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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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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Steric inhibition of resonance in Aniline and Benzoic acid [Edit]

My question is for what "approx" value of A (cyclohexane table) will a single ortho substitute will push NH2 and COOH (specifically for benzene derivatives)respectively out of plane, is it CH3 ...
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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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Validity of canonical forms of nitrobenzene [duplicate]

Are 4 of these canonical forms of nitrobenzene valid and distinct?
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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 <-> ...
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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 ...
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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

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 ...
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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 ...
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Rotational Barriers - Amide and Hydroxamic Acid

Why the barrier to rotation about the $\ce{C-N}$ bond higher in an amide than it is in a hydroxamic acid? (MO-based explanation preferred)
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Is my reasoning for resonance structures correct?

given this picture, which resonance structure is correct? I'm thinking 1 and 3. You can't have 2 because the carbon which originally had a negative charge would be making 5 bonds, and you can't have ...
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Why are the C-C bonds in benzene closer in length to double bonds than single bonds?

The $\ce{C-C}$ bonds in benzene are $\mathrm{140~pm}$ long which puts them in between single bonds and double bonds (given at $\mathrm{147-154~pm}$ and $\ce{134-135~pm}$ respectively, sourced from ...
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How to predict a good resonance structure?

I have to draw curved arrows to convert the above molecule to its resonance structure but I'm not entirely sure how. I believe the sulfur atom has one lone pair and the oxygen atom has 2 lone pairs. ...
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Stability of carbocation intermediates: secondary alkane versus primary allyl?

Say I have the following carbocations: The first is secondary; the second is resonance stabilized, but primary. Which is more stable and why? I've been looking around in my textbooks and haven't ...
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Why the H+ ion remains with the molecule even though there is no bond between it and hyperconjugative structure?

In hyperconjugation, it is known that form an $\alpha$ hydrogen, one $\sigma$ electron goes to the corresponding carbon carbon bond, and there is apparently or practically, no bond between the ...
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Why is sulfur dioxide more stable to UV radiation than ozone?

Ozone readily decomposes when impacted by UV radiation. Sulfur dioxide, having the same bond structure and valence electrons in each atom as ozone, is much more stable. Would someone please help ...
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Inductive effect of phenyl ring

I completely understand how phenyl group 'releases' or 'donates' electron through resonance, but how is that a phenyl group shows a weak -I effect, despite having electrons literally smeared on ...
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If both Nitric acid and Nitrate ion are stabilised through resonance, what makes Nitrate ion more stable in aqueous medium?

If both Nitric acid and Nitrate ion are stabilised through resonance, what makes Nitrate ion more stable in aqueous medium? Can the same argument be applied to Nitrous acid and Nitrite ion in aqueous ...
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Why is the original Pauling's theory of resonance that uses superposition of wavefunctions not used today?

I have recently studied superposition of states (also the famous Schrodinger's cat), measurement problem, decoherence & so on. I then read the resonance concept from Atkins' Physical Chemistry ...
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Why is the resonance concept not required in molecular orbital theory?

In valence bond theory, resonance plays a pivoting role; why isn't such concept needed in MO theory? Why is it told that "MO theory provides a global, delocalized perspective on chemical bonding"? ...
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Stability of Resonance Structures

So I was "happily" doing organic chemistry homework when I came across this question: I decided to take a look through my textbook to see what I was missing. The rules to compare resonance ...
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Which compound reacts faster in the Cannizzaro Reaction?

Which reacts faster in the Cannizzaro Reaction? a) $\ce{OHC-Ph-NO2}$ b) $\ce{OHC-Ph-OCH3}$ A better hydride releasing group will be a better reactant, obviously. Therefore my answer was b, as ...
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Which has greater +R strength Toluene or Anisole

I read that resonance in Toluene is initiated with the help of hyper-conjugation. Also hyper-conjugation is less stronger than Resonance/Mesomeric effect. But in toluene its resonance thats taking ...
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Carbonyl group Conjugation and IR spectroscopy

Here's the problem... Three isomeric structures with formula $\ce{C10H8O2}$ are shown: I understand that conjugation in the systems will affect the carbonyl stretching ...
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How is anilinium ion meta directing for electrophiles?

If we make a resonance structure for the anilinium ion, with positive charge at either the ortho or the para position, we get a pentavalent nitrogen, which is not possible. So, how is the anilinium ...
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Diels Alder with Anthracene and Maleic anhydride

I'm wondering why maleic anhydride interacts with the middle cycle of anthracene. My thought concering product based stability: I would have expected that a Diels Alder to the outer ring would be ...
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Is nitrogen of aniline sp² or sp³ hybridized? [duplicate]

I found a thread which discussed this which totally confused me. (refer to the part of the link which talks about $\ce{sp^2/sp^3}$) The question "How to rationalise the resonance structures and ...
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What are the correct resonance structures of nitrous oxide?

There was a question in one of my exam papers to draw the resonance structures for $\ce{N2O}$. But the resonance structures I drew were not given marks. The top 2 structures are the ones I drew and ...
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What are the resonance structures of 3-aminocyclohex-2-en-1-ylium?

How would you draw the resonance structure for the compound below: This is one of the resonance forms I think... but I'm sure there is another one too.
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Determining aromaticity of compounds

Which of the following planar structures would be aromatic? Could someone help me determining the aromaticity of the compounds? My Attempt: (i) Not an aromatic compound since it only has 4 ...
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PBP vs TBP geometry?

Why are the axial bond lengths greater than those of the equatorial bonds in a trigonal bi-pyramid (TBP) geometry molecule; but the opposite is true for pentagonal bi-pyramid (PBP) geometry molecules? ...
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Why is i-butane more stable than n-butane?

I would like to understand the term stability in organic chemistry. We know empirically that i-butane is more stable than n-butane. But why is it more stable? Is it because of formation enthalpies or ...
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Effect of different electron withdrawing/transition state stabilising groups in nucleophillic aromatic substitution

I have been asked the following question in my problem sheet: The only differemce between reaction A and reaction B is the electron withdrawing group that stabilises the anionic transition state ...