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6
votes
1answer
143 views

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 $\...
18
votes
3answers
849 views

Any false chemical element in history of chemistry?

Was there any false chemical element introduced in history of chemistry? I mean a substance that after a while proved that it was not an element.
14
votes
1answer
5k views

Synthesis of mandelic acid from benzaldehyde

For an upcoming exam, I have to describe the synthesis of 2-hydroxy-2-phenylacetic acid (mandelic acid) from benzaldehyde. The provided answers describe quite a long process, consisting of 8 stages. ...
0
votes
0answers
474 views

Basic chemistry equation with ammonia [closed]

A table in the book 'Chemistry NCEA Level 1' has 4 headings, the first of which is 'Volume (mL) ammonia solution provided (conc 2 g L-1)' Could someone please provide a comprehensive explanation of ...
16
votes
2answers
4k views

Liquid which neither dissolves in water nor oil

I am looking for a liquid which is not miscible (or very close) with water or vegetable oil. Ideally, I want to have a container which shows three layers (the three liquids) with clear boundary ...
7
votes
1answer
221 views

CHARMM parameter files for NBD (nitrobenzoxadiazole)

I have been looking all over the internet for forcefield parameters for a fluorescent probe called NBD (nitrobenzoxadiazole). Here is an example of an NBD labeled fatty. I have so far only found ...
5
votes
1answer
3k views

How would I calculate the Normality of a 0.00167 molar solution of KIO₃?

I need a 0.01 N solution of $\ce{KIO3}$ to use as a standard in a Winkler titration. The protocol that I am using specifies that this is 0.3567 g L-1, which I have calculated to be 0.00167 M based on ...
5
votes
1answer
2k views

Bond energies database

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 ...
6
votes
3answers
12k views

Synthesis of chloroquine from 4-amino-7-chloroquinoline

Can we get chloroquine from 4-amino-7-chloroquinoline (7-chloroquinolin-4-amine) by adding 4-chloro-N,N-diethylpentan-1-amine $(\ce{CH3CHCl(CH2)3N(Et)2})$ ?
5
votes
1answer
125 views

Do Na or Li need heat in order to react with Cl₂?

I've read how putting a burning piece of sodium in chlorine would produce white $\ce{NaCl}$ fumes. However, I can't find out whether Na or Li can react with $\ce{Cl2}$ without heating or burning.
9
votes
3answers
634 views

MacGyvering a sealed tube

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 ...
14
votes
1answer
4k views

Ceramics in “bullet proof” vests?

Kevlar 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 ...
8
votes
1answer
191 views

How to characterize gaseous ethylene that forms as byproduct?

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 the identity of the main product, but I thought ...
38
votes
5answers
60k views

Choosing the right condenser

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 ...
13
votes
1answer
8k views

Activated Carbon - Desorption in sunlight?

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 ...
15
votes
2answers
30k views

Why is nitric acid such a strong oxidizing agent?

In my teaching-lab experiments 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 ...
7
votes
1answer
1k views

What is the behavior of a Zwitterion during ion exchange chromatography?

We're interested in purifying a protein that has an azide moiety using ion exchange chromatography. Due to its unique structure, the moiety is a Zwitterion with a novel chemical behavior. My question ...
5
votes
1answer
19k views

The Chemistry behind creating Polylactic Acid (PLA)

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 + ...
77
votes
4answers
37k views

Bonding in diatomic C2, a carbon-carbon quadruple bond?

Carbon is well known to form single, double, and triple $\ce{C-C}$ bonds in compounds. There is a recent report (2012) that carbon forms a quadruple bond in diatomic carbon, $\ce{C2}$. The excerpt ...
26
votes
2answers
2k views

How should I go about picking a functional for DFT calculations?

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 ...
51
votes
1answer
1k views

How can I update a map/mesh and coordinates in a PyMol session file?

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 ...
27
votes
2answers
1k views

What is antisymmetric exchange? What is J-strain? Where does it come from?

I'm reading a paper1 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 ...
21
votes
3answers
11k views

Why does meltwater taste different?

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 ...
7
votes
1answer
1k views

Why is a metabisulfite / starch / HCl solution unstable?

In one variation of the iodine clock demonstration, you add two colorless solutions together and apparently nothing happens. After about 30 seconds to a minute, you get an "instantaneous" change to a ...
8
votes
1answer
1k views

How to calculate the equilibration time of two connected chambers of salt solution, initially at different concentrations?

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 $\ce{KNO3}$ solution. ...
31
votes
2answers
155k views

What do the different grades of chemicals mean?

When purchasing chemicals from Sigma, Fisher, or wherever, there are often -grade's attached to their description like reagent-grade, technical-grade, analytical-grade, or more niche-sounding biotech-...
21
votes
2answers
7k views

Chemical compounds responsible for the colors in flowers?

I know that anthocyanins are a class of compounds responsible for the purple colors found in flower petals. Anthocyanins (also anthocyans; from Greek: ἀνθός (anthos) = flower + κυανός (kyanos) = ...
6
votes
1answer
9k views

What is the order of stability of the resonance structures of furan?

I want to know which are the most stable furan resonance structures. I know that structure number 1 is the most stable, but which one comes after?
9
votes
1answer
162 views

Can a NOESY NMR experiment be halted partway through and give meaningful results?

Some NMR experiments can be halted partway through the acquisition and still give perfectly valid results: The traditional 1H experiment for example. Others, like a Saturation Transfer Difference ...
16
votes
1answer
13k views

When we heat a borax crystal, why does it first expand and then contract?

In the borax bead test, we take a crystal of borax and then heat it. A small loop is made in the end of a platinum or nichrome wire (as used in the flame test) and heated in a Bunsen flame until ...
7
votes
1answer
237 views

Why is it so difficult to create mock NMR spectra of macromolecules?

From what I understand, if you have a NMR spectra, you can determine the structure of a macromolecule but it is very difficult to determine what the NMR spectra of an expected structure would look ...
9
votes
3answers
3k views

13C NMR spectrum only showing solvent

This is my first time taking a $\ce{{}^{13}C-NMR}$ spectrum and while I'm aware the signal to noise ratio is much lower compared to $\ce{{}^{1}H-NMR}$, I didn't realize it was quite this bad. I took a ...
7
votes
4answers
4k views

Is the order of orientation of electron box diagrams meaningful or arbitrary?

Here is my interpretation when asked to: By drawing arrows in the appropriate boxes, complete the outer electron structures for Cu and Cu2+ I had no problem in drawing out the electron structure, ...
50
votes
1answer
10k views

Why does menthol (e.g. peppermint) feel cool to the tongue?

Especially when drinking water after the fact, mint can give a sharp cold sensation inside one's mouth. What process causes the sensation to occur?
23
votes
1answer
40k views

How does adding lemon juice to sugar make better caramel?

It's a common cooking advice: if you want a somewhat softer caramel, add some lemon juice to the sugar: To help prevent the caramel from crystallizing, you can add an acid to the sugar before you ...
22
votes
3answers
9k views

What open-source software can produce 3D PDF representation of molecules?

Most of the existing software I know (like VMD or Pymol) say that they can be used to create PDF files with 3D representations of molecules: actual 3D models, which you can rotate inside the Adobe ...
7
votes
2answers
474 views

Regenerating the imaginary data of a 2D NMR spectrum with a hilbert transform

2D spectrum take up a large amount of hard disk space. At my last lab it was standard practice to delete the imaginary portions of the spectrum with xfb n (We used ...
19
votes
2answers
4k views

What is a rigorous definition of gas volume, and how is the Van der Waals equation derived?

I am confused about the justification for the corrections to the ideal gas law in the Van der Waals equation: $$p=\frac{nRT}{V-nb}-a\left(\frac{n}{V}\right)^2$$ I understand that the equation ...
7
votes
1answer
5k views

Hanging a spoon on the face

Well, I have seen many comical acts where people balance a spoon (or a fork) on different parts of the face like on the tip of the nose, forehead etc. The do this by blowing moist air (see below) and ...
8
votes
2answers
4k views

How do copper sulphate and the like change crystal structure on adding water of hydration?

Copper sulphate, in its hydrated form, is crystalline, whereas the anhydrous form is amorphous. Gypsum has a similar story-- on heating the crystalline dihydrate we get an amorphous hemihydrate. (...
23
votes
1answer
5k views

How does oobleck work?

Oobleck is basically a mixture of cornstarch and water. It has the interesting property of going hard when pressure is applied. For example, it feels like a liquid when you swirl your fingers through ...
8
votes
1answer
10k views

What organic solvents are suitable to use with potassium permanganate?

I'm attempting to oxidize a substance with potassium permanganate and I was wondering what organic solvents I have at my disposal. The compound is soluble in chloroform and ethanol, but obviously ...
27
votes
2answers
2k views

What does this lambda–sigma notation mean?

I am currently reading the CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data by John C. Tebby (CRC Press, 1991) and on several figures (ex. pages 9 to 14) there is a caption that reads ...
39
votes
2answers
8k views

Why is arsenous acid denoted H3AsO3?

Inspired by this question, I'm wondering why arsenous acid is frequently denoted $\ce{H3AsO3}$, as opposed to $\ce{As(OH)3}$, which would appear to more accurately reflect its connectivity? [edit] I ...
17
votes
2answers
251 views

Rock that transfers image

This is a question that has been bugging me for over 15 years! In high school while studying elements our teacher showed us a clear white rock or element. It was simply flat on both sides but when ...
12
votes
3answers
105k views

How do I calculate the degree of dissociation in equilibrium?

In my textbook, for calculating the percentage dissociation of $\ce{HF}$ for the given equation: $$\ce{HF + H2O <=> H3O+ + F-}$$ The solution is: Initial Concentrations $$[\ce{HF}] = 0.08~\...
8
votes
1answer
477 views

What is the timescale of disulfide bond formation?

What is the timescale of disulfide bond formation in a given protein? What influences it? Finally, how does one actually measure it? From what I understand, the reduction and oxidation of bonds ...
19
votes
1answer
27k views

What are the differences between the HMQC and HSQC experiments?

This afternoon, I was having some trouble with an HSQC (Heteronuclear Single Quantum Coherence Spectroscopy) spectrum I was trying to acquire, and the spectroscopist recommended I try HMQC (...
19
votes
3answers
3k views

Choice of doping elements in semiconductors

In a typical semiconducting material, we start with silicon (group IV) and introduce atoms of group V or group III depending on whether we are constructing an n- or p-type semiconductor respectively. ...
9
votes
3answers
4k views

What causes the DNA fragments to stop moving in gel electrophoresis?

I'm currently studying VCE BioChemistry, and we're studying the separation of DNA strings of different lengths via gel electrophoresis. (This involves having 'clumps' of DNA at one end of a gel ...

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