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> are there other classes of compounds responsible for the red and yellow colors found in flowers?
Interest in colors, specifically dyes, was a real motivator for serious chemical work. Some of the early chemical efforts were trying to mimic Tyrian purple, also known as Royal Purple, because at one time it was worth... |
I've noticed that water obtained from melting ice cubes (by keeping them in the open) tastes different from water cooled to the same temperature.
Furthermore, the taste goes away if you keep it in the open for a sufficient duration of time.
I can think of these possible explanations:
- Dissolved gases being r... |
Why does meltwater taste different? |
> are there other classes of compounds responsible for the red and yellow colors found in flowers?
Interest in colors, specifically dyes, was a real motivator for serious chemical work. Some of the early efforts were aiming to mimic Tyrian purple, also known as Royal Purple, because in antiquity it was worth its wei... |
What is antisymmetric exchange? Where does it come from? |
I'm reading a paper<sup>1</sup> by Sanakis, *et al.* that characterises the magnetic coupling in the $\ce{Fe3S4}$ clusters present in bacterial ferredoxin II and beef heart aconitase as arising through something called 'antisymmetric exchange'. This looks like it may be a result of the apparent magnetic frustration of ... |
I'm reading a paper<sup>1</sup> by Sanakis, *et al.* that characterises the magnetic coupling in the $\ce{Fe3S4}$ clusters present in bacterial ferredoxin II and beef heart aconitase as arising through something called 'antisymmetric exchange'. This looks like it may be a result of the apparent magnetic frustration of ... |
What is antisymmetric exchange? What is J-strain? Where does it come from? |
At 256 scans you should see something if your compound has reasonable concentration. The rule of thumb I was taught as an undergrad was ~10 mg of compound for a $^{13}$C scan in under a mL of solvent (400-500 uL if you are measuring precisely, modified by probe size and whatnot of course)
As for an exact concentrat... |
I have a PyMol session file I was using to create my figures. It contains a protein and ligand broken into several groups of atoms with a fair bit of overlap. There are also a few meshes built from a density map for a few figures.
Unfortunately, I wasn't quite done with refinement, and now Refmac has given me shin... |
How can I update a map/mesh and coordinates in a PyMol session file? |
I've been looking to use time-dependent density functional theory, but reading the literature I keep getting overwhelmed by how many different functionals there are. How should I go about selecting which functional to use? |
How should I go about picking a functional for DFT calculations? |
Carbon is well known to form single, double, and triple C-C bonds in compounds. There is a [recent report][1] (2012) that carbon forms a quadruple bond in diatomic carbon, $\ce{C2}$. The excerpt below is taken from that report. The fourth bond seems pretty odd to me.
> $\ce{C2}$ and its isoelectronic molecules $\ce{... |
Bonding in $\ce{C2}$, a carbon-carbon quadruple bond? |
I've seen a few videos of persons creating plastics from starch by adding an acid, glycerol, and water, however no explanation of the chemistry.
Does anyone know what (C6-H10-O5)n + C3H8O3 + C2H4O2 + H2O => (C3H4O2)n + (what)?
or does it?
I only have a basic understanding of organic chemistry, so sorry is the equ... |
##For Structures and Energies: Answer Hazy, Try Again Later
People can talk on this subject for literally days.
It *mostly* comes down to computational expense *vs* accuracy - if you have a larger system, you can't afford the fancier functionals. The absolute highest accuracy state of the art functional-wise woul... |
I've seen a few videos of persons creating plastics from starch by adding an acid, glycerol, and water, however no explanation of the chemistry.
Does anyone know what (C6-H10-O5)n + C3H8O3 + C2H4O2 + H2O => (C3H4O2)n + (what)?
or does it?
I only have a basic understanding of organic chemistry, so sorry if the equ... |
I've seen a few videos of persons creating plastics from starch by adding an acid, glycerol, and water, however no explanation of the chemistry.
Does anyone know what $\ce{(C6H10O5)_{n} + C3H8O3 + C2H4O2 + H2O -> (C3H4O2)_{n} + (what)}$?
or does it?
I only have a basic understanding of organic chemistry, so sorry... |
We're interested in purifying a protein that has an [azide][1] moiety using ion exchange chromatography. Due to its unique structure, the moiety is a Zwitterion with a novel chemical behavior. My question is how will the molecule behave when I run it through an ion exchange column? Will it be considered positively char... |
What is the behavior of a Zwitterion during ion exchange chromatography? |
In lab I've seen that nitric acid solutions are able to facilitate the dissolution of metals such as silver, even though they are more active than hydrogen. Does anyone know why it is nitric acid is so special? |
Why is Nitric Acid such a strong oxidizing agent? |
I know how to measure the concentration of free thiols which is reflective of the redox potential of cellular compartment such as the cytoplasm or a lysosome. What other methods exist? |
What is a good method to measure the redox potential of a cellular system? |
I have some activated charcoal pads or small "pillows" that can be used to adsorb odors and chemical fumes from different materials.
The instructions say to put them out in sunlight to reactivate them once they have been used for a while.
What is the mechanism whereby sunlight is able to reactivate the charcoal?... |
Activated Carbon - Desorption in Sunlight? |
Activated Carbon - Desorption in sunlight? |
<p>Why do Magnesium and Lithium form *covalent* organometallic compounds? I think this question touches a more general question in chemistry: Why do some metallic elements form 'covalent' bonds at all? And the other version of this question would be why sodium or potassium does not usually form covalent bonds. The an... |
What are the advantages and disadvantages of the various types of condensers commonly found in the laboratory? Obviously more intricate pieces of glassware are more costly but assuming they are all available why would one use a Dimroth condenser vs. a Friedrichs when refluxing something? I've heard that Graham condense... |
I'm running a reaction that has ethylene gas as a byproduct. I have observed gas evolution as my reaction proceeded and I have other ways of verifying identify of the main product, but I thought it might be cool if I could also test for the presence of ethylene. Are there any simple tests I can use for this purpose? Ob... |
Can a NOESY NMR experiment be halted partway through and give meaningful results? |
Polylactic acid polymers are creating a lot of interest these days because they're biodegradable. On the downside, corn starch is often one of the starting materials...and corn is also used as a food source, so there's some [controversy][1] over the wisdom of this approach.
I think I've found a site that takes the a... |
Polylactic acid polymers are creating a lot of interest these days because they're biodegradable. On the downside, corn starch is often one of the starting materials...and corn is also used as a food source, so there's some [controversy][1] over the wisdom of this approach.
I think I've found a site that takes the a... |
[Kevlar][1] is an aramid fiber that is used in ballistics protection vests. From the structure (structure shown from Wikipedia article), you can see why it would work to dissipate the energy from a bullet since there is an extensive network of interactions between the linear chains. The wearer ends up bruised from the ... |
Ceramics in "bullet proof" vests? |
[Kevlar][1] is an aramid fiber that is used in ballistics protection vests. From the structure (structure shown from Wikipedia article), you can see why it would work to dissipate the energy from a bullet since there is an extensive network of interactions between the linear chains. The wearer ends up bruised from the ... |
I know how to measure the concentration of free thiols which is reflective of the redox potential of cellular compartment such as the cytoplasm or a lysosome.
What other methods exist? |
In the future please specify where your equation came from, justify its use and specify all of your parameters.
When only a concentration gradient is present, the diffusion coefficient, $D$, is typically described by Fick's first law of diffusion. To determine $D$ in these terms we must know the flux, $j$, and the g... |
In the future please specify where your equation came from, justify its use and specify all of your parameters.
When only a concentration gradient is present, the diffusion coefficient, $D$, is typically described by Fick's first law of diffusion. To determine $D$ in these terms we must know the flux, $j$, and the g... |
Is it possible (advisable?) to make a sealed tube by melting and twisting the end of a borosilicate test tube? One issue that I can think of is that the pressure might be too high if I then proceed to heat the tube. I thought that I could maybe connect the tube to a vacuum tube and heat it in the middle. Any experience... |
In the future please specify where your equation came from, justify its use and specify all of your parameters.
When only a concentration gradient is present, the diffusion coefficient, $D$, is typically described by Fick's first law of diffusion. To determine $D$ in these terms we must know the flux, $j$, and the g... |
You might start seeing signal if you set lb=1 (or, drastically, lb=2) and then type "wft" It won't give you a decent spectrum but you may at least see the beginnings of peaks.
Also, are you confident that this is a 1-H decoupled spectrum? If not, then your S/N is going to be very poor. |
@Mart 's comment impelled me to return to this question and correct my answer. I've deleted incorrect material and expanded the discussion to, hopefully, provide correct information. There is a good discussion (better than the reference previously cited) of the issue [here][1].
> [Reflux][2] is the process of bo... |
Possible? Doubtless. Advisable? Depends what you're sealing, I'm sure. The pressure won't be a problem though, if anything it'll be a partial vacuum inside and you'd have to heat it near the tube's melting point to get it back to atmospheric pressure. Consider that as you're heating the tube to seal it, you'll heat a ... |
@Mart 's comment impelled me to return to this question and correct my answer. I've deleted incorrect material and expanded the discussion to, hopefully, provide correct information. There is a good discussion (better than the reference previously cited) of the issue [here][1].
> [Reflux][2] is the process of bo... |
I am trying to build a system of two connected chambers, one of which is also connected to a cuvette, so I can perform a spectrometry experiment with different concentrations of KNO3 solution. In its simplest form, the cuvette and the first chamber would hold solution at the same concentration, while the second chamber... |
Do Na or Li need heat in order to react with Cl2? |
Do Na or Li need heat in order to react with Cl₂? |
From personal experience, Na(*s*) and Cl<sub>2</sub>(*g*) react at room temperature without added energy. Li(*s*) and Cl<sub>2</sub>(*g*) should do so also.
Consider the following heat of formation data harvested from [the NIST Chemistry Webbook](http://webbook.nist.gov):
For [NaCl](http://webbook.nist.gov/cgi/cb... |
Can we get Chloroquine from 7-Chloro-3-Amino quinoline by adding Cl-CHCH3-(CH2)3-N(Et)2 ? |
I've always seen benzyne (benzene with a triple bond) classified as an "intermediate". I really don't see why it needs to be an intermediate, though. The possible reasons I can come up with are flimsy:
- It has an unstable <em>sp</em><sup>2</sup>–<em>sp</em><sup>2</sup> $\pi$ bent bond: we have bent bonds with more... |
I’m looking for a public database of bond energies of biochemical compounds. Do you know about any?
Otherwise, which is the standard computational methodology to calculate them? Any references would be very appreciated.
Many thanks |
I’m looking for a public database of bond energies of biochemical compounds. Does one exist?
Otherwise, which is the standard computational methodology to calculate them? Any references would be very appreciated.
|
I need a 0.01 N solution of KIO<sub>3</sub> to use as a standard in a Winkler titration. The protocol that I am using specifies that this is 0.3567 g L<sup>-1</sup>, which I have calculated to be 0.00167 M based on 214 g mol<sup>-1</sup> for KIO<sub>3</sub>.
I like to understand the calculations in the protocols th... |
How would I calculate the Normality of a 0.00167 molar solution of $ce\{KIO3}$? |
How would I calculate the Normality of a 0.00167 molar solution of $\ce{KIO3}$? |
I need a 0.01 N solution of KIO<sub>3</sub> to use as a standard in a Winkler titration. The protocol that I am using specifies that this is 0.3567 g L<sup>-1</sup>, which I have calculated to be 0.00167 M based on 214 g mol<sup>-1</sup> for KIO<sub>3</sub>.
I like to understand the calculations in the protocols th... |
I need a 0.01 N solution of KIO<sub>3</sub> to use as a standard in a Winkler titration. The protocol that I am using specifies that this is 0.3567 g L<sup>-1</sup>, which I have calculated to be 0.00167 M based on 214 g mol<sup>-1</sup> for KIO<sub>3</sub>.
I like to understand the calculations in the protocols th... |
I need a 0.01 N solution of KIO<sub>3</sub> to use as a standard in a Winkler titration. The protocol that I am using specifies that this is 0.3567 g L<sup>-1</sup>, which I have calculated to be 0.00167 M based on 214 g mol<sup>-1</sup> for KIO<sub>3</sub>.
I like to understand the calculations in the protocols th... |
Can we get Chloroquine from 7-chloro-3-aminoquinoline by adding $\ce{CH3CHCl(CH2)3N(Et)2}$ ?
![proposed chloroquine synthesis][1]
[1]: https://i.stack.imgur.com/2TluG.png |
I have been looking all over the internet for parameters for a flourescent probe called NBD (nitrobenzoxadiazole). [Here][1] is an example of an NBD labbeld fatty.
I have so far only found parameters for AMBER or [GROMACS][2]. Also when folowing the articles from [these][3] [two][4] reviews, there seem to be no CHAR... |
I have been looking all over the internet for forcefield parameters for a fluorescent probe called NBD (nitrobenzoxadiazole). [Here][1] is an example of an NBD labeled fatty.
I have so far only found parameters for AMBER or [GROMACS][2]. Also when following the articles from [these][3] [two][4] reviews, there seem t... |
What are the advantages and disadvantages of the various types of condensers commonly found in the laboratory? Obviously more intricate pieces of glassware are more costly but assuming they are all available why would one use a Dimroth condenser vs. a Friedrichs when refluxing something? I've heard that Graham condense... |
How about Mercury and Gallium? Mercury is rather toxic, but you can buy Gallium online and it's a liquid at 85 degrees Fahrenheit - so it might work if you left it in some sunlight when you wanted the Gallium to be liquid.
If you don't plan on opening it often or need to worry about it breaking, I'd try Mercury. |
My intuition tells me that the nitrogen in the ring is more nucleophilic than the exocyclic amine. A quick-and-dirty electrostatic potential calculation using B88LYP/6-31G(d) on the PM3 geometry shows a large electron density (blue and violet) on the ring nitrogen and lower density (yellow) on the exocyclic amine:
!... |
For an upcoming exam, I have to describe the synthesis of 2-hydroxy-2-phenylacetic acid ([Mandelic acid][1]) from benzaldehyde. The provided answers describe quite a long process, consisting of 8 stages. However, I've been suggested a much simpler method, consisting of:
1. $\ce{C6H5CHO + HCN -> C6H5CH(OH)CN}$
2. ... |
Synthesizing Mandelic acid - way too simple? |
The direct reaction with HCN seems to be how the mandelic acid was synthesized in the 19th century. If you check how the reaction with sodium bisulfite is actually performed [(Organic Syntheses, Coll. Vol. 1, p.336 (1941); Vol. 6, p.58 (1926).)][1] you'll see that this is not more complicated than the direct HCN route ... |
The direct reaction with HCN seems to be how the mandelic acid was synthesized in the 19th century. If you check how the reaction with sodium bisulfite is actually performed [(Organic Syntheses, Coll. Vol. 1, p.336 (1941); Vol. 6, p.58 (1926).)][1] you'll see that this is not more complicated than the direct HCN route ... |
Any false chemical element in chemistry history? |
Any false chemical element in history of chemistry? |
I know that perchloric acid could be potentially explosive and some organic solvents could form dangerous peroxides.
I am going to do an electrodeposition in diethyleneglycol solution containing NH4Cl, ZnCl2 and FeCl2. Since in my case there are all elements to form HClO4 and I am going to heat everything up to 60 ... |
Is there any danger of forming explosive reaction products during the electrodeposition in Diethylene glycol? |
I know that perchloric acid could be potentially explosive and some organic solvents could form dangerous peroxides.
I am going to do an electrodeposition in diethyleneglycol solution containing $\ce{NH4Cl}$, $\ce{ZnCl2}$ and $\ce{FeCl2}$. Since in my case there are all elements to form $\ce{HClO4}$ and I am going ... |
I recently was told that once you find a good solvent mixture for separation on TLC, you should only use 10% of the more polar solvent (for silica) when you run your column. I tried it and it worked great! Since I'd never heard that before, is that a standard rule of thumb, or did I just get lucky? |
How to translate mobile phase from TLC to column? |
I recently was told that once you find a good solvent mixture for separation on Thin Layer Chromatography, you should only use 10% of the more polar solvent (for silica) when you run your column. I tried it and it worked great!
Since I'd never heard that before, is that a standard rule of thumb, or did I just get... |
How to translate mobile phase from Thin Layer Chromatography to column? |
When looking at a Diopside-Hedenbergite solid solution. What is the difference between an ionic and molecular activity model? Why does the moleclar model yield higher values? |
What is the difference between an ionic and molecular activity model? (Example: Diopside-Hedenbergite) |
I'm an electrical engineering and I hope you can give me some advice as I'm not much into the chem field.
I'm trying to start making my PCB (Printed Circuit Board) at home but I'd like to have some advice concerning how to handle and where to store these (potentially dangerous) chemicals.
I need NaOH as a developer... |
I'm an electrical engineering and I hope you can give me some advice as I'm not much into the chem field.
I'm trying to start making my PCB (Printed Circuit Board) at home but I'd like to have some advice concerning how to handle and where to store these (potentially dangerous) chemicals.
I need NaOH as a developer... |
I'm an electrical engineering and I hope you can give me some advice as I'm not much into chemistry.
I'm trying to start making my PCB (Printed Circuit Board) at home but I'd like to have some advice concerning how to handle and where to store these (potentially dangerous) chemicals.
I need NaOH as a developer, hyd... |
I'm working with some very basic free-radical initiated polymerization reactions. For the most part, I just follow a recipe I'm given (by a member of my group or the broader literature), it works, and I don't worry too much about the chemistry of why it works. Clearly, that will only work for so long, and I'd like to b... |
Are there any general rules for choosing initiators for a polymerization reaction? |
I'm posting a link to the theory behind BET: http://en.wikipedia.org/wiki/BET_theory. This theory is comprehensible My question is more geared towards what is physically and chemically happening within a BET device to get a reading? How does a BET device actually go about measuring the physisoprtion or chemisorpti... |
How does a BET device function? |
This is the [theory behind BET](http://en.wikipedia.org/wiki/BET_theory). The theory is comprehensible
My question is more geared towards what is physically and chemically happening within a BET device to get a reading? How does a BET device actually go about measuring the physisoprtion or chemisorption of a ma... |
I know that when dissolved in water, hydrogen halides (H-X), become acids. I know that HF forms a weak acid, but can it be generalized that all HX acids do so? |
Do hydrogen halides (HX) form strong or weak acids? |
If 1 mole means $6.02 \times 10^{23}$ entities, then why can't this mole concept be used for real life metric systems?
For example, instead of stating that there is $6.02 \times 10^{23}$ people, we can say there is 1 mole of people or 1 mole of TV sets, etc. |
Why shouldn't we use the mole concept in real life metric systems? |
In chemistry, the unit "mole" is used in many places, and is an important tool when working with quantities.
I have not seen it used elsewhere--for example, we never count people or TVs with the unit.
What makes the mole so useful in chemistry, and why isn't it used elsewhere? |
The mole is used extensively in chemistry, why not elsewhere? |
Borax, $\small\ce{Na2B4O7}$, is often marketed as a "laundry booster" under the brand "20 Mule Team Borax".
![enter image description here][1]
Other laundry products in the past have added [Sodium perborate](http://en.wikipedia.org/wiki/Sodium_perborate) (which can be produced from borax, hydrogen peroxide, and s... |
Does borax do anything more for "boosting" detergent than adding active oxygen would? |
Borax, $\small\ce{Na2B4O7}$, is often marketed as a "laundry booster" under the brand "20 Mule Team Borax". The unit crystal of borax can be seen below.
![enter image description here][1]
Other laundry products in the past have added [Sodium perborate](http://en.wikipedia.org/wiki/Sodium_perborate) (which can be... |
My symmetry lecture notes state that there are seven high-symmetry 3D point groups, which have more than one rotation axis of order greater than 2: $T$, $T_d$, $T_h$, $O$, $O_h$, $I$, $I_h$. I sometimes see them called the “cubic point groups”.
My point is: most molecules (or molecular fragments) I have encoutered i... |
Are all cubic point groups encountered? |
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