Questions tagged [resonance]

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 (use the [aromatic-compounds] tag instead)

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Can a delocalized pi bond show geometrical isomerism? [closed]

For example, can 1-phenyl-but-2-ene show geometrical isomerism? Would the restricted rotation be affected because of resonance? I tried looking this up, but couldn't find any explanation. Any help ...
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Why don't resonance occur in meta-substituted benzene? [closed]

[![Why there no resonance in meta xylene? Please explain][1]][1] [1]: https://i.stack.imgur.com/mZo3b.pngstrong text
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How many resonance structures can be drawn for the following molecule?

For Question 2; I think that the molecule can be drawn in three ways but the book says that the correct answer is option D i.e.,2 can anyone explain how ?
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How can we calculate the “degree” of conjugation?

So a conjugated system is a system of connected p orbitals or alternating single and multiple bonds. I know that conventionally, we count the number of adjacent parallel p orbitals or alternating ...
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Why hyperconjugation can't stabilize carbanion?

If Resonance can stabilize both carbo cation and anion then why can't hyperconjugation stabilize carbanion ? Since both Resonance and Hyperconjugation are pretty much the same, i.e both involve ...
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Confused about identifying delocalized electron pairs in Isoniazid

I have to identify delocalized electron pairs in Isoniazid (pairs not shown in the image below): I know the nitrogen in the ring has a localized electron pair, since it already forms a pi bond. I'm ...
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How does the relative acidity of 2,3-dinitrophenol compare to that of 2,4-dinitrophenol?

I am assuming that the -I inductive effect in 2,3-dinitrophenol is stronger than in 2,4-dinitrophenol since it operates through less bonds, therefore on inductive grounds it should have a lower $\...
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Why is an alkyne substituent on benzene is electron withdrawing, but alkane and alkene are electron donating?

Hammett constants for alkyls/vinyls/etc. are all negative (i.e. toluene), and my understanding is that they donate electrons through inductive/resonance effects. However, ethynylbenzene has a ...
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Relative Energies of Resonance Contributors & Stability of Borazine

We know that Borazine (Inorganic Benzene) is aromatic in nature. The following image shows the resonance contributors of borazine: What are the relative energies of these three resonance contributors?...
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Resonance structures and mechanism

I wrote the following resonance structures and our teacher wants us to write the curved arrows showing the mechanism as well... I was wondering if it's okay to show in which direction the mechanism ...
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80 views

What is the stability order of the carbocation and carboanion?

So I came up with examples as below: 1 2 Now I am confused about the +I and -I effect in these structures since to my knowledge it can only be applied when there is a substituent (I might be wrong)...
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Which of the following carbocations is more stable?

Which of the following carbocations is more stable? I know two major factors in determining carbocation stability: resonance and the number of carbon atoms neighboring the positive carbon. Does ...
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How can a conjugated system of open hydrocarbon chains have delocalization?

If conjugated systems have delocalized electrons, and delocalization takes place when there are two possible structures how come I can only find one for conjugated systems of chained hydrocarbons like ...
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Cross-conjugation

Could somebody please explain the concept of “cross-conjugation” (Organic Chemistry) to me? In what kind of conjugated systems is it observed, what are its effects on resonance of the system as a ...
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How does resonance fail in approximating chemical structures?

In the book "Concise Inorganic Chemistry" by Prof. JD Lee, it says here: These contributing structures do not actually exist. The $\ce{CO3^2-}$ does not consist of a mixture of these structures, ...
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Help in drawing resonance structures in case of polybasic acids

While drawing resonance structure of dibasic or tribasic acid, e.g. should I take out two $\ce{H+}$ (in dibasic) or three $\ce{H+}$ (in tribasic) together or one by while drawing resonance structure? ...
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Acidic strength order of mineral acids in acetic acid

Explain this acidic strength order $\ce{H2SO4} > \ce{HCl} > \ce{HNO3}$ in acetic acid. My Attempt Stability of conjugate base is proportional to the acidic strength of acids in acetic acid. $\...
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The most acidic hydrogen of 4‐hydroxybutanenitrile

Identify the most acidic hydrogen atom in the compound below: $$\ce{NC-CH2-CH2-CH2-OH}$$ My teacher said that the $\ce{H}$ connected to $\ce{O}$ is the most acidic since $\ce{O}$ is more ...
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Favoured position in nitration of pyrrole [duplicate]

I try to figure out the preferred position of nitration (determine whether compound A or B is the major product) by looking at the resonance structures of the intermediate cation. The solution then ...
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115 views

Is cyclo[18]carbon aromatic?

How does this compound even exist? Having such a massive ring strain. Is it even conjugated? As it's resonance structure will have all double bonds. Since it was reported to be found, there must be ...
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resonance structures and formal charges

hey so I have been stuck on this question for the past few hours and I can't seem to figure it out. I am moving the pi bond one carbon/bond at a time but I can't seem to come up with the correct ...
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Which of the resonance structures is more stable?

I am quoting a rule on resonance from Organic Chemistry by T.W. Graham Solomons, Craig B. Fryhle, 12th edition, page 25. Structures in which all the atoms have a complete valence shell of ...
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Why does indolizine undergo EAS on C3 and not C5 of the pyrrole ring?

In Clayden, Greeves, & Warren: Organic Chemistry Second Edition, it is said that indolizine (pyrrocoline) reacts in electrophilic aromatic substitution at the C3 of the pyrrole ring, as shown. I ...
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How does cross-conjugation destabilizes a molecule?

Wikipedia article on ortho effect suggests that o-toulic acid is more acidic than benzoic acid. This fact is rationalized by suggesting that steric effect causes COOH group to "twist" out of the plane ...
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Is the 1,4-adduct of carbonyl compounds ever a major product over the 1,2-adduct?

If, say, propenal undergoes nucleophilic addition of hydrazine, will the 1,2- adduct or the 1,4-adduct be preferred? Why? There is an obvious reasonace structure with an electrophilic beta carbon so ...
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Which compound has resonance structures? [closed]

Which compound has resonance structures? A. $\ce{C6H12}$ B. $\ce{CH3CHO}$ C. $\ce{NaBr}$ D. $\ce{Na2CO3}$ The answer key says D is correct, but I do not understand why $\ce{Na2CO3},$ which ...
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Will N,N‐diethylbenzamide show geometrical isomerism?

I know for a compound to show geometrical isomerism it should have site of restricted rotation; be connected to two different groups on either side of site of restricted rotation; the distance ...
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153 views

Why is p-methoxyphenol less acidic than phenol?

They have slightly different $\mathrm{p}K_\mathrm{a}$ values of 9.9 (phenol) vs 10.2 (p-methoxyphenol). They both have the same number of resonance structures too. My guess is that the resonance ...
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Molecular Orbitals (only pi system) of Allyl system using group theory

I have just started reading group theory and their applications in the MO theory. I tried to get the equations of the pi molecular orbitals of allyl system using group theory, but I am stuck at the ...
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Can there be geometrical isomerism in resonating structures [closed]

If a double bond which has two different substituents on each of it's two ends is showing resonance with one of the substituents would the double bond exhibit Geometrical isomerism?..if yes how so ...
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Reaction enthalpy using bond energy in resonating molecules

To find out and enthalpy of a reaction using bond energy we use the formula $$\Delta H = \sum\Delta_\mathrm{bond}H_\mathrm{reactants} - \sum\Delta_\mathrm{bond}H_\mathrm{products}$$ since we use all ...
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4-Bromophenol vs 4-aminophenol pKa in water comparison confusion

Recently the other week, I was asked the following question: Would you expect 4-aminophenol to have a higher or lower pKa than 4- bromophenol when measured in water? And I thought about this on ...
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Molecular Orbital Hybridization vs Delocalization for positive charge stabilization

While studying Molecular Orbital Theory, I ran into a comparison of basicity between pyridine and piperidine. The latter was concluded to be more basic because of the sp3 hybridization of the ...
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1answer
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How does hyperconjugation explain stability of partial positive charges?

Recently I was reading this answer to the question Why does boron add to the less substituted carbon in the hydroboration of an alkene?. See the transition state given in the above answer, and the ...
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1answer
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Does 2-chloro-1,3-dinitrobenzene show resonance?

I am preparing for my exam, and then I stuck up here. The answer to this question given by my teacher was No, this doesn't show resonance because there are two bulky groups alongside chlorine, due ...
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1answer
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Consequences of ortho effect on resonance

Consider any carboxylic acid with any group at ortho position. According to ortho effect, the resonance of the $\ce{C=O}$ with the ring is inhibited. Is this resonance entirely lost? Or some little ...
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Resonance forms of deprotonated hydroquinone

What resonance forms stabilize deprotonated hydroquinone? Deprotonated hydroquinone looks like this: Possible resonance forms include: 1 and 2 look reasonable: they don't carry multiple charges. My ...
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What is the physical origin of conjugation?

I had a question about the origins of conjugation in conjugated molecules. Take two ethylenes as compared to butadiene. Huckel seemed to argue that conjugation was the result of pi-pi stabilization ...
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Why is only one of the lone pairs on the oxygen in furan delocalized?

Both the lone pairs on the oxygen are in allylic positions, thus both should be able to participate in resonance. If both lone pairs can participate in resonance, why is only one of the lone pairs ...
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Relation between ionic resonance energy and polarity

The ionic resonance of the bonds are given as follows: $$ \begin{array}{cr} \ce{A-B} & 24.3 \\ \ce{A-C} & 50.6 \\ \ce{A-D} & 102.3 \\ \ce{A-E} & 105.9 \end{array} $$ Which of ...
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Resonating structures of (pentan‐2‐ylidene)oxidanium

Draw resonating strictures of the following compound: In this molecule there are two π-components, but they are not conjugated. According to me, as there is no conjugation, it should not have a ...
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232 views

Which has greater N-O bond length: NO or NOCl?

I came across this question. According to me NO should have a shorter bond length as it has a triple bond, while NOCl has a double bond. But the answer is given that NO has greater bond length than ...
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More stable carbocation, tertiary or benzylic? [duplicate]

This is a very confusing question that which is more stable, benzylic or tertiary butyl carbocation? Some sources say benzylic due to resonance some say tertiary due to +i effect and 9 ...
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Determination of the most acidic hydrogen in an organic compound

Identify the most acidic hydrogen in the compound below: Can someone please explain why is $\ce{H^\mathrm{a}}$ in the compound below more acidic than $\ce{H^\mathrm{b}}$? This is what is ...
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Partial Aromaticity and Anti-aromaticity [closed]

The following resonance structures are possible for the given compound. (a) promotes both aromaticity and Anti-aromaticity whereas (b) promotes aromaticity. In the resonance hybrid, (b) contributes ...
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Resonance in a non-planar molecule

I am well aware that the following compound is non-planar and hence, will not be anti-aromatic but non-aromatic. But I wonder whether resonance will occur to some extent i.e. whether any three ...
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Understanding Aromaticity

I was just doing a simple question and for no reason, I drew the resonating structures of the compound as shown. I can see that some of the resonating structures seem to be aromatic while others seem ...
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Are the C-C bond lengths different in 2-methyl propene

When we were first taught resonance it was with the example of benzene and I myself justified it by thinking that the double bond oscillates because no two carbon atoms are special and hence there is ...
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Stability and Resonance [duplicate]

The linked answers do attempt to clarify on 'stability' but I wanted an answer with specific connection to resonance. For example, the ethanoate ion can exist in many forms but, as we know from data,...
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Why (SO4)^2- does not create 4 double bonds

I looked this question up and still couldn't understand. Why, in $\ce{SO4^2-}$ don't the 4 oxygens create double bonds. In that case the all the oxygens will have 0 formal charge while the sulfur ...