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28
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What are t2g and eg in CFT?
In the crystal field theory (CFT), when the splitting of the d-orbital occurs, it gets divided into two parts.
The upper part with higher energy is the $\mathrm{e_g}$ and the lower part with lower energy is called the $\mathrm{t_{2g}}$ as in:
So…
NeilRoy
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How many molecules does it take to have a phase?
A single molecule can't be solid, liquid or gas. It's just a molecule. A mole of something can be any of the three. So, how many molecules does it take for phases to be meaningful?
I realize that this may depend on the molecules in question. The…
terdon
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28
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How do quantum software packages Work?
If one wants to calculate a moderate size Alkane (with say 10-15 carbons, assuming 100 electrons, with Restricted Hartree Fock based methods) we can simply say that the electron-electron part will be $100^4 = 100$ million integrals. If we remove the…
Aug
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Rationalising the order of reactivity of carbonyl compounds towards nucleophiles
This is immediately following ron's answer from Why is a ketone more nucleophilic than an ester?
One of the most simplest questions you can ask, how can you rationalise the order of reactivity towards nucleophiles, which is given as
acyl halide >…
Martin - マーチン
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28
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The importance of the cold chain in the food and the pharmaceutical industry
There are these everyday things that one should know as a scientist and especially as a chemist, but which never come to light in an academic curriculum — at least not in mine.
One such thing is the purpose of imperative non-disruption of the cold…
Sam
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Why isn't the American nickel magnetic?
I never thought that modern American nickels actually contained nickel anymore. However, according to this wiki article, the coins actually do contain 25% nickel, the rest being copper. And yet, no US coin produced today is officially magnetic. Why…
mpprogram6771
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When a candle burns, why does the top of wick glow if bottom of flame is hottest?
Totally an elementary question.
Staring at a candle, it appears that the bottom of the wick is dark whereas the top glows. However the bottom of the flame (the blue) is the hottest.
Is the reason for this that the concentration of liquid wax is…
ZAR
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The order of aromaticity of benzene, thiophene, pyrrole, furan, and pyridine
I have been taught that the order of aromaticity is: benzene > thiophene > pyrrole > furan. However, I have been unable to deduce any logical explanation for that order. Also, I wish to compare pyridine's aromaticity with these, but my professor…
Gaurang Tandon
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Electrophilic Aromatic Substitution: Are protonated OH-groups ortho-/para- or meta-directing?
In Electrophilic Aromatic Substitution ($\text{S}_{\text{E}}\text{Ar}$) reactions groups that can donate an electron pair into the aromatic ring, e.g. $\ce{-OH}$ or $\ce{-NH2}$, are ortho-/para-directing.
In the case of $\ce{-NH2}$-groups one has…
Philipp
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Products of Reimer–Tiemann reaction of 4-methylphenol
p-cresol (4-methylphenol), undergoes the Reimer–Tiemann reaction upon treatment with chloroform ($\ce{CHCl3}$) in alkaline medium. Which of the following is the major and minor product?
A. 2-hydroxy-5-methylbenzene-1,3-dicarbaldehyde
B.…
stochastic13
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27
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Why does mercury decolourise a gold ring?
I saw that a gold ring decolourised as it got in contact with mercury .
Why does this happen ? Is there any way to reverse this?
Chitra Lekha
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27
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Is the t-butyl carbocation more stable than the benzyl carbocation?
Various authors have different views regarding stability order of the benzyl and t-butyl carbocations.
$$\ce{PhCH2+ ; (CH3)3C+}$$
In my opinion, resonance effect dominates, so the benzylic carbocation should be more stable. But in the other case,…
Arvind Tiwari
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Why does water evaporate at room temperature?
When water temperature reaches $100\ ^\circ \mathrm{C}$, the molecules get so excited that the hydrogen atoms lose the bonds to the oxygen atom and therefore the water starts to become gas. I get that, but at room temperature ($23\ ^\circ…
nFu9DT
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While filling electrons, we follow Aufbau principle, but not while removing them. Why is this so?
I recently came across a question Why is the vanadium(3+) ion paramagnetic?, where the asker is wondering how $\ce{V^{3+}}$ is paramagnetic (he used Aufbau in reverse to remove the electrons), while the correct answerer to that question remarked…
Pritt says Reinstate Monica
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Is hybridization used in ab initio valence bond calculation?
Many general chemistry textbooks introduced the concept "hybridization" to construct a symmetry-adapted VB-type wavefunction. In the textbooks, usually the minimal basis is used and without optimizing all resonance forms.
My question is, in the ab…
user26143
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