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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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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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 ...
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161 views

Why should 2,6-Dimethyl-4-nitrophenol be more acidic than 3,5-Dimethyl-4-nitrophenol

I was trying to compare acidity of some organic compounds but can't understand some: Why should 2,6-dimethyl-4-nitrophenol be more acidic than 3,5-dimethyl-4-nitrophenol? I have been trying to ...
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Chirality vs Resonance in chemical structure

In a reference book, chirality of a molecule is explained as "handedness", like our right and left hand, which are mirror images of each other. These are also called as enantiomers. The nearest clue ...
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Why is chloroethene said to be a conjugated system?

Why is chloroethene said to be a conjugated system?Is it because of p orbitals present in chlorine or something?
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Polarity of the nitrate ion

We observe that nitrate ion has a trigonal planar geometry according to its lewis structure and the VSEPR theory. Its resonance hybrid consists of three contributing structure -three probable double ...
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Hyper conjugation in acetic acid?

While comparing the relative stabilities of acetic acid and formic acid why don't we consider the 3 possible hyper conjugative structures which would stabilize the positive charge on carbon thus ...
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What are the resonance structures for chlorite anion?

What are the possible resonance structures for $\ce{ClO_2^-}$? Assigning one double bond to the structure makes for formal charges of $\ce{O (-1) - Cl (0) = O (0) <-> O (-1) = Cl (0) - O (-1)}$. ...
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58 views

how to determine the bond order using the Lewis structure

What are the steps to follow to determine which has a higher bond order say $\ce{CO}$ and $\ce{CO3^{2-}}$ by drawing the Lewis structure?
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47 views

Need of hyperconjugation?

Recently I read about Hyperconjugation. But i have a doubt. What is the need of hyperconjugation in this structure when there is charge separation resulting in lesser stable structure.
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133 views

Resonance of Aromatic compounds

I have a confusion... Do compounds like tropolone, furan and thiophene which are aromatic show resonance? If yes then what are the resonating structures ? Also do all aromatic compounds show ...
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What is the reasoning behind the resonating structure of halo-benzene? [closed]

Can anyone explain the resonating structure of halo-benzene? How does the transfer of an electron from the halogen atom to the α-carbon and from there to ß-carbon and so on take place?
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82 views

Why aryl halides are very less reactive towards nucleophilic substitution reactions? [duplicate]

I've often herd that aryl halides are very less reactive towards nucleophilic substitution reactions. One of the reasons for this I found was that there is resonance effect in the compound, but how is ...
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Reactivity of thioesters with respect to nucleophilic attack

Why are thioesters relatively reactive with regard to nucleophilic attack? Prof says to wait until pchem 3 when we learn about orbital symmetry. He also said that sulfur’s d-orbitals (?!) don't have ...
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1answer
161 views

Higher energy π HOMO

Which is higher in energy? Cyclohexanone enol or cyclohex-2-en-1-ol? Okay from what I understand a higher pi HOMO is synonymous with more nucleophilic. So I would expect cyclohex-2-en-1-ol to have ...
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2answers
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Why is a hydroxyl group more activating than a methoxy group in electrophilic aromatic substitution?

Why is phenol more reactive towards electrophilic substitution than methoxybenzene? Isn't the lone pair on the methoxy group oxygen more available for participating in resonance into the ring than the ...
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Does resonance overrule hyper conjugation in terms of stability in alkenes?

Which of the following is more stable ? $\ce{CH2=C(CH3)-CH=CH2}$ $\ce{CH3-CH=CH-CH3}$ I was going for answer 2 because it has 6 hyper conjugative effects. I found the answer given to ...
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In which all substituents does Inductive effect overpower Mesomeric effect?

In most substituents, the mesomeric effect is considered stronger and more dominating than the inductive effect. A notable exception are the halogens. The reason behind this has been ...
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Diels-Alder without molecular orbital theory

So the prof got to Diels-Alder without discussing it in the context of molecular orbital theory. Instead we got a resonance picture of what happens... this is what he told us: 1) 1,3-butadiene has ...
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Why do certain groups withdraw/ donate electron to double bond or conjugated system in resonance effect?

Why for the Resonance effect certain group of substituents/functional group donate electron from the double bond or to a conjugated system while some withdraw electron from the double bond or to a ...
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Why is there a need for resonance?

Why are we able to show structures of compounds with different position of electron, but with same position of them? Shouldn't the structure become unstable due to this? Let's take benzene for the ...
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Resonance structure of cyclobutadiene?

I studied cyclobutadiene as an anti-aromatic compound. But I am unable to draw the resonance structures for cyclobutadiene. Can anyone help me? What is the driving force for the resonance to start? ...
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280 views

Which is more stable Carboxylate ion or phenoxide ion?

At first I thought that the answer would be the phenoxide ion as it has higher no. of resonating structure than carboxylate ion. But I was surprised to find the answer carboxylate ion. According to my ...
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Resonance in Propenal

I do not understand why the 3rd canonical form of propenal has the oxygen atom donating an electon. Oxygen in electronagetive so instead of taking electrons why is it giving? Maybe this why it is ...
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A different structure of Ozone?

The structure of ozone is shown as having a resonating form. However, what I am wondering is instead of using such an idea to explain the structure why can't we show the structure of ozone like ...
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How does Resonance stabilize a molecule?

How does resonance lower the potential energy of the molecule? Take $\ce{O3}$ as an example.
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What is it with resonance structures?

This is a concept I have never really understood. I mean to say is how can we include such a thing in a theory? How can we use them if we know that they don't actually exist? Are they some sort of ...
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What is the resonance structure of nitro-aminobenzene with a broken aromaticity?

According to my course of organic chemistry, nitro-aminobenzene has to break his aromaticity to delocalize the electrons of the amino-group in the nitro-group. I don't really see this, when I draw the ...
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Using MO theory, give an explanation for the C-C bond length in cyanogen

1. The problem statement, all variables and given/known data 2. The attempt at a solution I know that the MO diagram for CN- is this: I am unsure how to draw the MO diagram for cyanogen. I know ...
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Draw a simplified MO diagram for the pi system of Methyl vinyl ether

My attempt at the answers: i) 2 bond pairs and 2 lone pairs on oxygen atom therefore bond angle of slightly less than 109.5 degrees, around 104 degrees. ii) 120 degrees bond angle therefore sp2 ...
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Rationalizing enamine stabilities

The solutions manual said that enamine B with its roughly sp2 methyl group can force the nitrogen out of the plane and this messes around with the conjugation. How about the fact there is a ...
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Is phenoxide aromatic?

Is phenoxide ion aromatic? I read that is technically isn't aromatic because it violates some arcane rule, but I can't find any references in the literature. I don't see why it couldn't be ...
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Inductive vs resonance effects and the acidity of phenol

A lot of people rationalize the acidity of phenol by saying that resonance is responsible for much of phenol's acidity as opposed to aliphatic alcohols. However, this image suggests that in fact ...
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Why can't the conjugate base of benzoic acid be stabilized by conjugation with the aromatic ring?

All the carbon and oxygen atoms are sp2 hybridised and can have a p orbital in the correct plane yet only conjugation of the COO- group occurs. I can't think why. I can't draw resonance structures for ...
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Resonance contributors of sulphuric acid

Why only four resonance forms of sulphuric acid given in textbooks. I can draw eight of them.
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Resonance and reductions with sodium borohydride

I know that sodium borohydride doesn't work particularly well on resonance-stabilized carbonyl groups (i.e. esters) but what about this carbonyl in the center of the above picture? This appears to ...
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Acidity of substituted phenols

Phenol has a $pK_{a}$ approximately equal to $9.9$. When one studies the acidity of chlorophenols, one notices the following: First of all, chlorophenols are more acidic than phenol, due the ...
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Is resonance always stabilizing

Does resonance always stabilize a molecule or can resonance effects destabilize molecules? The only example I can think of in which resonance (more accurately, conjugation) destabilizes molecules is ...
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Why is C4 of butynone electrophilic?

A question asks whether C4 in 3-butyne-2-one can act as a nucleophile, electrophile, or acid (it can be more than one). The answer is that it can be both electrophilic and acidic. The acidity makes ...
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Why is structure B disfavored?

Our prof only told us that A is favored and B is not getting formed. I thought about the resonance structures and saw a contradiction to that what the prof told us. To be honest I think my argument ...
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Is aniline aromatic - How to treat the lone-pair electrons of nitrogen when applying Huckel's rule?

Why is aniline aromatic? Doesn't it have 8 pi electrons, thereby violating Huckel's rule? The way I see it, there are 6 pi electrons from the benzene ring, and an additional 2 from the sp2 ...
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Do acyl fluorides exhibit resonance donation or inductive withdrawal?

I know that in acyl chlorides, there is partial triple bond character in the $\ce{C=O}$ bond not because the chlorine is electronically donating (due to size mismatch with carbon) but because the ...
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Is Pyrene Aromatic?

Pyrene doesn't seem to be aromatic. However, sources claim that it is aromatic. Considerations: Pyrene is cyclic. ✓ Pyrene is flat (planar). ✓ Pyrene has 16 pi electrons. Every atom in the ring ...