All Questions

18
votes
1answer
1k views

What dictates the lifetime of a solvated electron in a given solvent?

Solvated electrons have a long lifetime in ammonia solutions, but their counterparts in water (called hydrated electrons) have a much smaller lifetime, of the order of microseconds in very pure water. ...
8
votes
1answer
109 views

Where do I find datasheets of zeolites?

I'm looking into uses of zeolites as water absorbers for heat storage and absorbtion cooling. However, I don't find hard numbers on the likes of absorption enthalpies at different temperatures, ...
6
votes
2answers
898 views

Z-matrix of a series of 5 colinear atoms

How can I write a Z-matrix for the following complex? O==C==O H--O \ H I have managed to write: ...
14
votes
1answer
126 views

Is there a theory behind selecting elements that may be successful in potential superconductors?

Looking at something like $\ce{YBa2Cu3O7}$ which was one of the first cuprate superconductors to be discovered, I'm always curious how the selection of these substances as likely superconductors comes ...
17
votes
1answer
3k views

Definitions of autocatalysis

Is there a formal definition or algorithm that can take a list of reactions and tell me whether it contains a set of species that can produce itself autocatalytically? It is clear that the following ...
10
votes
2answers
7k views

Gas chromatography/mass spectrometry: Can I use peak ratios and molecular mass to derive quantity?

Can derive the quantity of a substance from a GC/MS report if I know: the ratio to another substance in the data, the quantity of that second substance, and the molecular mass of both substances. ...
6
votes
2answers
141 views

Is a 2-D periodic structure isomorphic with the surface of a torus, a sphere, neither or both?

When I was reading through the ADF-BAND tutorials, one of the toy systems presented was a 1-D periodic structure involving 3 collinear hydrogen atoms. The tutorial pointed out that, topologically ...
22
votes
3answers
1k views

What is natural bond orbital theory used for?

My understanding is that the NBO methodology transforms the molecular orbital picture of a molecule into a collection of pairwise interactions (bond orbitals). This is obviously handy for didactic and ...
11
votes
3answers
2k views

Experimental calculation of solubility product constant

In order to calculate the $K_\mathrm{sp}$ of lead(II) iodide, I mixed $\pu{6.0 mL}$ of $\pu{0.01 M}$ $\ce{Pb(NO3)2}$, $\pu{6.0 mL}$ of $\pu{0.02 M}$ $\ce{KI}$, and $\pu{8.0 mL}$ of water, and a ...
15
votes
1answer
384 views

How does conductivity work for non-redoxed ions?

Related (very similar, but here I want a mechanism) https://physics.stackexchange.com/q/21827/7433 By the Kohlrausch law, all ions contribute to the conductivity of an electrolyte. Now, as I ...
11
votes
1answer
1k views

Are Pulay forces expensive to compute?

In a thesis I am reading, it is said that one of the reasons for using plane-wave basis sets for first-principles molecular dynamics (aka ab initio MD) is that the Pulay forces[1,2] that arise from an ...
21
votes
1answer
3k views

Why do thiols have such a propensity for bonding with mercury?

Historically, thiols $\ce{-SH}$ were known as "mercapto-" due to their strong propensity to bond with mercury. Certain drugs still carry this designation, though mercaptopurine has an $\ce{=S}$ group ...
12
votes
2answers
16k views

What are the major factors that influence LogP

The partition coefficient is a very useful metric in characterizing compounds particularly drugs. What chemical properties influence that partitioning? Are chemical moieties additive in their LogP? ...
9
votes
1answer
1k views

Effect of periodic acid on cyclohexane derivatives

Periodic acid (per-iodic acid, $\ce{HIO4}$ ) cleaves vicinal diols(to carbonyls) via a cyclic intermediate. Due to the cyclic intermediate, it needs a syn configuration for the $\ce{-OH}$ groups for ...
28
votes
3answers
791 views

What's a minimal yet chemically-meaningful kinetic system for an oscillating reaction?

Oscillating reactions are a funny aspect of chemistry. I have tried to find various simplified kinetic models of oscillating reactions such as the Belouzov-Zhabotinsky, the Briggs–Rauscher or the Bray–...
16
votes
1answer
1k views

Why does the sulfone ring in tazobactam open when the lactam is hydrolyzed?

One of the drugs I work with is a beta-lactam (4-membered ring with an amide bond) fused to a sulfone ring, tazobactam. It's relatively stable in water; the lactam is not significantly hydrolyzed ...
25
votes
3answers
4k views

How to identify zero order reactions?

I have come across many reactions that are zero order reactions but at one glance I'm unable to tell if they are zero order or not. Is there any criteria that can be used to identify these reactions ...
9
votes
1answer
2k views

What's the chemical nature of a dishwasher's rinsing agent?

It seems that a rinsing agent helps the dishes in the dishwasher dry much better than they do without it (which I recently noted on my new dishwasher). What molecules are used in the composition of ...
25
votes
2answers
3k views

What makes diazo compounds so unstable and explosive?

I once had an Orgo TA refer to a diazo compound as "diazo-boom-boom" (the technical term). I have always been curious as to the reason behind the instability and reactivity. According to Wikipedia ...
18
votes
2answers
2k views

What factors are important for quantitative analysis of a proton 1D-NMR spectrum?

Besides elucidating or verifying a chemical structure, NMR can also be used e.g. for quantifying a mixture of different chemicals. Depending on the quality of the spectrum and the specific substance,...
2
votes
2answers
382 views

A Chemdrawing software? [duplicate]

I would like to know about a Chemdrawing sotware for 2-d molecular structures. it should be mainly linux based (but if it supports other OS's then that would be great)
12
votes
3answers
6k views

How can we synthesize para-nitrophenol

During nitration of phenol, both para- and ortho-nitrophenols will be formed. Is there any way in which we can synthesize para-nitrophenol only?
7
votes
1answer
734 views

Brittle d-block metal trend

I remember seeing a periodic table that had the top-left corner of the d-block shaded and marked as "brittle". If I recall correctly, the elements were $\ce{Sc,Ti,V,Cr,Mn,Y,Zr,Nb,La}$. I think (sorry, ...
18
votes
2answers
8k views

How do I determine the absolute configuration experimentally?

Let's say I synthesized or isolated a chiral molecule and want to know the absolute configuration (R or S) of that molecule. I could obviously solve the structure by X-Ray crystallography, but that's ...
23
votes
3answers
1k views

Symmetry lost in orbitals?

I've always thought that orbitals lead to a loss of symmetry, and have never been able to give myself a satisfactory answer to this. I'll explain via an example: Let's take an $\ce{N^3+}$ atom. It's ...
21
votes
3answers
643 views

Non-integer hybridization

I've known that hybridization in distorted geometries is not exactly $sp^3$ or $sp^2$ or whatever. For example, $\ce{PH3}$ has nearly pure $p$ orbitals in the $\ce{P-H}$ bond, and the lone pair is in ...
13
votes
1answer
209 views

What is the geometric configuration of the four fluorine atoms during the synthesis of xenon tetrafluoride?

Neil Bartlett (1932–2008) first synthesized $\ce{XeF4}$ (and $\ce{XeF6}$) in 1962. In the synthesis, a nickel chamber is used, and heated to 400°C, causing the formation of $\ce{NiF4}$, which ...
18
votes
4answers
20k views

What is the difference between physical and chemical bonds?

If you characterize the chemical bonds to two categories physical and chemical bonds, how do you do it? Aren't all bonds chemical and physical? From the freedictionary.com, chemical bond: Any of ...
9
votes
6answers
3k views

A quick method for separating liquids?

I'm looking for a way to take 3 separate liquids (liquids which function as paint -- they will all be different colors), put them together into a container, and then rapidly separate them back to ...
44
votes
2answers
25k views

What makes banana bonds possible in diborane?

Diborane has the interesting property of having two 3-centered bonds that are each held together by only 2 electrons (see the diagram below, from Wikipedia). These are known as "banana bonds." I'm ...
14
votes
1answer
3k views

What is the meaning of the '2' on some Compressed Gas Hazard signs in the lab?

The main chemistry prep room at my institution (and also at the ambulance station) is labelled with the standard green compressed gas sign. However, there is a small '2' included within the diamond. ...
12
votes
4answers
54k views

General rules for deciding volatility

Given an organic compound, is there any way to decide if it is volatile (or compare volatility--everything is volatile in the end)? Volatility is due to the tendency to evaporate. The conclusion I ...
4
votes
1answer
10k views

What is the difference between cross-linked bond and secondary bond in polymers?

In solid materials, there are two kinds of bonds between polymers: primary and secondary. Primary bonds can be also called cross-linked bonds. What is the difference between the two (strength, type, ...
26
votes
3answers
2k views

What benefits do higher-rated NMR tubes provide?

You can buy NMR tubes in a huge variety of qualities, with an equally huge difference in price between the cheapest and the most expensive NMR tubes. They are usually rated for a specific spectrometer ...
12
votes
2answers
2k views

Why is benzyne an intermediate?

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:...
13
votes
1answer
2k views

Living-cationic vs cationic polymerization

To my understanding, cationic polymerization is a type of living polymerization but my teacher's notes and Wikipedia seem to suggest they're different. I can't see the difference. The same goes for ...
12
votes
1answer
683 views

How is the electron “trapped in the crystal” in irradiated NaCl?

Pennsylvania State University provides irradiated $\ce{NaCl}$ (180,000 rads of gamma radiation) to teachers for a very entertaining demonstration. The salt is orange after irradiation. When it is ...
24
votes
2answers
4k views

Pros and cons of Cartesian vs. Z-matrix representations of molecules?

Over the course of my studies, I have switched largely from using Z-matrix representations of molecular geometries in calculations to Cartesian representations. The software that I use now makes it ...
13
votes
2answers
403 views

Is aqueous medium necessary for complex formation? if so, why?

If dry ammonia gas is passed through anhydrous copper sulfate, will it turn blue (due to the formation of tetraamminecopper(II) complex)? Or will silver chloride form diamminesilver(I) complex in ...
22
votes
2answers
65k views

Why do different substances have different boiling points?

For example, why does for example oxygen turn into gas at a much lower temperature than water? Does it have anything to do with the molecular structure? A water molecule does have a more complex ...
20
votes
2answers
11k views

Why is distillation not a viable way to seperate ammonia from water?

Since the steam pressure of ammonia is higher than that of water, I would expect distillation to be a reasonable way of seperating a mixture of both. However, in industrial applications known to me ...
13
votes
1answer
287 views

Are buckminsterfullerene-corannulene complexes actually stabilised by π stacking?

According to wikipedia and the references given therein, $\pi\cdots\pi$ stacking interactions are the result of interaction between the quadrupole moments of two aromatic rings, rationalising the ...
20
votes
3answers
4k views

What makes an epoxide stable?

Overall ring strain seems to be a big issue when it comes to organic chemistry. That is why cyclopentane may be in an "envelope form" or why cyclobutane may be in a kinked, kite form. Both of these ...
27
votes
1answer
9k views

Why are there two Hydrogen atoms on some periodic tables?

Most periodic tables only feature one Hydrogen atom, on the top of the first group. But some, like the one I was given, also show Hydrogen in the 7th group, to left of Helium. Why are there two ...
22
votes
3answers
31k views

Are there any major exceptions when comparing electron affinity?

I was tasked with figuring out whether carbon or nitrogen has a more negative electron affinity value. I initially picked nitrogen, just because nitrogen has a higher $Z_\mathrm{eff}$, creating a ...
8
votes
3answers
5k views

Availabilty of magnesium ions in phosphate buffer

Phosphate buffer is a common buffer in biological applications, it's especially popular for NMR. Magnesium ions are necessary for many biological systems to work, though the amount of magnesium ions ...
9
votes
1answer
250 views

Why is it that the bigger the side-chain is, its hydrogen atoms tend to be more equatorial?

The most stable cyclohexane form is the chair conformation but on the other hand, the bigger the side-chain of the cyclohexane is, its hydrogen atoms become more equatorial rather than axial, which ...
25
votes
2answers
48k views

How do you separate enantiomers?

There are some stereochemical reactions that result in the presence of enantiomers. When moving forward with a practical organic synthesis, how does one usually separate them in order to continue with ...
73
votes
7answers
103k views

Why is the 2s orbital lower in energy than the 2p orbital when the electrons in 2s are usually farther from the nucleus?

My chemistry book explains that even though electrons in the 2p orbital are closer to the nucleus on average, electrons from the 2s orbital spend a very short time very close to the nucleus (...
59
votes
4answers
26k views

Why do elements in columns 6 and 11 assume 'abnormal' electron configurations?

When I look around for why copper and chromium only have one electron in their outermost s orbital and 5/10 in their outermost d orbital, I'm bombarded with the fact that they are more stable with a ...

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