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What is resonance, and are resonance structures real?
This answer is intended to clear up some misconceptions about resonance which have come up many times on this site.
Resonance is a part of valence bond theory which is used to describe delocalised ...
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Does benzene structure stand for a single resonance form or the whole molecule?
The answer is you are referring to neither of them. That is because resonance structures don't actually exist in reality. We only use them to give us a rough idea what the actually molecule and bonds ...
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Do non-classical carbanions exist?
Interesting question. It is much less studied and reported on than the case of non-classical carbocations, but I did find a few papers. Brown and Occolowitz (Ref.1) reported that deuterated bicyclo[3....
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Why are the C-C bonds in benzene closer in length to double bonds than single bonds?
one might expect that the bond lengths would be exactly intermediate between a single and a double bond
They actually are. The relevant reference structure, that can provide us lengths of single and ...
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Stability Comparison between the Tropylium and Tricyclopropylcarbinyl Carbocation
It seems likely that the tricyclopropylcarbinyl carbocation would be more stable than the tropylium carbocation for the reasons I'll outline below, but if you have a reference proving this point, it ...
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Why are the C-C bonds in benzene closer in length to double bonds than single bonds?
Why should they be bang in the middle? Or to better phrase the question: What reasoning are you applying to assume an averaged bond length?
Bonds don’t work as we laymen like to write them, with ...
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Do non-classical carbanions exist?
In addition to the species mentioned in the answer above, I found another one in Organic Chemistry by Morrison and Boyd(Seventh Edition)
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Trying to understand the statement: 'Resonance is not a flickering between the contributing states. '
When it comes to resonance, you should not take the notion of superposition of different states literally. Feynman mentioned it explicitly right from the get go, just read carefully what he says:
...
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What is resonance, and are resonance structures real?
Bon has a very nice example of motion potentially restricted because of a barrier, and although it turns out that this is not the case for the norbornyl cation, there are simpler examples that do show ...
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Which carbons in pyrrole have the highest electron density?
Interesting question, more subtle than I realized!
Theoretical approach: I would turn to resonance and induction as the rationale for electronic properties. I think all of your resonance forms may ...
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Which is the most acidic hydrogen in vitamin C
The correct anion is stabilized by the mighty resonance.
That's about it.
Hydrogen bonding is irrelevant, since it affects both variants the same way.
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Why is meta-nitrophenol less acidic than para-nitrophenol?
The acidity of nitrophenols (or any acid for that matter) is determined by the stability of the conjugate base. In the case of m-nitrophenol and p-nitrophenol, the relative stability can be determined ...
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What is the reason for the exceptional stability of tricyclopropyl-cyclopropenyl carbocation?
Questions like these always appear simple, when in fact they are not. First of all it has to be clear that stability is no absolute concept. In this case one could ask which of the cations is most ...
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Which is the most acidic hydrogen in vitamin C
Compare the $\ce{OH}$ bonds in Vitamin C (ascorbic acid) and decide which one is the most acidic. The most acidic proton in ascorbic acid is the one whose conjugate base is most resonance ...
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What is the most "important" resonance structure of SCN⁻?
I performed a quick calculation on the DF-BP86/def2-SVP level of theory and analysed it with Natural Resonance Theory (from the Natural Bond Orbital Theory).
This results in the following major ...
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What is a sigma complex?
Yes, it's anionic sigma complex, more precisely Meisenheimer complex. They are much more stable then arenium ions (Wheland intermediates) and can be isolated much more easily.
There was actually ...
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Which carbons in pyrrole have the highest electron density?
That is really not a fair question and even with a computational approach the differences are more or less marginal. The approach by electron pusher is certainly the way to go, and here is the ...
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Why is carbonic acid a weaker acid than acetic acid?
Before you ask "why", ask "if".
Carbonic acid is not weaker than acetic. In fact, it is stronger, just as one might expect by looking at that extra electron-withdrawing substituent. The trouble is, ...
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Natural Bond Orbital analysis: Significance of stabilization energy determined by 2nd order perturbation
TL;DR: Lewis $\to$ Non-Lewis $\mathbf{E(2)}$ values have no direct physical significance, are intrinsically un-measurable, and serve only to quantify the extent to which the "real" wavefunction for a ...
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Difference between Resonance Effect and Mesomeric Effect
The IUPAC gold book (IUPAC are the organisation which 'define' standards for things such as chemical nomenclature) describes them as being essentially synonymous. The following definitions are given (...
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Participation of Pi-bonds and lone pairs in resonance
You have probably misunderstood what the sentence actually means.
It means that only one, either $\pi$ bond or lone pair will participate in resonance if the atom has both.
For example, in pyridine,...
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Is 2-oxobicyclo[2.2.1]heptan-1-ide resonance stabilized?
The reason for this is, as Buttonwood suggested, the strain induced by the bicyclic norbonyl system. I already hinted in the comments that the anion is in a $\ce{sp^3}$ type orbital. What makes it ...
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How are the hybrid orbitals of sulfur hexafluoride shaped?
If you limit consideration to hybridization of atomic orbitals, a good reference to see is On the role of d orbitals in sulfur hexafluoride J. Am. Chem. Soc., 1986, 108 (13), pp 3586–3593.
First, it ...
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Which is the most acidic proton of (3Z)-3-ethylidenecyclopent-1-ene-1-carbaldehyde?
If you draw curly arrows for the deprotonations, it becomes clear that only the pathway in green is productive due to the ability to form an extended enolate.
If you deprotonated the green protons, ...
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Why is the compound 3,4-dihydroxy-3-cyclobutene-1,2-dione more acidic than acetic acid?
This molecule is commonly known as Squaric acid. The Wikipedia entry gives the possible resonance structures of the conjugate base (added here for convenience):
You can see that there are four ...
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Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine?
The reason for the decreased basicity is essentially the ortho-effect as outlined here: Ortho-effect in substituted aromatic acids and bases.
Your question on the other hand asks about a seeming ...
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Inductive effect of phenyl ring
As the $\mathrm{s}$ characteristic of an atom increases, so too does its electronegativity. Proof of this can be seen when comparing the $\mathrm{p}K_\mathrm{a}$'s of 2-carbon hydrocarbons. The $\...
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Is 2-oxobicyclo[2.2.1]heptan-1-ide resonance stabilized?
I think, in contrast to cyclohexanone, a resonance stabilization by
is less likely to happen as you already start with a bi-cyclic compound where the cycles involved are small to moderate. The then ...
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Does benzene structure stand for a single resonance form or the whole molecule?
I've seen the following drawing used instead of the three double bonds. The circle signifies that the ring is aromatic. It's an alternative that is used to show that all bonds are the same.
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