Resonance refers to the representation of the electronic structure of a molecular entity in terms of contributing structures. The tag should be applied to any question that concern resonance structures or resonance energy. This tag should not be applied to questions about aromatic compounds.

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Why is +M effect of OH greater than OR?

In some books it is written that +M (mesomeric effect) effect of OH is less than that of OR . The reason they give is inductive effect of R (group) which sounds senseful . But at some places it is ...
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How are the hybrid orbitals of sulfur hexafluoride shaped?

On the fluorine end the fluoride atoms are simply completing a $3p$ orbital. On the sulfur end one could posit a hybrid of one $3s$ orbital, two $3p$ orbitals and a three inner $2p$ orbitals. However,...
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Can atoms delocalize in molecules?

Electrons can delocalize over multiple equally probable bonding structures. Can atoms delocalize over multiple equally probably bonding structures in certain cases? It seems to me that any such ...
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How many resonating structures of Carbon Monoxide are there?

Anywhere I look, I get 3 resonating structures for CO molecule, like in this answer. However, according to the rules stated for drawing resonating structures in this site, I wonder why there can't be ...
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Open shell compounds

I was going through this article. Four common electron shift patterns have been recognized out of which the 2nd and 3rd patterns are: If there is an open valence shell , interchange it with the pi ...
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If I can't draw resonance structures for a pi system, does that mean it doesn't exist?

Whilst trying to answer this question I came across an interesting situation regarding the relationship between resonance structures and molecular orbitals. There are two places that you can ...
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What is resonance? Are resonance structures real?

My teacher told me about resonance and explained it as different structures which are flipping back and forth and that we only observe a sort of average structure. How does this work? Why do the ...
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Why is the cyclopropenyl anion “Not Aromatic”?

Is the following compound "Anti Aromatic" or "Not Aromatic" ? The above compound contains a single ring, has conjugation and also has $4 \ (=4n)$ electrons. So, according to Hückel's Rule, ...
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What is the IUPAC name of this Di-Benzene like compound? Is it Aromatic?

What is the IUPAC name of this compound? Is it Aromatic? The above compound has $12 \ \pi$ electrons and according to Hückel's Rule, it should not be aromatic because $12 \neq 4n+2$, but it ...
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help with resonance structure [closed]

need some help with finding resonance structures to this molecule, all the one I find do not obey octet, can someone help? I'll add the ones I made but I know they are not right and there is something ...
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Why is meta-nitrophenol less acidic than para-nitrophenol?

My professor said while explaining the acidic nature of phenol that meta-nitrophenol is less acidic than para-nitrophenol, and gave the reason that resonance doesn't play on meta, but I didn't get it.
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Does benzene structure stand for a single resonance form or the whole molecule?

It is known that benzene has two main resonance forms Often we still draw benzene molecule as one of them My question is, actually when we draw the lower figure, do we refer to the whole benzene ...
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Acidic strength of organic acids. Substituted PhCOOH acids

Could someone please explain the order of acidity of ortho, para and meta substituted benzoic acids with the substituent as methyl group? Methyl group operates +I and +R effect, I believe.
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N-O bonds in Nitric acid

The wikipedia article on nitric acid mentions the following structure of $\ce{HNO3}$ in which the two $\ce{N-O}$ bonds (other than that of $\ce{N-OH}$) are of different length i.e., $119.9\,\mathrm{...
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why can one double bond exist in some resonance structures but two can't?

I am doing some biology and have not done chemistry in ages. i have two concepts i am struggling with. 1)When drawing Lewis structures, am I right in assuming that the central atom will always ...
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Charge separation in resonance

I read that resonance structures in which charge separation is less contributes more to the hybrid than the ones with more charge separation. I am unable to understand why it is so. Doesn't two ...
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Why are anti aromatic compounds unstable?

Just like aromatic compounds, anti aromatic compounds have several resonance structures and some of them are also conjugated ( 1,3-cyclobutene). Why is it that just having 4n electrons makes them ...
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Resonance in phenoxide anion [duplicate]

Why is resonance possible in phenoxide anion as when the electron pair of oxygen is involved in conjugation we have 4 pairs of electrons in resonance which should imply that the ring has become anti ...
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Relative stability of carboxylic acid derivatives

This picture depicts the relative stability associated with resonance structure. My questions are: 1.1. Teacher says anhydride is less stable because of two reasons above. but it seems there's no ...
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stabilization by EWG in aromatic ring

I'm trying to grasp the Birch reduction. in lecture about it, it's said that the EWG stabilize ipso and para position of it through resonance. so I tried to understand by drawing resonances without ...
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Canonical structures of (1E)-prop-1-en-1-yl acetate

I have to find all of the possible canonical structures of this molecule And here's what I did Are they correct and if yes, did I miss any possibility?
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Why only the unstable resonating structure proceeds in the reaction?

For example, in the given image, I have starred the step where the relatively unstable resonating structure proceeds forward in the reaction. Why?
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Which will be the most acidic hydrogen in the following organic compounds?

Which will be the most acidic Hydrogen in both cases? Please explain. According to me, in the first compound 2 should be most acidic as in both 1 and 2, resonance occurs but 2 Carbon is closer to O, ...
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Why is HClO4 the strongest oxyacid?

Why is $\ce{HClO4}$ the strongest oxyacid? My effort: The structure of $\ce{HClO4}$ should be tetrahedral. So when there is a negative charge on oxygen, it should not be in resonance with other ...
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Thermodynamic control or kinetic control?

In my notes, it is written that the case 1 product will be major one. The explanation given is as follows:- However, since the pi clouds of alkenes are perpendicular to each other, the resonance ...
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What is an algorithm for drawing resonance structures?

Question What is an instance of a procedure for writing resonance structures for any given compound's name or structural formula? I would prefer any of these formats to represent the algorithm: ...
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Aromaticity & delocalization of electrons

Are these Anti aromatic/aromatic or non aromatic? 1. Here, if we were to consider the resonating structure(s) with charge separation One ring is aromatic and other is anti aromatic, and ...
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Halogen and inductive effect

background : As proved by rate of EAS, mesomeric or simply conjugated resonance is weaker for halogens than inductive and make them electron taking, with fluorine almost doing nothing due to ...
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Number of resonating structures (hypothetical)

To my knowledge, resonance happens where more than one lewis stucture can represent the compound with no shift in sigma bonds so, suppose in a simple conjugated system even like 1-3 pentadiene , two ...
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Why does fluorine stabilise a carbocation?

I have read that halogens have a stonger -I (inductive effect) than +M (mesomeric effect),then why do they stabilise a carbocation instead of destabilising it? I asked this doubt to my teacher and he ...
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Why does glucose 6 phosphate have lower pKa values than inorganic phosphate?

The pKa for lone phosphate is 2.16 7.21 12.32 Source and the pKa for glucose-6-phosphate (G6P) is 0.94 6.11 Source Because pKa is less positive, Ka is more positive as pKa= - log (Ka). So ...
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Understanding the mechanism of Blanc chloromethylation

I have seen this question: Mechanism for chloromethylation of benzene. The answer there uses a picture from wikipedia which confuses me. It gives $$\ce{H2C=O <=>C[HCl] H2C+-OH <-> H2C=O+H}...
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Resonance and inductive effects [duplicate]

What happens when a phenyl group itself is attached to a benzene? What are its I and R effects? For example: NH2 shows -I and +R I want to clarify this because there seems to be an inconsistency in ...
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Can we break the covalent bonds of water molecules using resonance frequencies?

Can we break the covalent bonds of water molecules $\ce{H2O}$ using resonance frequencies? What is the wavelegth of the water's molecule? Can we create a vibration like this and use it to separate ...
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Variation of activating effects in different media

Why do activating effects vary in different media? Explain it using the two compounds shown below. We know that different group on benzene ring can deactivate(e.g. $\ce{-NO2}$) or activate (e....
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Difference between Resonance Effect and Mesomeric Effect

While studying electron displacement effects in organic chemistry, I read that the Resonance Effect and Mesomeric Effect are the same. Every source I checked used the heading or opening "The Resonance ...
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Which of the following has higher enol content?

Which of the following has higher enol content? The enol form of (A) and (B) is: Both the enols have hydrogen bonding. If the oxygen were to accept the pi electrns from carbon forming a ...
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Why is diene more reactive than alkene?

The chemical reduction of 1,3-butadiene with sodium in alcohol gives mainly the 1,4-addition product that is but-2-ene. Under these condition the isolated double bond are not reduced. This suggest ...
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Why do alcohols not undergo resonance?

Take for example $\ce{CH3OH}$. The lone pair on the oxygen atom may be donated to form a double bond and giving $\ce{CH3-}$ and $\ce{O+}$ ? Is it because we cant have + charge on $\ce{O}$ atom?
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Resonance in ozone and benzene [duplicate]

In inorganic chemistry, I learnt that stability of some atoms like ozone cannot be explained by one structure alone and hence the hybrid of possible structures is taken and assumed to be the structure ...
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Number of resonance structures of nitrobenzene

I was studying about the resonance and here's my doubt: How many resonating structures are there in nitrobenzene? Is it 5 (as drawn) or is it 4 because first and the last structures are same or is ...
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Why does the phosphate ion have resonance structures?

My first-year chemistry teacher depicted $ \mathrm{PO_{4}^{3-}}$ as exhibiting the resonance structure inset below this question. However, I can't figure out what diagramming rules (which is what ...
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Stability of carbocations

We know that if a structure has all equivalent resonance structures, then it will be highly stabilised. So then why benzylic carbocation is more stable than other cyclic allylic carbocations, though ...
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Origin of different colour for thio analogue of indigo from blue to red

Why the thio analogue of indigo is red? What is the reason behind change of colour from indigo to red just by change of N to S. What I get is that there will be electronegativity, lone pair ...
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Are the lone pair electrons on an carbonyl oxygen in sp2 orbitals?

Carbonyl Group Double Bonds [...] One pair of the oxygen lone pairs are located in 2s while the other pair are in 2p orbital where its axis is directed perpendicular to the direction of the ...
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Why does O2NCl only have two resonance structures?

Why is it that $\ce{O2NCl}$ has only two resonance structures? More specifically, why is the Lewis drawing where $\ce{N}$ is double bonded to $\ce{Cl}$ not considered a resonance structure along with ...
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Find the order of acidic strength

Arrange the following in decreasing order of acidity I think it's S>P>R>Q (Q) forms an anti aromatic conjugate base. So its the least acidic compound here. (R) forms forms a conjugate base which ...
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Trying to understand the statement: 'Resonance is not a flickering between the contributing states. '

So, the famous resonance definition: it is the weighted average of different Lewis structures.... Well, this is purely wrong. Resonance is nothing but quantum 'superposition of the wavefunctions ...
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What is a sigma complex?

According to Wikipedia, "sigma complex" refers to an arenium ion. The suffix "-ium" denotes a positively charged ion. So, it is correct to call the resonance structures in the below picture ...
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Is 2-oxobicyclo[2.2.1]heptan-1-ide resonance stabilized?

Is the following compound resonance stabilized? I think its not resonance stabilized because the p-orbital of carbanion and pure p-orbital of carbonyl carbon are not in same plane. So they can't ...