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Leaving group With poor leaving groups, the E1cB mechanism is favored, but as the leaving group's ability changes, the reaction shifts from having a rate determining loss of leaving group from carbanionic intermediate B "via" TS BC" through having a rate determining deprotonation step "via" TS AB" (not pictured) to a c... | https://en.wikipedia.org/wiki?curid=241440 |
Leaving group Mixed acyl-trifluoromethanesulfonyl anhydrides smoothly undergo Friedel-Crafts acylation without a catalyst, unlike the corresponding acyl halides, which require a strong Lewis acid. Methyl triflate, however, does not participate in Friedel-Crafts alkylation reactions with electron-neutral aromatic rings.... | https://en.wikipedia.org/wiki?curid=241440 |
Leaving group The strongly electrophilic nature of these compounds engendered by their attachment to extremely labile R-X (R = alkyl, X = Cl, Br, I) leaving groups is illustrated by their propensity to alkylate very weak nucleophiles. Heating neat samples of (CH)Cl [CHBCl] under reduced pressure resulted in methylation... | https://en.wikipedia.org/wiki?curid=241440 |
Nitrogen triiodide is the inorganic compound with the formula NI. It is an extremely sensitive contact explosive: small quantities explode with a loud, sharp snap when touched even lightly, releasing a purple cloud of iodine vapor; it can even be detonated by alpha radiation. NI has a complex structural chemistry that ... | https://en.wikipedia.org/wiki?curid=241564 |
Nitrogen triiodide This results in a very low activation energy for its decomposition, a reaction made even more favorable due to the great stability of N. has no practical commercial value due to its extreme shock sensitivity, making it impossible to store, transport, and utilize for controlled explosions. Whereas pur... | https://en.wikipedia.org/wiki?curid=241564 |
Clinical trial Clinical trials are experiments or observations done in clinical research. Such prospective biomedical or behavioral research studies on human participants are designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, diet... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Certain functions necessary to the trial, such as monitoring and lab work, may be managed by an outsourced partner, such as a contract research organization or a central laboratory. Only 10 percent of all drugs started in human clinical trials become approved drugs. Some clinical trials involve healthy s... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial In the US, the elderly constitute 14% of the population, while they consume over one-third of drugs. People over 55 (or a similar cutoff age) are often excluded from trials because their greater health issues and drug use complicate data interpretation, and because they have different physiological capac... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Examples of clinical trial goals include assessing the safety and relative effectiveness of a medication or device: While most clinical trials test one alternative to the novel intervention, some expand to three or four and may include a placebo. Except for small, single-location trials, the design and o... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial An example of the former in the field of vascular surgery is the Open versus Endovascular Repair (OVER trial) for the treatment of abdominal aortic aneurysm, which compared the older open aortic repair technique to the newer endovascular aneurysm repair device. An example of the latter are clinical trial... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Although they survived and did not contract smallpox, there was no control group to assess whether this result was due to the inoculation or some other factor. Similar experiments performed by Edward Jenner over his smallpox vaccine were equally conceptually flawed. The first proper clinical trial was co... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial The treatment of group five stopped after six days when they ran out of fruit, but by that time one sailor was fit for duty while the other had almost recovered. Apart from that, only group one also showed some effect of its treatment. After 1750, the discipline began to take its modern shape. John Hayga... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Among his major ideas, was the importance of randomization – the random assignment of individuals to different groups for the experiment; replication – to reduce uncertainty, measurements should be repeated and experiments replicated to identify sources of variation; blocking – to arrange experimental un... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial He became famous for a landmark study carried out in collaboration with Richard Doll on the correlation between smoking and lung cancer. They carried out a case-control study in 1950, which compared lung cancer patients with matched control and also began a sustained long-term prospective study into the ... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial The drug development process will normally proceed through phases I-IV over many years, frequently involving a decade or longer. If the drug successfully passes through phases I, II, and III, it will usually be approved by the national regulatory authority for use in the general population. Phase IV tria... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial In many cases, giving a placebo to a person suffering from a disease may be unethical. To address this, it has become a common practice to conduct "active comparator" (also known as "active control") trials. In trials with an active control group, subjects are given either the experimental treatment or a... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial The protocol contains a precise study plan to assure safety and health of the trial subjects and to provide an exact template for trial conduct by investigators. This allows data to be combined across all investigators/sites. The protocol also informs the study administrators (often a contract research o... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Generally, children cannot autonomously provide informed consent, but depending on their age and other factors, may be required to provide informed assent. In any clinical trial, the number of subjects, also called the sample size, has a large impact on the ability to reliably detect and measure the effe... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Clinical trials are only a small part of the research that goes into developing a new treatment. Potential drugs, for example, first have to be discovered, purified, characterized, and tested in labs (in cell and animal studies) before ever undergoing clinical trials. In all, about 1,000 potential drugs ... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial It is a challenge to find the appropriate patients and obtain their consent, especially when they may receive no direct benefit (because they are not paid, the study drug is not yet proven to work, or the patient may receive a placebo). In the case of cancer patients, fewer than 5% of adults with cancer ... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial A CRO is contracted to perform all the administrative work on a clinical trial. For phases 2, 3 and 4, the CRO recruits participating researchers, trains them, provides them with supplies, coordinates study administration and data collection, sets up meetings, monitors the sites for compliance with the c... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial In the context of a clinical trial, quality typically refers to the absence of errors which can impact decision making, both during the conduct of the trial and in use of the trial results. Janet Yang uses the Interactional Justice Model to test the effects of willingness to talk with a doctor and clinic... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial management systems are often used by research sponsors or CROs to help plan and manage the operational aspects of a clinical trial, particularly with respect to investigational sites. Advanced analytics for identifying researchers and research sites with expertise in a given area utilize public and priva... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial This technology provides many more data points and is far more convenient for patients, because they have fewer visits to trial sites. Clinical trials are closely supervised by appropriate regulatory authorities. All studies involving a medical or therapeutic intervention on patients must be approved by ... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial The International Conference of Harmonisation Guidelines for Good Clinical Practice is a set of standards used internationally for the conduct of clinical trials. The guidelines aim to ensure the "rights, safety and well being of trial subjects are protected". The notion of informed consent of participat... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial In response to specific cases in which unfavorable data from pharmaceutical company-sponsored research were not published, the Pharmaceutical Research and Manufacturers of America published new guidelines urging companies to report all findings and limit the financial involvement in drug companies by res... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial In 2001, the editors of 12 major journals issued a joint editorial, published in each journal, on the control over clinical trials exerted by sponsors, particularly targeting the use of contracts which allow sponsors to review the studies prior to publication and withhold publication. They strengthened e... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial In some cases, the male partners of these women are also excluded or required to take birth control measures. Throughout the clinical trial, the sponsor is responsible for accurately informing the local site investigators of the true historical safety record of the drug, device or other medical treatment... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial The sponsor and the local site investigators are jointly responsible for writing a site-specific informed consent that accurately informs the potential subjects of the true risks and potential benefits of participating in the study, while at the same time presenting the material as briefly as possible an... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial These adverse event reports contain the opinion of both the investigator at the site where the adverse event occurred, and the sponsor, regarding the relationship of the adverse event to the study treatments. Local investigators also are responsible for making an independent judgment of these reports, an... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial The IRB scrutinizes the study for both medical safety and protection of the patients involved in the study, before it allows the researcher to begin the study. It may require changes in study procedures or in the explanations given to the patient. A required yearly "continuing review" report from the inv... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial any study of a drug, biological product or device in humans submitted in a marketing application or reclassification petition that the applicant or FDA relies on to establish that the product is effective (including studies that show equivalence to an effective product) or any study in which a single inv... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial At the same time, coordination between Europe, Japan and the United States led to a joint regulatory-industry initiative on international harmonization named after 1990 as the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) Curre... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial costs vary depending on trial phase, type of trial, and disease studied. A study of clinical trials conducted in the United States from 2004 to 2012 found the average cost of phase I trials to be between $1.4 million and $6.6 million, depending on the type of disease. Phase II trials ranged from $7 milli... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Investigators are often compensated for their work in clinical trials. These amounts can be small, just covering a partial salary for research assistants and the cost of any supplies (usually the case with national health agency studies), or be substantial and include 'overhead' that allows the investiga... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial Requirements differ according to the trial needs, but typically volunteers would be screened in a medical laboratory for: It has been observed that participants in clinical trials are disproportionately white. This may reduce the validity of findings in respect of non-white patients. Depending on the kin... | https://en.wikipedia.org/wiki?curid=241717 |
Clinical trial People who hold a higher stake or interest in the treatment provided in a clinical trial showed a greater likelihood of seeking information about clinical trials. Cancer patients reported more optimistic attitudes towards clinical trials than the general population. Having a more optimistic outlook on cl... | https://en.wikipedia.org/wiki?curid=241717 |
Outline of organic chemistry The following outline is provided as an overview of and topical guide to organic chemistry: Organic chemistry is the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of carbon-based compounds, hydrocarbons, and their der... | https://en.wikipedia.org/wiki?curid=241742 |
Chemical species A chemical species is a chemical substance or ensemble composed of chemically identical molecular entities that can explore the same set of molecular energy levels on a characteristic or delineated time scale. These energy levels determine the way the chemical species will interact with others (engagin... | https://en.wikipedia.org/wiki?curid=241761 |
Chlordane Chlordane, or chlordan, is an organochlorine compound used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. was banned 10 years earlier for food crops like corn and citrus, and on lawns and domest... | https://en.wikipedia.org/wiki?curid=241799 |
Chlordane Hexachlorocyclopentadiene forms a Diels-Alder adduct with cyclopentadiene to give Chlordene intermediate [3734-48-3]; chlorination of this adduct gives predominantly two chlordane isomers, α and β, in addition to other products such as "trans"-nonachlor and heptachlor. The β-isomer is popularly known as gamma... | https://en.wikipedia.org/wiki?curid=241799 |
Chlordane It has an environmental half-life of 10 to 20 years. In the years 1948–1988 chlordane was a common pesticide for corn and citrus crops, as well as a method of home termite control. Pathways of exposure to chlordane include ingestion of crops grown in chlordane-contaminated soil, inhalation of air in chlordane... | https://en.wikipedia.org/wiki?curid=241799 |
Chlordane Oxychlordane (CHClO), the primary metabolite of chlordane, and heptachlor epoxide, the primary metabolite of heptachlor, along with the two other main components of the chlordane mixture, "cis"-nonachlor and "trans"-nonachlor, are the main bioaccumulating constituents. "trans"-Nonachlor is more toxic than tec... | https://en.wikipedia.org/wiki?curid=241799 |
Chlordane The non-cancer health effects of chlordane compounds, which include diabetes, insulin resistance, migraines, respiratory infections, immune-system activation, anxiety, depression, blurry vision, confusion, intractable seizures as well as permanent neurological damage, probably affects more people than cancer.... | https://en.wikipedia.org/wiki?curid=241799 |
Chlordane Mycoremediation of chlordane in soil have found that contamination levels were reduced. The fungus "Phanerochaete chrysosporium" has been found to reduce concentrations of chlordane by 21% in water in 30 days and in solids in 60 days. | https://en.wikipedia.org/wiki?curid=241799 |
1,2-Dibromoethane 1,2-Dibromoethane, also known as ethylene dibromide (EDB), is an organobromine compound with the chemical formula . Although trace amounts occur naturally in the ocean, where it is formed probably by algae and kelp, it is mainly synthetic. It is a dense colorless liquid with a faint sweet odor, detect... | https://en.wikipedia.org/wiki?curid=241806 |
1,2-Dibromoethane In the latter process, 1,2-dibromoethane reacts with magnesium, producing ethylene and magnesium bromide, and exposes a freshly etched portion of magnesium to the substrate. causes changes in the metabolism and severe destruction of living tissues. The known empirical LD50 values for 1,2-dibromoethane... | https://en.wikipedia.org/wiki?curid=241806 |
Diborane Diborane(6), generally known as diborane is the chemical compound consisting of boron and hydrogen with the formula BH. It is a colorless, pyrophoric gas with a repulsively sweet odor. Synonyms include boroethane, boron hydride, and diboron hexahydride. is a key boron compound with a variety of applications. I... | https://en.wikipedia.org/wiki?curid=241810 |
Diborane The lengths of the B-H bonds and the B-H bonds are 1.33 and 1.19 Å respectively, and this difference in the lengths of these bonds reflects the difference in their strengths, the B-H bonds being relatively weaker. The weakness of the B-H vs B-H bonds is indicated by their vibrational signatures in the infrared... | https://en.wikipedia.org/wiki?curid=241810 |
Diborane For example, using iodine as an oxidizer: Another small-scale synthesis uses potassium hydroborate and phosphoric acid as starting materials. is a highly reactive and versatile reagent that has numerous applications. Its dominating reaction pattern involves formation of adducts with Lewis bases. Often such ini... | https://en.wikipedia.org/wiki?curid=241810 |
Diborane is used as a reducing agent roughly complementary to the reactivity of lithium aluminium hydride. The compound readily reduces carboxylic acids to the corresponding alcohols, whereas ketones react only sluggishly. was first synthesised in the 19th century by hydrolysis of metal borides, but it was never analys... | https://en.wikipedia.org/wiki?curid=241810 |
Diborane The structure was re-confirmed by electron diffraction measurement in 1951 by K. Hedberg and V. Schomaker, with the confirmation of the structure shown in the schemes on this page. William Nunn Lipscomb, Jr. further confirmed the molecular structure of boranes using X-ray crystallography in the 1950s, and deve... | https://en.wikipedia.org/wiki?curid=241810 |
Diborane Skin and eye irritation can also occur. Studies in animals have shown that diborane causes the same type of effects observed in humans. People exposed for a long time to low amounts of diborane have experienced respiratory irritation, seizures, fatigue, drowsiness, confusion, and occasional transient tremors. | https://en.wikipedia.org/wiki?curid=241810 |
Hydraulic fluid A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoes, hydraulic brakes, power steering systems, transmissions,... | https://en.wikipedia.org/wiki?curid=241812 |
Hydraulic fluid Some examples include: glycol, esters, organophosphate ester, polyalphaolefin, propylene glycol, and silicone oils. NaK-77, a eutectic alloy of sodium and potassium, can be used as a hydraulic fluid in high-temperature and high-radiation environments, for temperature ranges of 10 to 1400 °F (-12 to 760 ... | https://en.wikipedia.org/wiki?curid=241812 |
Hydraulic fluid ASTM standards ASTM-D-6006, Guide for Assessing Biodegradability of Hydraulic Fluids and ASTM-D-6046, Standard Classification of Hydraulic Fluids for Environmental Impact are relevant. Anti-wear (AW) hydraulic oils are made from a petroleum base fluid and commonly contain the anti-wear additive Zinc dia... | https://en.wikipedia.org/wiki?curid=241812 |
Hydraulic fluid Use of the wrong type of fluid can lead to failure of the power steering pump. Because industrial hydraulic systems operate at hundreds to thousands of PSI and temperatures reaching hundreds of degrees Celsius, severe injuries and death can result from component failures and care must always be taken wh... | https://en.wikipedia.org/wiki?curid=241812 |
Hydraulic fluid In modern commercial aircraft these are electrically driven pumps; should all the engines fail in flight the pilot will deploy a propeller-driven electric generator called a Ram Air Turbine (RAT) which is concealed under the fuselage. This provides electrical power for the hydraulic pumps and control sy... | https://en.wikipedia.org/wiki?curid=241812 |
SN2 reaction The S2 reaction is a type of reaction mechanism that is common in organic chemistry. In this mechanism, one bond is broken and one bond is formed synchronously, i.e., in one step. S2 is a kind of nucleophilic substitution reaction mechanism. Since "two" reacting species are involved in the slow (rate-deter... | https://en.wikipedia.org/wiki?curid=241878 |
SN2 reaction If the substrate under nucleophilic attack is chiral, then this often leads to inversion of configuration (stereochemistry), called a Walden inversion. In an example of the S2 reaction, the attack of Br (the nucleophile) on an ethyl chloride (the electrophile) results in ethyl bromide, with chloride ejecte... | https://en.wikipedia.org/wiki?curid=241878 |
SN2 reaction Structures that can form highly stable cations by simple loss of the leaving group, for example, as a resonance-stabilized carbocation, are especially likely to react via an S1 pathway in competition with S2. Like the substrate, steric hindrance affects the nucleophile's strength. The methoxide anion, for ... | https://en.wikipedia.org/wiki?curid=241878 |
SN2 reaction Polar aprotic solvents, like tetrahydrofuran, are better solvents for this reaction than polar protic solvents because polar protic solvents will hydrogen bond to the nucleophile, hindering it from attacking the carbon with the leaving group. A polar aprotic solvent with low dielectric constant or a hinder... | https://en.wikipedia.org/wiki?curid=241878 |
SN2 reaction In other words, the rate of S1 reactions depend only on the concentration of the substrate while the S2 reaction rate depends on the concentration of both the substrate and nucleophile. It has been shown that except in uncommon (but predictable cases) primary and secondary substrates go exclusively by the ... | https://en.wikipedia.org/wiki?curid=241878 |
SN2 reaction The examples in textbooks of secondary substrates going by the S1 mechanism invariably involve the use of bromide (or other good nucleophile) as the leaving group have confused the understanding of alkyl nucleophilic substitution reactions at secondary carbons for 80 years. Work with the 2-adamantyl system... | https://en.wikipedia.org/wiki?curid=241878 |
SN2 reaction As steric hindrance around the electrophilic center increases, as with isobutyl bromide, substitution is disfavored and elimination is the predominant reaction. Other factors favoring elimination are the strength of the base. With the less basic benzoate substrate, isopropyl bromide reacts with 55% substit... | https://en.wikipedia.org/wiki?curid=241878 |
Nuclear chemistry is the sub-field of chemistry dealing with radioactivity, nuclear processes, and transformations in the nuclei of atoms, such as nuclear transmutation and nuclear properties. It is the chemistry of radioactive elements such as the actinides, radium and radon together with the chemistry associated with... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry These include radiotherapy in medical applications; the use of radioactive tracers within industry, science and the environment; and the use of radiation to modify materials such as polymers. It also includes the study and use of nuclear processes in "non-radioactive" areas of human activity. For inst... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry They then attempted to separate these radioactive fractions further, to isolate a smaller fraction with a higher specific activity (radioactivity divided by mass). In this way, they isolated polonium and radium. It was noticed in about 1901 that high doses of radiation could cause an injury in humans.... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry To Rutherford, the gold foil experiment implied that the positive charge was confined to a very small nucleus leading first to the Rutherford model, and eventually to the Bohr model of the atom, where the positive nucleus is surrounded by the negative electrons. In 1934 Marie Curie's daughter (Irène J... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry Using a X-ray generator, studied the biological effects of radiation as it became a common treatment option and diagnostic method. Fricke proposed and subsequently proved that the energy from X - rays were able to convert water into activated water, allowing it to react with dissolved species. Radioch... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry More recently, a combination of radiochemical methods and nuclear physics has been used to try to make new 'superheavy' elements; it is thought that islands of relative stability exist where the nuclides have half-lives of years, thus enabling weighable amounts of the new elements to be isolated. For ... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry This non-reprocessing policy was started in March 1977 because of concerns about nuclear weapons proliferation. President Jimmy Carter issued a Presidential directive which indefinitely suspended the commercial reprocessing and recycling of plutonium in the United States. This directive was likely an ... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry It is normal to dissolve the used fuel in nitric acid, after the removal of the insoluble matter the uranium and plutonium are extracted from the highly active liquor. It is normal to then back extract the loaded organic phase to create a "medium active" liquor which contains mostly uranium and pluton... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry The PUREX process can be modified to make a UREX ("UR"anium "EX"traction) process which could be used to save space inside high level nuclear waste disposal sites, such as Yucca Mountain nuclear waste repository, by removing the uranium which makes up the vast majority of the mass and volume of used f... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry In common with PUREX this process operates by a solvation mechanism. As an alternative to TRUEX, an extraction process using a malondiamide has been devised. The DIAMEX ("DIAM"ide"EX"traction) process has the advantage of avoiding the formation of organic waste which contains elements other than carbo... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry This is the "UNiversal" "EX"traction process which was developed in Russia and the Czech Republic, it is a process designed to remove all of the most troublesome (Sr, Cs and minor actinides) radioisotopes from the raffinates left after the extraction of uranium and plutonium from used nuclear fuel. Th... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry The radioactive nature of technetium makes this corrosion protection impractical in almost all situations. It has also been shown that TcO anions react to form a layer on the surface of activated carbon (charcoal) or aluminium. A short review of the biochemical properties of a series of key long lived... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry This effort is being coordinated in a project funded by the Coordinated Action supported by the European Atomic Energy Community's 7th Framework Program.. Although NucWik is primarily aimed at teachers, anyone interested in nuclear and radiochemistry is welcome and can find a lot of information and ma... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry Thus, if the reaction changes in rate when protons are replaced by deuteriums, it is reasonable to assume that the breaking of the bond to hydrogen is part of the step which determines the rate. Cosmogenic isotopes are formed by the interaction of cosmic rays with the nucleus of an atom. These can be ... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry For short-lived isotopes such as C, very rapid synthetic methods have been developed to permit the rapid addition of the radioactive isotope to the molecule. For instance a palladium catalysed carbonylation reaction in a microfluidic device has been used to rapidly form amides and it might be possible... | https://en.wikipedia.org/wiki?curid=242001 |
Nuclear chemistry In a medical setting, NMR is often known simply as "magnetic resonance" imaging, as the word 'nuclear' has negative connotations for many people. | https://en.wikipedia.org/wiki?curid=242001 |
Reaction rate The reaction rate or rate of reaction is the speed at which reactants are converted into products. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a fire is a reaction that takes place in fractions of a sec... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate The rate of reaction differs from the rate of increase of concentration of a product P by a constant factor (the reciprocal of its stoichiometric number) and for a reactant A by minus the reciprocal of the stoichiometric number. The stoichiometric numbers are included so that the defined rate is independe... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate For an open system, the full mass balance must be taken into account: where "F" is the inflow rate of A in molecules per second, "F" the outflow, and "v" is the instantaneous reaction rate of A (in number concentration rather than molar) in a given differential volume, integrated over the entire system vo... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate If the basis is a specific catalyst site that may be rigorously counted by a specified method, the rate is given in units of s and is called a turnover frequency. Factors that influence the reaction rate are the nature of the reaction, concentration, pressure, reaction order, temperature, solvent, electro... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate However, the main reason that temperature increases the rate of reaction is that more of the colliding particles will have the necessary activation energy resulting in more successful collisions (when bonds are formed between reactants). The influence of temperature is described by the Arrhenius equation.... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate This energy is in one way or another stored in the reacting particles (it may break bonds, promote molecules to electronically or vibrationally excited states...) creating intermediate species that react easily. As the intensity of light increases, the particles absorb more energy and hence the rate of re... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate All the factors that affect a reaction rate, except for concentration and reaction order, are taken into account in the reaction rate coefficient (the coefficient in the rate equation of the reaction). For a chemical reaction "a" A + "b" B → "p" P + "q" Q, the rate equation or rate law is a mathematical e... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate For complex (multistep) reactions, however, this is often not true and the rate equation is determined by the detailed mechanism, as illustrated below for the reaction of H and NO. For elementary reactions or reaction steps, the order and stoichiometric coefficient are both equal to the molecularity or nu... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate Not all of these steps affect the rate of reaction; normally the slowest elementary step controls the reaction rate. For this example, a possible mechanism is: Reactions 1 and 3 are very rapid compared to the second, so the slow reaction 2 is the rate determining step. This is a bimolecular elementary rea... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate "A" is the pre-exponential factor or frequency factor. The values for "A" and "E" are dependent on the reaction. There are also more complex equations possible, which describe temperature dependence of other rate constants that do not follow this pattern. Temperature Is a measure of the average kinetic en... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate Products are formed only when the colliding particles possess a certain minimum energy called threshold energy. As a rule of thumb, reaction rates for many reactions double for every 10 degrees Celsius increase in temperature, For a given reaction, the ratio of its rate constant at a higher temperature to... | https://en.wikipedia.org/wiki?curid=242006 |
Reaction rate As an example of the possible magnitude of the pressure effect, some organic reactions were shown to double the reaction rate when the pressure was increased from atmospheric (0.1 MPa) to 50 MPa (which gives Δ"V" = −0.025 L/mol). | https://en.wikipedia.org/wiki?curid=242006 |
Calcium carbide Calcium carbide, also known as calcium acetylide, is a chemical compound with the chemical formula of CaC. Its main use industrially is in the production of acetylene and calcium cyanamide. The pure material is colorless, however pieces of technical-grade calcium carbide are grey or brown and consist of... | https://en.wikipedia.org/wiki?curid=242643 |
Calcium carbide As an example, the British and German standards for the content of the coarser fractions are 295 L/kg and 300 L/kg respectively (at 101 kPa pressure and temperature). Impurities present in the carbide include phosphide, which produces phosphine when hydrolysed. This reaction was an important part of the... | https://en.wikipedia.org/wiki?curid=242643 |
Calcium carbide This reaction was the basis of the industrial manufacture of acetylene, and is the major industrial use of calcium carbide. Today acetylene is mainly manufactured by the partial combustion of methane or appears as a side product in the ethylene stream from cracking of hydrocarbons. Approximately 400,000... | https://en.wikipedia.org/wiki?curid=242643 |
Calcium carbide Carbide lamps were still used extensively in slate, copper, and tin mines where methane is not a serious hazard. Most miners' lamps have now been replaced by electric lamps. Carbide lamps are still used for mining in some less wealthy countries, for example in the silver mines near Potosí, Bolivia. Carb... | https://en.wikipedia.org/wiki?curid=242643 |
Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. has two stereoisomeric forms (- and -enantiomers), though only the -isomer exists naturally. The salts and esters of mal... | https://en.wikipedia.org/wiki?curid=243074 |
Malic acid Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential, allowing water to enter the cell and promote aperture o... | https://en.wikipedia.org/wiki?curid=243074 |
Malic acid The process of malolactic fermentation converts malic acid to much milder lactic acid. occurs naturally in all fruits and many vegetables, and is generated in fruit metabolism. Malic acid, when added to food products, is denoted by E number E296. is the source of extreme tartness in United States-produced co... | https://en.wikipedia.org/wiki?curid=243074 |
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