proteins are cross-linked to their cognate binding sites on the chromosome and analyzed to determine what genes are regulated by the proteins. Formaldehyde is also used as a denaturing agent in RNA gel electrophoresis , preventing RNA from forming secondary structures. A solution of 4% formaldehyde fixes pathology tissue specimens at about one mm per hour at room temperature.
Formaldehyde and 18 M (concentrated) sulfuric acid makes Marquis reagent —which can identify alkaloids and other compounds.
In photography, formaldehyde is used in low concentrations for the process C-41 (color negative film) stabilizer in the final wash step, [ 63 ] as well as in the process E-6 pre-bleach step, to make it unnecessary in the final wash. Due to improvements in dye coupler chemistry, more modern (2006 or later) E-6 and C-41 films do not need formaldehyde, as their dyes are already stable.
In view of its widespread use, toxicity, and volatility, formaldehyde poses a significant danger to human health. [ 64 ] [ 65 ] In 2011, the US National Toxicology Program described formaldehyde as "known to be a human carcinogen". [ 66 ] [ 67 ] [ 68 ]
Concerns are associated with chronic (long-term) exposure by inhalation as may happen from thermal or chemical decomposition of formaldehyde-based resins and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). As formaldehyde resins are used in many construction materials , it is one of the more common indoor air pollutants . [ 69 ] [ 70 ] At concentrations above 0.1 ppm in air, formaldehyde can irritate the eyes and mucous membranes . [ 71 ] Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, and can trigger or aggravate asthma symptoms. [ 72 ] [ 73 ]
The CDC considers formaldehyde as a systemic poison. Formaldehyde poisoning can cause permanent changes in the nervous system 's functions. [ 74 ]
A 1988 Canadian study of houses with urea-formaldehyde foam insulation found that formaldehyde levels as low as 0.046 ppm were positively correlated with eye and nasal irritation. [ 75 ] A 2009 review of studies has shown a strong association between exposure to formaldehyde and the development of childhood asthma . [ 76 ]
A theory was proposed for the carcinogenesis of formaldehyde in 1978. [ 77 ] In 1987 the United States Environmental Protection Agency (EPA) classified it as a probable human carcinogen , and after more studies the WHO International Agency for Research on Cancer (IARC) in 1995 also classified it as a probable human carcinogen . Further information and evaluation of all known data led the IARC to reclassify formaldehyde as a known human carcinogen [ 78 ] associated with nasal sinus cancer and nasopharyngeal cancer . [ 79 ] Studies in 2009 and 2010 have also shown a positive correlation between exposure to formaldehyde and the development of leukemia , particularly myeloid leukemia . [ 80 ] [ 81 ] Nasopharyngeal and sinonasal cancers are relatively rare, with a combined annual incidence in the United States of < 4,000 cases. [ 82 ] [ 83 ] About 30,000 cases of myeloid leukemia occur in the United States each year. [ 84 ] [ 85 ] Some evidence suggests that workplace exposure to formaldehyde contributes to sinonasal cancers. [ 86 ] Professionals exposed to formaldehyde in their occupation, such as funeral industry workers and embalmers , showed an increased risk of leukemia and brain cancer compared with the general population. [ 87 ] Other factors are important in determining individual risk for the development of leukemia or nasopharyngeal cancer. [ 86 ] [ 88 ] [ 89 ] In yeast, formaldehyde is found to perturb pathways for DNA repair and cell cycle. [ 90 ]
In the residential environment, formaldehyde exposure comes from a number of routes; formaldehyde can be emitted by treated wood products, such as plywood or particle board , but it is produced by paints, varnishes , floor finishes, and cigarette smoking as well. [ 91 ] In July 2016, the U.S. EPA released a prepublication version of its final rule on Formaldehyde Emission Standards for Composite Wood Products. [ 92 ] These new rules impact manufacturers, importers, distributors, and retailers of products containing composite wood, including fiberboard, particleboard, and various laminated products, who must comply with more stringent record-keeping and labeling requirements. [ 93 ]
The U.S. EPA allows no more than 0.016 ppm formaldehyde in the air in new buildings constructed for that agency. [ 94 ] [ failed verification ] A U.S. EPA study found a new home measured 0.076 ppm when brand new and 0.045 ppm after 30 days. [ 95 ] The Federal Emergency Management Agency (FEMA) has also announced limits on the formaldehyde levels in trailers purchased by that agency. [ 96 ] The EPA recommends the use of "exterior-grade" pressed-wood products with phenol instead of urea resin to limit formaldehyde exposure, since pressed-wood products containing formaldehyde resins are often a significant source of formaldehyde in homes. [ 79 ]
The eyes are most sensitive to formaldehyde exposure: The lowest level at which many people can begin to smell formaldehyde ranges between 0.05 and 1 ppm. The maximum concentration value at the workplace is 0.3 ppm. [ 97 ] [ need quotation to verify ] In controlled chamber studies, individuals begin to sense eye irritation at about 0.5 ppm; 5 to 20 percent report eye irritation at 0.5 to 1 ppm; and greater certainty for sensory irritation occurred at 1 ppm and above. While some agencies have used a level as low as 0.1 ppm as a threshold for irritation, the expert panel found that a level of 0.3 ppm would protect against nearly all irritation. In fact, the expert panel found that a level of 1.0 ppm would avoid eye irritation—the most sensitive endpoint—in 75–95% of all people exposed. [ 98 ]
Formaldehyde levels in building environments are affected by a number of factors. These include the potency of formaldehyde-emitting products present, the ratio of the surface area of emitting materials to volume of space, environmental factors, product age, interactions with other materials, and ventilation conditions. Formaldehyde emits from a variety of construction materials, furnishings, and consumer products. The three products that emit the highest concentrations are medium density fiberboard , hardwood plywood, and particle board. Environmental factors such as temperature and relative humidity can elevate levels because formaldehyde has a high vapor pressure . Formaldehyde levels from building materials are the highest when a building first opens because materials would have less time to off-gas. Formaldehyde levels decrease over time as the sources suppress.
In operating rooms , formaldehyde is produced as a byproduct of electrosurgery and is present in surgical smoke, exposing surgeons and healthcare workers to potentially unsafe concentrations. [ 99 ]
Formaldehyde levels in air can be sampled and tested in several ways, including impinger, treated sorbent, and passive monitors. [ 100 ] The National Institute for Occupational Safety and Health (NIOSH) has measurement methods numbered 2016, 2541, 3500, and 3800. [ 101 ]
In June 2011, the twelfth edition of the National Toxicology Program (NTP) Report on Carcinogens (RoC) changed the listing status of formaldehyde from "reasonably anticipated to be a human carcinogen" to "known to be a human carcinogen." [ 66 ] [ 67 ] [ 68 ] Concurrently, a National Academy of Sciences (NAS) committee was convened and issued an independent review of the draft U.S. EPA IRIS assessment of formaldehyde, providing a comprehensive health effects assessment and quantitative estimates of human risks of adverse effects. [ 102 ]
For most people, irritation from formaldehyde is temporary and reversible, although formaldehyde can cause allergies and is part of the standard patch test series. In 2005–06, it was the seventh-most-prevalent allergen in patch tests (9.0%). [ 103 ] People with formaldehyde allergy are advised to avoid formaldehyde releasers as well (e.g., Quaternium-15 , imidazolidinyl urea , and diazolidinyl urea ). [ 104 ] People who suffer allergic reactions to formaldehyde tend to display lesions on the skin in the areas that have had direct contact with the substance, such as the neck or thighs (often due to formaldehyde released from permanent press finished clothing) or dermatitis on the face (typically from cosmetics). [ 55 ] Formaldehyde has been banned in cosmetics in both Sweden [ 105 ] and Japan . [ 106 ]
In humans, ingestion of as little as 30 millilitres (1.0 US fl oz) of 37% formaldehyde solution can cause death. Other symptoms associated with ingesting such a solution include gastrointestinal damage (vomiting, abdominal pain), and systematic damage (dizziness). [ 74 ] Testing for formaldehyde is by blood and/or urine by gas chromatography–mass spectrometry . Other methods to detect formaldehyde include infrared detection, gas detector tubes, gas detectors using electrochemical sensors, and high-performance liquid chromatography (HPLC). HPLC is the most sensitive. [ 107 ]
The fifteenth edition (2021) of the U.S. National Toxicology Program Report on Carcinogens notes that currently in the U.S. “The general population can be exposed to formaldehyde primarily from breathing indoor or outdoor air, from tobacco smoke, from use of cosmetic products containing formaldehyde, and, to a more limited extent, from ingestion of food and water.” Affected water includes groundwater, surface water, and bottled water. It also notes that occupational exposure can be significant. [ 108 ]
Formaldehyde in food can be present naturally, added as an inadvertent contaminant, or intentionally added as a preservative, disinfectant, or bacteriostatic agent . Cooking and smoking food can also result in formaldehyde being produced in food. Foods that the U.S. National Toxicology Program has reported to have higher levels compared to other foods are fish, seafood, and smoked ham. It also notes formaldehyde in food generally occurs in a bound form and that formaldehyde is unstable in an aqueous solution . [ 109 ]
Scandals have broken in both the 2005 Indonesia food scare and 2007 Vietnam food scare regarding the addition of formaldehyde to foods to extend shelf life. In 2011, after a four-year absence, Indonesian authorities found foods with formaldehyde being sold in markets in a number of regions across the country. [ 110 ] In August 2011, at least at two Carrefour supermarkets, the Central Jakarta Livestock and Fishery Sub-Department found cendol containing 10 parts per million of formaldehyde. [ 111 ] In 2014, the owner of two noodle factories in Bogor , Indonesia, was arrested for using formaldehyde in noodles. [ 112 ] Foods known to be contaminated included noodles, salted fish, and tofu. Chicken and beer were also rumored to be contaminated. In some places, such as China, manufacturers still use formaldehyde illegally as a preservative in foods, which exposes people to formaldehyde ingestion. [ 113 ]
In 2011 in Nakhon Ratchasima , Thailand, truckloads of rotten chicken were treated with formaldehyde for sale in which "a large network", including 11 slaughterhouses run by a criminal gang, were implicated. [ 114 ] In 2012, 1 billion rupiah (almost US$100,000) of fish imported from Pakistan to Batam , Indonesia, were found laced with formaldehyde. [ 115 ]
Formalin contamination of foods has been reported in Bangladesh , with stores and supermarkets selling fruits, fishes, and vegetables that have been treated with formalin to keep them fresh. [ 116 ] However, in 2015, a Formalin Control Bill was passed in the Parliament of Bangladesh with a provision of life-term imprisonment as the maximum punishment as well as a maximum fine of 2,000,000 BDT but not less than 500,000 BDT for importing, producing, or hoarding formalin without a license. [ 117 ]
In the early 1900s, formaldehyde was frequently added by US milk plants to milk bottles as a method of pasteurization due to the lack of knowledge and concern [ 118 ] regarding formaldehyde's toxicity. [ 119 ] [ 120 ]
Formaldehyde was one of the chemicals used in 19th century industrialised food production that was investigated by Dr. Harvey W. Wiley with his famous 'Poison Squad' as part of the US Department of Agriculture . This led to the 1906 Pure Food and Drug Act , a landmark event in the early history of food regulation in the United States . [ 121 ]
Formaldehyde is banned from use in certain applications (preservatives for liquid-cooling and processing systems, slimicides , metalworking-fluid preservatives, and antifouling products) under the Biocidal Products Directive. [ 122 ] [ 123 ] In the EU, the maximum allowed concentration of formaldehyde in finished products is 0.2%, and any product that exceeds 0.05% has to include a warning that the product contains formaldehyde. [ 55 ]
In the United States, Congress passed a bill July 7, 2010, regarding the use of formaldehyde in hardwood plywood , particle board , and medium density fiberboard . The bill limited the allowable amount of formaldehyde emissions from these wood products to 0.09 ppm, and required companies to meet this standard by January 2013. [ 124 ] The final U.S. EPA rule specified maximum emissions of "0.05 ppm formaldehyde for hardwood plywood, 0.09 ppm formaldehyde for particleboard, 0.11 ppm formaldehyde for medium-density fiberboard, and 0.13 ppm formaldehyde for thin medium-density fiberboard." [ 125 ]
Formaldehyde was declared a toxic substance by the 1999 Canadian Environmental Protection Act . [ 126 ]
The FDA is proposing a ban on hair relaxers with formaldehyde due to cancer concerns. [ 127 ] | https://en.wikipedia.org/wiki/OCH2 |
4CMN , 2KIE , 2QV2 , 3QBT , 3QIS
4952
320634
ENSG00000122126
ENSMUSG00000001173
Q01968
Q6NVF0
NM_000276 NM_001587 NM_001318784
NM_177215
NP_000267 NP_001305713 NP_001578
NP_796189
Inositol polyphosphate 5-phosphatase OCRL-1 , also known as Lowe oculocerebrorenal syndrome protein , is an enzyme encoded by the OCRL gene located on the X chromosome in humans. [ 5 ]
This gene encodes an inositol polyphosphate 5-phosphatase. The responsible gene locus is at Xq26.1. This phosphatase enzyme is in part responsible for regulating membrane trafficking actin polymerization, and is located in several subcellular parts of the trans-Golgi network.
Deficiencies in OCRL-1 are associated with oculocerebrorenal syndrome [ 6 ] and also have been linked to Dent's disease . [ 7 ] [ 8 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OCRL |
Carbonyl selenide is a chemical compound with the chemical formula O = C = Se . It is a linear molecule that is primarily of interest for research purposes.
Carbonyl selenide is a colorless gas with an unpleasant odor. [ 1 ] Although the compound is quite stable, its solutions gradually revert to elemental selenium and carbon monoxide . [ 2 ]
Carbonyl selenide can be produced by treating selenium with carbon monoxide in the presence of amines . [ 3 ]
It is used in organoselenium chemistry as a means of incorporating selenium into organic compounds , e.g. for the preparation of selenocarbamates ( O -selenocarbamates R−O−C(=Se)−NR'R" and Se -selenocarbamates, R−Se−C(=O)−NR'R" , where R is organyl and R' and R" are any group, typically H or organyl). [ 3 ] | https://en.wikipedia.org/wiki/OCSe |
In wireless networking, On-Demand Multicast Routing Protocol is a protocol for routing multicast and unicast traffic throughout Ad hoc wireless mesh networks .
ODMRP creates routes on demand, rather than proactively creating routes as OLSR does. This suffers from a route acquisition delay, although it helps reduce network traffic in general. To help reduce the problem of this delay, some implementations send the first data packet along with the route discovery packet.
Because some links may be asymmetric, the path from one node to another is not necessarily the same as the reverse path of these nodes.
This computer networking article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/ODMRP |
OECD Guidelines for the Testing of Chemicals ( OECD TG ) are a set of internationally accepted specifications for the testing of chemicals decided on by the Organisation for Economic Co-operation and Development (OECD). They were first published in 1981. They are split into five sections:
Guidelines are numbered with three digit numbers, the section number being the first number. Sometimes guidelines are suffixed with a letter.
Guidelines are under constant review, with guidelines being periodically updated, new guidelines being adopted, and guidelines being withdrawn. Previous guidelines are maintained on the website for reference purposes. Animal welfare concerns are dealt with by ensuring that animal tests are only permitted where necessary.
The guidelines are available in both English and French . | https://en.wikipedia.org/wiki/OECD_Guidelines_for_the_Testing_of_Chemicals |
OELib was an open source Cheminformatics library written by Matt Stahl and based on the ideas of OBabel. [ 1 ] Its actual GPLed C++ and Java based successors are OpenBabel and JOELib , [ 2 ] with Its commercial successor being called OEChem . [ citation needed ]
This software-engineering -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OELib |
Oxygen difluoride is a chemical compound with the formula OF 2 . As predicted by VSEPR theory , the molecule adopts a bent molecular geometry . [ citation needed ] It is a strong oxidizer and has attracted attention in rocketry for this reason. [ 5 ] With a boiling point of −144.75 °C, OF 2 is the most volatile (isolable) triatomic compound. [ 6 ] The compound is one of many known oxygen fluorides .
Oxygen difluoride was first reported in 1929; it was obtained by the electrolysis of molten potassium fluoride and hydrofluoric acid containing small quantities of water . [ 7 ] [ 8 ] The modern preparation entails the reaction of fluorine with a dilute aqueous solution of sodium hydroxide , with sodium fluoride as a side-product:
It is a covalently bonded molecule with a bent molecular geometry and a F-O-F bond angle of 103 degrees. Its powerful oxidizing properties are suggested by the oxidation number of +2 for the oxygen atom instead of its normal −2.
Above 200 °C, OF 2 decomposes to oxygen and fluorine by a radical mechanism.
OF 2 reacts with many metals to yield oxides and fluorides . Nonmetals also react: phosphorus reacts with OF 2 to form PF 5 and POF 3 ; sulfur gives SO 2 and SF 4 ; and unusually for a noble gas , xenon reacts (at elevated temperatures) yielding XeF 4 and xenon oxyfluorides.
Oxygen difluoride reacts with water to form hydrofluoric acid :
It can oxidize sulfur dioxide to sulfur trioxide and elemental fluorine :
However, in the presence of UV radiation , the products are sulfuryl fluoride ( SO 2 F 2 ) and pyrosulfuryl fluoride ( S 2 O 5 F 2 ):
Oxygen difluoride is considered an unsafe gas due to its oxidizing properties. It reacts explosively with water. [ 9 ] Hydrofluoric acid produced by the hydrolysis of OF 2 with water is highly corrosive and toxic, capable of causing necrosis , leaching calcium from the bones and causing cardiovascular damage, among a host of other highly toxic effects. Other acute poisoning effects include: pulmonary edema , bleeding lungs, headaches, etc. [ 10 ] Chronic exposure to oxygen difluoride, like that of other chemicals that release fluoride ions, can lead to fluorosis and other symptoms of chronic fluoride poisoning . Oxygen difluoride may be associated with kidney damage. [ 10 ] The maximum workplace exposure limit is 0.05 ppm. [ 11 ] [ 10 ]
In Robert L. Forward 's science fiction novel Camelot 30K , oxygen difluoride was used as a biochemical solvent by fictional life forms living in the solar system's Kuiper belt . While OF 2 would be a solid at 30 K, the fictional alien lifeforms were described as endothermic , maintaining elevated body temperatures and liquid OF 2 blood by radiothermal heating. | https://en.wikipedia.org/wiki/OF2 |
Hydroxide is a diatomic anion with chemical formula OH − . It consists of an oxygen and hydrogen atom held together by a single covalent bond , and carries a negative electric charge . It is an important but usually minor constituent of water . It functions as a base , a ligand , a nucleophile , and a catalyst . The hydroxide ion forms salts , some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical .
The corresponding electrically neutral compound HO • is the hydroxyl radical . The corresponding covalently bound group −OH of atoms is the hydroxy group .
Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry .
Many inorganic substances which bear the word hydroxide in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups .
The hydroxide ion is naturally produced from water by the self-ionization reaction: [ 2 ]
The equilibrium constant for this reaction, defined as
has a value close to 10 −14 at 25 °C, so the concentration of hydroxide ions in pure water is close to 10 −7 mol∙dm −3 , to satisfy the equal charge constraint. The pH of a solution is equal to the decimal cologarithm of the hydrogen cation concentration; [ note 2 ] the pH of pure water is close to 7 at ambient temperatures. The concentration of hydroxide ions can be expressed in terms of pOH , which is close to (14 − pH), [ note 3 ] so the pOH of pure water is also close to 7. Addition of a base to water will reduce the hydrogen cation concentration and therefore increase the hydroxide ion concentration (decrease pH, increase pOH) even if the base does not itself contain hydroxide. For example, ammonia solutions have a pH greater than 7 due to the reaction NH 3 + H + ⇌ NH + 4 , which decreases the hydrogen cation concentration, which increases the hydroxide ion concentration. pOH can be kept at a nearly constant value with various buffer solutions .
In an aqueous solution [ 4 ] the hydroxide ion is a base in the Brønsted–Lowry sense as it can accept a proton [ note 4 ] from a Brønsted–Lowry acid to form a water molecule. It can also act as a Lewis base by donating a pair of electrons to a Lewis acid. In aqueous solution both hydrogen ions and hydroxide ions are strongly solvated, with hydrogen bonds between oxygen and hydrogen atoms. Indeed, the bihydroxide ion H 3 O − 2 has been characterized in the solid state. This compound is centrosymmetric and has a very short hydrogen bond (114.5 pm ) that is similar to the length in the bifluoride ion HF − 2 (114 pm). [ 3 ] In aqueous solution the hydroxide ion forms strong hydrogen bonds with water molecules. A consequence of this is that concentrated solutions of sodium hydroxide have high viscosity due to the formation of an extended network of hydrogen bonds as in hydrogen fluoride solutions.
In solution, exposed to air, the hydroxide ion reacts rapidly with atmospheric carbon dioxide , which acts as a lewis acid, to form, initially, the bicarbonate ion.
The equilibrium constant for this reaction can be specified either as a reaction with dissolved carbon dioxide or as a reaction with carbon dioxide gas (see Carbonic acid for values and details). At neutral or acid pH, the reaction is slow, but is catalyzed by the enzyme carbonic anhydrase , which effectively creates hydroxide ions at the active site.
Solutions containing the hydroxide ion attack glass . In this case, the silicates in glass are acting as acids. Basic hydroxides, whether solids or in solution, are stored in airtight plastic containers.
The hydroxide ion can function as a typical electron-pair donor ligand , forming such complexes as tetrahydroxoaluminate/tetrahydroxido aluminate [Al(OH) 4 ] − . It is also often found in mixed-ligand complexes of the type [ML x (OH) y ] z + , where L is a ligand. The hydroxide ion often serves as a bridging ligand , donating one pair of electrons to each of the atoms being bridged. As illustrated by [Pb 2 (OH)] 3+ , metal hydroxides are often written in a simplified format. It can even act as a 3-electron-pair donor, as in the tetramer [PtMe 3 (OH)] 4 . [ 5 ]
When bound to a strongly electron-withdrawing metal centre, hydroxide ligands tend to ionise into oxide ligands. For example, the bichromate ion [HCrO 4 ] − dissociates according to
with a p K a of about 5.9. [ 6 ]
The infrared spectra of compounds containing the OH functional group have strong absorption bands in the region centered around 3500 cm −1 . [ 7 ] The high frequency of molecular vibration is a consequence of the small mass of the hydrogen atom as compared to the mass of the oxygen atom, and this makes detection of hydroxyl groups by infrared spectroscopy relatively easy. A band due to an OH group tends to be sharp. However, the band width increases when the OH group is involved in hydrogen bonding. A water molecule has an HOH bending mode at about 1600 cm −1 , so the absence of this band can be used to distinguish an OH group from a water molecule.
When the OH group is bound to a metal ion in a coordination complex , an M−OH bending mode can be observed. For example, in [Sn(OH) 6 ] 2− it occurs at 1065 cm −1 . The bending mode for a bridging hydroxide tends to be at a lower frequency as in [( bipyridine )Cu(OH) 2 Cu( bipyridine )] 2+ (955 cm −1 ). [ 8 ] M−OH stretching vibrations occur below about 600 cm −1 . For example, the tetrahedral ion [Zn(OH) 4 ] 2− has bands at 470 cm −1 ( Raman -active, polarized) and 420 cm −1 (infrared). The same ion has a (HO)–Zn–(OH) bending vibration at 300 cm −1 . [ 9 ]
Sodium hydroxide solutions, also known as lye and caustic soda, are used in the manufacture of pulp and paper , textiles , drinking water , soaps and detergents , and as a drain cleaner . Worldwide production in 2004 was approximately 60 million tonnes . [ 10 ] The principal method of manufacture is the chloralkali process .
Solutions containing the hydroxide ion are generated when a salt of a weak acid is dissolved in water. Sodium carbonate is used as an alkali, for example, by virtue of the hydrolysis reaction
An example of the use of sodium carbonate as an alkali is when washing soda (another name for sodium carbonate) acts on insoluble esters , such as triglycerides , commonly known as fats, to hydrolyze them and make them soluble.
Bauxite , a basic hydroxide of aluminium , is the principal ore from which the metal is manufactured. [ 11 ] Similarly, goethite (α-FeO(OH)) and lepidocrocite (γ-FeO(OH)), basic hydroxides of iron , are among the principal ores used for the manufacture of metallic iron. [ 12 ]
Aside from NaOH and KOH, which enjoy very large scale applications, the hydroxides of the other alkali metals also are useful. Lithium hydroxide (LiOH) is used in breathing gas purification systems for spacecraft , submarines , and rebreathers to remove carbon dioxide from exhaled gas. [ 13 ]
The hydroxide of lithium is preferred to that of sodium because of its lower mass. Sodium hydroxide , potassium hydroxide , and the hydroxides of the other alkali metals are also strong bases . [ 14 ]
Beryllium hydroxide Be(OH) 2 is amphoteric . [ 15 ] The hydroxide itself is insoluble in water, with a solubility product log K * sp of −11.7. Addition of acid gives soluble hydrolysis products, including the trimeric ion [Be 3 (OH) 3 (H 2 O) 6 ] 3+ , which has OH groups bridging between pairs of beryllium ions making a 6-membered ring. [ 16 ] At very low pH the aqua ion [Be(H 2 O) 4 ] 2+ is formed. Addition of hydroxide to Be(OH) 2 gives the soluble tetrahydroxoberyllate or tetrahydroxido beryllate anion, [Be(OH) 4 ] 2− .
The solubility in water of the other hydroxides in this group increases with increasing atomic number . [ 17 ] Magnesium hydroxide Mg(OH) 2 is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: calcium hydroxide , strontium hydroxide , and barium hydroxide . A solution or suspension of calcium hydroxide is known as limewater and can be used to test for the weak acid carbon dioxide. The reaction Ca(OH) 2 + CO 2 ⇌ Ca 2+ + HCO − 3 + OH − illustrates the basicity of calcium hydroxide. Soda lime , which is a mixture of the strong bases NaOH and KOH with Ca(OH) 2 , is used as a CO 2 absorbent.
The simplest hydroxide of boron B(OH) 3 , known as boric acid , is an acid. Unlike the hydroxides of the alkali and alkaline earth hydroxides, it does not dissociate in aqueous solution. Instead, it reacts with water molecules acting as a Lewis acid, releasing protons.
A variety of oxyanions of boron are known, which, in the protonated form, contain hydroxide groups. [ 18 ]
Aluminium hydroxide Al(OH) 3 is amphoteric and dissolves in alkaline solution. [ 15 ]
In the Bayer process [ 19 ] for the production of pure aluminium oxide from bauxite minerals this equilibrium is manipulated by careful control of temperature and alkali concentration. In the first phase, aluminium dissolves in hot alkaline solution as Al(OH) − 4 , but other hydroxides usually present in the mineral, such as iron hydroxides, do not dissolve because they are not amphoteric. After removal of the insolubles, the so-called red mud , pure aluminium hydroxide is made to precipitate by reducing the temperature and adding water to the extract, which, by diluting the alkali, lowers the pH of the solution. Basic aluminium hydroxide AlO(OH), which may be present in bauxite, is also amphoteric.
In mildly acidic solutions, the hydroxo/hydroxido complexes formed by aluminium are somewhat different from those of boron, reflecting the greater size of Al(III) vs. B(III). The concentration of the species [Al 13 (OH) 32 ] 7+ is very dependent on the total aluminium concentration. Various other hydroxo complexes are found in crystalline compounds. Perhaps the most important is the basic hydroxide AlO(OH), a polymeric material known by the names of the mineral forms boehmite or diaspore , depending on crystal structure. Gallium hydroxide , [ 15 ] indium hydroxide , and thallium(III) hydroxide are also amphoteric. Thallium(I) hydroxide is a strong base. [ 20 ]
Carbon forms no simple hydroxides. The hypothetical compound C(OH) 4 ( orthocarbonic acid or methanetetrol) is unstable in aqueous solution: [ 21 ]
Carbon dioxide is also known as carbonic anhydride, meaning that it forms by dehydration of carbonic acid H 2 CO 3 (OC(OH) 2 ). [ 22 ]
Silicic acid is the name given to a variety of compounds with a generic formula [SiO x (OH) 4−2 x ] n . [ 23 ] [ 24 ] Orthosilicic acid has been identified in very dilute aqueous solution. It is a weak acid with p K a1 = 9.84, p K a2 = 13.2 at 25 °C. It is usually written as H 4 SiO 4 , but the formula Si(OH) 4 is generally accepted. [ 6 ] [ dubious – discuss ] Other silicic acids such as metasilicic acid (H 2 SiO 3 ), disilicic acid (H 2 Si 2 O 5 ), and pyrosilicic acid (H 6 Si 2 O 7 ) have been characterized. These acids also have hydroxide groups attached to the silicon; the formulas suggest that these acids are protonated forms of poly oxyanions .
Few hydroxo complexes of germanium have been characterized. Tin(II) hydroxide Sn(OH) 2 was prepared in anhydrous media. When tin(II) oxide is treated with alkali the pyramidal hydroxo complex Sn(OH) − 3 is formed. When solutions containing this ion are acidified, the ion [Sn 3 (OH) 4 ] 2+ is formed together with some basic hydroxo complexes. The structure of [Sn 3 (OH) 4 ] 2+ has a triangle of tin atoms connected by bridging hydroxide groups. [ 25 ] Tin(IV) hydroxide is unknown but can be regarded as the hypothetical acid from which stannates , with a formula [Sn(OH) 6 ] 2− , are derived by reaction with the (Lewis) basic hydroxide ion. [ 26 ]
Hydrolysis of Pb 2+ in aqueous solution is accompanied by the formation of various hydroxo-containing complexes, some of which are insoluble. The basic hydroxo complex [Pb 6 O(OH) 6 ] 4+ is a cluster of six lead centres with metal–metal bonds surrounding a central oxide ion. The six hydroxide groups lie on the faces of the two external Pb 4 tetrahedra. In strongly alkaline solutions soluble plumbate ions are formed, including [Pb(OH) 6 ] 2− . [ 27 ]
In the higher oxidation states of the pnictogens , chalcogens , halogens , and noble gases there are oxoacids in which the central atom is attached to oxide ions and hydroxide ions. Examples include phosphoric acid H 3 PO 4 , and sulfuric acid H 2 SO 4 . In these compounds one or more hydroxide groups can dissociate with the liberation of hydrogen cations as in a standard Brønsted–Lowry acid. Many oxoacids of sulfur are known and all feature OH groups that can dissociate. [ 28 ]
Telluric acid is often written with the formula H 2 TeO 4 ·2H 2 O but is better described structurally as Te(OH) 6 . [ 29 ]
Orthoperiodic acid [ note 6 ] can lose all its protons, eventually forming the periodate ion [IO 4 ] − . It can also be protonated in strongly acidic conditions to give the octahedral ion [I(OH) 6 ] + , completing the isoelectronic series, [E(OH) 6 ] z , E = Sn, Sb, Te, I; z = −2, −1, 0, +1. Other acids of iodine(VII) that contain hydroxide groups are known, in particular in salts such as the mesoperiodate ion that occurs in K 4 [I 2 O 8 (OH) 2 ]·8H 2 O. [ 30 ]
As is common outside of the alkali metals, hydroxides of the elements in lower oxidation states are complicated. For example, phosphorous acid H 3 PO 3 predominantly has the structure OP(H)(OH) 2 , in equilibrium with a small amount of P(OH) 3 . [ 31 ] [ 32 ]
The oxoacids of chlorine , bromine , and iodine have the formula O n −1 / 2 A(OH), where n is the oxidation number : +1, +3, +5, or +7, and A = Cl, Br, or I. The only oxoacid of fluorine is F(OH), hypofluorous acid . When these acids are neutralized the hydrogen atom is removed from the hydroxide group. [ 33 ]
The hydroxides of the transition metals and post-transition metals usually have the metal in the +2 (M = Mn, Fe, Co, Ni, Cu, Zn) or +3 (M = Fe, Ru, Rh, Ir) oxidation state. None are soluble in water, and many are poorly defined. One complicating feature of the hydroxides is their tendency to undergo further condensation to the oxides, a process called olation . Hydroxides of metals in the +1 oxidation state are also poorly defined or unstable. For example, silver hydroxide Ag(OH) decomposes spontaneously to the oxide (Ag 2 O). Copper(I) and gold(I) hydroxides are also unstable, although stable adducts of CuOH and AuOH are known. [ 34 ] The polymeric compounds M(OH) 2 and M(OH) 3 are in general prepared by increasing the pH of an aqueous solution of the corresponding metal cation until the hydroxide precipitates out of solution. On the converse, the hydroxides dissolve in acidic solution. Zinc hydroxide Zn(OH) 2 is amphoteric, forming the tetrahydroxido zincate ion Zn(OH) 2− 4 in strongly alkaline solution. [ 15 ]
Numerous mixed ligand complexes of these metals with the hydroxide ion exist. In fact, these are in general better defined than the simpler derivatives. Many can be made by deprotonation of the corresponding metal aquo complex .
Vanadic acid H 3 VO 4 shows similarities with phosphoric acid H 3 PO 4 though it has a much more complex vanadate oxoanion chemistry. Chromic acid H 2 CrO 4 , has similarities with sulfuric acid H 2 SO 4 ; for example, both form acid salts A + [HMO 4 ] − . Some metals, e.g. V, Cr, Nb, Ta, Mo, W, tend to exist in high oxidation states. Rather than forming hydroxides in aqueous solution, they convert to oxo clusters by the process of olation , forming polyoxometalates . [ 35 ]
In some cases, the products of partial hydrolysis of metal ion, described above, can be found in crystalline compounds. A striking example is found with zirconium (IV). Because of the high oxidation state, salts of Zr 4+ are extensively hydrolyzed in water even at low pH. The compound originally formulated as ZrOCl 2 ·8H 2 O was found to be the chloride salt of a tetrameric cation [Zr 4 (OH) 8 (H 2 O) 16 ] 8+ in which there is a square of Zr 4+ ions with two hydroxide groups bridging between Zr atoms on each side of the square and with four water molecules attached to each Zr atom. [ 36 ]
The mineral malachite is a typical example of a basic carbonate. The formula, Cu 2 CO 3 (OH) 2 shows that it is halfway between copper carbonate and copper hydroxide . Indeed, in the past the formula was written as CuCO 3 ·Cu(OH) 2 . The crystal structure is made up of copper, carbonate and hydroxide ions. [ 36 ] The mineral atacamite is an example of a basic chloride. It has the formula Cu 2 Cl(OH) 3 . In this case the composition is nearer to that of the hydroxide than that of the chloride: CuCl 2 ·3Cu(OH) 2 . [ 37 ] Copper forms hydroxyphosphate ( libethenite ), arsenate ( olivenite ), sulfate ( brochantite ), and nitrate compounds. White lead is a basic lead carbonate, (PbCO 3 ) 2 ·Pb(OH) 2 , which has been used as a white pigment because of its opaque quality, though its use is now restricted because it can be a source for lead poisoning . [ 36 ]
The hydroxide ion appears to rotate freely in crystals of the heavier alkali metal hydroxides at higher temperatures so as to present itself as a spherical ion, with an effective ionic radius of about 153 pm. [ 38 ] Thus, the high-temperature forms of KOH and NaOH have the sodium chloride structure, [ 39 ] which gradually freezes in a monoclinically distorted sodium chloride structure at temperatures below about 300 °C. The OH groups still rotate even at room temperature around their symmetry axes and, therefore, cannot be detected by X-ray diffraction . [ 40 ] The room-temperature form of NaOH has the thallium iodide structure. LiOH, however, has a layered structure, made up of tetrahedral Li(OH) 4 and (OH)Li 4 units. [ 38 ] This is consistent with the weakly basic character of LiOH in solution, indicating that the Li–OH bond has much covalent character.
The hydroxide ion displays cylindrical symmetry in hydroxides of divalent metals Ca, Cd, Mn, Fe, and Co. For example, magnesium hydroxide Mg(OH) 2 ( brucite ) crystallizes with the cadmium iodide layer structure, with a kind of close-packing of magnesium and hydroxide ions. [ 38 ] [ 41 ]
The amphoteric hydroxide Al(OH) 3 has four major crystalline forms: gibbsite (most stable), bayerite , nordstrandite , and doyleite . [ note 7 ] All these polymorphs are built up of double layers of hydroxide ions—the aluminium atoms on two-thirds of the octahedral holes between the two layers—and differ only in the stacking sequence of the layers. [ 42 ] The structures are similar to the brucite structure. However, whereas the brucite structure can be described as a close-packed structure, in gibbsite the OH groups on the underside of one layer rest on the groups of the layer below. This arrangement led to the suggestion that there are directional bonds between OH groups in adjacent layers. [ 43 ] This is an unusual form of hydrogen bonding since the two hydroxide ions involved would be expected to point away from each other. The hydrogen atoms have been located by neutron diffraction experiments on α-AlO(OH) ( diaspore ). The O–H–O distance is very short, at 265 pm; the hydrogen is not equidistant between the oxygen atoms and the short OH bond makes an angle of 12° with the O–O line. [ 44 ] A similar type of hydrogen bond has been proposed for other amphoteric hydroxides, including Be(OH) 2 , Zn(OH) 2 , and Fe(OH) 3 . [ 38 ]
A number of mixed hydroxides are known with stoichiometry A 3 M III (OH) 6 , A 2 M IV (OH) 6 , and AM V (OH) 6 . As the formula suggests these substances contain M(OH) 6 octahedral structural units. [ 45 ] Layered double hydroxides may be represented by the formula [M z + 1− x M 3+ x (OH) 2 ] q + (X n − ) q ⁄ n · y H 2 O . Most commonly, z = 2, and M 2+ = Ca 2+ , Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , or Zn 2+ ; hence q = x .
Potassium hydroxide and sodium hydroxide are two well-known reagents in organic chemistry .
The hydroxide ion may act as a base catalyst . [ 46 ] The base abstracts a proton from a weak acid to give an intermediate that goes on to react with another reagent. Common substrates for proton abstraction are alcohols , phenols , amines , and carbon acids . The p K a value for dissociation of a C–H bond is extremely high, but the pK a alpha hydrogens of a carbonyl compound are about 3 log units lower. Typical p K a values are 16.7 for acetaldehyde and 19 for acetone . [ 47 ] Dissociation can occur in the presence of a suitable base.
The base should have a p K a value not less than about 4 log units smaller, or the equilibrium will lie almost completely to the left.
The hydroxide ion by itself is not a strong enough base, but it can be converted to one by adding sodium hydroxide to ethanol
to produce the ethoxide ion. The pK a for self-dissociation of ethanol is about 16, so the alkoxide ion is a strong enough base. [ 48 ] The addition of an alcohol to an aldehyde to form a hemiacetal is an example of a reaction that can be catalyzed by the presence of hydroxide. Hydroxide can also act as a Lewis-base catalyst. [ 49 ]
The hydroxide ion is intermediate in nucleophilicity between the fluoride ion F − , and the amide ion NH − 2 . [ 50 ] Ester hydrolysis under alkaline conditions (also known as base hydrolysis )
is an example of a hydroxide ion serving as a nucleophile. [ 51 ]
Early methods for manufacturing soap treated triglycerides from animal fat (the ester) with lye .
Other cases where hydroxide can act as a nucleophilic reagent are amide hydrolysis, the Cannizzaro reaction , nucleophilic aliphatic substitution , nucleophilic aromatic substitution , and in elimination reactions . The reaction medium for KOH and NaOH is usually water but with a phase-transfer catalyst the hydroxide anion can be shuttled into an organic solvent as well, for example in the generation of the reactive intermediate dichlorocarbene . | https://en.wikipedia.org/wiki/OH- |
Formic acid (from Latin formica ' ant ' ), systematically named methanoic acid , is the simplest carboxylic acid . It has the chemical formula HCOOH and structure H−C(=O)−O−H . This acid is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Esters , salts , and the anion derived from formic acid are called formates . Industrially, formic acid is produced from methanol . [ 5 ]
Formic acid, which has a pungent, penetrating odor, is found naturally in insects, weeds, fruits and vegetables, and forest emissions. It appears in most ants and in stingless bees of the genus Oxytrigona . [ 6 ] [ 7 ] Wood ants from the genus Formica can spray formic acid on their prey or to defend the nest. The puss moth caterpillar ( Cerura vinula ) will spray it as well when threatened by predators. It is also found in the trichomes of stinging nettle ( Urtica dioica ). Apart from that, this acid is incorporated in many fruits such as pineapple (0.21 mg per 100 g), apple (2 mg per 100 g) and kiwi (1 mg per 100 g), as well as in many vegetables, namely onion (45 mg per 100 g), eggplant (1.34 mg per 100 g) and, in extremely low concentrations, cucumber (0.11 mg per 100 g). [ 8 ] Formic acid is a naturally occurring component of the atmosphere primarily due to forest emissions. [ 9 ]
As early as the 15th century, some alchemists and naturalists were aware that ant hills give off an acidic vapor. The first person to describe the isolation of this substance (by the distillation of large numbers of ants) was the English naturalist John Ray , in 1671. [ 10 ] [ 11 ] Ants secrete the formic acid for attack and defense purposes. Formic acid was first synthesized from hydrocyanic acid by the French chemist Joseph Gay-Lussac . In 1855, another French chemist, Marcellin Berthelot , developed a synthesis from carbon monoxide similar to the process used today. [ 12 ]
Formic acid was long considered a chemical compound of only minor interest in the chemical industry. In the late 1960s, significant quantities became available as a byproduct of acetic acid production. It now finds increasing use as a preservative and antibacterial in livestock feed. [ 12 ]
Formic acid is a colorless liquid having a pungent, penetrating odor [ 13 ] at room temperature, comparable to the related acetic acid . Formic acid is about ten times stronger than acetic acid having a (logarithmic) dissociation constant of 3.745 compared to 4.756 for acetic acid. [ 3 ]
It is miscible with water and most polar organic solvents , and is somewhat soluble in hydrocarbons . In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules. [ 14 ] [ 15 ] Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law . [ 15 ] Solid formic acid, which can exist in either of two polymorphs , consists of an effectively endless network of hydrogen-bonded formic acid molecules. Formic acid forms a high-boiling azeotrope with water (107.3 °C; 77.5% formic acid). Liquid formic acid tends to supercool .
Formic acid readily decomposes by dehydration in the presence of concentrated sulfuric acid to form carbon monoxide and water:
Treatment of formic acid with sulfuric acid is a convenient laboratory source of CO. [ 16 ] [ 17 ]
In the presence of platinum , it decomposes with a release of hydrogen and carbon dioxide .
Soluble ruthenium catalysts are also effective for producing carbon monoxide-free hydrogen. [ 18 ]
Formic acid shares most of the chemical properties of other carboxylic acids . Because of its high acidity, solutions in alcohols form esters spontaneously; in Fischer esterifications of formic acid, it self-catalyzes the reaction and no additional acid catalyst is needed. [ 19 ] Formic acid shares some of the reducing properties of aldehydes , reducing solutions of metal oxides to their respective metal. [ 20 ]
Formic acid is a source for a formyl group for example in the formylation of N -methylaniline to N -methylformanilide in toluene . [ 21 ]
In synthetic organic chemistry , formic acid is often used as a source of hydride ion, as in the Eschweiler–Clarke reaction :
It is used as a source of hydrogen in transfer hydrogenation , as in the Leuckart reaction to make amines , and (in aqueous solution or in its azeotrope with triethylamine ) for hydrogenation of ketones . [ 22 ]
Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with alkenes . Formic acids and alkenes readily react to form formate esters . In the presence of certain acids, including sulfuric and hydrofluoric acids , however, a variant of the Koch reaction occurs instead, and formic acid adds to the alkene to produce a larger carboxylic acid. [ 23 ]
An unstable formic anhydride , H(C=O)−O−(C=O)H, can be obtained by dehydration of formic acid with N , N ′ -dicyclohexylcarbodiimide in ether at low temperature. [ 24 ]
In 2009, the worldwide capacity for producing formic acid was 720 thousand tonnes (1.6 billion pounds) per year, roughly equally divided between Europe (350 thousand tonnes or 770 million pounds, mainly in Germany) and Asia (370 thousand tonnes or 820 million pounds, mainly in China) while production was below 1 thousand tonnes or 2.2 million pounds per year in all other continents. [ 25 ] It is commercially available in solutions of various concentrations between 85 and 99 w/w %. [ 14 ] As of 2009 [update] , the largest producers are BASF , Eastman Chemical Company , LC Industrial , and Feicheng Acid Chemicals , with the largest production facilities in Ludwigshafen (200 thousand tonnes or 440 million pounds per year, BASF, Germany), Oulu (105 thousand tonnes or 230 million pounds, Eastman, Finland), Nakhon Pathom (n/a, LC Industrial), and Feicheng (100 thousand tonnes or 220 million pounds, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States. [ 25 ]
Regenerating CO 2 to make useful products, that displace incumbent fossil fuel based pathways is a more impactful process than CO 2 sequestration.
Both formic acid and CO (carbon monoxide) are C1 (one carbon molecules). Formic is a hydrogen-rich liquid which can be transported and easily donates its hydrogen to enable a variety of condensation and esterification reactions to make a wide variety of derivative molecules. CO, while more difficult to transport as a gas, is also one of the primary constituents of syngas useful in synthesizing a wide variety of molecules.
CO 2 electrolysis is distinct from photosynthesis and offers a promising alternative to accelerate decarbonization. By converting CO 2 into products using clean electricity, we reduce CO 2 emissions in two ways: first and most simply by the amount of CO 2 that is regenerated, but the second way is less obvious but even more consequential by avoiding the CO 2 emissions otherwise generated by making these same products from fossil fuels. This is known as carbon displacement or abatement.
CO 2 electrolysis holds promise for reducing atmospheric CO 2 levels and providing a sustainable method for producing chemicals, materials, and fuels. Its efficiency and scalability are active areas of research, but now also commercialization, aiming to make it a viable commercial technology for both carbon management and molecule production. [ 26 ]
When methanol and carbon monoxide are combined in the presence of a strong base , the result is methyl formate , according to the chemical equation : [ 14 ]
In industry, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80 °C and 40 atm. The most widely used base is sodium methoxide . Hydrolysis of the methyl formate produces formic acid:
Efficient hydrolysis of methyl formate requires a large excess of water. Some routes proceed indirectly by first treating the methyl formate with ammonia to give formamide , which is then hydrolyzed with sulfuric acid :
A disadvantage of this approach is the need to dispose of the ammonium sulfate byproduct. This problem has led some manufacturers to develop energy-efficient methods of separating formic acid from the excess water used in direct hydrolysis. In one of these processes, used by BASF , the formic acid is removed from the water by liquid-liquid extraction with an organic base. [ citation needed ]
A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals. At one time, acetic acid was produced on a large scale by oxidation of alkanes , by a process that cogenerates significant formic acid. [ 14 ] This oxidative route to acetic acid has declined in importance so that the aforementioned dedicated routes to formic acid have become more important. [ citation needed ]
The catalytic hydrogenation of CO 2 to formic acid has long been studied. This reaction can be conducted homogeneously. [ 27 ] [ 28 ] [ 29 ]
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process . [ 30 ] [ 31 ] A Keggin-type polyoxometalate (H 5 PV 2 Mo 10 O 40 ) is used as the homogeneous catalyst to convert sugars, wood, waste paper, or cyanobacteria to formic acid and CO 2 as the sole byproduct. Yields of up to 53% formic acid can be achieved. [ citation needed ]
In the laboratory, formic acid can be obtained by heating oxalic acid in glycerol followed by steam distillation. [ 32 ] Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. If the reaction mixture is heated to higher temperatures, allyl alcohol results. The net reaction is thus:
Another illustrative method involves the reaction between lead formate and hydrogen sulfide , driven by the formation of lead sulfide . [ 33 ]
Formate is formed by the electrochemical reduction of CO 2 (in the form of bicarbonate ) at a lead cathode at pH 8.6: [ 34 ]
or
If the feed is CO 2 and oxygen is evolved at the anode, the total reaction is:
Formic acid is named after ants which have high concentrations of the compound in their venom, derived from serine through a 5,10-methenyltetrahydrofolate intermediate. [ 35 ] The conjugate base of formic acid, formate, also occurs widely in nature. An assay for formic acid in body fluids, designed for determination of formate after methanol poisoning, is based on the reaction of formate with bacterial formate dehydrogenase . [ 36 ]
A major use of formic acid is as a preservative and antibacterial agent in livestock feed. It arrests certain decay processes and causes the feed to retain its nutritive value longer,
In Europe, it is applied on silage , including fresh hay, to promote the fermentation of lactic acid and to suppress the formation of butyric acid ; it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value. [ 14 ] It is widely used to preserve winter feed for cattle , [ 37 ] and is sometimes added to poultry feed to kill E. coli bacteria. [ 38 ] [ 39 ] Use as a preservative for silage and other animal feed constituted 30% of the global consumption in 2009. [ 25 ]
Beekeepers use formic acid as a miticide against the tracheal mite ( Acarapis woodi ) and the Varroa destructor mite and Varroa jacobsoni mite . [ 40 ]
Formic acid can be used directly in formic acid fuel cells or indirectly in hydrogen fuel cells . [ 41 ] [ 42 ]
Electrolytic conversion of electrical energy to chemical fuel has been proposed as a large-scale source of formate by various groups. [ 43 ] The formate could be used as feed to modified E. coli bacteria for producing biomass . [ 44 ] [ 45 ] Natural methylotroph microbes can feed on formic acid or formate.
Formic acid has been considered as a means of hydrogen storage . [ 46 ] The co-product of this decomposition, carbon dioxide, can be rehydrogenated back to formic acid in a second step. Formic acid contains 53 g/L hydrogen at room temperature and atmospheric pressure, which is three and a half times as much as compressed hydrogen gas can attain at 350 bar pressure (14.7 g/L). Pure formic acid is a liquid with a flash point of 69 °C, much higher than that of gasoline (−40 °C) or ethanol (13 °C). [ citation needed ]
It is possible to use formic acid as an intermediary to produce isobutanol from CO 2 using microbes. [ 47 ] [ 48 ]
Formic acid has a potential application in soldering . Due to its capacity to reduce oxide layers, formic acid gas can be blasted at an oxide surface to increase solder wettability . [ citation needed ]
Formic acid is used as a volatile pH modifier in HPLC and capillary electrophoresis . Formic acid is often used as a component of mobile phase in reversed-phase high-performance liquid chromatography (RP-HPLC) analysis and separation techniques for the separation of hydrophobic macromolecules, such as peptides, proteins and more complex structures including intact viruses. Especially when paired with mass spectrometry detection, formic acid offers several advantages over the more traditionally used phosphoric acid . [ 49 ] [ 50 ]
Formic acid is also significantly used in the production of leather, including tanning (23% of the global consumption in 2009 [ 25 ] ), and in dyeing and finishing textiles (9% of the global consumption in 2009 [ 25 ] ) because of its acidic nature. Use as a coagulant in the production of rubber [ 14 ] consumed 6% of the global production in 2009. [ 25 ]
Formic acid is also used in place of mineral acids for various cleaning products, [ 14 ] such as limescale remover and toilet bowl cleaner . Some formate esters are artificial flavorings and perfumes.
Formic acid application has been reported to be an effective treatment for warts . [ 51 ]
Formic acid has low toxicity (hence its use as a food additive), with an LD 50 of 1.8 g/kg (tested orally on mice). The concentrated acid is corrosive to the skin. [ 14 ]
Formic acid is readily metabolized and eliminated by the body. Nonetheless, it has specific toxic effects; the formic acid and formaldehyde produced as metabolites of methanol are responsible for the optic nerve damage, causing blindness, seen in methanol poisoning . [ 52 ] Some chronic effects of formic acid exposure have been documented. Some experiments on bacterial species have demonstrated it to be a mutagen . [ 53 ] Chronic exposure in humans may cause kidney damage. [ 53 ] Another possible effect of chronic exposure is development of a skin allergy that manifests upon re-exposure to the chemical.
Concentrated formic acid slowly decomposes to carbon monoxide and water, leading to pressure buildup in the containing vessel. For this reason, 98% formic acid is shipped in plastic bottles with self-venting caps. [ citation needed ]
The hazards of solutions of formic acid depend on the concentration. The following table lists the Globally Harmonized System of Classification and Labelling of Chemicals for formic acid solutions: [ citation needed ]
Formic acid in 85% concentration is flammable, and diluted formic acid is on the U.S. Food and Drug Administration list of food additives. [ 54 ] The principal danger from formic acid is from skin or eye contact with the concentrated liquid or vapors. The U.S. OSHA Permissible Exposure Level ( PEL ) of formic acid vapor in the work environment is 5 parts per million (ppm) of air. [ 55 ] | https://en.wikipedia.org/wiki/OHCHO |
Carbonic acid is a chemical compound with the chemical formula H 2 C O 3 . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature . [ 5 ] [ 6 ] The interconversion of carbon dioxide and carbonic acid is related to the breathing cycle of animals and the acidification of natural waters . [ 4 ]
In biochemistry and physiology, the name "carbonic acid" is sometimes applied to aqueous solutions of carbon dioxide . These chemical species play an important role in the bicarbonate buffer system , used to maintain acid–base homeostasis . [ 7 ]
In chemistry , the term "carbonic acid" strictly refers to the chemical compound with the formula H 2 CO 3 . Some biochemistry literature effaces the distinction between carbonic acid and carbon dioxide dissolved in extracellular fluid.
In physiology , carbon dioxide excreted by the lungs may be called volatile acid or respiratory acid .
At ambient temperatures, pure carbonic acid is a stable gas. [ 6 ] There are two main methods to produce anhydrous carbonic acid: reaction of hydrogen chloride and potassium bicarbonate at 100 K in methanol and proton irradiation of pure solid carbon dioxide . [ 3 ] Chemically, it behaves as a diprotic Brønsted acid . [ 8 ] [ 9 ]
Carbonic acid monomers exhibit three conformational isomers : cis–cis, cis–trans, and trans–trans. [ 10 ]
At low temperatures and atmospheric pressure , solid carbonic acid is amorphous and lacks Bragg peaks in X-ray diffraction . [ 11 ] But at high pressure, carbonic acid crystallizes, and modern analytical spectroscopy can measure its geometry.
According to neutron diffraction of dideuterated carbonic acid ( D 2 CO 3 ) in a hybrid clamped cell ( Russian alloy / copper-beryllium ) at 1.85 GPa, the molecules are planar and form dimers joined by pairs of hydrogen bonds . All three C-O bonds are nearly equidistant at 1.34 Å , intermediate between typical C-O and C=O distances (respectively 1.43 and 1.23 Å). The unusual C-O bond lengths are attributed to delocalized π bonding in the molecule's center and extraordinarily strong hydrogen bonds. The same effects also induce a very short O—O separation (2.13 Å), through the 136° O-H-O angle imposed by the doubly hydrogen-bonded 8-membered rings. [ 4 ] Longer O—O distances are observed in strong intramolecular hydrogen bonds, e.g. in oxalic acid , where the distances exceed 2.4 Å. [ 11 ]
In even a slight presence of water, carbonic acid dehydrates to carbon dioxide and water , which then catalyzes further decomposition. [ 6 ] For this reason, carbon dioxide can be considered the carbonic acid anhydride .
The hydration equilibrium constant at 25 °C is [ H 2 CO 3 ]/[CO 2 ] ≈ 1.7×10 −3 in pure water [ 12 ] and ≈ 1.2×10 −3 in seawater . [ 13 ] Hence the majority of carbon dioxide at geophysical or biological air-water interfaces does not convert to carbonic acid, remaining dissolved CO 2 gas. However, the uncatalyzed equilibrium is reached quite slowly: the rate constants are 0.039 s −1 for hydration and 23 s −1 for dehydration.
In the presence of the enzyme carbonic anhydrase , equilibrium is instead reached rapidly, and the following reaction takes precedence: [ 14 ] HCO 3 − + H + ↽ − − ⇀ CO 2 + H 2 O {\displaystyle {\ce {HCO3^- {+}H^+ <=> CO2 {+}H2O}}}
When the created carbon dioxide exceeds its solubility, gas evolves and a third equilibrium CO 2 ( soln ) ↽ − − ⇀ CO 2 ( g ) {\displaystyle {\ce {CO_2 (soln) <=> CO_2 (g)}}} must also be taken into consideration. The equilibrium constant for this reaction is defined by Henry's law .
The two reactions can be combined for the equilibrium in solution: HCO 3 − + H + ↽ − − ⇀ CO 2 ( soln ) + H 2 O K 3 = [ H + ] [ HCO 3 − ] [ CO 2 ( soln ) ] {\displaystyle {\begin{aligned}{\ce {HCO3^{-}{}+ H+{}<=> CO2(soln){}+ H2O}}&&K_{3}={\frac {[{\ce {H+}}][{\ce {HCO3^-}}]}{[{\ce {CO2(soln)}}]}}\end{aligned}}} When Henry's law is used to calculate the denominator care is needed with regard to units since Henry's law constant can be commonly expressed with 8 different dimensionalities. [ 15 ]
In wastewater treatment and agriculture irrigation, carbonic acid is used to acidify the water similar to sulfuric acid and sulfurous acid produced by sulfur burners. [ 16 ]
In the beverage industry , sparkling or "fizzy water" is usually referred to as carbonated water . It is made by dissolving carbon dioxide under a small positive pressure in water. Many soft drinks treated the same way effervesce .
Significant amounts of molecular H 2 CO 3 exist in aqueous solutions subjected to pressures of multiple gigapascals (tens of thousands of atmospheres) in planetary interiors. [ 17 ] [ 18 ] Pressures of 0.6–1.6 GPa at 100 K , and 0.75–1.75 GPa at 300 K are attained in the cores of large icy satellites such as Ganymede , Callisto , and Titan , where water and carbon dioxide are present. Pure carbonic acid, being denser, is expected to have sunk under the ice layers and separate them from the rocky cores of these moons. [ 19 ]
Carbonic acid is the formal Brønsted–Lowry conjugate acid of the bicarbonate anion, stable in alkaline solution . The protonation constants have been measured to great precision, but depend on overall ionic strength I . The two equilibria most easily measured are as follows: CO 3 2 − + H + ↽ − − ⇀ HCO 3 − β 1 = [ HCO 3 − ] [ H + ] [ CO 3 2 − ] CO 3 2 − + 2 H + ↽ − − ⇀ H 2 CO 3 β 2 = [ H 2 CO 3 ] [ H + ] 2 [ CO 3 2 − ] {\displaystyle {\begin{aligned}{\ce {CO3^{2-}{}+ H+{}<=> HCO3^-}}&&\beta _{1}={\frac {[{\ce {HCO3^-}}]}{[{\ce {H+}}][{\ce {CO3^{2-}}}]}}\\{\ce {CO3^{2-}{}+ 2H+{}<=> H2CO3}}&&\beta _{2}={\frac {[{\ce {H2CO3}}]}{[{\ce {H+}}]^{2}[{\ce {CO3^{2-}}}]}}\end{aligned}}} where brackets indicate the concentration of species . At 25 °C, these equilibria empirically satisfy [ 20 ] log ( β 1 ) = 0 .54 I 2 − 0 .96 I + 9 .93 log ( β 2 ) = − 2 .5 I 2 − 0 .043 I + 16 .07 {\displaystyle {\begin{alignedat}{6}\log(\beta _{1})=&&0&.54&I^{2}-0&.96&I+&&9&.93\\\log(\beta _{2})=&&-2&.5&I^{2}-0&.043&I+&&16&.07\end{alignedat}}} log( β 1 ) decreases with increasing I , as does log( β 2 ) . In a solution absent other ions (e.g. I = 0 ), these curves imply the following stepwise dissociation constants : p K 1 = log ( β 2 ) − log ( β 1 ) = 6.77 p K 2 = log ( β 1 ) = 9.93 {\displaystyle {\begin{alignedat}{3}p{\text{K}}_{1}&=\log(\beta _{2})-\log(\beta _{1})&=6.77\\p{\text{K}}_{2}&=\log(\beta _{1})&=9.93\end{alignedat}}} Direct values for these constants in the literature include p K 1 = 6.35 and p K 2 - p K 1 = 3.49 . [ 21 ]
To interpret these numbers, note that two chemical species in an acid equilibrium are equiconcentrated when p K = p H . In particular, the extracellular fluid ( cytosol ) in biological systems exhibits p H ≈ 7.2 , so that carbonic acid will be almost 50%-dissociated at equilibrium.
The Bjerrum plot shows typical equilibrium concentrations, in solution, in seawater , of carbon dioxide and the various species derived from it, as a function of pH . [ 8 ] [ 9 ] As human industrialization has increased the proportion of carbon dioxide in Earth's atmosphere , the proportion of carbon dioxide dissolved in sea- and freshwater as carbonic acid is also expected to increase. This rise in dissolved acid is also expected to acidify those waters, generating a decrease in pH. [ 22 ] [ 23 ] It has been estimated that the increase in dissolved carbon dioxide has already caused the ocean's average surface pH to decrease by about 0.1 from pre-industrial levels. | https://en.wikipedia.org/wiki/OHCOOH |
OJSC Dolomite ( Russian : ОАО Доломит ) forms part of the Russia metallurgical complex, being the only producer of metallurgical dolomite in the Central Black Earth economic region . The company mines 55% of the total amount of dolomite produced in Russia and 43% in CIS. It is part of the NLMK Group. [ 1 ]
The company has explored the Dankov dolomite field ( Lipetsk Oblast ) since 1932. [ 2 ] The product mix includes fluxed and converter dolomite, dolomite flour, crushed rock for construction and road works. The facility is located near to developed transport infrastructure, which is strategically advantageous for its customers.
In 2005 the Company production reached 1.9 mln. tonnes. Dolomite is mainly sold in the domestic market. The main customers are steelmaking companies; their share is 69% of the total sales volume. NLMK's share in the company's sales structure amounted to 51% in 2005.
This Russian corporation or company article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OJSC_Dolomite |
OLAC , the Open Language Archives Community , is an initiative to create a unified means of searching online databases of language resources for linguistic research. The information about resources is stored in XML format for easy searching. OLAC was founded in 2000, and is hosted at the Linguistic Data Consortium webserver at the University of Pennsylvania .
OLAC advises on best practices in language archiving, and works to promote interoperation between language archives.
The OLAC metadata set is based on the complete set of Dublin Core metadata terms DCMT, but the format allows for the use of extensions to express community-specific qualifiers. It is often contrasted to IMDI (ISLE Metadata Initiative).
The OLAC metadata is based on five primary attributes, refine, code, scheme, lang, and langs , although the last attribute is only for completed metadata sets. [ 1 ] Each attribute serves a different function and is applicable in a different section of the metadata.
There are currently 23 different elements that OLAC lists on its metadata page. Elements may be used more than once, and not every element is required in a metadata submission. Each element's entry on the official OLAC page includes the name of the element, its function, notes on its usage, and examples of its coding. [ 1 ]
In addition, OLAC provides a list of metadata extensions to augment descriptions. [ 3 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OLAC |
An organic light-emitting diode ( OLED ), also known as organic electroluminescent ( organic EL ) diode , [ 1 ] [ 2 ] is a type of light-emitting diode (LED) in which the emissive electroluminescent layer is an organic compound film that emits light in response to an electric current. This organic layer is situated between two electrodes ; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors , and portable systems such as smartphones and handheld game consoles . A major area of research is the development of white OLED devices for use in solid-state lighting applications. [ 3 ] [ 4 ] [ 5 ]
There are two main families of OLED: those based on small molecules and those employing polymers . Adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC) which has a slightly different mode of operation. An OLED display can be driven with a passive-matrix (PMOLED) or active-matrix ( AMOLED ) control scheme. In the PMOLED scheme, each row and line in the display is controlled sequentially, one by one, [ 6 ] whereas AMOLED control uses a thin-film transistor (TFT) backplane to directly access and switch each individual pixel on or off, allowing for higher resolution and larger display sizes. OLEDs are fundamentally different from LEDs , which are based on a p–n diode crystalline solid structure. In LEDs, doping is used to create p- and n-regions by changing the conductivity of the host semiconductor . OLEDs do not employ a crystalline p-n structure. Doping of OLEDs is used to increase radiative efficiency by direct modification of the quantum-mechanical optical recombination rate. Doping is additionally used to determine the wavelength of photon emission. [ 7 ]
OLED displays are made in a similar way to LCDs, including manufacturing of several displays on a mother substrate that is later thinned and cut into several displays. Substrates for OLED displays come in the same sizes as those used for manufacturing LCDs. For OLED manufacture, after the formation of TFTs (for active matrix displays), addressable grids (for passive matrix displays), or indium tin oxide (ITO) segments (for segment displays), the display is coated with hole injection, transport and blocking layers, as well with electroluminescent material after the first two layers, after which ITO or metal may be applied again as a cathode . Later, the entire stack of materials is encapsulated. The TFT layer, addressable grid, or ITO segments serve as or are connected to the anode , which may be made of ITO or metal. [ 8 ] OLEDs can be made flexible and transparent, with transparent displays being used in smartphones with optical fingerprint scanners and flexible displays being used in foldable smartphones .
André Bernanose and co-workers at the Nancy-Université in France made the first observations of electroluminescence in organic materials in the early 1950s. They applied high alternating voltages in air to materials such as acridine orange dye, either deposited on or dissolved in cellulose or cellophane thin films . The proposed mechanism was either direct excitation of the dye molecules or excitation of electrons . [ 9 ] [ 10 ] [ 11 ] [ 12 ]
In 1960, Martin Pope and some of his co-workers at New York University in the United States developed ohmic dark-injecting electrode contacts to organic crystals. [ 13 ] [ 14 ] [ 15 ] They further described the necessary energetic requirements ( work functions ) for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern OLED devices. Pope's group also first observed direct current (DC) electroluminescence under vacuum on a single pure crystal of anthracene and on anthracene crystals doped with tetracene in 1963 [ 16 ] using a small area silver electrode at 400 volts . The proposed mechanism was field-accelerated electron excitation of molecular fluorescence.
Pope's group reported in 1965 [ 17 ] that in the absence of an external electric field, the electroluminescence in anthracene crystals is caused by the recombination of a thermalized electron and hole, and that the conducting level of anthracene is higher in energy than the exciton energy level. Also in 1965, Wolfgang Helfrich and W. G. Schneider of the National Research Council in Canada produced double injection recombination electroluminescence for the first time in an anthracene single crystal using hole and electron injecting electrodes, [ 18 ] the forerunner of modern double-injection devices. In the same year, Dow Chemical researchers patented a method of preparing electroluminescent cells using high-voltage (500–1500 V) AC-driven (100–3000 Hz) electrically insulated one millimetre thin layers of a melted phosphor consisting of ground anthracene powder, tetracene, and graphite powder. [ 19 ] Their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules.
The first Polymer LED (PLED) to be created was by Roger Partridge at the National Physical Laboratory in the United Kingdom. It used a film of polyvinylcarbazole up to 2.2 micrometers thick located between two charge-injecting electrodes. The light generated was readily visible in normal lighting conditions though the polymer used had 2 limitations; low conductivity and the difficulty of injecting electrons. [ 20 ] Later development of conjugated polymers would allow others to largely eliminate these problems. His contribution has often been overlooked due to the secrecy NPL imposed on the project. When it was patented in 1974 [ 21 ] it was given a deliberately obscure "catch all" name while the government's Department for Industry tried and failed to find industrial collaborators to fund further development. [ 22 ] [ 23 ] [ 24 ] [ 25 ] [ 26 ]
Chemists Ching Wan Tang and Steven Van Slyke at Eastman Kodak built the first practical OLED device in 1987. [ 27 ] This device used a two-layer structure with separate hole transporting and electron transporting layers such that recombination and light emission occurred in the middle of the organic layer; this resulted in a reduction in operating voltage and improvements in efficiency. [ citation needed ]
Research into polymer electroluminescence culminated in 1990, with J. H. Burroughes at the Cavendish Laboratory at Cambridge University , UK, reporting a high-efficiency green light-emitting polymer-based device using 100 nm thick films of poly(p-phenylene vinylene) . [ 28 ] Moving from molecular to macromolecular materials solved the problems previously encountered with the long-term stability of the organic films and enabled high-quality films to be easily made. [ 28 ] Subsequent research developed multilayer polymers and the new field of plastic electronics and OLED research and device production grew rapidly. [ 29 ] White OLEDs, pioneered by J. Kido et al. at Yamagata University , Japan in 1995, achieved the commercialization of OLED-backlit displays and lighting. [ 30 ] [ 31 ]
In 1999, Kodak and Sanyo had entered into a partnership to jointly research, develop, and produce OLED displays. They announced the world's first 2.4-inch active-matrix, full-color OLED display in September the same year. [ 32 ] In September 2002, they presented a prototype of 15-inch HDTV format display based on white OLEDs with color filters at the CEATEC Japan. [ 33 ]
Manufacturing of small molecule OLEDs was started in 1997 by Pioneer Corporation , followed by TDK in 2001 and Samsung - NEC Mobile Display (SNMD), which later became one of the world's largest OLED display manufacturers - Samsung Display, in 2002. [ 34 ]
The Sony XEL-1 , released in 2007, was the first OLED television. [ 35 ] Universal Display Corporation , one of the OLED materials companies, holds a number of patents concerning the commercialization of OLEDs that are used by major OLED manufacturers around the world. [ 36 ] [ 37 ]
On 5 December 2017, JOLED , the successor of Sony and Panasonic 's printable OLED business units, began the world's first commercial shipment of inkjet-printed OLED panels. [ 38 ] [ 39 ]
A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode , all deposited on a substrate . The organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over part or all of the molecule. These materials have conductivity levels ranging from insulators to conductors, and are therefore considered organic semiconductors . The highest occupied and lowest unoccupied molecular orbitals ( HOMO and LUMO ) of organic semiconductors are analogous to the valence and conduction bands of inorganic semiconductors. [ 40 ]
Originally, the most basic polymer OLEDs consisted of a single organic layer. One example was the first light-emitting device synthesised by J. H. Burroughes et al. , which involved a single layer of poly(p-phenylene vinylene) . However multilayer OLEDs can be fabricated with two or more layers in order to improve device efficiency. As well as conductive properties, different materials may be chosen to aid charge injection at electrodes by providing a more gradual electronic profile, [ 41 ] or block a charge from reaching the opposite electrode and being wasted. [ 42 ] Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layer and an emissive layer. Developments in OLED architecture in 2011 improved quantum efficiency (up to 19%) by using a graded heterojunction. [ 43 ] In the graded heterojunction architecture, the composition of hole and electron-transport materials varies continuously within the emissive layer with a dopant emitter. The graded heterojunction architecture combines the benefits of both conventional architectures by improving charge injection while simultaneously balancing charge transport within the emissive region. [ 44 ]
During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. Anodes are picked based upon the quality of their optical transparency, electrical conductivity, and chemical stability. [ 45 ] A current of electrons flows through the device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron holes into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton , a bound state of the electron and hole. This happens closer to the electron-transport layer part of the emissive layer, because in organic semiconductors holes are generally more mobile than electrons. [ citation needed ] The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation whose frequency is in the visible region . The frequency of this radiation depends on the band gap of the material, in this case the difference in energy between the HOMO and LUMO.
As electrons and holes are fermions with half integer spin , an exciton may either be in a singlet state or a triplet state depending on how the spins of the electron and hole have been combined. Statistically three triplet excitons will be formed for each singlet exciton. Decay from triplet states ( phosphorescence ) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent OLED emissive layers and devices. Phosphorescent organic light-emitting diodes (PHOLEDs) or emissive layers make use of spin–orbit interactions to facilitate intersystem crossing between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency.
Indium tin oxide (ITO) is commonly used as the anode material. It is transparent to visible light and has a high work function which promotes injection of holes into the HOMO level of the organic layer. A second conductive (injection) layer is typically added, which may consist of PEDOT:PSS , [ 46 ] as the HOMO level of this material generally lies between the work function of ITO and the HOMO of other commonly used polymers, reducing the energy barriers for hole injection. Metals such as barium and calcium are often used for the cathode as they have low work functions which promote injection of electrons into the LUMO of the organic layer. [ 47 ] Such metals are reactive, so they require a capping layer of aluminium to avoid degradation. Two secondary benefits of the aluminum capping layer include robustness to electrical contacts and the back reflection of emitted light out to the transparent ITO layer.
Experimental research has proven that the properties of the anode, specifically the anode/hole transport layer (HTL) interface topography plays a major role in the efficiency, performance, and lifetime of organic light-emitting diodes. Imperfections in the surface of the anode decrease anode-organic film interface adhesion, increase electrical resistance, and allow for more frequent formation of non-emissive dark spots in the OLED material adversely affecting lifetime. Mechanisms to decrease anode roughness for ITO/glass substrates include the use of thin films and self-assembled monolayers. Also, alternative substrates and anode materials are being considered to increase OLED performance and lifetime. Possible examples include single crystal sapphire substrates treated with gold (Au) film anodes yielding lower work functions, operating voltages, electrical resistance values, and increasing lifetime of OLEDs. [ 48 ]
Single carrier devices are typically used to study the kinetics and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes. As current through the device is composed of only one type of charge carrier, either electrons or holes, recombination does not occur and no light is emitted. For example, electron only devices can be obtained by replacing ITO with a lower work function metal which increases the energy barrier of hole injection. Similarly, hole only devices can be made by using a cathode made solely of aluminium, resulting in an energy barrier too large for efficient electron injection. [ 49 ] [ 50 ] [ 51 ]
Balanced charge injection and transfer are required to get high internal efficiency, pure emission of luminance layer without contaminated emission from charge transporting layers, and high stability. A common way to balance charge is optimizing the thickness of the charge transporting layers but is hard to control. Another way is using the exciplex. Exciplex formed between hole-transporting (p-type) and electron-transporting (n-type) side chains to localize electron-hole pairs. Energy is then transferred to luminophore and provide high efficiency. An example of using exciplex is grafting Oxadiazole and carbazole side units in red diketopyrrolopyrrole-doped Copolymer main chain shows improved external quantum efficiency and color purity in no optimized OLED. [ 52 ]
Organic small-molecule electroluminescent materials have the advantages of a wide variety, easy to purify, and strong chemical modifications. In order to make the luminescent materials to emit light as required, some chromophores or unsaturated groups such as alkene bonds and benzene rings will usually be introduced in the molecular structure design to change the size of the conjugation range of the material, so that the photophysical properties of the material changes. In general, the larger the range of π-electron conjugation system, the longer the wavelength of light emitted by the material. For instance, with the increase of the number of benzene rings, the fluorescence emission peak of benzene , naphthalene , anthracene , [ 53 ] and tetracene gradually red-shifted from 283 nm to 480 nm. Common organic small molecule electroluminescent materials include aluminum complexes, anthracenes , biphenyl acetylene aryl derivatives, coumarin derivatives, [ 54 ] and various fluorochromes. Efficient OLEDs using small molecules were first developed by Ching W. Tang et al. [ 55 ] at Eastman Kodak . The term OLED traditionally refers specifically to this type of device, though the term SM-OLED is also in use. [ 40 ]
Molecules commonly used in OLEDs include organometallic chelates (for example Alq 3 , used in the organic light-emitting device reported by Tang et al. ), fluorescent and phosphorescent dyes and conjugated dendrimers . A number of materials are used for their charge transport properties, for example triphenylamine and derivatives are commonly used as materials for hole transport layers. [ 56 ] Fluorescent dyes can be chosen to obtain light emission at different wavelengths, and compounds such as perylene , rubrene and quinacridone derivatives are often used. [ 57 ] Alq 3 has been used as a green light emitter, electron transport material and as a host for yellow light and red light emitting dyes.
Because of the structural flexibility of small-molecule electroluminescent materials, thin films can be prepared by vacuum vapor deposition, which is more expensive and of limited use for large-area devices. The vacuum coating system, however, can make the entire process from film growth to OLED device preparation in a controlled and complete operating environment, helping to obtain uniform and stable films, thus ensuring the final fabrication of high-performance OLED devices.However, small molecule organic dyes are prone to fluorescence quenching [ 58 ] in the solid state, resulting in lower luminescence efficiency. The doped OLED devices are also prone to crystallization, which reduces the luminescence and efficiency of the devices. Therefore, the development of devices based on small-molecule electroluminescent materials is limited by high manufacturing costs, poor stability, short life, and other shortcomings. Coherent emission from a laser dye-doped tandem SM-OLED device, excited in the pulsed regime, has been demonstrated. [ 59 ] The emission is nearly diffraction limited with a spectral width similar to that of broadband dye lasers. [ 60 ]
Researchers report luminescence from a single polymer molecule, representing the smallest possible organic light-emitting diode (OLED) device. [ 61 ] Scientists will be able to optimize substances to produce more powerful light emissions. Finally, this work is a first step towards making molecule-sized components that combine electronic and optical properties. Similar components could form the basis of a molecular computer. [ 62 ]
Polymer light-emitting diodes (PLED, P-OLED), also light-emitting polymers (LEP), involve an electroluminescent conductive polymer that emits light when connected to an external voltage. They are used as a thin film for full-spectrum colour displays. Polymer OLEDs are quite efficient and require a relatively small amount of power for the amount of light produced.
Vacuum deposition is not a suitable method for forming thin films of polymers. If the polymeric OLED films are made by vacuum vapor deposition, the chain elements will be cut off and the original photophysical properties will be compromised. However, polymers can be processed in solution, and spin coating is a common method of depositing thin polymer films. This method is more suited to forming large-area films than thermal evaporation. No vacuum is required, and the emissive materials can also be applied on the substrate by a technique derived from commercial inkjet printing. [ 63 ] [ 64 ] However, as the application of subsequent layers tends to dissolve those already present, formation of multilayer structures is difficult with these methods. The metal cathode may still need to be deposited by thermal evaporation in vacuum. An alternative method to vacuum deposition is to deposit a Langmuir-Blodgett film .
Typical polymers used in PLED displays include derivatives of poly( p -phenylene vinylene) and polyfluorene . Substitution of side chains onto the polymer backbone may determine the colour of emitted light [ 65 ] or the stability and solubility of the polymer for performance and ease of processing. [ 66 ] While unsubstituted poly(p-phenylene vinylene) (PPV) is typically insoluble, a number of PPVs and related poly(naphthalene vinylene)s (PNVs) that are soluble in organic solvents or water have been prepared via ring opening metathesis polymerization . [ 67 ] [ 68 ] [ 69 ] These water-soluble polymers or conjugated poly electrolytes (CPEs) also can be used as hole injection layers alone or in combination with nanoparticles like graphene. [ 70 ]
Phosphorescent organic light-emitting diodes use the principle of electrophosphorescence to convert electrical energy in an OLED into light in a highly efficient manner, [ 72 ] [ 73 ] with the internal quantum efficiencies of such devices approaching 100%. [ 74 ] PHOLEDs can be deposited using vacuum deposition through a shadow mask. [ 75 ]
Typically, a polymer such as poly( N-vinylcarbazole ) is used as a host material to which an organometallic complex is added as a dopant. Iridium complexes [ 73 ] such as Ir(mppy) 3 [ 71 ] as of 2004 were a focus of research, although complexes based on other heavy metals such as platinum [ 72 ] have also been used.
The heavy metal atom at the centre of these complexes exhibits strong spin-orbit coupling, facilitating intersystem crossing between singlet and triplet states. By using these phosphorescent materials, both singlet and triplet excitons will be able to decay radiatively, hence improving the internal quantum efficiency of the device compared to a standard OLED where only the singlet states will contribute to emission of light.
Applications of OLEDs in solid state lighting require the achievement of high brightness with good CIE coordinates (for white emission). The use of macromolecular species like polyhedral oligomeric silsesquioxanes (POSS) in conjunction with the use of phosphorescent species such as Ir for printed OLEDs have exhibited brightnesses as high as 10,000 cd/m 2 . [ 76 ]
The bottom-emission organic light-emitting diode (BE-OLED) is the architecture that was used in the early-stage AMOLED displays. It had a transparent anode fabricated on a glass substrate, and a shiny reflective cathode. Light is emitted from the transparent anode direction. To reflect all the light towards the anode direction, a relatively thick metal cathode such as aluminum is used. For the anode, high-transparency indium tin oxide (ITO) was a typical choice to emit as much light as possible. [ 77 ] Organic thin-films, including the emissive layer that actually generates the light, are then sandwiched between the ITO anode and the reflective metal cathode. The downside of bottom emission structure is that the light has to travel through the pixel drive circuits such as the thin-film transistor (TFT) substrate, and the area from which light can be extracted is limited and the light emission efficiency is reduced.
An alternative configuration is to switch the mode of emission. A reflective anode, and a transparent (or more often semi-transparent) cathode are used so that the light emits from the cathode side, and this configuration is called top-emission OLED (TE-OLED). Unlike BEOLEDs where the anode is made of transparent conductive ITO, this time the cathode needs to be transparent, and the ITO material is not an ideal choice for the cathode because of a damage issue due to the sputtering process. [ 78 ] Thus, a thin metal film such as pure Ag and the Mg:Ag alloy are used for the semi-transparent cathode due to their high transmittance and high conductivity . [ 79 ] In contrast to the bottom emission, light is extracted from the opposite side in top emission without the need of passing through multiple drive circuit layers. Thus, the light generated can be extracted more efficiently.
Using deuterium instead of hydrogen, in other words deuterated compounds, in red light , green light , blue light and white light OLED light emitting material layers and other layers nearby in OLED displays can improve their brightness by up to 30%. This is achieved by improving the current handling capacity, and lifespan of these materials. [ 80 ] [ 81 ] [ 82 ] [ 83 ]
Making indentations shaped like lenses on a transparent layer through which light passes from an OLED light emitting material, reduces the amount of scattered light within the display and directs it forward, improving brightness. [ 84 ] [ 85 ] [ 86 ] [ 87 ] [ 88 ]
When light waves meet while traveling along the same medium, wave interference occurs. This interference can be constructive or destructive. It is sometimes desirable for several waves of the same frequency to sum up into a wave with higher amplitudes.
Since both electrodes are reflective in TEOLED, light reflections can happen within the diode, and they cause more complex interferences than those in BEOLEDs. In addition to the two-beam interference, there exists a multi-resonance interference between two electrodes. Because the structure of TEOLEDs is similar to that of the Fabry-Perot resonator or laser resonator , which contains two parallel mirrors comparable to the two reflective electrodes), [ 89 ] this effect is especially strong in TEOLED. This two-beam interference and the Fabry-Perot interferences are the main factors in determining the output spectral intensity of OLED. This optical effect is called the "micro-cavity effect."
In the case of OLED, that means the cavity in a TEOLED could be especially designed to enhance the light output intensity and color purity with a narrow band of wavelengths, without consuming more power. In TEOLEDs, the microcavity effect commonly occurs, and when and how to restrain or make use of this effect is indispensable for device design. To match the conditions of constructive interference, different layer thicknesses are applied according to the resonance wavelength of that specific color. The thickness conditions are carefully designed and engineered according to the peak resonance emitting wavelengths of the blue light (460 nm), green light (530 nm), and red light (610 nm) color LEDs. This technology greatly improves the light-emission efficiency of OLEDs, and are able to achieve a wider color gamut due to high color purity.
In " white + color filter method ", also known as WOLED, [ 90 ] red, green, and blue emissions are obtained from the same white-light LEDs using different color filters. [ 91 ] With this method, the OLED materials produce white light, which is then filtered to obtain the desired RGB colors. This method eliminated the need to deposit three different organic emissive materials side by side, so only one kind of OLED material per layer is used to produce white light. It also eliminated the uneven degradation rate of blue pixels vs. red and green pixels. Disadvantages of this method are low color purity and contrast. Also, the filters absorb most of the emitted light, requiring the background white light to be relatively strong to compensate for the drop in brightness, and thus the power consumption for such displays can be higher.
Color filters can also be implemented into bottom- and top-emission OLEDs. By adding the corresponding RGB color filters after the semi-transparent cathode, even purer wavelengths of light can be obtained. The use of a microcavity in top-emission OLEDs with color filters also contributes to an increase in the contrast ratio by reducing the reflection of incident ambient light. [ 92 ] In a conventional panel, a circular polarizer was installed on the panel surface. While this was provided to prevent the reflection of ambient light, it also reduced the light output. By replacing this polarizing layer with color filters, the light intensity is not affected, and essentially all ambient reflected light can be cut, allowing a better contrast on the display panel. This potentially reduced the need for brighter pixels and can lower the power consumption.
Transparent OLEDs use transparent or semi-transparent contacts on both sides of the device to create displays that can be made to be both top and bottom emitting (transparent). TOLEDs can greatly improve contrast, making it much easier to view displays in bright sunlight. [ 93 ] This technology can be used in head-up displays , smart windows or augmented reality applications.
Graded heterojunction OLEDs gradually decrease the ratio of electron holes to electron transporting chemicals. [ 43 ] This results in almost double the quantum efficiency of existing OLEDs.
Stacked OLEDs use a pixel architecture that stacks the red, green, and blue subpixels on top of one another instead of next to one another, leading to substantial increase in gamut and color depth, [ 94 ] and greatly reducing pixel gap. Other display technologies with RGB (and RGBW) pixels mapped next to each other, tend to decrease potential resolution.
Tandem OLEDs are similar but have 2 layers of the same color stacked together. This improves the brightness of OLED displays. [ 95 ] [ 96 ]
In contrast to a conventional OLED, in which the anode is placed on the substrate, an inverted OLED uses a bottom cathode that can be connected to the drain end of an n-channel TFT, especially for the low-cost amorphous silicon TFT backplane useful in the manufacturing of AMOLED displays. [ 97 ]
All OLED displays (passive and active matrix) use a driver IC, often mounted using the chip-on-glass (COG) technology with an anisotropic conductive film . [ 98 ]
The most commonly used patterning method for organic light-emitting displays is shadow masking during film deposition, [ 99 ] also called the "RGB side-by-side" method or "RGB pixelation" method. Metal sheets with multiple apertures made of low thermal expansion material, such as nickel alloy, are placed between the heated evaporation source and substrate, so that the organic or inorganic material from the evaporation source is masked off, or blocked by the sheet from reaching the substrate in most locations, so the materials are deposited only on the desired locations on the substrate, and the rest is deposited and remains on the sheet. Almost all small OLED displays for smartphones have been manufactured using this method.
Fine metal masks (FMMs) made by photochemical machining , reminiscent of old CRT shadow masks , are used in this process. The dot density of the mask will determine the pixel density of the finished display. [ 100 ] Fine Hybrid Masks (FHMs) are lighter than FFMs, reducing bending caused by the mask's own weight, and are made using an electroforming process. [ 101 ] [ 102 ] This method requires heating the electroluminescent materials at 300 °C using a thermal method in a high vacuum of 10 −5 Pa. An oxygen meter ensures that no oxygen enters the chamber as it could damage (through oxidation) the electroluminescent material, which is in powder form. The mask is aligned with the mother substrate before every use, and it is placed just below the substrate. The substrate and mask assembly are placed at the top of the deposition chamber. [ 103 ] Afterwards, the electrode layer is deposited, by subjecting silver and aluminum powder to 1000 °C, using an electron beam. [ 104 ] Shadow masks allow for high pixel densities of up to 2,250 DPI (890 dot/cm). High pixel densities are
necessary for virtual reality headsets . [ 105 ]
Although the shadow-mask patterning method is a mature technology used from the first OLED manufacturing, it causes many issues like dark spot formation due to mask-substrate contact or misalignment of the pattern due to the deformation of shadow mask. Such defect formation can be regarded as trivial when the display size is small, however it causes serious issues when a large display is manufactured, which brings significant production yield loss. To circumvent such issues, white emission devices with 4-sub-pixel color filters (white, red, green and blue) have been used for large televisions. In spite of the light absorption by the color filter, state-of-the-art OLED televisions can reproduce color very well, such as 100% NTSC , and consume little power at the same time. This is done by using an emission spectrum with high human-eye sensitivity, special color filters with a low spectrum overlap, and performance tuning with color statistics into consideration. [ 106 ] This approach is also called the "Color-by-white" method.
There are other types of emerging patterning technologies to increase the manufacturability of OLEDs.
Patternable organic light-emitting devices use a light or heat activated electroactive layer. A latent material ( PEDOT-TMA ) is included in this layer that, upon activation, becomes highly efficient as a hole injection layer. Using this process, light-emitting devices with arbitrary patterns can be prepared. [ 107 ]
Colour patterning can be accomplished by means of a laser, such as a radiation-induced sublimation transfer (RIST). [ 108 ]
Organic vapour jet printing (OVJP) uses an inert carrier gas, such as argon or nitrogen , to transport evaporated organic molecules (as in organic vapour phase deposition). The gas is expelled through a micrometre -sized nozzle or nozzle array close to the substrate as it is being translated. This allows printing arbitrary multilayer patterns without the use of solvents.
Like ink jet material deposition , inkjet etching (IJE) deposits precise amounts of solvent onto a substrate designed to selectively dissolve the substrate material and induce a structure or pattern. Inkjet etching of polymer layers in OLEDs can be used to increase the overall out-coupling efficiency. In OLEDs, light produced from the emissive layers of the OLED is partially transmitted out of the device and partially trapped inside the device by total internal reflection (TIR). This trapped light is wave-guided along the interior of the device until it reaches an edge where it is dissipated by either absorption or emission. Inkjet etching can be used to selectively alter the polymeric layers of OLED structures to decrease overall TIR and increase out-coupling efficiency of the OLED. Compared to a non-etched polymer layer, the structured polymer layer in the OLED structure from the IJE process helps to decrease the TIR of the OLED device. IJE solvents are commonly organic instead of water-based due to their non-acidic nature and ability to effectively dissolve materials at temperatures under the boiling point of water. [ 109 ]
Transfer-printing is an emerging technology to assemble large numbers of parallel OLED and AMOLED devices efficiently. It takes advantage of standard metal deposition, photolithography , and etching to create alignment marks commonly on glass or other device substrates. Thin polymer adhesive layers are applied to enhance resistance to particles and surface defects. Microscale ICs are transfer-printed onto the adhesive surface and then baked to fully cure adhesive layers. An additional photosensitive polymer layer is applied to the substrate to account for the topography caused by the printed ICs, reintroducing a flat surface. Photolithography and etching removes some polymer layers to uncover conductive pads on the ICs. Afterwards, the anode layer is applied to the device backplane to form the bottom electrode. OLED layers are applied to the anode layer with conventional vapor deposition , and covered with a conductive metal electrode layer. As of 2011 [update] transfer-printing was capable to print onto target substrates up to 500 mm × 400 mm. This size limit needs to expand for transfer-printing to become a common process for the fabrication of large OLED/AMOLED displays. [ 110 ]
Experimental OLED displays using conventional photolithography techniques instead of FMMs have been demonstrated, allowing for large substrate sizes (as it eliminates the need for a mask that needs to be as large as the substrate) and good yield control. [ 111 ] Visionox has announced the use of photolithography for depositing OLED emissive materials. [ 112 ]
For a high resolution display like a TV, a thin-film transistor (TFT) backplane is necessary to drive the pixels correctly. As of 2019, low-temperature polycrystalline silicon (LTPS) – TFT is widely used for commercial AMOLED displays due to its superior current handling capacity over amorphous silicon (a-Si) TFTs. [ 113 ] LTPS-TFT has variation of the performance in a display, so various compensation circuits have been reported. [ 114 ] Due to the size limitation of the excimer laser used for LTPS, the AMOLED size was limited. To cope with the hurdle related to the panel size, amorphous-silicon/microcrystalline-silicon backplanes have been reported with large display prototype demonstrations. [ 115 ] An indium gallium zinc oxide (IGZO) backplane can also be used. Large OLED displays usually use AOS (amporphous oxide semiconductor) TFT transistors instead, also called oxide TFTs [ 116 ] and these are usually based on IGZO. [ 117 ]
Many AMOLED displays use LTPO TFT transistors. These transistors offer stability at low refresh rates, and variable refresh rates, which allows for power saving displays that do not show visual artifacts. [ 118 ] [ 119 ] [ 120 ]
The different manufacturing process of OLEDs has several advantages over flat panel displays made with LCD technology.
The biggest technical problem for OLEDs is the limited lifetime of the organic materials. One 2008 technical report on an OLED TV panel found that after 1,000 hours, the blue luminance degraded by 12%, the red by 7% and the green by 8%. [ 128 ] In particular, blue OLEDs at that time had a lifetime of around 14,000 hours to half original brightness (five years at eight hours per day) when used for flat-panel displays. This is lower than the typical lifetime of LCD, LED or PDP technology; each rated for about 25,000–40,000 hours to half brightness, depending on manufacturer and model. One major challenge for OLED displays is the formation of dark spots due to the ingress of oxygen and moisture, which degrades the organic material over time whether or not the display is powered. [ 129 ] [ 130 ] [ 131 ] In 2016, LG Electronics reported an expected lifetime of 100,000 hours, up from 36,000 hours in 2013. [ 132 ] A US Department of Energy paper shows that the expected lifespans of OLED lighting products goes down with increasing brightness, with an expected lifespan of 40,000 hours at 25% brightness, or 10,000 hours at 100% brightness. [ 133 ] [ 134 ] Compared to LCDs , OLEDs may be more susceptible to screen burn-in and/or brightness degradation.
Degradation occurs because of the accumulation of nonradiative recombination centers and luminescence quenchers in the emissive zone. It is said that the chemical breakdown in the semiconductors occurs in four steps:
In 2007, experimental OLEDs were created which can sustain 400 cd/m 2 of luminance for over 198,000 hours for green OLEDs and 62,000 hours for blue OLEDs. [ 136 ] In 2012, OLED lifetime to half of the initial brightness was improved to 900,000 hours for red, 1,450,000 hours for yellow and 400,000 hours for green at an initial luminance of 1,000 cd/m 2 . [ 137 ] Proper encapsulation is critical for prolonging an OLED display's lifetime, as the OLED light emitting electroluminescent materials are sensitive to oxygen and moisture. When exposed to moisture or oxygen, the electroluminescent materials in OLEDs degrade as they oxidize, generating black spots and reducing or shrinking the area that emits light, reducing light output. This reduction can occur in a pixel by pixel basis. This can also lead to delamination of the electrode layer, eventually leading to complete panel failure.
Degradation occurs three orders of magnitude faster when exposed to moisture than when exposed to oxygen. Encapsulation can be performed by applying an epoxy adhesive with dessicant, [ 138 ] by laminating a glass sheet with epoxy glue and dessicant [ 139 ] followed by vacuum degassing, or by using Thin-Film Encapsulation (TFE), [ 140 ] which is a multi-layer coating of alternating organic and inorganic layers. The organic layers are applied using inkjet printing, and the inorganic layers are applied using Atomic Layer Deposition (ALD). The encapsulation process is carried out under a nitrogen environment, using UV-curable LOCA glue and the electroluminescent and electrode material deposition processes are carried out under a high vacuum. The encapsulation and material deposition processes are carried out by a single machine, after the thin-film transistors have been applied. The transistors are applied in a process that is the same for LCDs. The electroluminescent materials can also be applied using inkjet printing. [ 141 ] [ 142 ] [ 143 ] [ 104 ] [ 144 ] [ 138 ] [ 145 ]
The OLED material used to produce blue light degrades much more rapidly than the materials used to produce other colors; in other words, blue light output will decrease relative to the other colors of light. This variation in the differential color output will change the color balance of the display, and is much more noticeable than a uniform decrease in overall luminance. [ 146 ] This can be avoided partially by adjusting the color balance, but this may require advanced control circuits and input from a knowledgeable user. More commonly, though, manufacturers optimize the size of the R, G and B subpixels to reduce the current density through the subpixel in order to equalize lifetime at full luminance. For example, a blue subpixel may be 75% larger than the green subpixel. The red subpixel may be 10% larger than the green.
Improvements to the efficiency and lifetime of blue OLEDs is vital to the success of OLEDs as replacements for LCD technology. Considerable research has been invested in developing blue OLEDs with high external quantum efficiency , as well as a deeper blue color. [ 147 ] [ 148 ] [ 149 ]
Since 2012, research focuses on organic materials exhibiting thermally activated delayed fluorescence (TADF), discovered at Kyushu University OPERA and UC Santa Barbara CPOS . TADF would allow stable and high-efficiency solution processable (meaning that the organic materials are layered in solutions producing thinner layers) blue emitters, with internal quantum efficiencies reaching 100%. [ 150 ] Early in 2017, [ 54 ] TADF materials based on oxygen-based fully bridged boron-type electron accepttors had achieved huge breakthrough in their proprities. The external quantum efficiency of TADF-OLED for blue and green light had achieved 38%, with thin full-width half-maximum and high color purity. In 2022, Han et al. [ 151 ] synthesized a new D-A type luminescent material, TDBA-Cz, and used the m-AC-DBNA synthesized by Meng et al. as a control to investigate the effect of the substitution site of the carbazole unit as an electron donor on the oxygen-bridged triphenylboron electron acceptor unit on the photophysical properties of the overall molecule. It was found that the introduction of two carbazole units into the same benzene ring of the oxygen-bridged triphenylboron electron acceptor unit could effectively suppress the conformational relaxation of the molecule during the radiative transition, resulting in narrow bandwidth blue light emission. In addition, TDBA-Cz is the first reported blue material to achieve both a FWHM down to 45 nm and a maximum EQE of 21.4% in a non-doped TADF-OLED.
Blue TADF emitters are expected to market by 2020 [ 152 ] [ 153 ] and would be used for WOLED displays with phosphorescent color filters, as well as blue OLED displays with ink-printed QD color filters .
Water can instantly damage the organic materials of the displays. Therefore, improved sealing processes are important for practical manufacturing. Water damage especially may limit the longevity of more flexible displays. [ 154 ]
As an emissive display technology, OLEDs rely completely upon converting electricity to light, unlike most LCDs which are to some extent reflective. E-paper leads the way in efficiency with ~ 33% ambient light reflectivity, enabling the display to be used without any internal light source. The metallic cathode in an OLED acts as a mirror, with reflectance approaching 80%, leading to poor readability in bright ambient light such as outdoors. However, with the proper application of a circular polarizer and antireflective coatings , the diffuse reflectance can be reduced to less than 0.1%. With 10,000 fc incident illumination (typical test condition for simulating outdoor illumination), that yields an approximate photopic contrast of 5:1. Advances in OLED technologies, however, enable OLEDs to become actually better than LCDs in bright sunlight. The AMOLED display in the Galaxy S5 , for example, was found to outperform all LCD displays on the market in terms of power usage, brightness and reflectance. [ 155 ]
While an OLED will consume around 40% of the power of an LCD displaying an image that is primarily black, for the majority of images it will consume 60–80% of the power of an LCD. However, an OLED can use more than 300% power to display an image with a white background, such as a document or web site. [ 156 ] This can lead to reduced battery life in mobile devices when white backgrounds are used.
Many OLEDs use pulse width modulation to display colour/brightness gradations. For example, a pixel instructed to display gray will flicker on and off rapidly, creating a subtle strobe effect. [ 157 ] The alternative way to decrease brightness would be to decrease power to the display, which would eliminate screen flicker to the detriment of colour balance , which deteriorates as brightness decreases. However, use of PWM gradations may be more harmful for eye health. [ 158 ]
Almost all OLED manufacturers rely on material deposition equipment that is only made by a handful of companies, [ 159 ] the most notable one being Canon Tokki , a unit of Canon Inc. although Ulvac and Sunic System are also notable. [ 160 ] [ 161 ] Canon Tokki is reported to have a near-monopoly of the giant OLED-manufacturing vacuum machines, notable for their 100-metre (330 ft) size. [ 162 ] Apple has relied solely on Canon Tokki in its bid to introduce its own OLED displays for the iPhones released in 2017. [ 163 ] The electroluminescent materials needed for OLEDs are also made by a handful of companies, some of them being Merck, Universal Display Corporation and LG Chem. [ 164 ] The machines that apply these materials can operate continuously for 5–6 days, and can process a mother substrate in 5 minutes. [ 165 ]
OLED displays are mainly made by Samsung Display and LG Display. [ 166 ] OLED technology is used in commercial applications such as displays for mobile phones and portable digital media players , car radios and digital cameras among others, as well as lighting. [ 167 ] Such portable display applications favor the high light output of OLEDs for readability in sunlight and their low power drain. Portable displays are also used intermittently, so the lower lifespan of organic displays is less of an issue. Prototypes have been made of flexible and rollable displays which use OLEDs' unique characteristics. Applications in flexible signs and lighting are also being developed. [ 168 ] OLED lighting offers several advantages over LED lighting, such as higher quality illumination, more diffuse light source, and panel shapes. [ 167 ] Philips Lighting has made OLED lighting samples under the brand name "Lumiblade" available online [ 169 ] and Novaled AG based in Dresden, Germany, introduced a line of OLED desk lamps called "Victory" in September, 2011. [ 170 ]
The first OLED display on a cell phone was Motorola 's Timeport P8767 in 2000, [ 171 ] although this technology was not widely adopted until a few years later appearing on many Motorola and Samsung color and clamshell cell phones, as well as some HTC , LG and Sony Ericsson models. [ 172 ] Nokia introduced OLED mobile phones in the late 2000s including the N85 and the N86 8MP , both of which feature an AMOLED display. OLED technology can also be found in digital media players such as the Creative ZEN V , the iriver clix , the Zune HD and the Sony Walkman X Series .
The Google and HTC Nexus One smartphone includes an AMOLED screen, as does HTC's own Desire and Legend phones. However, due to supply shortages of the Samsung-produced displays, certain HTC models will use Sony's SLCD displays in the future, [ 173 ] while the Google and Samsung Nexus S smartphone will use "Super Clear LCD" instead in some countries. [ 174 ]
OLED displays were used in watches made by Fossil (JR-9465) and Diesel (DZ-7086). Other manufacturers of OLED panels include Anwell Technologies Limited (Hong Kong), [ 175 ] AU Optronics (Taiwan), [ 176 ] Chimei Innolux Corporation (Taiwan), [ 177 ] LG (Korea), [ 178 ] and others. [ 179 ]
DuPont stated in a press release in May 2010, that they can produce a 50-inch OLED TV in two minutes with a new printing technology. If this can be scaled up in terms of manufacturing, then the total cost of OLED TVs would be greatly reduced. DuPont also states that OLED TVs made with this less expensive technology can last up to 15 years if left on for a normal eight-hour day. [ 180 ] [ 181 ]
The use of OLEDs may be subject to patents held by Universal Display Corporation , Eastman Kodak , DuPont , General Electric , Royal Philips Electronics , numerous universities and others. [ 182 ] By 2008, thousands of patents associated with OLEDs, came from larger corporations and smaller technology companies. [ 40 ]
Flexible OLED displays have been used by manufacturers to create curved displays such as the Galaxy S7 Edge but they were not in devices that can be flexed by the users. [ 183 ] Samsung demonstrated a roll-out display in 2016. [ 184 ]
On 31 October 2018, Royole , a Chinese electronics company, unveiled the world's first foldable screen phone featuring a flexible OLED display. [ 185 ] On 20 February 2019, Samsung announced the Samsung Galaxy Fold with a foldable OLED display from Samsung Display, its majority-owned subsidiary. [ 186 ] At MWC 2019 on 25 February 2019, Huawei announced the Huawei Mate X featuring a foldable OLED display from BOE . [ 187 ] [ 188 ]
The 2010s also saw the wide adoption of tracking gate-line in pixel (TGP), which moves the driving circuitry from the borders of the display to in between the display's pixels, allowing for narrow bezels. [ 189 ]
In 2023 the German startup Inuru has announced to manufacture low-cost OLED with printing for packaging and fashion applications. [ 190 ]
Textiles incorporating OLEDs are an innovation in the fashion world and pose for a way to integrate lighting to bring inert objects to a whole new level of fashion. The hope is to combine the comfort and low cost properties of textile with the OLEDs properties of illumination and low energy consumption. Although this scenario of illuminated clothing is highly plausible, challenges are still a road block. Some issues include: the lifetime of the OLED, rigidness of flexible foil substrates, and the lack of research in making more fabric like photonic textiles. [ 191 ]
The number of automakers using OLEDs is still rare and limited to the high-end of the market. For example, the 2010 Lexus RX features an OLED display instead of a thin film transistor (TFT-LCD) display.
A Japanese manufacturer Pioneer Electronic Corporation produced the first car stereos with a monochrome OLED display, which was also the world's first OLED product. [ 192 ] The Aston Martin DB9 incorporated the world's first automotive OLED display, [ 193 ] which was manufactured by Yazaki , [ 194 ] followed by the 2004 Jeep Grand Cherokee and the Chevrolet Corvette C6. [ 195 ] The 2015 Hyundai Sonata and Kia Soul EV use a 3.5-inch white PMOLED display.
By 2004, Samsung Display, a subsidiary of South Korea 's largest conglomerate and a former Samsung- NEC joint venture, was the world's largest OLED manufacturer, producing 40% of the OLED displays made in the world, [ 196 ] and as of 2010, has a 98% share of the global AMOLED market. [ 197 ] The company is leading the world of OLED industry, generating $100.2 million out of the total $475 million revenues in the global OLED market in 2006. [ 198 ] As of 2006, it held more than 600 American patents and more than 2800 international patents, making it the largest owner of AMOLED technology patents. [ 198 ]
Samsung SDI announced in 2005, the world's largest OLED TV at the time, at 21 inches (53 cm). [ 199 ] This OLED featured the highest resolution at the time, of 6.22 million pixels. In addition, the company adopted active matrix-based technology for its low power consumption and high-resolution qualities. This was exceeded in January 2008, when Samsung showcased the world's largest and thinnest OLED TV at the time, at 31 inches (78 cm) and 4.3 mm. [ 200 ]
In May 2008, Samsung unveiled an ultra-thin 12.1 inch (30 cm) laptop OLED display concept, with a 1,280×768 resolution with infinite contrast ratio. [ 201 ] According to Woo Jong Lee, Vice President of the Mobile Display Marketing Team at Samsung SDI, the company expected OLED displays to be used in notebook PCs as soon as 2010. [ 202 ]
In October 2008, Samsung showcased the world's thinnest OLED display, also the first to be "flappable" and bendable. [ 203 ] It measures just 0.05 mm (thinner than paper), yet a Samsung staff member said that it is "technically possible to make the panel thinner". [ 203 ] To achieve this thickness, Samsung etched an OLED panel that uses a normal glass substrate. The drive circuit was formed by low-temperature polysilicon TFTs. Also, low-molecular organic EL materials were employed. The pixel count of the display is 480 × 272. The contrast ratio is 100,000:1, and the luminance is 200 cd/m 2 . The colour reproduction range is 100% of the NTSC standard.
At the Consumer Electronics Show (CES) in January 2010, Samsung demonstrated a laptop computer with a large, transparent OLED display featuring up to 40% transparency [ 204 ] and an animated OLED display in a photo ID card. [ 205 ]
Samsung's 2010 AMOLED smartphones used their Super AMOLED trademark, with the Samsung Wave S8500 and Samsung i9000 Galaxy S being launched in June 2010. In January 2011, Samsung announced their Super AMOLED Plus displays, which offer several advances over the older Super AMOLED displays: real stripe matrix (50% more sub pixels), thinner form factor, brighter image and an 18% reduction in energy consumption. [ 206 ]
At CES 2012, Samsung introduced the first 55" TV screen that uses Super OLED technology. [ 207 ]
On 8 January 2013, at CES Samsung unveiled a unique curved 4K Ultra S9 OLED television, which they state provides an "IMAX-like experience" for viewers. [ 208 ]
On 13 August 2013, Samsung announced availability of a 55-inch curved OLED TV (model KN55S9C) in the US at a price point of $8999.99. [ 209 ]
On 6 September 2013, Samsung launched its 55-inch curved OLED TV (model KE55S9C) in the United Kingdom with John Lewis. [ 210 ]
Samsung introduced the Galaxy Round smartphone in the Korean market in October 2013. The device features a 1080p screen, measuring 5.7 inches (14 cm), that curves on the vertical axis in a rounded case. The corporation has promoted the following advantages: A new feature called "Round Interaction" that allows users to look at information by tilting the handset on a flat surface with the screen off, and the feel of one continuous transition when the user switches between home screens. [ 211 ]
Samsung released a new line of OLED TVs in 2022, its first using the technology since 2013. [ 212 ] They use panels sourced from Samsung Display; previously, LG was the sole manufacturer of OLED panels for TVs. [ 213 ]
The Sony CLIÉ PEG-VZ90 was released in 2004, being the first PDA to feature an OLED screen. [ 214 ] Other Sony products to feature OLED screens include the MZ-RH1 portable minidisc recorder, released in 2006 [ 215 ] and the Walkman X Series . [ 216 ]
At the 2007, Las Vegas Consumer Electronics Show (CES), Sony showcased a 11-inch (28 cm), (resolution 960×540) and 27-inch (69 cm), full HD resolution at 1920 × 1080 OLED TV models. [ 217 ] Both claimed 1,000,000:1 contrast ratios and total thicknesses (including bezels) of 5 mm. In April 2007, Sony announced it would manufacture 1000 11-inch (28 cm) OLED TVs per month for market testing purposes. [ 218 ] On 1 October 2007, Sony announced that the 11-inch (28 cm) model XEL-1 , was the first commercial OLED TV [ 35 ] and it was released in Japan in December 2007. [ 219 ]
In May 2007, Sony publicly unveiled a video of a 2.5-inch (6.4 cm) flexible OLED screen which is only 0.3 millimeters thick. [ 220 ] At the Display 2008 exhibition, Sony demonstrated a 0.2 mm thick 3.5 inches (8.9 cm) display with a resolution of 320×200 pixels and a 0.3 mm thick 11-inch (28 cm) display with 960×540 pixels resolution, one-tenth the thickness of the XEL-1. [ 221 ] [ 222 ]
In July 2008, a Japanese government body said it would fund a joint project of leading firms, which is to develop a key technology to produce large, energy-saving organic displays. The project involves one laboratory and 10 companies including Sony Corp. NEDO said the project was aimed at developing a core technology to mass-produce 40 inch or larger OLED displays in the late 2010s. [ 223 ]
In October 2008, Sony published results of research it carried out with the Max Planck Institute over the possibility of mass-market bending displays, which could replace rigid LCDs and plasma screens. Eventually, bendable, see-through displays could be stacked to produce 3D images with much greater contrast ratios and viewing angles than existing products. [ 224 ]
Sony exhibited a 24.5" (62 cm) prototype OLED 3D television during the Consumer Electronics Show in January 2010. [ 225 ]
In January 2011, Sony announced the PlayStation Vita handheld game console (the successor to the PSP ) will feature a 5-inch OLED screen. [ 226 ]
On 17 February 2011, Sony announced its 25" (63.5 cm) OLED Professional Reference Monitor aimed at the Cinema and high end Drama Post Production market. [ 227 ]
On 25 June 2012, Sony and Panasonic announced a joint venture for creating low cost mass production OLED televisions by 2013. [ 228 ] Sony unveiled its first OLED TV since 2008 at CES 2017 called A1E. It revealed two other models in 2018 one at CES 2018 called A8F and other a Master Series TV called A9F. At CES 2019 they unveiled another two models one the A8G and the other another Bravia Series TV called A9G. Then, at CES 2020 , they revealed the A8H, which was effectively an A9G in terms of picture quality but with some compromises due to its lower cost. At the same event, they also revealed a 48-inch version of the A9G, making this its smallest OLED TV since the XEL-1. [ 229 ] [ 230 ] [ 231 ] [ 232 ]
On 9 April 2009, LG acquired Kodak 's OLED business and started to utilize white OLED technology. [ 233 ] [ 234 ] As of 2010, LG Electronics produced one model of OLED television, the 15-inch (38 cm) 15EL9500 [ 235 ] and had announced a 31-inch (79 cm) OLED 3D television for March 2011. [ 236 ] On 26 December 2011, LG officially announced the "world's largest 55-inch (140 cm) OLED panel" and featured it at CES 2012. [ 237 ] In late 2012, LG announces the launch of the 55EM9600 OLED television in Australia. [ 238 ]
In January 2015, LG Display signed a long-term agreement with Universal Display Corporation for the supply of OLED materials and the right to use their patented OLED emitters. [ 239 ]
As of 2022, LG produces the world's largest OLED TV, at 97 inches. [ 240 ] [ 241 ]
Lumiotec is the first company in the world developing and selling, since January 2011, mass-produced OLED lighting panels with such brightness and long lifetime. Lumiotec is a joint venture of Mitsubishi Heavy Industries, ROHM, Toppan Printing, and Mitsui & Co.
On 1 June 2011, Mitsubishi Electric installed a 6-meter OLED 'sphere' in Tokyo's Science Museum. [ 242 ]
On 6 January 2011, Los Angeles-based technology company Recom Group introduced the first small screen consumer application of the OLED at the Consumer Electronics Show in Las Vegas. This was a 2.8" (7 cm) OLED display being used as a wearable video name tag. [ 243 ] At the Consumer Electronics Show in 2012, Recom Group introduced the world's first video mic flag incorporating three 2.8" (7 cm) OLED displays on a standard broadcaster's mic flag. The video mic flag allowed video content and advertising to be shown on a broadcasters standard mic flag. [ 244 ]
On 6 January 2016, Dell announced the Ultrasharp UP3017Q OLED monitor at the Consumer Electronics Show in Las Vegas. [ 245 ] The monitor was announced to feature a 30-inch (76 cm) 4K UHD OLED panel with a 120 Hz refresh rate, 0.1 millisecond response time, and a contrast ratio of 400,000:1. The monitor was set to sell at a price of $4,999 and release in March, 2016, just a few months later. As the end of March rolled around, the monitor was not released to the market and Dell did not speak on reasons for the delay. Reports suggested that Dell canceled the monitor as the company was unhappy with the image quality of the OLED panel, especially the amount of color drift that it displayed when viewed from the sides. [ 246 ] On 13 April 2017, Dell finally released the UP3017Q OLED monitor to the market at a price of $3,499 ($1,500 less than its original spoken price of $4,999 at CES 2016). In addition to the price drop, the monitor featured a 60 Hz refresh rate and a contrast ratio of 1,000,000:1. As of June, 2017, the monitor is no longer available to purchase from Dell's website.
Apple began using OLED panels in its watches in 2015 and in its laptops in 2016 with the introduction of an OLED touchbar to the MacBook Pro. [ 247 ] In 2017, Apple announced the introduction of their tenth anniversary iPhone X with their own optimized OLED display licensed from Universal Display Corporation. [ 248 ] With the exception of the iPhone SE line, iPhone XR and iPhone 11, all iPhones released since then have also featured OLED displays. In 2024, Apple announced the 7th generation iPad Pro , which featured a "tandem OLED" [ 249 ] panel in an attempt to increase the panel's brightness.
A third model of Nintendo 's Switch , a hybrid gaming system, features an OLED panel in place of the original model's LCD panel. Announced in the summer of 2021, it was released on 8 October 2021. [ 250 ]
In 2014, Mitsubishi Chemical Corporation (MCC), a subsidiary of Mitsubishi Chemical Holdings , developed an OLED panel with a 30,000-hour life, twice that of conventional OLED panels. [ 251 ]
The search for efficient OLED materials has been extensively supported by simulation methods; it is possible to calculate important properties computationally, independent of experimental input, [ 252 ] [ 253 ] making materials development cheaper.
On 18 October 2018, Samsung showed of their research roadmap at their 2018 Samsung OLED Forum. This included Fingerprint on Display (FoD), Under Panel Sensor (UPS), Haptic on Display (HoD) and Sound on Display (SoD). [ 254 ]
Various venders are also researching cameras under OLEDs (Under Display Cameras). According to IHS Markit Huawei has partnered with BOE , Oppo with China Star Optoelectronics Technology (CSOT), Xiaomi with Visionox . [ 255 ]
In 2020, researchers at the Queensland University of Technology (QUT) proposed using human hair which is a source of carbon and nitrogen to create OLED displays. [ 256 ]
In 2025, researchers from the University of Turku and Cornell University developed a model showing that polariton OLEDs could dramatically improve efficiency. By leveraging hybrid light-matter states, polariton OLEDs could increase dark-to-bright state conversion by up to 10 million times. The breakthrough demonstrated the potential of single-molecule strong coupling, though large-scale application would remain challenging due to the need for new device architectures or molecules. [ 257 ] | https://en.wikipedia.org/wiki/OLED |
OLGA is a modelling tool for transportation of oil , natural gas and water in the same pipeline , so-called multiphase transportation. The name is short for "oil and gas simulator". The main challenge with multiphase fluid flow is the formation of slugs (plugs of oil and water) in the pipelines, which causes large problems at the receiving end at the platform or the onshore plant. The modelling tool makes it possible to calculate the fluid flow and safely bring the flow to the receiving destination on shore, on a platform or a production ship through the pipes.
The idea for the tool was conceived in 1979 by two researchers at IFE , Norway: Dag Malnes and Kjell Bendiksen. [ 1 ] The first version of OLGA was financed by Statoil and was ready in 1980. The tool was developed further by IFE in collaboration with SINTEF in the 1980s.
January 1, 1984 a joint industry agreement was signed by Statoil, IFE and SINTEF on the continued development of OLGA. IFE had the main responsibility for developing the model, while the technical experiments were performed in SINTEF’s laboratory at Tiller.
Until 2012 the SPT Group [ 2 ] owned the rights to OLGA. In March 2012, Schlumberger announced an agreement with Altor Fund II for the acquisition of SPT Group. The acquisition was completed in Q2. SPT Group, founded in 1971, was headquartered in Norway employing approximately 280 people in 11 countries at the time of the acquisition. The tool has been under continuous and still ongoing development, among others in the HORIZON II project where IFE and SPT Group are partners. OLGA has a global market share of about 90%. The technology is regarded as a central success for Norwegian petroleum research.
OLGA has enabled the development of oil and gas fields at deeper seas and farther from shore than would otherwise be possible without this technology, for example the fields Troll, Ormen Lange and Snøhvit. [ 3 ] | https://en.wikipedia.org/wiki/OLGA_(technology) |
The OMA Instant Messaging and Presence Service ( IMPS ) is an Open Mobile Alliance enabler for Instant Messaging and Presence. The Wireless Village consortium developed the first cut of the specifications. After Wireless Village was merged with OMA, its specs became OMA IMPS 1.0 specifications. IMPS is widely deployed [ citation needed ] but not necessarily marketed. Interworking between several operators IMPS platforms is being performed under a GSMA initiative that encourages interworking and deployment of Instant Messaging.
Vanilla terminals often [ citation needed ] have IMPS clients.
On Nokia , the chat client is accessed via the " My Presence " menu.
On Sony Ericsson , it's called "My Friends".
On Motorola , it's called "IM". The phones' chat clients are generally designed to be provider neutral, so you have to put in the Wireless Village server settings.
If your phone doesn't have an inbuilt chat client, you might still be able to get a third-party chat application that runs on your phone's Symbian , Java ME , BREW , or other application environment. You need to get a chat client which is " Wireless Village compliant presence-enabled".
Note that it is still necessary for the operator to provide the IM service and/or one will have to connect to a third party server for connection with others for IM'ing.
This is only a partial list. | https://en.wikipedia.org/wiki/OMA_Instant_Messaging_and_Presence_Service |
OMDoc (Open Mathematical Documents) is a semantic markup format for mathematical documents. While MathML only covers mathematical formulae and the related OpenMath standard only supports formulae and “content dictionaries” containing definitions of the symbols used in formulae, OMDoc covers the whole range of written mathematics.
OMDoc allows for mathematical expressions on three levels:
On each level, formal syntax and informal natural language can be used, depending on the application.
OMDoc is a semantic markup language that allows writing down the meaning of texts about mathematics. In contrast to LaTeX , for example, it is not primarily presentation-oriented. An OMDoc document need not specify what its contents should look like. A conversion to LaTeX and XHTML (with Presentation MathML for the formulae) is possible, though. To this end, the presentation of each symbol can be defined.
Today, OMDoc is used in the following settings:
OMDoc has been developed by the German mathematician and computer scientist Michael Kohlhase since 1998. So far, there have been the following releases:
It is planned to create the infrastructure for a “ semantic web for technology and science” based on OMDoc. To this end, OMDoc is being extended towards sciences other than mathematics. The first result is PhysML , an OMDoc variant extended towards physics .
For a better integration with other Semantic Web applications, an OWL ontology of OMDoc is under development, as well as an export facility to RDF . | https://en.wikipedia.org/wiki/OMDoc |
The OMEGA process ("Only MEG Advantage") [ 1 ] is a chemical process discovered by the Shell Global Solutions company that is used to produce ethylene glycol from ethylene . This process comprises two steps, the controlled oxidation of ethylene to ethylene oxide , and the net hydrolysis of ethylene oxide to monoethylene glycol (MEG). [ 2 ] The first chemical plant using the OMEGA process was started in South Korea. [ 3 ] Subsequent OMEGA plants have been started in Saudi Arabia [ 4 ] and Singapore. [ 5 ] Shell claims that this process, compared to conventional ones, does not produce higher glycols, uses less steam and water, and generates less waste. [ 1 ]
To produce ethylene oxide, ethylene is oxidized with dioxygen in the presence of a silver catalyst. Some ethylene is over-oxidized to carbon dioxide and water, which is wasteful; early processes only gave ~ 65% selectivity for ethylene oxide as a result. In the OMEGA process, over-oxidation is reduced by including ethyl chloride as a moderator. [ 2 ]
Conventionally, monoethylene glycol (HOC 2 H 4 OH) is produced by the controlled hydrolysis of ethylene oxide (C 2 H 4 O). The monoethylene glycol product is also able to react with ethylene oxide to give diethylene glycol , and so on; sequential reaction with ethylene oxide is how poly(ethylene glycol) is produced. Due to monoethylene glycol's high boiling point, purification by distillation is energy intensive.
In the OMEGA process, the ethylene oxide reacts with carbon dioxide (CO 2 ) to yield ethylene carbonate (C 3 H 4 O 3 ). Ethylene carbonate is subsequently hydrolyzed to monoethylene glycol and carbon dioxide. The carbon dioxide is released in this step again and can be fed back into the process circuit. This process is 99.5% selective for monoethylene glycol. [ 2 ]
This part of the OMEGA process was originally developed by Mitsubishi Chemicals , and it has been exclusively licensed to Shell. [ 2 ] | https://en.wikipedia.org/wiki/OMEGA_process |
OMEMO is an extension to the Extensible Messaging and Presence Protocol ( XMPP ) for multi-client end-to-end encryption developed by Andreas Straub . According to Straub, OMEMO uses the Double Ratchet Algorithm "to provide multi-end to multi-end encryption, allowing messages to be synchronized securely across multiple clients, even if some of them are offline". [ 1 ] The name "OMEMO" is a recursive acronym for "OMEMO Multi-End Message and Object Encryption".
It is an open standard based on the Double Ratchet Algorithm and the Personal Eventing Protocol (PEP, XEP-0163). [ 2 ] OMEMO offers future and forward secrecy and deniability with message synchronization and offline delivery.
In comparison with OTR , the OMEMO protocol offers many-to-many encrypted chat, offline messages queuing, forward secrecy, file transfer, verifiability and deniability at the cost of slightly larger message size overhead. [ 3 ]
The protocol was developed and first implemented by Andreas Straub as a Google Summer of Code project in 2015. The project's goal was to implement a double-ratchet-based multi-end to multi-end encryption scheme into an Android XMPP-based instant messaging client called Conversations .
It was introduced in Conversations and submitted to the XMPP Standards Foundation (XSF) as a proposed XMPP Extension Protocol (XEP) in the autumn of 2015 and got accepted as XEP-0384 in December 2016. [ 1 ]
In July 2016, the ChatSecure project announced that they would implement OMEMO in the next releases. ChatSecure v4.0 supports OMEMO and was released on January 17, 2017. [ 4 ] [ 5 ]
A first experimental release of an OMEMO plugin for the cross-platform XMPP client Gajim was made available on December 26, 2015. [ 6 ]
In June 2016, the non-profit computer security consultancy firm Radically Open Security published an analysis of the OMEMO protocol. [ 7 ]
Selected clients supporting OMEMO (full list of clients also exists [ 8 ] ): | https://en.wikipedia.org/wiki/OMEMO |
OMNIS (Office des Mines Nationales et des Industries Stratégiques, formerly known as Office Militaire National pour les Industries Stratégiques) is the Malagasy government organisation, operating under the auspices of the Ministry of Energy, responsible for:
Hydrocarbons: – Putting in place and updating the legal framework for upstream oil and gas activities in Madagascar – Acquisition of technical exploration data (geological, geophysical and drilling) – Promotion of potentially hydrocarbon-bearing areas – Management of existing and newly acquired exploration data – Laboratory analysis of samples (rock, oil and gas)
Mining: – Promotion of the Malagasy mining sector – Development of basic sectoral infrastructure relevant to various minerals – Undertaking of minerals research including energy minerals (radioactive minerals, fossil fuels, etc.) – Development of and feasibility studies for mining projects, minerals production, etc. – Assistance and support to national and international mining sector companies – Promotion of partnership contracts
The acting Director General of OMNIS is Mr. Joeli Valerien Lalaharisaina, who was formerly its Deputy Director General. | https://en.wikipedia.org/wiki/OMNIS |
OMNeT++ ( O bjective M odular Ne twork T estbed in C ++ ) [ 1 ] is a modular, component-based C++ simulation library and framework, primarily for building network simulators. [ 2 ] [ 3 ] [ 4 ] OMNeT++ can be used for free for non-commercial simulations like at academic institutions and for teaching. [ 5 ] OMNEST is an extended version of OMNeT++ for commercial use. [ 6 ] [ 7 ]
OMNeT++ itself is a simulation framework without models for network protocols like IP or HTTP . The main computer network simulation models are available in several external frameworks. The most commonly used one is INET [ 8 ] [ 9 ] which offers a variety of models for all kind of network protocols and technologies like for IPv6 , BGP . INET also offers a set of mobility models to simulate the node movement in simulations. The INET models are licensed under the LGPL or GPL . [ 10 ] NED (NEtwork Description) is the topology description language of OMNeT++.
To manage and reduce the time to carry out large-scale simulations, additional tools have been developed, for example, based on Python . [ 11 ] | https://en.wikipedia.org/wiki/OMNeT++ |
ONETEP (Order-N Electronic Total Energy Package) is a linear-scaling density functional theory software package able to run on parallel computers . [ 1 ] It uses a basis of non-orthogonal generalized Wannier functions (NGWFs) expressed in terms of periodic cardinal sine (psinc) functions, which are in turn equivalent to a basis of plane-waves . ONETEP therefore combines the advantages of the plane-wave approach (controllable accuracy and variational convergence of the total energy with respect to the size of the basis) with computational effort that scales linearly with the size of the system. [ 2 ] The ONETEP approach involves simultaneous optimization of the density kernel (a generalization of occupation numbers to non-orthogonal basis, which represents the density matrix in the basis of NGWFs) and the NGWFs themselves. The optimized NGWFs then provide a minimal localized basis set, which can be considerably smaller in size, but of equal or higher accuracy, than the unoptimized basis sets used in most linear-scaling approaches.
ONETEP has been developed by a UK-centric group of academics based at the universities of Cambridge , Southampton , Warwick , Imperial College London and Gdańsk University of Technology . It is available to academics at a reduced rate, and licenses can be obtained for non-academic usage from the developers or through Accelrys ' Materials Studio package. The latest academic version 6.0 was released on 15 September 2020. | https://en.wikipedia.org/wiki/ONETEP |
The ONIOM (short for ' O ur own N -layered I ntegrated molecular O rbital and M olecular mechanics' [ 1 ] ) method is a computational approach developed by Keiji Morokuma and co-workers. ONIOM is a hybrid method that enables different ab initio , semi-empirical , or molecular mechanics methods to be applied to different parts of a molecule/system in combination to produce reliable geometry and energy at reduced computational cost. [ 2 ] [ 3 ] [ 4 ]
The ONIOM computational approach has been found to be particularly useful for modeling biomolecular systems [ 5 ] as well as for transition metal complexes and catalysts . [ 6 ]
This quantum chemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/ONIOM |
Trioctylphosphine oxide ( TOPO ) is an organophosphorus compound with the formula OP(C 8 H 17 ) 3 . Frequently referred to as TOPO, this compound is used as an extraction or stabilizing agent. It is an air-stable white solid at room temperature. It is lipophilic, and like other phosphine oxides serves as a Lewis base owing to a partial negative charge at the O atom.
TOPO is usually prepared by oxidation of trioctylphosphine, which in turn is produced by alkylation of phosphorus trichloride .
The main use of TOPO is in solvent extraction of metals, especially uranium. [ 3 ] The high lipophilicity and high polarity are properties key to this application. Its high polarity , which results from the dipolar phosphorus-oxygen bond, allows this compound to bind to metal ions. The octyl groups confer solubility in low polarity solvents such as kerosene . [ 4 ]
In the research laboratory, both trioctylphosphine and TOPO are frequently useful as a capping ligand for the production of quantum dots such as those consisting of CdSe . In these cases, TOPO serves as solvent for the synthesis and solubilizes the growing nanoparticles . TOPO-coated quantum dots are typically soluble in chloroform , toluene , and (to a lesser extent) hexane . [ 5 ] | https://en.wikipedia.org/wiki/OP(C8H17)3 |
This group of standards, created by the OPC Foundation , provides COM specifications for communicating data from devices and applications that provide historical data, such as databases. The specifications provides for access to raw, interpolated and aggregate data (data with calculations).
OPC Historical Data Access, also known as OPC HDA, is used to exchange archived process data. This is in contrast to the OPC Data Access (OPC DA) specification that deals with real-time data. OPC technology is based on client / server architecture. Therefore, an OPC client, such as a trending application or spreadsheet, can retrieve data from an OPC compliant data source, such as a historian, using OPC HDA.
Similar to the OPC Data Access specification, OPC Historical Data Access also uses Microsoft's DCOM to transport data. DCOM also provides OPC HDA with full security features such as user authentication and authorization, as well as communication encryption services. OPC HDA Clients and Servers can reside on separate PCs, even if they are separated by a firewall. To do this, system integrators must configure DCOM properly as well as open ports in the firewall. If using the Windows firewall, users only need to open a single port.
This standards - or measurement -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OPC_Historical_Data_Access |
OPC Unified Architecture ( OPC UA ) is a cross-platform, open-source, IEC62541 standard for data exchange from sensors to cloud applications developed by the OPC Foundation . Distinguishing characteristics are: [ 1 ]
Although developed by the same organization, OPC UA differs significantly from its predecessor, Open Platform Communications (OPC). The Foundation's goal for OPC UA was to provide a path forward from the original OPC communications model (namely the Microsoft Windows -only process exchange COM/ DCOM ) that would better meet the emerging needs of industrial automation . [ 3 ]
After more than three years of specification work and another year for a prototype implementation, the first version of the Unified Architecture was released in 2006. [ 4 ]
The current version of the specification is on 1.04 (22 November 2017 [ 5 ] ). The new version of OPC UA now has added publish/subscribe in addition to the client/server communications infrastructure.
Although the original binding to COM/ DCOM helped OPC to distribute well, it had several drawbacks:
These drawbacks along with a number of other considerations pushed the decision to develop a new and independent stack for OPC UA, which replaces COM/DCOM. The main characteristics of this communication stack were:
This communication stack reflects the beginning of various innovations. The OPC UA architecture is a service-oriented architecture (SOA) and is based on different logical levels.
OPC Base Services are abstract method descriptions, which are protocol independent and provide the basis for OPC UA functionality. The transport layer puts these methods into a protocol, which means it serializes/deserializes the data and transmits it over the network.
Two protocols are specified for this purpose. One is a binary TCP protocol, optimized for high performance and the second is Web service -oriented.
The OPC information model is a Mesh Network based on nodes . These nodes can include any kind of meta information, and are similar to the objects of object-oriented programming (OOP). A node can have attributes for read access (DA, HDA), methods that can be called (Commands), and triggered events that can be transmitted (AE, DataAccess, DataChange). Nodes hold process data as well as other types of metadata . The OPC namespace contains the type model.
Client software can verify what profiles a server supports. This is necessary to obtain information, if a server only supports DA functionality or additionally AE, HDA, etc. Additionally, information can be obtained about whether a server supports a given profile. New and important features of OPC UA are:
At the OPC UA DevCon in October 2006, in Munich the first prototypes were presented live. Various UA Servers have been shown on a Beckhoff programmable logic controller and an embedded test board from Euros. The Beckhoff PLC is based on Windows XP Embedded and the embedded controller is based on the real-time operating system Euros. The company Embedded Labs Ltd demonstrated an OPC UA Server based on their own C++ UA Stack executing on a single chip ARM microcontroller with 64kB RAM . In October 2012 the German Fraunhofer-Application Center IOSB-INA and the Institute for industrial Information Technologies (inIT) showed that an OPC UA server is scalable down to 15 kB RAM and 10 kB ROM and therefore usable at chip level. [ 6 ]
The OPC UA specification is a multi-part specification and consists of the following parts:
Additionally, part 100 Devices, and part 200 Industrial Automation are also available. These build on the core set of specifications, and adds new common definitions that then are used in different companion specifications. E.g. both OPC UA for Analyser Devices and OPC UA for Machinery builds directly on part 100.
In contrast to the COM-based specifications, the UA specifications are not pure application specifications. They describe typically UA internal mechanisms, which get handled through the communication stack and are normally only of interest for those that port a stack to a specific target or those that want to implement their own UA stack.
The OPC UA application developers code against the OPC UA API and therefore mainly use API documentation. Nevertheless, part 3, 4, and 5 may be of interest for application developers. [ 7 ]
The architecture of a UA application, independent of whether it is the server or client part, is structured into levels.
Some parts equalize to the former COM Proxy/Stubs and get provided by the OPC Foundation. The portability level is new; it simplifies porting the UA ANSI C stack to other target platforms. A port layer for Windows and Linux is also provided by the OPC Foundation.
UA Security consists of authentication and authorization, encryption and data integrity via signatures. For Web Services the WS-SecureConversation gets used and is therefore compatible with .NET and other SOAP implementations. For the binary variant, the algorithms of WS-SecureConversation have been followed and also converted to a binary equivalent. This is named as UA Secure Conversation.
There is also a mixed version where the code is binary, but the transport layer is SOAP. This is a compromise between efficient binary coding and firewall-friendly transmission. Binary coding always requires UA Secure Conversation.
The authentication uses X.509 certificates exclusively. It relies on the application developer to choose which certificate store the UA application gets bound to. For instance, it is possible to use the public key infrastructure (PKI) of an Active Directory .
The OPC UA standard defines 25 built-in data types:
UA APIs are available in several programming languages. Commercial SDKs are available for C, C++, Java, and .NET. Open-source stacks are available at least for C, C++, Java, Javascript(node), Tcl and Python .
The .NET implementation uses ANSI C for the lower levels and implements the rest natively in .NET. That means only the handling of the socket and the Message-Chunking gets integrated from the ANSI C stack. De-serialization takes place directly in .NET and therefore gets converted directly into .NET structures and objects. This provides better performance than de-serializing into a C structure first and then copying the data to a .NET structure afterwards.
Various stacks for Java were being developed. [ when? ] Similar to .NET, there are principally three variants:
Alternatively, there is the simple variant to only support the WebService protocol. For that, a SOAP Toolkit that supports WS-Security is needed.
IEC 62541 [ 10 ] is a standard for OPC Unified Architecture. | https://en.wikipedia.org/wiki/OPC_Unified_Architecture |
Phosphoryl chloride (commonly called phosphorus oxychloride ) is a colourless liquid with the formula P O Cl 3 . It hydrolyses in moist air releasing phosphoric acid and fumes of hydrogen chloride . It is manufactured industrially on a large scale from phosphorus trichloride and oxygen or phosphorus pentoxide . [ 4 ] It is mainly used to make phosphate esters .
Like phosphate, POCl 3 is tetrahedral in shape. [ 6 ] It features three P−Cl bonds and one strong P–O bond, with an estimated bond dissociation energy of 533.5 kJ/mol. Unlike in the case of POF 3 , the Schomaker-Stevenson rule predicts appropriate bond length for the P–O bond only if the P–O bond is treated as a double bond, P=O. [ citation needed ] More modern treatments explain the tight P–O bond as a combination of lone pair transfer from the phosphorus to the oxygen atom and a dative π back-bond that produces an effective [P + ]-[O − ] configuration. [ 7 ]
Phosphoryl chloride exists as neutral POCl 3 molecules in the solid , liquid and gas states. This is unlike phosphorus pentachloride which exists as neutral PCl 5 molecules in the gas and liquid states but adopts the ionic form [PCl 4 ] + [PCl 6 ] − (tetrachlorophosphonium hexachlorophosphate(V)) in the solid state. The average bond lengths in the crystal structure of POCl 3 are 1.98 Å for P–Cl and 1.46 Å for P=O. [ 5 ]
It has a critical pressure of 3.4 atm . [ 8 ] With a freezing point of 1 °C and boiling point of 106 °C, the liquid range of POCl 3 is rather similar to water. Also like water, POCl 3 autoionizes , owing to the reversible formation of [POCl 2 ] + cations (dichlorooxophosphonium cations) and Cl − anions .
POCl 3 reacts with water to give hydrogen chloride and phosphoric acid :
Intermediates in the conversion have been isolated, including pyrophosphoryl chloride , O(−P(=O)Cl 2 ) 2 . [ 9 ]
Upon treatment with excess alcohols and phenols , POCl 3 gives phosphate esters :
Such reactions are often performed in the presence of an HCl acceptor such as pyridine or an amine .
POCl 3 can also act as a Lewis base , forming adducts with a variety of Lewis acids such as titanium tetrachloride :
The aluminium chloride adduct ( POCl 3 ·AlCl 3 ) is quite stable, and so POCl 3 can be used to remove AlCl 3 from reaction mixtures, for example at the end of a Friedel-Crafts reaction .
POCl 3 reacts with hydrogen bromide in the presence of Lewis-acidic catalysts to produce POBr 3 .
Phosphoryl chloride can be prepared by many methods. Phosphoryl chloride was first reported in 1847 by the French chemist Adolphe Wurtz by reacting phosphorus pentachloride with water. [ 10 ]
The commercial method involves oxidation of phosphorus trichloride with oxygen : [ 11 ]
An alternative method involves the oxidation of phosphorus trichloride with potassium chlorate : [ 12 ]
The reaction of phosphorus pentachloride ( PCl 5 ) with phosphorus pentoxide ( P 4 O 10 ).
The reaction can be simplified by chlorinating a mixture of PCl 3 and P 4 O 10 , generating the PCl 5 in situ .
The reaction of phosphorus pentachloride with boric acid or oxalic acid : [ 12 ]
Reduction of tricalcium phosphate with carbon in the presence of chlorine gas: [ 13 ]
The reaction of phosphorus pentoxide with sodium chloride is also reported: [ 13 ]
Phosphoryl chloride is used on an industrial scale for the manufacture of phosphate esters (organophosphates). These have a wide range of uses, including as flame retardants ( bisphenol A diphenyl phosphate , TCPP and tricresyl phosphate ), plasticisers for PVC and related polymers ( 2-ethylhexyl diphenyl phosphate ) and hydraulic fluids. [ 11 ] POCl 3 is also used in the production of organophosphate insecticides.
In the semiconductor industry, POCl 3 is used as a safe liquid phosphorus source in diffusion processes. The phosphorus acts as a dopant used to create n-type layers on a silicon wafer.
In the laboratory, POCl 3 is a reagent in dehydrations. One example involves conversion of formamides to isonitriles (isocyanides); [ 14 ] primary amides to nitriles : [ 15 ]
In a related reaction, certain aryl-substituted amides can be cyclized using the Bischler-Napieralski reaction .
Such reactions are believed to proceed via an imidoyl chloride . In certain cases, the imidoyl chloride is the final product. For example, pyridones and pyrimidones can be converted to chloro- derivatives such as 2-chloropyridines and 2-chloropyrimidines, which are intermediates in the pharmaceutical industry. [ 16 ]
In the Vilsmeier-Haack reaction , POCl 3 reacts with amides to produce a "Vilsmeier reagent", a chloro- iminium salt, which subsequently reacts with electron-rich aromatic compounds to produce aromatic aldehydes upon aqueous work-up. [ 17 ] | https://en.wikipedia.org/wiki/OPCl3 |
The OPLS (Optimized Potentials for Liquid Simulations) force field was developed by Prof. William L. Jorgensen at Purdue University and later at Yale University , and is being further developed commercially by Schrödinger, Inc .
The functional form of the OPLS force field is very similar to that of AMBER :
E ( r N ) = E b o n d s + E a n g l e s + E d i h e d r a l s + E n o n b o n d e d {\displaystyle E\left(r^{N}\right)=E_{\mathrm {bonds} }+E_{\mathrm {angles} }+E_{\mathrm {dihedrals} }+E_{\mathrm {nonbonded} }}
E b o n d s = ∑ b o n d s K r ( r − r 0 ) 2 {\displaystyle E_{\mathrm {bonds} }=\sum _{\mathrm {bonds} }K_{r}(r-r_{0})^{2}\,}
E a n g l e s = ∑ a n g l e s k θ ( θ − θ 0 ) 2 {\displaystyle E_{\mathrm {angles} }=\sum _{\mathrm {angles} }k_{\theta }(\theta -\theta _{0})^{2}\,}
E d i h e d r a l s = ∑ d i h e d r a l s ( V 1 2 [ 1 + cos ( ϕ − ϕ 1 ) ] + V 2 2 [ 1 − cos ( 2 ϕ − ϕ 2 ) ] + V 3 2 [ 1 + cos ( 3 ϕ − ϕ 3 ) ] + V 4 2 [ 1 − cos ( 4 ϕ − ϕ 4 ) ] ) {\displaystyle E_{\mathrm {dihedrals} }=\sum _{\mathrm {dihedrals} }\left({\frac {V_{1}}{2}}\left[1+\cos(\phi -\phi _{1})\right]+{\frac {V_{2}}{2}}\left[1-\cos(2\phi -\phi _{2})\right]+{\frac {V_{3}}{2}}\left[1+\cos(3\phi -\phi _{3})\right]+{\frac {V_{4}}{2}}\left[1-\cos(4\phi -\phi _{4})\right]\right)}
E n o n b o n d e d = ∑ i > j f i j ( A i j r i j 12 − C i j r i j 6 + q i q j e 2 4 π ϵ 0 r i j ) {\displaystyle E_{\mathrm {nonbonded} }=\sum _{i>j}f_{ij}\left({\frac {A_{ij}}{r_{ij}^{12}}}-{\frac {C_{ij}}{r_{ij}^{6}}}+{\frac {q_{i}q_{j}e^{2}}{4\pi \epsilon _{0}r_{ij}}}\right)}
with the combining rules A i j = A i i A j j {\displaystyle A_{ij}={\sqrt {A_{ii}A_{jj}}}} and C i j = C i i C j j {\displaystyle C_{ij}={\sqrt {C_{ii}C_{jj}}}} .
Intramolecular nonbonded interactions E n o n b o n d e d {\displaystyle E_{\mathrm {nonbonded} }} are counted only for atoms three or more bonds apart; 1,4 interactions are scaled down by the "fudge factor" f i j = 0.5 {\displaystyle f_{ij}=0.5} , otherwise f i j = 1.0 {\displaystyle f_{ij}=1.0} . All the interaction sites are centered on the atoms; there are no "lone pairs".
Several sets of OPLS parameters have been published. There is OPLS-ua (united atom), which includes hydrogen atoms next to carbon implicitly in the carbon parameters, and can be used to save simulation time. OPLS-aa (all atom) includes every atom explicitly. Later publications include parameters for other specific functional groups and types of molecules such as carbohydrates. OPLS simulations in aqueous solution typically use the TIP4P or TIP3P water model .
A distinctive feature of the OPLS parameters is that they were optimized to fit experimental properties of liquids, such as density and heat of vaporization, in addition to fitting gas-phase torsional profiles.
The reference implementations of the OPLS force field are the BOSS and MCPRO programs developed by Jorgensen. Other packages such as TINKER , GROMACS , PCMODEL , Abalone , LAMMPS , Desmond and NAMD also implement OPLS force fields.
This computational chemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OPLS |
ORCA was a mobile-optimized web application used as a component of the " get out the vote " (GOTV) efforts for Mitt Romney's 2012 presidential campaign . It was intended to enable volunteers in polling stations around the country to report which voters had turned out, so that "missing" Republican voters and underperforming precincts could be targeted for last-minute efforts to get voters to the polls. According to Romney himself, it would provide an "unprecedented advantage" to the campaign to "ensure that every last supporter makes it to the polls."
The system had major technical problems during Election Day that prevented many volunteers from using it. It crashed periodically and at one point was intentionally taken down when a surge of traffic from campaign volunteers was misinterpreted as a denial of service attack . Frustrated volunteers reported being unable to access ORCA and criticised a lack of prior briefing, misleading instructions and patchy on-the-day support. A Romney aide commented that " Orca is lying on the beach with a harpoon in it." The system's failings have been attributed by technology writers to a combination of factors including not doing prior quality assurance or beta testing, inadequate documentation and poor design.
The Romney campaign subsequently defended ORCA as a success, though campaign officials admitted that the system "had its challenges". Conservative activists and writers blamed ORCA for depressing Republican turnout on election day. While political scientists have rebutted these claims, suggesting that it probably did not have a decisive effect on the outcome, it may have negatively affected turnout figures. ORCA has been compared unfavorably with a "get out the vote" and data effort from President Obama, including Project Narwhal , seen as more robust.
In the 2008 US presidential election , the Obama campaign utilized a system called Houdini to enable volunteers to report voting data to a national hotline. [ 1 ] While this system encountered problems, [ 2 ] the 2012 Romney campaign 's ORCA system aimed to go further by enabling volunteers to report such data to campaign headquarters in real time via their smartphones . It was intended to be rolled out to around 37,000 volunteers at polling places in swing states. [ 3 ]
Gail Gitcho, the Romney campaign's communications director, told PBS on November 5 that with the deployment of ORCA on election day, the campaign would be able to tell who had voted in which precincts. [ 3 ] She described the system's key function as not being to predict the outcome, but to identify low turnouts in target precincts so that the campaign could take action by contacting missing voters and urging them to go to the polls. Gitcho commented: "The Obama campaign likes to brag about their ground operation, but it's nothing compared to this." [ 4 ] The name ORCA was chosen to reference the Obama GOTV system, called Project Narwhal ; in nature, the orca or killer whale is the only known non-human predator of narwhals . [ 4 ]
In a training call for Republican volunteers on October 31, they were told: "There's nothing that the Obama data team, there's nothing that the Obama campaign, there's nothing that President Obama himself can do to even come close to what we are putting together here." [ 1 ] According to reports, "The governor [Romney] loves seeing data, he loves seeing numbers and he's a very strategic person; he's a very smart man. So he actually loves being inside these war rooms, seeing the data come in and seeing exactly what's going on out there, so we can all put our heads together and say, 'Okay, we need to move resources here. We need to shift resources from here.'" [ 1 ] The campaign's spokeswoman Andrea Saul told the Huffington Post that ORCA would provide Romney with "an enormous advantage ... By knowing the current results of a state, we can continue to adjust and micro target our get-out-the-vote efforts to ensure a Romney victory." [ 1 ]
According to the campaign, ORCA would identify how between 18 and 23 million people had voted on election day, providing "the most accurate ballot projections ever" and ensuring "hyper-accuracy of our supporter targeting as we work to turn them out to the polls." [ 5 ] In a pre-election video, Romney told volunteers: "As part of this task force, you'll be the key link in providing critical, real-time information to me and to the staff so that we can ensure that every last supporter makes it to the polls. With state-of-the-art technology, and an extremely dedicated group of volunteers, our campaign will have an unprecedented advantage on Election Day." [ 6 ]
The Obama campaign declined to comment on ORCA but Scott Goodstein, the external online director for the 2008 Obama campaign, questioned whether it would actually make much difference to potential voters who were sitting out the election. He commented, "In a national campaign, what additional things are the headquarters really going to do to move resources? Will an additional auto-call last minute really make a difference in a market like Northeast Ohio , which has been saturated for three months full of auto-calls?" [ 1 ] Some pro-Democrat bloggers expressed concerns that the system would facilitate voter suppression but the ORCA training material emphasized that Romney volunteers should under no circumstances talk to or confront voters. [ 1 ]
The system was initially reported to have been developed by an application consulting firm and Microsoft, [ 3 ] but later reports attributed its development to "an internal 'skunkworks'" comprising "a makeshift team of IT people and volunteers", rather than an outside consultancy, while a number of small consulting companies helped with the implementation of ORCA during election day. [ 2 ] According to campaign insiders, it was kept secret among "a close circle in Boston" and state officials were not informed of how it would operate until only a few days before the election. [ 7 ] Volunteer users of ORCA in Boston were given no hands-on training until the day of the election itself, when the system was turned on at 6 am. [ 3 ]
ORCA was conceived by Rich Beeson, the campaign's political director, and Dan Centinello, Romney's director of voter contact. [ 3 ] Centinello served as the political manager of the Orca project. [ 2 ]
ORCA spending represented only a small portion of the campaign's overall investment in information technology. [ 2 ]
ORCA was designed to work on a variety of devices, including iPhones and iPads , Android phones and tablets and BlackBerry phones. [ 1 ]
The system was designed to show the names and addresses of every eligible voter in a particular precinct. When the voter had gone through the polling station, a logged-in volunteer would simply slide a bar on their phone screen to note that fact. If there were any problems in the polling station, such as erroneous voting lists, illegal activities or issues with the voting machines, they could press an on-screen yellow button to send an alert to the campaign's lawyers. A Twitter -style instant messenger system would also enable volunteers and the campaign to share information in real time. Those without smartphones were also catered for; the Romney campaign would provide a list of voters to enable volunteers to check off individual names and phone the information into the campaign's headquarters. [ 1 ] The data they gathered would be monitored by 800 volunteers at campaign headquarters on the floor of TD Garden in Boston via a Web-based application; it would be used to coordinate contacts throughout election day to pro-Romney voters who had not shown up at the polls. As a fallback, a voice response system would also be established, to allow mobile phone users to call in information if the online system was not working. [ 3 ] The voice response system was brought in the night before the election, setup on the floor of TD Garden, and went live on election day.
ORCA consisted of 11 back-end database servers and a single web server and application server providing the front end. The servers were said to have all been hosted in Boston . [ 3 ]
Throughout election day, volunteers experienced frequent and widespread problems using ORCA, [ 5 ] which crashed periodically. [ 7 ] As volunteers tried to log in, the surge of traffic caused the system to collapse altogether for about an hour and a half, leading to scenes of panic among Romney staffers at the TD Garden. The Romney campaign's digital director, Zac Moffatt, conceded: "The Garden definitely kind of buckled under the strain. The system wasn't ready for the amount of information incoming." [ 6 ] The traffic surge was so great that at one point Comcast , the campaign's Internet Service Provider, shut off its network connection in the belief that it was coming under a denial of service attack . [ 3 ] Reporter Erin McPike tweeted that some suspected that the system had been hacked and that Republican sources had confirmed to her that something had gone wrong. [ 8 ] One Romney aide commented that "ORCA is lying on the beach with a harpoon in it." [ 5 ]
John Ekdahl Jr., a Romney volunteer and web developer in Jacksonville, Florida , wrote a widely discussed account of his experiences with ORCA. The Romney campaign had sent him a 60-page document listing voters and instructions the day before the election, which he struggled to print, but when he reached his local polling station on election day he was told that he needed a certificate to be allowed to work there. The certification was not mentioned in his documentation and his attempts to reach campaign headquarters got nowhere, causing him to give up by 2 pm. Calling ORCA "an unmitigated disaster," Ekdahl said that he was "hearing almost universal condemnation of the thing. It seemed like the basic coordination between ground ops and overall team was lacking." [ 6 ] Ekdahl also called the training manuals vague and uninformative; ORCA was regularly described as an "app", leading to volunteers looking unsuccessfully for it on the iOS App Store and Google Play . In fact, it was a web application, a mobile-enabled website that did not require additional software to use. [ 6 ] [ 8 ] The training materials were also riddled with errors such as duplicate checklist items and erroneous responses to frequently asked questions. ORCA exclusively used an HTTP Secure (HTTPS) connection but its designers had apparently forgotten to redirect those attempting to use the equivalent HTTP address to the HTTPS address. Anyone who incorrectly typed in an address beginning with "www" was unable to reach the system, causing many volunteers to assume that it was down. [ 8 ]
Other volunteers reported being unable to get through to technical support and found themselves receiving either a busy signal or a "try again later" message. One volunteer wrote on a Romney campaign message board: "I have called the ORCA helpline. It was supposed to be live at 5 a.m. ... still getting a recording. Com [ sic ] on Boston we can't help Mitt if you won't help us.!!!!!" [ 6 ] Many volunteers could not get their security PINs to work. According to a campaign official in Colorado, "we were called by hundreds (or more) volunteers who couldn't use the app or the backup phone system. The usernames and passwords were wrong, but the reset password tool didn't work, and we couldn't change phone PINs. We were told the problems were limited and asked to project confidence, have people use pencil and paper, and try to submit again later. Then at 6 p.m. they admitted they had issued the wrong PINs to every volunteer in Colorado , and reissued new PINS (which also didn't work)." [ 6 ] In North Carolina , another campaign official said that "the system went down for a half hour during peak voting, but for hundreds or more, it never worked all day... Many members of our phone bank got up and left." [ 8 ] One frustrated volunteer tweeted that it was "a clusterf**k [ sic ] of biblical proportions." [ 8 ]
Ekdahl described the effect of ORCA as being that "30,000+ of the most active and fired-up volunteers were wandering around confused and frustrated when they could have been doing anything else to help, like driving people to the polls, phone-banking, walking door-to-door, etc." [ 9 ] Campaign workers were left "flying blind", as several put it, unable to identify non-voters or precincts which needed a last-minute robocalling campaign to drive up turnout. The targeted information promised by the campaign did not materialize and only the generic raw vote tallies were available in key areas. [ 7 ] According to the Washington Examiner , by late afternoon on election day ORCA was still predicting a Romney victory with somewhere between 290–300 electoral college votes – nearly 100 more than Romney actually received. [ 5 ] A Romney campaign official told ABC News , which predicted on the eve of the election that Obama would win by a 50%–47% margin, [ 10 ] "Your numbers don't matter to us." [ 9 ] Without accurate information from ORCA, Republican officials instead turned to using public news sources or calling counties for information on the outcome of votes in those areas. [ 7 ]
Moffatt acknowledged that "without a doubt, ORCA had its challenges" [ 11 ] but argued that the system had actually worked, despite the reports of problems: "We don't think Orca's problems had a material impact on the campaign, it was not election determinative. We had 30,000 plus volunteers across the country putting information into the system. We had 91 percent of all counties report into the system, 14.3 million voters were accounted for as having voted, and we received 5,397 reports on voting issues, such as instances where they ran out of ballots. The information came in, so you can't say it didn't work. You run into issues because it's so massive in scale." [ 5 ] He noted that the Romney campaign had had only six months to develop its system, whereas Obama had the benefit of six years of preparation. [ 5 ] Another Romney aide told National Review's Katrina Trinko that in fact ORCA's problems had "no relation to the outcome. We achieved in a large part what we set out to do in the swing states in terms of our electorate. The reality is the President did what he said he was going to do. The Obama campaign said that they were going to increase turnout from 2008, and they were able to do that. And that had nothing to do with a reporting system on Election Day." [ 12 ]
Conservative writer Joel B. Pollak suggested that ORCA had ended up suppressing Romney's own vote by tying up campaign volunteers at a critical time. He noted the narrow margin in the key swing states – only some 500,000 to 700,000 votes – and calculated that if each of the 37,000 ORCA volunteers had brought 20 voters to the polls in those states, the gap could have been closed. [ 13 ] Ekdahl saw a "bitter irony" in the fact that "a supposedly small government candidate gutted the local structure of GOTV efforts in favor of a centralized, faceless organization in a far off place (in this case, their Boston headquarters)." [ 13 ] Erick Erickson of RedState compared the system to Shamu , a 1970s SeaWorld orca, "because it bit the leg of the campaign and wouldn't let go." While political scientists doubted that its failure had made much of a difference to the outcome, they suggested that if it had worked properly it could have resulted in a closer election. Lara Brown of Villanova University said that it was likely that ORCA had "had a substantial effect" on the turnout, particularly in rural counties of Ohio where Romney had underperformed. [ 14 ]
The ORCA system had not received extensive beta testing before election day, nor did the campaign know how it would interact with the data infrastructure in the TD Garden until the day itself. [ 9 ] Ekdahl said that he had raised concerns about the lack of testing beforehand. He had asked whether it had been stress tested, whether redundancy had been put in place and whether steps had been taken to combat an external attack on the system, but "these types of questions were brushed aside (truth be told, they never took one of my questions). They assured us that the system had been relentlessly tested and would be a tremendous success." [ 11 ] Moffatt admitted that the system had been "beta-tested in a different environment ... There was so much data coming in – 1200 records or more per minute – it shut down the system for a time. Users were frustrated by lag, and some people dropped off and we experienced attrition as a result." [ 5 ]
Robert X. Cringely , writing in InfoWorld , concluded that "everything in the Orca rollout went great, except for a failure to do any quality assurance, proof its documentation, or beta test in the seven months from conception to implementation. Whoever was behind Orca apparently also failed to hire a competent Web designer, anticipate server loads, beef up its bandwidth, or notify its ISP to expect a bump in traffic." [ 15 ] Sean Gallagher of Ars Technica commented that the key failure was the dependency on automated testing rigs, which "can't show what the system's performance will look like to the end user. And whatever testing environment Romney's campaign team and IT consultants used, it wasn't one that mimicked the conditions of Election Day. As a result, Orca's launch on Election Day was essentially a beta test of the software – not something most IT organizations would do in such a high-stakes environment." [ 3 ]
Slate writer Sasha Issenberg argued that the problems ran far deeper than ORCA's technical failings, as the Romney campaign had been left behind by the cutting edge of data science . He noted that while a system like ORCA could not have changed the demographics, data science did make a great difference to the ability of the two campaigns to target and mobilize their voters. As he put it, "The Democrats have it and the Republicans don't." He suggested that ORCA's ability to affect the outcome had been over-hyped by the Romney campaign, as there was only so much that could be done on election day itself: "On short notice, you can send robocalls, reorder a call list and employ paid phone banks, but you are not radically changing the shape of the electorate. They acted like they had invented the wheel, but really all it would have been was a slightly better tread on the tire." [ 5 ] | https://en.wikipedia.org/wiki/ORCA_(computer_system) |
ORCA [ 1 ] [ 2 ] [ 3 ] [ 4 ] is a general-purpose quantum chemistry package featuring a variety of methods including semi-empirical , density functional theory , many-body perturbation , coupled cluster , and multireference methods. ORCA provides an easy-to-learn input structure and thus high accessibility of quantum chemical approaches and workflows. The ORCA program package is mainly developed by Frank Neese , the department of molecular theory and spectroscopy at the Max-Planck-Institut für Kohlenforschung (MPI KoFo), and the FACCTs GmbH which also manages commercial licensing to industry. ORCA is generally freely available for academic use.
The development of ORCA started in 1997, while Frank Neese was on his PostDoc at Stanford University . Since then the ORCA development went on, following Neese to his stations at the University of Bonn , the Max-Planck-Institute for Chemical Energy Conversion , and finally the Max-Planck-Institut für Kohlenforschung . Since then, the ORCA development team grew constantly involving the whole department of molecular theory and spectroscopy at the MPI KoFo and various external academic developers contributing to ORCA.
In 2016, Frank Neese co-founded the FACCTs GmbH as a spin-off of the Max-Planck-Society to commercially license the ORCA program package to industry. In contrast to many other commercialized quantum chemistry programs, ORCA remains freely available for academic use.
Since its first release, the number of active users and developers grew steadily peaking in 67000 registered users and 3300 citations to ORCA in 2023. [ 5 ]
Beginning with version 4.0, only major and feature releases are shown.
This quantum chemistry -related article is a stub . You can help Wikipedia by expanding it .
This article about chemistry software is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/ORCA_(quantum_chemistry_program) |
Busek Company Incorporated is an American spacecraft propulsion company that builds thrusters , electronics , and various systems for spacecraft .
Busek was founded in 1985 by Vlad Hruby in Natick, Massachusetts . [ 1 ] Busek started as a laboratory outside of Boston , Massachusetts .
The first US Hall thruster flown in space, Busek's BHT-200, was launched aboard the Air Force Research Laboratory's (AFRL) TacSat-2 satellite. The Busek thruster was part of the Microsatellite Propulsion Integration (MPI) Experiment and was integrated on TacSat-2 under the direction of the DoD Space Test Program. TacSat-2 launched on December 16, 2006 from the NASA Wallops Flight Facility . [ 2 ]
The first electrospray thruster that made it to space was manufactured by Busek and launched aboard the European Space Agency's LISA Pathfinder satellite on December 3, 2015. The micro-newton colloid-style electric thruster was developed under contract with NASA's Jet Propulsion Laboratory (NASA ST-7 Program) and part of NASA's Disturbance Reduction System (DRS), which serves a critical role in the LISA Pathfinder science mission. [ 3 ] [ 4 ]
Aerojet , under license with Busek, [ 5 ] [ 6 ] manufactured the 4 kW Hall thruster (the BPT-4000) which was flown aboard the USAF AEHF communications spacecraft.
In 2023, Busek announced the successful on-orbit commissioning of its BHT-350 Hall-effect thrusters on 80 OneWeb satellites, launched in December 2022 and January 2023 on SpaceX Falcon 9 rockets. The new OneWeb communications satellites use the thrusters for orbit-raising, station-keeping, collision avoidance and de-orbiting at the conclusion of each satellite’s mission. [ 7 ]
Busek will be providing Hall thrusters for NASA 's Artemis Program . As part of the Power and Propulsion Element , Busek's 6 kW Hall thrusters will work in combination with NASA's Advanced Electric Propulsion System to provide orbit-raising and station-keeping capabilities for the Lunar Gateway . The Lunar Gateway's polar near-rectilinear halo orbit (NRHO) will require periodic orbit adjustment, and electric propulsion will use solar energy for this task. [ 8 ]
Busek has demonstrated experimental xenon Hall thrusters at power levels exceeding 20kW. [ 9 ] Busek has also developed Hall thrusters that operate on iodine , [ 10 ] [ 11 ] bismuth , [ 12 ] [ 13 ] carbon dioxide , [ 14 ] magnesium , [ 15 ] zinc , [ 16 ] and other substances. An iodine fueled 200 W Busek Hall thruster will fly on NASA's iSat ( Iodine Satellite ) mission. Busek is also preparing a 600 Watt iodine Hall thruster system for future Discovery Class missions. [ 17 ]
Other publicized Busek technologies include RF ion engines [ 18 ] and a resistojet rocket . [ 19 ] Another focus is CubeSat propulsion, proposed for the 2018 Lunar IceCube mission. [ 20 ]
As of July 2012 [update] , Busek was working on a DARPA -funded program called DARPA Phoenix , which aimed to recycle some parts of on-orbit spacecraft. [ 21 ]
In September 2013, NASA awarded an 18‑month Phase I contract to Busek to develop an experimental concept called a High Aspect Ratio Porous Surface (HARPS) microthruster system for use in tiny CubeSat spacecraft. [ 22 ] [ 23 ]
In March 2021, Busek and Maxar Technologies completed an end-to-end hot fire test campaign validating the 6-kilowatt solar electric propulsion (SEP) subsystem for the Power and Propulsion Element (PPE) of NASA’s Gateway in lunar orbit. [ 24 ]
In order to deal with space debris , Busek proposed in 2014 a remotely controlled vehicle to rendezvous with this debris, capture it, and attach a smaller deorbit satellite to the debris. The remotely controlled vehicle would then drag the debris/smallsat-combination, using a tether, to the desired location. The larger satellite would then tow the debris/smallsat combination to either deorbit or move it to a higher graveyard orbit by means of electric propulsion . The larger satellite, named the Orbital Debris Remover , or ORDER, would carry over 40 SUL ( Satellite on an Umbilical Line ) deorbit satellites and sufficient propellant for a large number of orbital maneuvers required to effect a 40-satellite debris removal mission over many years. Busek projected the cost for such a space tug to be US$80 million . [ 25 ] | https://en.wikipedia.org/wiki/ORDER_(spacecraft) |
In molecular genetics , an ORFeome refers to the complete set of open reading frames (ORFs) in a genome . The term may also be used to describe a set of cloned ORFs. [ 1 ] ORFs correspond to the protein coding sequences (CDS) of genes . ORFs can be found in genome sequences by computer programs such as GENSCAN and then amplified by PCR . While this is relatively trivial in bacteria the problem is non-trivial in eukaryotic genomes because of the presence of introns and exons as well as splice variants .
The usage of complete ORFeomes reflects a new trend in biology that can be succinctly summarized as omics . ORFeomes are used for the study of protein-protein interactions, [ 2 ] [ 3 ] protein microarrays , the study of antigens, [ 4 ] and other fields of study.
Complete ORF sets have been cloned for a number of organisms including Brucella melitensis , [ 5 ] Chlamydia pneumoniae , [ 6 ] Escherichia coli , [ 7 ] Neisseria gonorrhoeae , [ 8 ] Pseudomonas aeruginosa , [ 9 ] Schizosaccharomyces pombe , Staphylococcus aureus [ 10 ] and human herpesviruses [ 11 ]
A partial human ORFeome has also been produced. [ 12 ] [ 13 ] | https://en.wikipedia.org/wiki/ORFeome |
The ORTF stereo technique , also known as side-other-side , is a microphone technique used to record stereo sound . It was devised around 1960 at the now-defunct Office de Radiodiffusion Télévision Française (ORTF).
This technique combines both the volume difference and the timing difference as sound arrives on- and off-axis at two cardioid microphones spread to a 110° angle, and spaced 17 cm apart. [ 1 ]
The microphones should be as similar as possible, preferably a frequency-matched pair of an identical type and model.
The result is a realistic stereo field that has reasonable compatibility with mono playback. Since the cardioid polar pattern rejects off-axis sound, less of the ambient room characteristics are picked up. This means the mics can be placed further away from the sound sources, resulting in a blend that may be more appealing. Furthermore, the availability of purpose-built microphone mounts makes ORTF easy to achieve.
As with all microphone arrangements, the spacing and angle can be manually adjusted slightly by ear for the best sound, which may vary depending on room acoustics, source characteristics, and other factors. This arrangement is defined as it is because it was the outcome of considerable research and experimentation, and its results are predictable and repeatable.
These interchannel differences are not the same as interaural differences, as produced by artificial head recordings. Even the spacing of 17 cm is not strictly based on interaural ear spacing. The recording angle for this microphone system is ±48° = 96°. [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/ORTF_stereo_technique |
ORiN (Open Robot/Resource interface for the Network) is a standard network interface for FA ( factory automation ) systems. The Japan Robot Association proposed ORiN in 2002, and the ORiN Forum develops and maintains the ORiN standard.
The installation of PC ( Personal Computer ) applications in the factory has increased dramatically recently. Various types of application software systems, such as production management systems, process management systems, operation monitoring systems and failure analysis systems, have become vital to factory operation. These software systems are becoming indispensable for the manufacturing system.
However, most of these software systems are only compatible with specific models or specific manufacturers of the FA system. This is because the software system is “ custom made ” depending on the specific special network or protocol. Once this type of application is installed in a factory and if there are no resident software engineers for the system, the improvement of the system will stop, the cost-effectiveness of the system will be worsen, and the total value of the system will deteriorate.
Another recent problem in production is the rapid increase of the product demand at the initial stage of the product release. The manufactures will lose the chance of possible profit if they cannot meet the demand. To cope with the problem, manufacturing industry is trying to achieve the vertical upstart of the production, and high re-usability of both hardware and software is the key for the goal.
To solve these problems, ORiN was developed as a standard PC application platform.
ORiN was originally developed as a standard platform for robot applications. Nowadays, ORiN became a manufacturing application program platform for handling wider range of resources including robots and other FA devices like programmable logic controllers (PLC) and numerical control (NC) systems, or more generic resources like databases and local file systems . ORiN specifications are on software only and are independent from hardware. Therefore, ORiN can be smoothly integrated with other existing technologies only by developing software. By using ORiN, development of manufacture-independent and model-independent application becomes easy.
By utilizing ORiN, various application software development and active multi-vender system construction by third-party companies are expected. In addition, on economy side, increase of manufacturing competitiveness , expansion of FA market, advancement of software industry in FA, and creation of FA engineering industry are also expected.
ORiN is independent from hardware, and all ORiN specifications are for software. ORiN (Version 2) is composed of the following three key technology specifications.
With these three key standard technologies, ORiN provides following features. | https://en.wikipedia.org/wiki/ORiN |
OS/4 is a discontinued operating system , introduced in 1972, from UNIVAC for their 9400, 9480, and 9700 computer systems. It is an enhanced version of UNIVAC's 9400 Disc Operating System. OS/4 is a disc-resident system requiring 64 KB of main memory , two disc drives , a punched-card reader and a printer . The resident memory footprint is approximately 24 KB. [ 1 ]
UNIVAC intended to replace OS/4 with a new system known as OS/7 ; however, OS/7 development was discontinued in 1975 when the 9700 was made part of the new UNIVAC Series 90 line as the 90/70. [ 2 ] [ 3 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OS/4 |
OS/7 is a discontinued operating system from Sperry Univac for its 90/60 and 90/70 computer systems. The system was first announced in November 1971 for Univac's 9700 system and was originally scheduled for delivery in March 1973. [ 1 ] [ 2 ] However, the delivery slipped by nearly a year, which impacted the 9700 marketing effort. It was first demonstrated by Univac on the new 90/60 system in October 1973. The official release was then planned for January 1974. [ 2 ] OS/7 was abruptly discontinued in 1975 in favor of VS/9, Univac's name for RCA 's VMOS operating system. [ 3 ] [ 4 ]
"OS/7 is a multi-tasking, multi-programming system that utilizes a roll-in, roll-out capability to keep the CPU optimally busy." [ 5 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OS/7 |
OSS/J (a.k.a. OSS through Java ) is a TM Forum [ 1 ] technical program whose primary goal is to develop open interface standards ( APIs ) for the integration of Business Support Systems (BSS) & Operations Support System (OSS).
OSS/J addresses the concerns of Frameworx implementation stakeholders by providing open standard APIs based on the NGOSS framework, particularly the Frameworx Shared Information/Data Model (SID). Work is underway to organize the OSS/J APIs against the NGOSS Telecom Application Map (TAM).
The OSS/J APIs are multi-technology based and include Java , XML , and Web Services integration profiles. Each integration profile consists of specifications, a reference implementation, and a conformance test suite (TCK).
The OSS/J APIs are developed under the Java Community Process [ 2 ] and can be downloaded for free [ 3 ] from the TM Forum OSS/J web site. [ 4 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OSS/J |
OSS/J (a.k.a. OSS through Java ) is a TM Forum [ 1 ] technical program whose primary goal is to develop open interface standards ( APIs ) for the integration of Business Support Systems (BSS) & Operations Support System (OSS).
OSS/J addresses the concerns of Frameworx implementation stakeholders by providing open standard APIs based on the NGOSS framework, particularly the Frameworx Shared Information/Data Model (SID). Work is underway to organize the OSS/J APIs against the NGOSS Telecom Application Map (TAM).
The OSS/J APIs are multi-technology based and include Java , XML , and Web Services integration profiles. Each integration profile consists of specifications, a reference implementation, and a conformance test suite (TCK).
The OSS/J APIs are developed under the Java Community Process [ 2 ] and can be downloaded for free [ 3 ] from the TM Forum OSS/J web site. [ 4 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OSS_through_Java |
OSv (stylized OS v ) is a cloud computing focused [ 1 ] computer operating system released on September 16, 2013. It is a special-purpose operating system built to run as a guest on top of a virtual machine, thus it does not include drivers for bare-metal hardware.
It is a unikernel , designed to run a single Linux executable or an application written in one of the supported runtime environments (such as Java ). [ 2 ] For this reason, it does not support a notion of users (it's not a multiuser system) or processes - everything runs in a single address space , [ 3 ] there is no difference between users address space and kernel address space. Using a single address space removes some of the time-consuming operations associated with context switching . [ 4 ]
It uses large amounts of code from the FreeBSD operating system, in particular the network stack and the ZFS file system. OSv can be managed using a REST Management API and an optional command-line interface written in Lua .
This operating-system -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/OSv |
OVN ( Open Virtual Network ) is a system to support virtual network abstraction. OVN complements the existing capabilities of Open vSwitch to add native support for virtual network abstractions, such as virtual L2 and L3 overlays and security groups.
OVN is a network virtualization platform that separates the physical network topology from the logical one. [ 2 ] Users are able to connect virtual and physical interfaces with logical switches and routers, regardless of the underlying physical topology. Users are also able to define security policies and load-balancing to these logical instances. OVN uses Open vSwitch for its switching fabric and uses tunnels to provide the logical/physical separation.
Open source bindings for OVN are available for a number of platforms, such as OpenStack [ 3 ] and Kubernetes . [ 4 ] OVN is the software-defined networking (SDN) platform used in a number of Red Hat products, including Red Hat Virtualization, [ 5 ] OpenStack, [ 6 ] and OpenShift. [ 7 ]
OVN is written in platform-independent C language , which provides easy portability to various environments. The source code is licensed under the Apache License 2.0.
As of May 2018, features provided by OVN include the following: | https://en.wikipedia.org/wiki/OVN |
The OWSD-Elsevier Foundation Awards for Early-Career Women Scientists in the Developing World are awarded annually to early-career women scientists in selected developing countries in four regions: Latin America and the Caribbean , East and Southeast Asia and the Pacific , Central and South Asia, and Sub-Saharan Africa . [ 1 ] [ 2 ]
The Organization for Women in Science for the Developing World (OWSD), the Elsevier Foundation , and The World Academy of Sciences have partnered to recognize achievements of early-career women scientists in developing countries since the award was launched in 2011 as the Elsevier Foundation-OWSD Awards for Young Women Scientists from the Developing World . [ 3 ] [ 1 ] The award program is open to female scientists who live and work in one of 81 developing countries. [ 1 ] Nominations are generally submitted within ten years of the nominee earning a PhD . [ 4 ] [ 5 ]
The maximum number of recipients is currently restricted to five per year: one from each of the four OWSD-recognized regions, plus one additional outstanding candidate, and the awards are granted with a rotating theme annually among three general fields: biological sciences (agriculture, biology and medicine), engineering/innovation & technology, and physical sciences (including chemistry, mathematics and physics). [ 6 ] [ 1 ] There were six awardees in 2022 as two outstanding candidates were recognised.
As of 2014, the award included an honorarium of US$ 5,000, an entire year of access to Elsevier's ScienceDirect publication database, and an expense-paid trip to the annual meeting of the American Association for the Advancement of Science , where the awarding ceremony is held. [ 4 ]
Recipients have included:
The 2011 awards recognized eleven contributors to biology, physics, and chemistry. [ 7 ]
The 2013 awards were focused on medical science and public health. [ 5 ]
The 2014 awards were focused on chemistry. [ 8 ]
In 2015, the awards were focused on physics and mathematics. [ 8 ]
The 2016 awards focused on medical science and public health. [ 9 ]
The 2017 awards were focused on engineering and technology. [ 10 ]
The 2018 awards focused on mathematics, chemistry, and physics.
The 2019 awards focused on medical science and public health. [ 1 ]
The 2020 awards recognised researchers working in engineering, innovation and technology. [ 14 ]
The 2021 awards recognised researchers in the physical sciences. [ 16 ]
The 2022 awards recognised six researchers in climate action and the environment. [ 18 ] [ 19 ] | https://en.wikipedia.org/wiki/OWSD-Elsevier_Foundation_Award |
O mark is the name of the circle symbol "◯". [ citation needed ] It is often used in East Asia to express affirmation . Its use is similar to that of the checkmark ("✓") in the Western world . Its opposite is the X mark ("✗" or "×").
The symbol's names and meanings vary across cultures. In Japanese it is called marujirushi ( 丸印 ) or maru ( 丸 ) and expresses affirmation. In Korean it is called gongpyo ( 공표 ; 空標 ; lit. ball mark) and expresses affirmation.
Japan interprets the symbol as an affirmation.
Japan employs a number of related symbols (◎ ○ △ ×) in a system that expresses degrees of affirmation. A bullseye "◎" ( nijūmaru ; 二重丸 ) is often used for "excellent", the circle is a plain affirmation, the triangle "△" ( sankaku ; 三角 ) means "so-so" or "partially applicable", and the "×" expresses disagreement. This system is widely known in Japan, and thus often used without explanation. Ad-hoc adjustments are usually explained.
The hanamaru ( 花丸 , 'flower O mark') is a variant of the O mark. It is typically drawn as a spiral surrounded by rounded flower petals, suggesting a flower. It is frequently used in praising or complimenting children, and the motif often appears in children's characters and logos. The hanamaru is frequently written on tests if a student has achieved full marks or an otherwise outstanding result. It is sometimes used in place of an O mark in grading written response problems if a student's answer is especially good. Some teachers add rotations to the spiral for exceptional answers.
Two circles ◯◯ (marumaru) are often used as a placeholder - either because a variety of words, names or numbers could be used in that position, or because of censorship.
Unicode provides various related symbols, including:
U+2B55 ⭕ HEAVY LARGE CIRCLE has both text and emoji presentations , as shown in the table. It defaults to emoji presentation.
The emoji U+1F4AE 💮 WHITE FLOWER looks similar to hanamaru , although it represents a rubber stamp commonly used to grade students' written answers and is not usually recognized as hanamaru . | https://en.wikipedia.org/wiki/O_mark |
Oak Investment Partners is a private equity firm focusing on venture capital investments in companies developing communications systems, information technology , new Internet media, healthcare services and retail.
The firm, founded in 1978, is based in Greenwich, Connecticut , with offices in Norwalk, Connecticut , Minneapolis and Palo Alto , California. Since inception, Oak had invested in more than 480 companies and had raised more than $8.4 billion in investor commitments across 12 private equity funds. [ 1 ] Ann Lamont is a founder and managing partner. [ 2 ]
In May 2006, Oak raised its 12th fund, at $2.56 billion, reportedly the largest venture capital fund ever raised. [ 3 ]
In 2015, Indian-born employee Iftikar Ahmed was sued by the U.S. Securities and Exchange Commission on suspicion of stealing US$65 million from the firm. [ 4 ] Ahmed was believed to have fled to India . In August 2015, Fortune reported that Mr. Ahmed had been detained in an Indian prison from May 22 until July 23 and that his passport had been confiscated. [ 5 ]
This article about a private equity or venture capital firm based in the United States is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Oak_Investment_Partners |
In hydrology , oasification is the antonym to desertification by soil erosion . This technique has limited application and is normally considered for much smaller areas than those threatened by desertification. [ citation needed ]
Oasification is also a developing direction of environmental engineering .
To help the oasification process, engineers aim to develop a thriving dense woody plant cover to redress the hydrological, edaphic and botanical degradation affecting a slope. This is done through appropriate soil preparation and the introduction of suitable plant species. It is also necessary to make adequate water harvesting systems—ideally taking advantage of the degradation process of the slope, collecting runoff water in ponds around the sites to be forested.
The term "oasification" was coined in 1999 by Andrés Martínez de Azagra Paredes, PhD Forest Engineer and professor on Hydraulics and Forest Hydrology at E.T.S. of Agroforestry Engineering in Palencia , University of Valladolid , Spain .
In oasification, soil and nutrient harvesting are regarded as fundamental component parts in the reclamation process of a degraded slope. Besides harvesting water, oasification preserves and accumulates soil and nutrients, helping to control water erosion—a common problem in dry climates. Ludwig et al. (1997) reported about sloping areas under semiarid conditions in Australia where the landscape is naturally divided into source and sink zones ( surface runoff and run-on areas), which are sometimes reclaimed by plant species through retention of water soil and litter.
A common approach is the planting of various common horticulturally significant trees, which "are adapted to dry environments...these plants act as windbreaks and the extensive root network binds the soil thus reducing water erosion especially at the beginning of the rainy season when soil cover is at its lowest. Deciduous activity returns large amounts of organic matter to the soil in the form of leaf material which in tum support more vegetation biomass, and hence more soil cover and consequently erosion control. Eventually, ecosystems are reclaimed and desertification controlled." [ 1 ] Some of the trees deployed in this way include olive, cashew, date palm, fig, guava, mango, tamarind, pomegranate, papaya, lasoda, and jojoba. [ 1 ] Drought-tolerant legumes that provide additional biomass and fix nitrogen include green gram ( Phaseolus aureus ), black gram ( Vigna mungo ), chickpea ( Cicer arictinum ), cowpea ( Vigna unguiculata ), and lentil ( Lens esculenta ). [ 1 ]
Not only plants can effectively prevent land degradation, but microorganisms are also an effective biological measure to prevent land desertification. Microorganisms can greatly help the artificially cultivated sand control plants to survive in the oasis, thus reducing the waste of resources during recultivation. “Microbial control of land desertification includes organisms such as mosses, lichens, cyanobacteria and slime molds to restore soil nutrients, The use of engineered biocrust‐forming cyanobacteria with these traits (vs. non‐engineered) has the effect of restoring soil fertility. potential to further increase soil fertility and to reduce soil erosion, thus accelerating the recovery of degraded drylands. (Maestre et al., 2017).”
There are drawbacks to overbuilding oases. Water use in oases is often influenced by plants, climate and human activities. This means that managers not only need to maintain a balance between direct human and natural water use, but also find ways to preserve water near oases. If there is no way to distribute it properly, it will cause serious consequences. | https://en.wikipedia.org/wiki/Oasification |
Oasis is a piece of software developed by the United States Central Intelligence Agency (CIA) that converts audio signals such as cellphone calls and television and radio broadcasts into readable and searchable text. [ 1 ] It is designed to intelligently analyze an audio signal such as a cellphone call in order to identify and label each speaker (Male 1, Male 2, Female 1, and so forth). Oasis is also able to intelligently reference terms, such as by linking " car bomb " with " terrorism ". Oasis will eventually be able to recognize key languages such as Arabic and Chinese , as well as English .
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Oasis_(software) |
The oasis effect refers to the creation of a local microclimate that is cooler than the surrounding dry area due to evaporation or evapotranspiration of a water source or plant life and higher albedo of plant life than bare ground. [ 1 ] The oasis effect is so-named because it occurs in desert oases . [ 2 ] Urban planners can design a city's layout to optimize the oasis effect to combat the urban heat island effect. [ 3 ] Since it depends on evaporation, the oasis effect differs by season . [ 1 ] [ 2 ]
An oasis contains moisture from a water source and/or plants. When that water evaporates or transpirates , heat from the surroundings is used to convert liquid to gas in an endothermic process , which results in cooler local temperatures. [ 4 ] Moreover, vegetation has a higher albedo than bare ground, and reflects more sunlight , leading to lower land temperatures , lower air temperatures, and a cooler local microclimate .
The oasis effect occurs most prominently during the summer because warmer temperatures lead to more evaporation. [ 1 ] In the winter, the oasis effect operates differently. Instead of making the oasis cooler, the oasis effect makes it warmer at night. This occurs through the fact that trees block heat from leaving the land. Basically, radiation cannot be emitted back into the atmosphere because the trees intercept and absorb it. [ 2 ]
The oasis effect plays a role in urban development because plants and bodies of water result in cooler cities . Accordingly, cities with parks will have lower temperatures because plants have higher albedo than bare ground or roads . Areas with higher albedo reflect more light than they absorb , leading to cooler temperatures. [ 5 ] Normally, cities are hotter than their suburbs due to dense population, dark buildings and roads, and pollution; this is known as the urban heat island effect. However, by careful placement of trees , parks, and plant life, cities can create their own oasis effect. [ 6 ] By maintaining plant life throughout a city, urban planners can produce an oasis effect [ 7 ] to counter the urban heat island effect; even a small scattering of trees can significantly reduce local temperatures. However, concerns can arise in arid regions with limited water sources where city planners may not want to leave water sources out in the open to evaporate, and may not want to sacrifice water for upkeep of plants. [ 5 ] | https://en.wikipedia.org/wiki/Oasis_effect |
The traditional Korean color spectrum , also known as Obangsaek ( Korean : 오방색 ; lit. five direction colors), is the color scheme of the five Korean traditional colors of white , black , blue , red and yellow . [ 1 ] [ 2 ] In Korean traditional arts and traditional textile patterns, the colors of Obangsaek represent five cardinal directions : [ 1 ] Obangsaek theory is a combination of Five Elements and Five Colours theory and originated in China .
These colors are also associated with the Five Elements of Culture of Korea : [ 1 ] | https://en.wikipedia.org/wiki/Obangsaek |
Obash is a bash script obfuscator written in the C programming language . obash encodes and encrypts bash shell scripts into executable binaries much like shc , the project that inspired it, but uses AES-256 encryption and the key and initialization vector are retrieved from the hardware instead of being hard coded into the binary itself. The obash project was started to address some of the issues that affect shc, the main one being able to see the original shell script source by simply issuing ps -ef . Although the objectives are the same, obash shares no code with shc and was built from scratch from the ground up, any code similarities are purely accidental and dictated by the shared objectives.
Obash is still a work in progress but the master branch on GitHub generally has usable sources while the testing branch may be in a transition state at any given time.
Obash takes the input script and AES-256 encrypts it, and also base64 encodes the AES ciphertext so that it can be used to declare an unsigned char array.
It then produces an intermediate C file which is basically the interpreter (see interpreter.c ), functions, text array containing the ciphertext, the optional key and IV for reusable binaries (not bound to the hardware) and the main. The intermediate C file is then compiled into an executable.
The intermediate C file is built in the following manner (see mk_sh_c function in functions.c ):
See recreate_interpreter_header script for details on how interpreter.h is created from interpreter.c.
The key and IV are not hard-coded into the binary (unless you decide to build a reusable static binary with the -r flag) but are retrieved each time from the hardware (hence binding it to a machine). In case of a reusable static binary (built with the -r flag) then the uuid and serial are in the binary itself but will be manipulated anyway by makekey and makeiv so that they are not usable immediately should anyone ever inspect the binary itself.
Although the whereabouts from where the serial and uuid are retrieved is traceable and is not a secret (machine uuid and serial number for non reusable and random hex digits for reusable) these should be then manipulated in a way that they are not directly usable as is. In the code there is a comment suggesting where this should be done (see makekey and makeiv functions in functions.c): each and every one of you using obash is encouraged to do so or it would be fairly easy to extract the script source from the obfuscated binary.. In the distributed code, as an example, the "-" are stripped from the uuid and the serial is padded to reach the suggested length for the cipher used. | https://en.wikipedia.org/wiki/Obash |
Obcells are hypothetical proto-organisms or the earliest form of life. The term was first proposed by Thomas Cavalier-Smith in 2001. According to Cavalier-Smith's theory for the origin of the first cell, two cup-shaped obcells or hemicells fused to make a protocell with double-lipid layer envelope, internal genome and ribosomes, protocytosol, and periplasm. [ 1 ]
The beginning of life and living organisms is difficult to specifically date as proto-organisms' earliest existence left no paleontological clues. Cavalier-Smith argues that initially there was primordial soup which contained amino acids , the building blocks for proteins . Replication and phosphorylation were not relevant until the prebiotic soup started to become organized into the "nucleic acid" era. Although still not "living," the substances during this period could replicate and undergo organized chemical processes. Based on these orderly processes, the world transitioned into an obcell world which included coding for proteins and chromosomes and the symbiotic interactions between membranes, genes, and enzymes. Obcells probably had a single membrane that was lipid-dense and also had specific cytoskeletal proteins that gave the obcells its curvature. These skeletal proteins were probably contained within the obcell's protoperiplasm.
Based on the high concentration of phosphate in the Earth's crust, [ 2 ] the universal metabolism of pyrophosphate and polyP in modern cells, [ 3 ] the ability to form phosphates abiotically, and its simplicity compared to nucleotides and nucleic acids , replication probably began on phosphate-rich mineral surfaces and involved phosphate related enzymes . Replicases are necessary for the genetic code to have existed, so Cavalier-Smith argues that "polyP kinases and pyrophosphate kinases may have been among the earliest protein-coded catalysts." If these did exist, then polyP-binding proteins would have been the most useful source of energy for the obcells. Due to its anionic properties, it is quite plausible that while immersed in the nucleotide and nucleic acid rich environment, polyP-binding proteins could have polymerized with these substances. Therefore, obcells with exonucleases attached to their membrane would have had an advantage for replication compared to those that did not. [ 1 ] In modern cells, glucokinases typically have two different phosphate-binding domains, mainly containing the amino acids glycine , threonine , and aspartate . [ 4 ] Therefore, Cavalier-Smith proposes that these shared domains could have originated in obcells to bind to pyrophosphate. [ 1 ]
Cavalier-Smith argues that the most plausible location for obcells to survive and grow in number on Earth was by the land-water interface, not by oceanic seafloor vents. [ 1 ] Due to their likely dependence on polyP and pyrophosphate for energy over adenosine triphosphate , obcells would likely congregate in areas where these minerals were formed in high concentrations. Polyphosphate could easily be formed by the seashore in "small salty pools, porous sediments, or protosoils."
At lower temperatures, nucleic acids are more stable [ 5 ] and shorter chain lipids can form membranes easier. [ 2 ] Combined with their dependence on polyP and pyrophosphate, the lower temperatures at the land-water interface the most likely habitat for obcells to evolve. In these conditions, the extreme temperature changes and heterogeneity of external components could induce sharp changes in the structure and function of colonizing obcells which is more likely to lead to the evolution of protocells compared to stable temperatures and homogeneous external components. [ 1 ]
From the obcells' dependence on polyP and pyrophosphate for energy, their metabolism did not rely on oxidative phosphorylation or photophosphorylation . These processes were too complex for the simple nature of obcells. Cavalier-Smith calls the obcells' phosphorylation of these minerals for energy "lithophosphorylation", which is simple and possible from the existence of kinases that could catalyze polyP- binding proteins and pyrophosphate-binding proteins. From this, it is likely that obcells had these kinases on their surfaces to react with these external polyP-binding and pyrophosphate proteins. Polyphosphate and pyrophosphate were possibly small enough to diffuse into obcells. Therefore, it also likely that some of these kinases were in the obcell lumen to react with these proteins and then store them for later use. This storage would be beneficial for obcells in times when the concentration of external polyP-binding proteins and pyrophosphate-binding proteins would vary. [ 1 ]
Since obcells were cup-shaped and could expose their chromosomes to the harsh environment, to protect their genetic information and any signaling factors, obcells could attach to polyphosphate surfaces using local adhesin proteins. During division, division proteins would begin to pinch the obcell in half, separating the internal components between the two daughter obcells. As this pinching was occurring, the structural integrity of the membrane began to weaken and the two halves would migrate towards the polyphosphate surface. Adhesin proteins would attach these ends to the surface and division would be complete. [ 1 ]
Over several millions of years, obcells managed to survive off division only. Eventually, obcells evolved to fuse into proto-organisms for added protection of their internal components and the decreased probability of the loss of oligosaccharides during division. Two obcells would come in contact with each other and would adhere together by the adhesion proteins at the rims of both. This adhesion could also be firmer than on the polyphosphate surfaces without restricting division and growth. The fusions of obcells lead to the creation of cytosol, compared to obcell division. From this, the membrane began to change into a cytoplasmic side and an outer side, the preliminary double membrane of modern protocells. In order to prevent the obcells from completely fusing together, it is believed that the after the two obcells adhered together, the adhesin proteins continued to act as plugs. These points of adhesion could have allowed transport for some substances between the cytosol and environment, but these could have evolved into Bayer's patches which are breaks between the cytoplasmic side and outer side of the membrane in gram-negative bacteria . [ 1 ] | https://en.wikipedia.org/wiki/Obcell |
In astronautics , a powered flyby , or Oberth maneuver , is a maneuver in which a spacecraft falls into a gravitational well and then uses its engines to further accelerate as it is falling, thereby achieving additional speed. [ 1 ] The resulting maneuver is a more efficient way to gain kinetic energy than applying the same impulse outside of a gravitational well. The gain in efficiency is explained by the Oberth effect , wherein the use of a reaction engine at higher speeds generates a greater change in mechanical energy than its use at lower speeds. In practical terms, this means that the most energy-efficient method for a spacecraft to burn its fuel is at the lowest possible orbital periapsis , when its orbital velocity (and so, its kinetic energy) is greatest. [ 1 ] In some cases, it is even worth spending fuel on slowing the spacecraft into a gravity well to take advantage of the efficiencies of the Oberth effect. [ 1 ] The maneuver and effect are named after the Transylvanian Saxon physicist and a founder of modern rocketry Hermann Oberth , who first described them in 1927. [ 2 ]
Because the vehicle remains near periapsis only for a short time, for the Oberth maneuver to be most effective the vehicle must be able to generate as much impulse as possible in the shortest possible time. As a result the Oberth maneuver is much more useful for high-thrust rocket engines like liquid-propellant rockets , and less useful for low-thrust reaction engines such as ion drives , which take a long time to gain speed. Low thrust rockets can use the Oberth effect by splitting a long departure burn into several short burns near the periapsis. The Oberth effect also can be used to understand the behavior of multi-stage rockets : the upper stage can generate much more usable kinetic energy than the total chemical energy of the propellants it carries. [ 2 ]
In terms of the energies involved, the Oberth effect is more effective at higher speeds because at high speed the propellant has significant kinetic energy in addition to its chemical potential energy. [ 2 ] : 204 At higher speed the vehicle is able to employ the greater change (reduction) in kinetic energy of the propellant (as it is exhausted backward and hence at reduced speed and hence reduced kinetic energy) to generate a greater increase in kinetic energy of the vehicle. [ 2 ] : 204
Because kinetic energy equals mv 2 /2, this change in velocity imparts a greater increase in kinetic energy at a high velocity than it would at a low velocity. For example, considering a 2 kg rocket:
This greater change in kinetic energy can then carry the rocket higher in the gravity well than if the propellant were burned at a lower speed.
The thrust produced by a rocket engine is independent of the rocket’s velocity relative to the surrounding atmosphere. A rocket acting on a fixed object, as in a static firing, does no useful work on the rocket; the rocket's chemical energy is progressively converted to kinetic energy of the exhaust, plus heat. But when the rocket moves, its thrust acts through the distance it moves. Force multiplied by displacement is the definition of mechanical work . The greater the velocity of the rocket and payload during the burn the greater is the displacement and the work done, and the greater the increase in kinetic energy of the rocket and its payload. As the velocity of the rocket increases, progressively more of the available kinetic energy goes to the rocket and its payload, and less to the exhaust.
This is shown as follows. The mechanical work done on the rocket ( W {\displaystyle W} ) is defined as the dot product of the force of the engine's thrust ( F → {\displaystyle {\vec {F}}} ) and the displacement it travels during the burn ( s → {\displaystyle {\vec {s}}} ):
If the burn is made in the prograde direction, F → ⋅ s → = ‖ F ‖ ⋅ ‖ s ‖ = F ⋅ s {\displaystyle {\vec {F}}\cdot {\vec {s}}=\|F\|\cdot \|s\|=F\cdot s} . The work results in a change in kinetic energy
Differentiating with respect to time, we obtain
or
where v {\displaystyle v} is the velocity. Dividing by the instantaneous mass m {\displaystyle m} to express this in terms of specific energy ( e k {\displaystyle e_{k}} ), we get
where a {\displaystyle a} is the acceleration vector.
Thus it can be readily seen that the rate of gain of specific energy of every part of the rocket is proportional to speed and, given this, the equation can be integrated ( numerically or otherwise) to calculate the overall increase in specific energy of the rocket.
Integrating the above energy equation is often unnecessary if the burn duration is short. Short burns of chemical rocket engines close to periapsis or elsewhere are usually mathematically modeled as impulsive burns, where the force of the engine dominates any other forces that might change the vehicle's energy over the burn.
For example, as a vehicle falls toward periapsis in any orbit (closed or escape orbits) the velocity relative to the central body increases. Briefly burning the engine (an "impulsive burn") prograde at periapsis increases the velocity by the same increment as at any other time ( Δ v {\displaystyle \Delta v} ). However, since the vehicle's kinetic energy is related to the square of its velocity, this increase in velocity has a non-linear effect on the vehicle's kinetic energy, leaving it with higher energy than if the burn were achieved at any other time. [ 3 ]
If an impulsive burn of Δ v is performed at periapsis in a parabolic orbit , then the velocity at periapsis before the burn is equal to the escape velocity ( V esc ), and the specific kinetic energy after the burn is [ 4 ]
where V = V esc + Δ v {\displaystyle V=V_{\text{esc}}+\Delta v} .
When the vehicle leaves the gravity field, the loss of specific kinetic energy is
so it retains the energy
which is larger than the energy from a burn outside the gravitational field ( 1 2 Δ v 2 {\displaystyle {\tfrac {1}{2}}\Delta v^{2}} ) by
When the vehicle has left the gravity well, it is traveling at a speed
For the case where the added impulse Δ v is small compared to escape velocity, the 1 can be ignored, and the effective Δ v of the impulsive burn can be seen to be multiplied by a factor of simply
and one gets
Similar effects happen in closed and hyperbolic orbits .
If the vehicle travels at velocity v at the start of a burn that changes the velocity by Δ v , then the change in specific orbital energy (SOE) due to the new orbit is
Once the spacecraft is far from the planet again, the SOE is entirely kinetic, since gravitational potential energy approaches zero. Therefore, the larger the v at the time of the burn, the greater the final kinetic energy, and the higher the final velocity.
The effect becomes more pronounced the closer to the central body, or more generally, the deeper in the gravitational field potential in which the burn occurs, since the velocity is higher there.
So if a spacecraft is on a parabolic flyby of Jupiter with a periapsis velocity of 50 km/s and performs a 5 km/s burn, it turns out that the final velocity change at great distance is 22.9 km/s, giving a multiplication of the burn by 4.58 times.
It may seem that the rocket is getting energy for free, which would violate conservation of energy . However, any gain to the rocket's kinetic energy is balanced by a relative decrease in the kinetic energy the exhaust is left with (the kinetic energy of the exhaust may still increase, but it does not increase as much). [ 2 ] : 204 Contrast this to the situation of static firing, where the speed of the engine is fixed at zero. This means that its kinetic energy does not increase at all, and all the chemical energy released by the fuel is converted to the exhaust's kinetic energy (and heat).
At very high speeds the mechanical power imparted to the rocket can exceed the total power liberated in the combustion of the propellant; this may also seem to violate conservation of energy. But the propellants in a fast-moving rocket carry energy not only chemically, but also in their own kinetic energy, which at speeds above a few kilometres per second exceed the chemical component. When these propellants are burned, some of this kinetic energy is transferred to the rocket along with the chemical energy released by burning. [ 5 ]
The Oberth effect can therefore partly make up for what is extremely low efficiency early in the rocket's flight when it is moving only slowly. Most of the work done by a rocket early in flight is "invested" in the kinetic energy of the propellant not yet burned, part of which they will release later when they are burned. | https://en.wikipedia.org/wiki/Oberth_effect |
In mathematics , the Oberwolfach problem is an open problem that may be formulated either as a problem of scheduling seating assignments for diners,
or more abstractly as a problem in graph theory , on the edge cycle covers of complete graphs . It is named after the Oberwolfach Research Institute for Mathematics , where the problem was posed in 1967 by Gerhard Ringel . [ 1 ] It is known to be true for all sufficiently-large complete graphs.
In conferences held at Oberwolfach, it is the custom for the participants to dine together in a room with circular tables, not all the same size, and with assigned seating that rearranges the participants from meal to meal. The Oberwolfach problem asks how to make a seating chart for a given set of tables so that all tables are full at each meal and all pairs of conference participants are seated next to each other exactly once. An instance of the problem can be denoted as O P ( x , y , z , … ) {\displaystyle OP(x,y,z,\dots )} where x , y , z , … {\displaystyle x,y,z,\dots } are the given table sizes. Alternatively, when some table sizes are repeated, they may be denoted using exponential notation; for instance, O P ( 5 3 ) {\displaystyle OP(5^{3})} describes an instance with three tables of size five. [ 1 ]
Formulated as a problem in graph theory, the pairs of people sitting next to each other at a single meal can be represented as a disjoint union of cycle graphs C x + C y + C z + ⋯ {\displaystyle C_{x}+C_{y}+C_{z}+\cdots } of the specified lengths, with one cycle for each of the dining tables. This union of cycles is a 2- regular graph, and every 2-regular graph has this form. If G {\displaystyle G} is this 2-regular graph and has n {\displaystyle n} vertices, the question is whether the complete graph K n {\displaystyle K_{n}} of order n {\displaystyle n} can be represented as an edge-disjoint union of copies of G {\displaystyle G} . [ 1 ]
In order for a solution to exist, the total number of conference participants (or equivalently, the total capacity of the tables, or the total number of vertices of the given cycle graphs) must be an odd number. For, at each meal, each participant sits next to two neighbors, so the total number of neighbors of each participant must be even, and this is only possible when the total number of participants is odd. The problem has, however, also been extended to even values of n {\displaystyle n} by asking, for those n {\displaystyle n} , whether all of the edges of the complete graph except for a perfect matching can be covered by copies of the given 2-regular graph. Like the ménage problem (a different mathematical problem involving seating arrangements of diners and tables), this variant of the problem can be formulated by supposing that the n {\displaystyle n} diners are arranged into n / 2 {\displaystyle n/2} married couples, and that the seating arrangements should place each diner next to each other diner except their own spouse exactly once. [ 2 ]
The only instances of the Oberwolfach problem that are known not to be solvable are O P ( 3 2 ) {\displaystyle OP(3^{2})} , O P ( 3 4 ) {\displaystyle OP(3^{4})} , O P ( 4 , 5 ) {\displaystyle OP(4,5)} , and O P ( 3 , 3 , 5 ) {\displaystyle OP(3,3,5)} . [ 3 ] It is widely believed that all other instances have a solution.
This conjecture is supported by recent non-constructive and asymptotic solutions for large complete graphs of order greater than a lower bound that is however unquantified. [ 4 ] [ 5 ]
Cases for which a constructive solution is known include:
Kirkman's schoolgirl problem , of grouping fifteen schoolgirls into rows of three in seven different ways so that each pair of girls appears once in each triple, is a special case of the Oberwolfach problem, O P ( 3 5 ) {\displaystyle OP(3^{5})} . The problem of Hamiltonian decomposition of a complete graph K n {\displaystyle K_{n}} is another special case, O P ( n ) {\displaystyle OP(n)} . [ 10 ]
Alspach's conjecture , on the decomposition of a complete graph into cycles of given sizes, is related to the Oberwolfach problem, but neither is a special case of the other.
If G {\displaystyle G} is a 2-regular graph with n {\displaystyle n} vertices, formed from a disjoint union of cycles of certain lengths, then a solution to the Oberwolfach problem for G {\displaystyle G} would also provide a decomposition of the complete graph into ( n − 1 ) / 2 {\displaystyle (n-1)/2} copies of each of the cycles of G {\displaystyle G} . However, not every decomposition of K n {\displaystyle K_{n}} into this many cycles of each size can be grouped into disjoint cycles that form copies of G {\displaystyle G} , and on the other hand not every instance of Alspach's conjecture involves sets of cycles that have ( n − 1 ) / 2 {\displaystyle (n-1)/2} copies of each cycle. | https://en.wikipedia.org/wiki/Oberwolfach_problem |
Obeya (from Japanese Ōbeya 大部屋 "large room") is a team spirit improvement tool at an administrative level, originating from a long history of learning & improving. It is considered a component of lean manufacturing . Obeya objectives are rapid decision-making, reduction in rework and reconsiderations, and reduction in unnecessary discussions. The Obeya Association enumerates 11 Obeya Principles that define Obeya and guide its improvement.
The earliest notion of concept is believed to be the Analects of Confucius nearly 2500 years ago ( China , 206 BC–220 AD). The use of Obeya rooms has been proven by many companies to be successful.
The Obeya can be understood as a team spirit improvement tool at an administrative level. It originated from a long history of learning & improving. Often associated in product development, an Obeya room can also be a place for software development, a command center, managing new business strategy, workflow and project management. This tool forces people to work together without distractions and creates a great atmosphere to generate new ideas. Conceptually akin to a traditional "war room", an Obeya will contain visually engaging charts and graphs depicting such information as program timing, milestones and progress-to-date and countermeasures to existing technical or scheduling issues.
It is considered a component of lean manufacturing and in particular the Toyota Production System . [ 1 ] A variety of different analogies have been drawn between an obeya and other real life systems and structures. One such example is the bridge of a ship, where many different crewmates come together to support the operation of a complex entity by allowing all roles to be connected and understood. Obeya has been described as "the brain of the system".
During the product and process development, all individuals involved in managerial planning meet in a "great room" to speed up communication and decision-making. This is intended to increase efficiency and bring a better flow to the project, as well as an understanding of one's role within the cycle of the process.
The objectives behind an Obeya are rapid decision-making, reduction in rework and reconsiderations, and reduction in unnecessary discussions. [ 2 ]
Moreover, it is a method where multiple information sources are combined for optimal decision making, involving multiple parties simultaneously. This makes it an excellent governing model for organizations that work Agile, Lean, or plan to do so.
The Obeya model is an inclusive organizational model as opposed to the hierarchical organizational models. So, an Obeya makes it possible to "design" for collaboration. In an Obeya strategy meets execution and (quite literally) the people involved in these subjects respectfully engage in conversation with each other.
Obeya's objectives involve helping to answer the following questions:
Set up by the Obeya Association, [ 3 ] the 11 Obeya Principles define Obeya and guide its improvement – regardless of what methodology or approach you choose for your Obeya setup. Developed, used, tried and tested by the founders of the Obeya Association; Dolf Reijnders and Bart Bongers, [ 4 ] as well as other Obeya practitioners worldwide; the 11 Obeya Principles serve as guiding star for all that is Obeya related.
There are common traits and characteristics that are shared by most Obeya that are represented in the 11 Obeya Principles. The Obeya Principles collect and synthesize these characteristics and aid best practice sharing. They are meant to guide Obeya use and development. The Obeya Principles provide a common language and a conceptual foundation of Obeya.
An Obeya means to work across 4 quadrants: Mindset, Alignment , Workspace and Content . The 11 Principles further define how to approach work in an Obeya in every quadrant. The relative order of the separate Principles are regardless of their relevance.
The combination of the principles with the roles Obeya Builders and Obeya Hosts [ 5 ] provide a solid framework to approach Obeya. It provides grip in your Obeya setup without loss of flexibility.
Mindset
Alignment
Workspace
Content
The Analects of Confucius 2500 years ago ( China , 206 BC–220 AD). seem to be the earliest notion of what later developed into many different management philosophies. It is believed to have been written up by Confucius disciples over the course of 30 to 50 years. The Analects could be regarded as influential social and ethical philosophy. Rich, diverse and over 2500 years old, Confucian tradition teaches about the idea that good life lies in social relations, starting with family and extending into friends and community. Confucianism highlights the question of what roles we occupy in our lifetime and what our obligations are regarding those roles. Confucius proposed learning as a cycle of stages. in which early stages are focused around improving understanding. Next. We need to think critically about what we (want to) learn, according to Confucius , simultaneously. We see the development of actual physical places where' the way is practiced 'evolving throughout Eastern history, making use of visual stimulation. It's not hard to draw links to modern day Obeya use. Confucianism favors light government, informal means of social control and emotional harmony. Confucius can be considered an educator. encouraging constant questioning in the pursuit of learning.
Later in history on the other side of the world, the West started building upon an idea what we would now call a scientific approach . Francis Bacon (1561-1626 AD), an English philosopher and statesman, can be regarded as highly influential. He argued for inductive reasoning and careful observation (often derived from nature) to avoid misleading. One of Bacons' goals in life was to uncover truth. His methodological ways to uncover truth (science) also show a clear link to modern day Obeya's. It is believed that Bacons 'approach provided the roots of Plan-Do-Check-Act ( PDCA ) improvement cycles as proposed by Shewhart and Deming and eventually laid the foundations for SCRUM and Agile . With the start of the Industrial Age roughly from the 1800s on, management practices evolve, and Eastern and Western management philosophies start to influence each other. In Japan , Toyota successfully adopted Deming's ideas, which lead to the Toyota Production system ( TPS ). Resulting in higher standards for manufacturing. The resulting competition motivated American manufacturers to implement statistical quality control in the United States . From the 1980s, both MIT and Harvard play vital roles in modeling management practices and providing empirical data / analyses. Visual management and the use of Obeya rooms became an integral part of said practices and are still becoming increasingly popular in modern days. Researching Obeya's rich historical background shows:
The use of Obeya rooms has been proven by many companies to be successful. Some examples of large businesses that use such a room are Toyota , Nike , Boeing , and Volvo . These rooms help to promote problem solving among teams, as well as building communication and encourage team building. Silos are sections of companies that only communicate within their specific divisions or departments. Obeya rooms are designed to reduce silos within companies and increase communication.
An obeya room gives leaders a clear view of what everyone is working on, as well as why and how. They also can see how their own department's efforts support or hinder their colleagues. [ 6 ]
The roots of what is now a valuable management practice can be found across continents with many disciplines influencing each other throughout history. One of the more recognizable modern examples involving Obeya was at Toyota during the G21 (Globe 21st century) Project, while building the Prius. Chief Engineer of the G21 project, Takeshi Uchiyamada "felt that he lacked the necessary authority to make the optimal decisions and thought he could be overrun by experienced discipline leaders in a way that was not optimal for the project as such". [ 2 ] This need for support from the other leaders that Uchiyamada identified, is what manifested for him the first use of Obeya "large room" in this environment. The Obeya, was instituted "as an arena for all his discussions with the discipline leaders. In this room, the other discipline leaders would be present, and documents and data would be available to all." [ 2 ]
The Obeya Room has been proven to be the ticket to success and team building for leading shoe manufacturer, Nike Europe. They began to incorporate the use of Obeya room for their IT department. When they began to use the Obeya room they, "decided to focus on the Portfolio and Project Management function within Technology, for which we already had a lot of information." [ 7 ] As use of Obeya rooms in this instance proved to be successful, the more Nike used the Obeya Room in other departments as well. Nike also realized that the more they focused on the success of the Obeya room, the effect was nothing short of positive. Mathijssen also states, "In our experience, an Obeya room creates a safety zone to make goals and problems visible, so they can be discussed openly, which leads to creative problem solving and innovation." [ 7 ] All of which are the primary goals for the Obeya room no matter what business it is part of; a comfortable space for innovation, open communication, and problem solving.
Toyota Industrial Equipment Manufacturing Inc. (TIEM) implemented the obeya room and saw it as a "valuable contributor to their lean enterprises". [ 8 ] It is referred as the adrenaline room , where managers go beyond reporting data and keeping teams up to date, but make a commitment to move forward with daily goals. Through active collaboration and support of all associates, real-time ideas get to build and real-time issues get solved. [ 9 ]
Many manufacturing companies have implemented the obeya room across factory operations. However, the Obeya room could not be implemented across all functions, which led to iObeya . iObeya is a digital visual management platform that mimics the obeya room experience virtually. It lets many firms collaborate effectively in a virtual setting. [ 10 ] Jusko has reported that both Volvo and PSA Group are using iObeya to support their global collaboration efforts. [ 8 ] | https://en.wikipedia.org/wiki/Obeya |
The Obfuscated Perl Contest was a competition for programmers of Perl which was held annually between 1996 and 2000. Entrants to the competition aimed to write "devious, inhuman, disgusting, amusing, amazing, and bizarre Perl code". [ 1 ] It was run by The Perl Journal and took its name from the International Obfuscated C Code Contest . [ 2 ]
The entries were judged on aesthetics, output and incomprehensibility. One entrant per year received the Best of Show award.
Entrants were advised to try and demonstrate a range of Perl knowledge, while being humorous, surprising and deceitful. Code which purposely crashed the judges' machines was discouraged.
The competition was typically divided into four categories, which, in the last contest, included: | https://en.wikipedia.org/wiki/Obfuscated_Perl_Contest |
ObjectARX ( AutoCAD Runtime eXtension) is an API for customizing and extending AutoCAD . The ObjectARX SDK is published by Autodesk and freely available under license from Autodesk. [ 1 ] The ObjectARX SDK consists primarily of C++ headers and libraries that can be used to build Windows DLLs that can be loaded into the AutoCAD process and interact directly with the AutoCAD application. ObjectARX modules use the file extensions .arx and .dbx instead of the more common .dll .
ObjectARX is the most powerful of the various AutoCAD APIs, and the most difficult to master. The typical audience for the ObjectARX SDK includes professional programmers working either as commercial application developers or as in-house developers at companies using AutoCAD.
New versions of the ObjectARX SDK are released with each new AutoCAD release, and ObjectARX modules built with a specific SDK version are typically limited to running inside the corresponding version of AutoCAD. Recent versions of the ObjectARX SDK include support for the .NET platform by providing managed wrapper classes for native objects and functions.
The native classes and libraries that are made available via the ObjectARX API are also used internally by the AutoCAD code. As a result of this tight linkage with AutoCAD itself, the libraries are very compiler specific, and work only with the same compiler that Autodesk uses to build AutoCAD. Historically, this has required ObjectARX developers to use various versions of Microsoft Visual Studio , with different versions of the SDK requiring different versions of Visual Studio.
Although ObjectARX is specific to AutoCAD, Open Design Alliance announced in 2008 [ 2 ] a new API called DRX (included in their DWGdirect library) that attempts to emulate the ObjectARX API in products like IntelliCAD that use the DWGdirect libraries.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/ObjectARX |
Object process methodology ( OPM ) is a conceptual modeling language and methodology for capturing knowledge and designing systems , specified as ISO / PAS 19450. [ 1 ] Based on a minimal universal ontology of stateful objects and processes that transform them, OPM can be used to formally specify the function, structure, and behavior of artificial and natural systems in a large variety of domains.
OPM was conceived and developed by Dov Dori . The ideas underlying OPM were published for the first time in 1995. [ 2 ] Since then, OPM has evolved and developed.
In 2002, the first book on OPM [ 3 ] was published, and on December 15, 2015, after six years of work by ISO TC184/SC5, ISO adopted OPM as ISO/PAS 19450. [ 1 ] A second book on OPM was published in 2016. [ 4 ]
Since 2019, OPM has become a foundation for a Professional Certificate program in Model-Based Systems Engineering - MBSE at EdX . Lectures are available as web videos on Youtube .
Object process methodology (OPM) is a conceptual modeling language and methodology for capturing knowledge and designing systems. Based on a minimal universal ontology of stateful objects and processes that transform them, OPM can be used to formally specify the function, structure, and behavior of artificial and natural systems in a large variety of domains. Catering to human cognitive abilities, an OPM model represents the system under design or study bimodally in both graphics and text for improved representation, understanding, communication, and learning.
In OPM, an object is anything that does or does not exist. Objects are stateful —they may have states, such that at each point in time, the object is at one of its states or in transition between states. A process is a thing that transforms an object by creating or consuming it, or by changing its state.
OPM is bimodal; it is expressed both visually/graphically in object-process diagrams (OPD) and verbally/textually in Object-Process Language (OPL), a set of automatically generated sentences in a subset of English. A patented software package called OPCAT, for generating OPD and OPL, is freely available. [ 5 ]
The shift to the object-oriented (OO) paradigm for computer programming languages , which occurred in the 1980s and 1990s, was followed by the idea that programming should be preceded by object-oriented analysis and design of the programs, and, more generally, the systems those programs represent and serve. Thus, in the early 1990s, over 30 object-oriented analysis and design methods and notations flourished, leading to what was known as the "methods war". [ 6 ]
Around that time, in 1991, Dov Dori , who then joined Technion – Israel Institute of Technology as faculty said in his 2016 book Model-Based Systems Engineering with OPM and SysML that he:
realized that just as the procedural approach to software was inadequate, so was the “pure” OO approach, which puts objects as the sole “first class” citizens, with “methods” (or “services”) being their second-class subordinate procedures.
Dori published the first paper on OPM in 1995. [ 2 ]
In 1997, Unified Modeling Language (UML), by the Object Management Group (OMG), became the de facto standard for software design. UML 1.1 was submitted to the OMG in August 1997 and adopted by the OMG in November 1997.
The first book on OPM, Object-Process Methodology: a Holistic Systems Paradigm , was published in 2002, [ 3 ] and OPM has since been applied in many domains. [ 7 ] [ 8 ]
In August 2014, the ISO adopted OPM as ISO/PAS 19450. [ 1 ]
A second book on OPM, which also covers SysML, was published in 2016. [ 4 ]
Object-Process Methodology (OPM) is a systems modeling paradigm that integrates two aspects inherent in any system: its structure and its behavior. Structure is represented via objects and structural relations among them, such as aggregation-participation (whole-part relation) and generalization-specialization ("is-a" relation). Behavior is represented by processes and how they transform objects: How they create or consume objects, or how they change the states of an object. [ 4 ] : 2
OPM offers a way to model systems of almost any domain, be it artificial or natural. [ 4 ] : x [ 9 ]
OPM consists of object process diagramׂs (OPD) and a corresponding set of sentences in a subset of English, called Object Process Language (OPL). OPL is generated automatically by OPCAT, [ 5 ] a software tool that supports modeling in OPM. [ 10 ]
OPD is the one and only kind of diagram of OPM. This uniqueness of diagram kind is a major contributor to OPM's simplicity, and it is in sharp contrast to UML, which has 14 kinds of diagrams, and to SysML, which has nine such kinds. [ 11 ] An OPD graphically describes objects, processes and links among them. Links can be structural and procedural. Structural links connect objects to objects or processes to processes, expressing the static system aspect—how the system is structured. Procedural links connect objects to processes, expressing the dynamic system aspect—how the system changes over time. The entire system is represented by a set of hierarchically organized OPDs, such that the root OPD, called the systems diagram (SD), specifies the "bird's eye" view of the system, and lower-level OPDs specify the system in increasing levels of detail. All the OPDs in the system's OPD set are "aware" of each other, with each showing the system, or part of it, at some level of detail. The entire system is specified in its entirety by the union of the details (model facts) appearing in all the OPDs.
Each OPD construct (i.e., two or more things connected by one or more links) is translated to a sentence in OPL—a subset of natural English. The power of OPL lies in the fact that it is readable by humans but also interpretable by computers. These are the stages where the most important design decisions are made. The graphics-text bimodality of OPM makes it suitable to jointly model requirements by a team that involves both the customer or his domain expert on one hand, and the system architect, modelers, and designers on the other hand. [ 4 ] : 3
OPM models are not just static graphical and textual representations of the system—they are also executable. A correct OPM model constructed in OPCAT can be simulated by animating it, visually expressing how the system behaves over time to achieve its function at all detail levels. An incorrect OPM model will not execute all the way through, and will indicate where and why it is stuck, effectively serving as a visual debugger.
In his foreword to Dori's book Model-Based Systems Engineering with OPM and SysML , Edward F. Crawley said:
OPM semantics was originally geared towards systems engineering, as it can model information, hardware, people, and regulation. However, in recent years OPM started to serve also researchers in molecular biology, yielding new published findings related to the mRNA lifecycle. This is a clear indication of the universality of the object-and-process ontology. [ 4 ] : vi [ 12 ]
OPM has two main parts: the language and the methodology. The language is bimodal—it is expressed in two complementary ways (modalities): the visual, graphical part—a set of one or more object-process diagrams (OPDs), and a corresponding textual part—a set of sentences in object-process language (OPL), which is a subset of English.
The top-level OPD is the system diagram (SD), which provides the context for the system's function. For man-made systems this function is expected to benefit a person or a group of people—the beneficiary. The function is the main process in SD, which also contains the objects involved in this process: the beneficiary, the operand (the object upon which the process operates), and possibly the attribute whose value the process changes.
OPM graphical elements are divided into entities, expressed as closed shapes, and relations, expressed as links that connect entities.
Entities are the building blocks of OPM. They include objects and processes, collectively called things, and object states.
Once the event triggers a process, the event ceases to exist.
Objects and processes are symmetric in many regards and have much in common in terms of relations, such as aggregation, generalization, and characterization.
To apply OPM in a useful manner, the modeler has to make the essential distinction between objects and processes, as a prerequisite for successful system analysis and design. By default, a noun shall identify an object.
OPM things have three generic attributes:
OPM thing generic attributes have the following default values:
A procedural link is one of three kinds:
An event link and a condition link express an event and a condition, respectively. Control links occur either between an object and a process or between two processes.
More information and examples can be found in Model-Based Systems Engineering with OPM and SysML , Chapter 13 "The Dynamic System Aspect". [ 4 ]
Structural links specify static, time-independent, long-lasting relations in the system. A structural link connects two or more objects or two or more processes, but not an object and a process, except in the case of an exhibition-characterization link.
More information and examples can be found in Model-Based Systems Engineering with OPM and SysML , Chapter 3.3 "Adding structural links". [ 4 ]
Object multiplicity shall refer to a requirement or constraint specification on the quantity or count of object instances associated with a link. Unless a multiplicity specification is present, each end of a link shall specify only one thing instance. The syntax of an OPL sentence that includes an object with multiplicity shall include the object multiplicity preceding the object name, with the object name appearing in its plural form. Multiplicity specifications may appear in the following cases:
Object multiplicity may include arithmetic expressions, which shall use the operator symbols "+", "–", "*", "/", "(", and ")" with their usual semantics and shall use the usual textual correspondence in the corresponding OPL sentences.
An integer or an arithmetic expression may constrain object multiplicity. Graphically, expression constraints shall appear after a semicolon separating them from the expression that they constrain and shall use the equality/inequality symbols "=", "<", ">", "<=", and ">=", the curly braces "{" and "}" for enclosing set members, and the membership operator "in" (element of, ∈), all with their usual semantics. The corresponding OPL sentence shall place the constraint phrase in bold letters after the object to which the constraint applies in the form ", where constraint".
The expression of object multiplicity for structural and procedural links specifies integer values or parameter symbols that resolve to integer values. In contrast, the values associated with attributes of objects or processes may be integer or real values, or parameter symbols that resolve to integer or real values, as well as character strings and enumerated values. Graphically, a labelled, rounded-corner rectangle placed inside the attribute to which it belongs shall denote an attribute value with the value or value range (integers, real numbers, or string characters) corresponding to the label name. In OPL text, the attribute value shall appear in bold face without capitalization.
The syntax for an object with an attribute value OPL sentence shall be: Attribute of Object is value .
The syntax for an object with an attribute value range OPL sentence shall be: Attribute of Object range is value-range . A structural or a procedural link connecting with an attribute that has a real number value may specify a relationship constraint, which is distinct from an object multiplicity.
Graphically, an attribute value constraint is an annotation by a number, integer or real, or a symbol parameter, near the attribute end of the link and aligning with the link.
The logical operators AND, XOR, and OR among procedural relations enable specification of elaborate process precondition and postcondition. Separate, non-touching links shall have the semantics of logical AND.
Here, unlocking the safe requires all three keys.
A link fan shall follow the semantics of either a XOR or an OR operator. The link fan end that is common to the links shall be the convergent link end. The link end that is not common to the links shall be the divergent link end.
The XOR operator shall mean that exactly one of the things in the span of the link fan exists, if the divergent link end has objects, or happens, if the divergent link end has processes. Graphically, a dashed arc across the links in the link fan with the arc focal point at the convergent end point of contact shall denote the XOR operator.
The OR operator shall mean that at least one of the two or more things in the span of the link fan exists, if the divergent link end has objects, or happens, if the divergent end has processes. Graphically, two concentric dashed arcs across the links with their focal point at the convergent end point of contact shall denote the OR operator.
The definition of system purpose, scope, and function in terms of boundary, stakeholders and preconditions is the basis for determining whether other elements should appear in the model. This determines the scope of the system model.
OPM provides abstracting and refining mechanisms to manage the expression of model clarity and completeness. [ 1 ] [ 4 ]
For man-made systems this function is expected to benefit a person or a group of people—the beneficiary. After the function of the system aligns with the functional value expectation of its main beneficiary, the modeler identifies and adds other principal stakeholders to the OPM model.
The resulting top-level OPD is the system diagram (SD), which includes the stakeholder group, in particular the beneficiary group, and additional top-level environmental things, which provide the context for the system's operation. The SD should contain only the central and important things—those things indispensable for understanding the function and context of the system. The function is the main process in SD, which also contains the objects involved in this process: the beneficiary, the operand (the object upon which the process operates), and possibly the attribute of the operand whose value the process changes. SD should also contain an object representing the system that enables the function. The default name of this system is created by adding the word "System" to the name of the function. For example, if the function is Car Painting, the name of the system would be Car Painting System.
Establishing an appropriate balance requires careful management of context during model development. However, the modeler may take advantage of the union of information provided by the entire OPD set of an OPM system model and have one OPD which is clear and unambiguous but not complete, and another that focuses on completeness for some smaller part of the system by adding more details.
OPM shall provide abstracting and refining mechanisms to manage the expression of model clarity and completeness. These mechanisms shall enable presenting and viewing the system, and the things that comprise it, in various contexts that are interrelated by the objects, processes and relations that are common amongst them.
The inverse of state suppression shall be state expression, i.e., refining the OPD by adding the information
concerning possible object states. The OPL corresponding to the OPD shall express only the states of the
objects that are depicted.
It reveals a set of things that are hierarchically below the unfolded thing. The result is a hierarchy tree, the root of which is the unfolded thing. Linked to the root are the things that constitute the context of the unfolded thing. Conversely, folding is a mechanism for abstraction or composition, which applies to an unfolded hierarchical tree.
In-zooming is a kind of unfolding, which is applicable to aggregation-participation only and has additional semantics. For processes, in-zooming enables modeling the sub-processes, their temporal order, their interactions with objects, and passing of control to and from this context. For objects, in-zooming creates a distinct context that enables modeling the constituent objects spatial or logical order. Graphically, the timeline within the context of an in-zoomed process flows from the top of its process ellipse symbol to the ellipse bottom.
The model, as seen in the image of OPD metamodel, elaborates the OPD Construct concept. The purpose of this model is to distinguish Basic Construct from another possible OPD Construct. A Basic Construct is a specialization of OPD Construct, which consists of exactly two Things connected by exactly one Link. The non-basic constructs include, among others, those with link fans or more than two refinees.
A modeller could add a process to the model, by adding states disconnected and connected of Thing Set.
The purpose of the model thus includes the action of transforming a disconnected Thing Set to a connected Thing Set using the Link Set as an instrument of connection.
OPM model of Thing, is a model for an OPM Thing, showing its specialization into Object and Process, as depicted in the image of model of thing below. A set of States characterize Object, which can be empty, in a Stateless Object, or non-empty in the case of a Stateful Object.
A Stateful Object with s States gives rise to a set of s stateless State-Specific Objects, one for each State.
A particular State-Specific Object refers to an object in a specific state. Modelling the concept of State-Specific Object as both an Object and a State enables simplifying the conceptual model by referring to an object and any one or its states by simply specifying Object.
OPM model of Thing generic properties, depicts Thing and its Perseverance, Essence, and Affiliation generic properties modelled as attribute refinees of an exhibition-characterization link. Perseverance is the discriminating attribute between Object and Process.
Both new-diagram in-zooming and new-diagram out-zooming create a new OPD context from an existing OPD context. New-diagram in-zooming starts with an OPD of relatively less details and adds elaboration or refinement as a descendant OPD that applies to a specific thing in the less detailed OPD.
The current version of OPM is ISO/PAS 19450:2015 as specified in Automation Systems and Integration — Object-Process Methodology. [ 1 ] The specification in Dori's 2016 book is a superset of ISO/PAS 19450:2015. [ 4 ]
The previous version of OPM was specified in Dori's 2002 book. [ 3 ]
The current OPCAT version is 4.1. It is available freely from Technion's Enterprise Systems Modeling Laboratory. [ 5 ]
A previous OPCAT version, 3.1, with fewer capabilities, is also available from the same site. Both are coded in Java. The first OPCAT version, OPCAT 1.X, was written in Visual C++ in 1998.
In the beginning of 2016 a team of students under the management of Dori began working on the new generation of OPCAT which will be called OPCloud. [ 13 ] As suggested by the name of the software, it will be a cloud-based application, and will enable users to create OPM models using a web-based application. [ 14 ]
ISO —the International Organization for Standardization—is an independent, non-governmental international organization with a membership of 162 national standards bodies, which develops voluntary, consensus-based, market relevant International Standards that support innovation and provide solutions to global challenges. These standards provide world-class specifications for products, services and systems, to ensure quality, safety and efficiency.
In June 2008, Richard Martin approached Dov Dori after his presentation at the INCOSE International Symposium in Utrecht, the Netherlands, to inquire about the possibility of creating an International Standard for OPM. [ 15 ] Martin, convener of ISO TC184/SC5/WG1 for automation systems interoperability architecture and modelling, had for some time been searching for methodologies offering more than static information and process modeling. [ citation needed ] He provided Dori with a simple example to model that could demonstrate both the modelling capability of OPM and its dynamic simulation opportunity. [ citation needed ]
In May 2010, Dori presented a brief overview of OPM and his demonstration model at the ISO Technical Committee 184/Sub-Committee 5 (TC184/SC5) plenary meeting, which then adopted a resolution to create an OPM Study Group for the purpose of examining the potential for OPM to enhance the standards created by SC5. [ 16 ]
The OPM Study Group began its work in October 2010 and issued an interim report for the 2011 SC5 Plenary. [ 15 ] The report included several uses of OPM to model existing SC5 standards and led to an initial motivation for the standardization of OPM with the realization that being text-based, ISO standards are prone to suffer from inconsistencies and incomplete information. This deficiency could be significantly reduced if the standards were model-based rather than text-based, and OPM offered a useful underlying modeling paradigm for this purpose.
A final OPM Study Group Report and a draft for a metamodel for model-based standards authoring document were delivered at the 2012 SC5 Plenary. [ 17 ] As the OPM Study Group effort progressed, it became obvious that OPM could also serve as a solid and comprehensive basis for model-based systems engineering (MBSE) and for modeling both natural and man-made systems. [ citation needed ]
TC184/SC5/WG1 participants received the first draft of the OPM PAS in September 2011 with 16 pages, 2 annexes and a bibliography for a total of 25 pages. [ citation needed ] Most of the content simply identified sub-clause headings and space holder graphics. [ citation needed ] By the 2012 SC5 Plenary, the PAS draft included 10 full clauses describing OPM features and 6 annexes totaling 86 pages. [ citation needed ] One annex was an EBNF (Extended Backus-Naur Form, used to formally specify context free languages, enabling parsing of programming languages) specification for OPL and another detailed OPD graph grammar. To facilitate verification of the EBNF specification, David Shorter wrote a script to evaluate consistency and completeness of the EBNF statement set. [ citation needed ] Further effort to add meaningful examples and complete all of the identified sections resulted in a draft of 138 pages by the time of the 2013 SC5 Plenary. [ citation needed ] Subsequently, the working draft was registered with the SC5 Secretariat as a Committee Draft for initial circulation to SC5 members. [ citation needed ]
Because the SC5 resolution calling for the OPM specification indicated that the document was to be registered as a Publicly Available Specification (PAS), it would have only one acceptance ballot opportunity. In April 2014, the New Work Item Proposal and revised Committee Draft for ISO/PAS 19450 was delivered to SC5 for consideration. [ citation needed ] By now the Committee Draft was 98 pages plus front matter, four annexes and 30 bibliographic references, totaling 183 pages. [ citation needed ] In March 2015, ISO registered the result of balloting for ISO/PAS 19450 as 8 Approve, 1 Approve with comments, and 1 abstain. [ citation needed ]
ISO/PAS 19450 was formally published with a total of 162 pages by ISO on December 15, 2015, culminating a six-year effort to provide the standardization community with a formal specification for a new approach to modeling that binds together graphics and textual representations into a single paradigm suitable for automated simulation of model behavior.
SysML is defined as an extension of the Unified Modeling Language (UML) using UML's profile mechanism . [ 11 ]
The differences between OPM and UML are highly perceivable during the analysis and design stages. While UML is a multi-model, OPM supports a single unifying structure-behavior model. The crucial differences stem from the structure-oriented approach of UML, in which behavior is spread over thirteen diagram types, a fact that inevitably invokes the model multiplicity problem. [ 18 ] First, using the OPM approach enables to view at main diagram (SD) the main process, objects and the connection between them. [ 3 ] [ page needed ] In addition, it is easy to understand what is the main system's benefit (presented at the SD). In OPM, it's also easier to understand the main three aspects of the system: behavior, structure and functionality (contrary to UML which describes these aspects with different types of diagrams). [ 3 ] [ page needed ] Database unfolding modeling contributes to the understanding of system and all details which is stored in the system. In addition, creating in-zooming enables simplifying the model. OPM requires extensive knowledge of systematic processes such as how the system saved the path and gets decisions.
While both languages aim at the same purpose of providing a means for general-purpose systems engineering, these languages take different approaches in realizing this goal. SysML is a profile of UML (Unified Modeling Language).
The OPM-to SysML translation is one-to-many in the sense that a single OPM element (entity or link) usually translates to several SysML elements that belong in different SysML diagram types. For example, an OPM process, which is defined as an entity that transforms (generates, consumes, or changes the state of) an object, can be mapped to any subset of the following SysML entities:
As OPM and SysML are two distinct and differently designed languages, not all the constructs in one language have equivalent constructs in the other language. | https://en.wikipedia.org/wiki/Object_Process_Methodology |
An object code optimizer , sometimes also known as a post pass optimizer or, for small sections of code, peephole optimizer , forms part of a software compiler . It takes the output from the source language compile step - the object code or binary file - and tries to replace identifiable sections of the code with replacement code that is more algorithmically efficient (usually improved speed).
The main advantage of re-optimizing existing programs was that the stock of already compiled customer programs ( object code ) could be improved almost instantly with minimal effort, reducing CPU resources at a fixed cost (the price of the proprietary software ). A disadvantage was that new releases of COBOL, for example, would require (charged) maintenance to the optimizer to cater for possibly changed internal COBOL algorithms. However, since new releases of COBOL compilers frequently coincided with hardware upgrades , the faster hardware would usually more than compensate for the application programs reverting to their pre-optimized versions (until a supporting optimizer was released).
Some binary optimizers do executable compression , which reduces the size of binary files using generic data compression techniques, reducing storage requirements and transfer and loading times, but not improving run-time performance. Actual consolidation of duplicate library modules would also reduce memory requirements.
Some binary optimizers utilize run-time metrics ( profiling ) to introspectively improve performance using techniques similar to JIT compilers.
More recently developed "binary optimizers" for various platforms, some claiming novelty but, nevertheless, essentially using the same (or similar) techniques described above, include: | https://en.wikipedia.org/wiki/Object_code_optimizer |
In computer programming , an object orgy is a situation in which objects are insufficiently encapsulated via information hiding , allowing unrestricted access to their internals. This is a common failure (or anti-pattern ) in object-oriented design or object-oriented programming , and it can lead to increased maintenance needs and problems, and even unmaintainable complexity.
The results of an object orgy are mainly a loss of the benefits of encapsulation, including:
Encapsulation may be weakened in several ways, including:
An object may also make its internal data accessible by passing references to them as arguments to methods or constructors of other classes, which may retain references.
In contrast, objects holding references to one another, though sometimes described as a form of object orgy, does not by itself breach encapsulation.
Members may be declared public to avoid the effort or syntactic overhead of providing proper accessors for them. This may increase readability of the class, but at the cost of the consequences described above.
For some languages, a member intended to be readable by other objects can be made modifiable because the language has no convenient construct for read-only access.
An object orgy may be a symptom of coding to an immature and anemic design, when a designer has insufficiently analysed the interactions between objects. It can also arise from laziness or haste in implementing a design, especially if a programmer does not communicate enough with a designer, or from reluctance to revise a design when problems arise, which also encourages many other anti-patterns.
Many programmers view objects as anemic data repositories and manipulate them violating Information Hiding , Encapsulation and Design by Contracts principles.
In general, encapsulation is broken because the design of other classes requires it, and a redesign is needed. If that is not the case, it may be sufficient to re-code the system according to best practices. Once the interfaces are published irrevocably, it may be too late to fix them. | https://en.wikipedia.org/wiki/Object_orgy |
In optical engineering , an objective is an optical element that gathers light from an object being observed and focuses the light rays from it to produce a real image of the object. Objectives can be a single lens or mirror , or combinations of several optical elements. They are used in microscopes , binoculars , telescopes , cameras , slide projectors , CD players and many other optical instruments. Objectives are also called object lenses , object glasses , or objective glasses .
The objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass , with very short focal length . This is brought very close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube. The objective itself is usually a cylinder containing one or more lenses that are typically made of glass; its function is to collect light from the sample.
One of the most important properties of microscope objectives is their magnification . The magnification typically ranges from 4× to 100×. It is combined with the magnification of the eyepiece to determine the overall magnification of the microscope; a 4× objective with a 10× eyepiece produces an image that is 40 times the size of the object.
A typical microscope has three or four objective lenses with different magnifications, screwed into a circular "nosepiece" which may be rotated to select the required lens. These lenses are often color coded for easier use. The least powerful lens is called the scanning objective lens , and is typically a 4× objective. The second lens is referred to as the small objective lens and is typically a 10× lens. The most powerful lens out of the three is referred to as the large objective lens and is typically 40–100×.
Numerical aperture for microscope lenses typically ranges from 0.10 to 1.25, corresponding to focal lengths of about 40 mm to 2 mm, respectively.
Historically, microscopes were designed such that the objective lens would form an image in a specific plane near the eyepiece, which the eyepiece would re-image. Such microscopes were characterized by the mechanical tube length ; the distance between the mounting locations for the objective and the eyepiece. [ 1 ] Early English microscopes used a mechanical tube length of 10 inches (250 mm). In the 20th century most microscopes used the Royal Microscopical Society standard of 160 millimeters, while many Leitz microscopes used 170 millimeters. Objectives had to be chosen to match the mechanical tube length of the microscope.
Modern microscopes are often designed to use infinity correction , in which the light coming out of the objective lens is focused at infinity . [ 2 ] [ 3 ] This is denoted on the objective with the infinity symbol (∞).
The objective pupil diameter [ 3 ] , also known as entrance pupil diameter [ 4 ] or back aperture diameter, refers to the diameter of the rear opening of an objective lens. In dry infinity corrected objectives, this diameter D {\displaystyle D} is
D = 2 × N A × f o b j {\displaystyle D=2\times NA\times f_{obj}}
where N A {\displaystyle NA} is the numerical aperture, and f o b j {\displaystyle f_{obj}} is the effective focal length. Magnification M {\displaystyle M} and effective focal length are related by [ 5 ]
f t u b e = M f o b j {\displaystyle f_{tube}=Mf_{obj}}
where f t u b e {\displaystyle f_{tube}} is the tube lens focal length. Tube lens focal lengths vary by manufacturer: Leica and Nikon typically use 200 mm, Olympus uses 180 mm, and Zeiss uses 165 mm [ 3 ] .
Particularly in biological applications, samples are usually observed under a glass cover slip , which introduces distortions to the image. Objectives which are designed to be used with such cover slips will correct for these distortions, and typically have the thickness of the cover slip they are designed to work with written on the side of the objective (typically 0.17 mm).
In contrast, so called "metallurgical" objectives are designed for reflected light and do not use glass cover slips.
The distinction between objectives designed for use with or without cover slides is important for high numerical aperture (high magnification) lenses, but makes little difference for low magnification objectives.
Basic glass lenses will typically result in significant and unacceptable chromatic aberration . Therefore, most objectives have some kind of correction to allow multiple colors to focus at the same point. The easiest correction is an achromatic lens , which uses a combination of crown glass and flint glass to bring two colors into focus. Achromatic objectives are a typical standard design.
In addition to oxide glasses, fluorite lenses are often used in specialty applications. These fluorite or semi-apochromat objectives deal with color better than achromatic objectives. To reduce aberration even further, more complex designs such as apochromat and superachromat objectives are also used.
All these types of objectives will exhibit some spherical aberration . While the center of the image will be in focus, the edges will be slightly blurry. When this aberration is corrected, the objective is called a "plan" objective, and has a flat image across the field of view.
The working distance (sometimes abbreviated WD) is the distance between the sample and the objective. As magnification increases, working distances generally shrinks. When space is needed, special long working distance objectives can be used.
Some microscopes use an oil-immersion or water-immersion lens, which can have magnification greater than 100, and numerical aperture greater than 1. These objectives are specially designed for use with refractive index matching oil or water, which must fill the gap between the front element and the object. These lenses give greater resolution at high magnification. Numerical apertures as high as 1.6 can be achieved with oil immersion. [ 6 ]
The traditional screw thread used to attach the objective to the microscope was standardized by the Royal Microscopical Society in 1858. [ 7 ] It was based on the British Standard Whitworth , with a 0.8 inch diameter and 36 threads per inch. This "RMS thread" or "society thread" is still in common use today. Alternatively, some objective manufacturers use designs based on ISO metric screw thread such as M26 × 0.75 and M25 × 0.75 .
Camera lenses (usually referred to as "photographic objectives" instead of simply "objectives" [ 8 ] ) need to cover a large focal plane so are made up of a number of optical lens elements to correct optical aberrations . Image projectors (such as video, movie, and slide projectors) use objective lenses that simply reverse the function of a camera lens, with lenses designed to cover a large image plane and project it at a distance onto another surface. [ 9 ]
In a telescope the objective is the lens at the front end of a refracting telescope (such as binoculars or telescopic sights ) or the image-forming primary mirror of a reflecting or catadioptric telescope . A telescope's light-gathering power and angular resolution are both directly related to the diameter (or "aperture") of its objective lens or mirror. The larger the objective, the brighter the objects will appear and the more detail it can resolve. | https://en.wikipedia.org/wiki/Objective_(optics) |
As an adjective, obligate means "by necessity" (antonym facultative ) and is used mainly in biology in phrases such as: | https://en.wikipedia.org/wiki/Obligate |
An obligate aerobe is an organism that requires oxygen to grow. [ 1 ] Through cellular respiration , these organisms use oxygen to metabolise substances, like sugars or fats, to obtain energy. [ 1 ] [ 2 ] In this type of respiration, oxygen serves as the terminal electron acceptor for the electron transport chain . [ 1 ] Aerobic respiration has the advantage of yielding more energy ( adenosine triphosphate or ATP ) than fermentation or anaerobic respiration , [ 3 ] but obligate aerobes are subject to high levels of oxidative stress . [ 2 ]
Among organisms, almost all animals, most fungi , and several bacteria are obligate aerobes. [ 2 ] Examples of obligately aerobic bacteria include Mycobacterium tuberculosis ( acid-fast ), [ 2 ] [ 5 ] Bacillus ( Gram-positive ), [ 2 ] and Nocardia asteroides ( Gram-positive ). [ 2 ] [ 6 ] With the exception of the yeasts , most fungi are obligate aerobes. [ 1 ] Also, almost all algae are obligate aerobes. [ 1 ]
A unique obligate aerobe is Streptomyces coelicolor which is gram-positive , soil-dwelling, and belongs to the phylum Actinomycetota . [ 7 ] It is unique because the genome of this obligate aerobe encodes numerous enzymes with functions that are usually attributed to anaerobic metabolism in facultatively and strictly anaerobic bacteria . [ 7 ]
When obligate aerobes are in a temporarily oxygen-deprived environment, they need survival strategies to avoid death. [ 8 ] Under these conditions, Mycobacterium smegmatis can quickly switch between fermentative hydrogen production and hydrogen oxidation with either oxygen or fumarate reduction depending on the availability of electron acceptor . [ 8 ] This example is the first time that hydrogen production has been seen in an obligate aerobe. [ 8 ] It also confirms the fermentation in a mycobacterium and is evidence that hydrogen plays a role in survival as well as growth. [ 8 ]
Problems can also arise in oxygen-rich environments, most commonly attributed to oxidative stress . This occurrence is when there is an imbalance of free radicals and antioxidants in the cells of the organism, largely due to pollution and radiation in the environment. Obligate aerobes survive this phenomenon by using the organism's immune system to correct the imbalance. [ 9 ]
This microbiology -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Obligate_aerobe |
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