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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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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3answers
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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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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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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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44 views

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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62 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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28 views

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 ...
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What are the total amount of resonance structures for these two cations and which is the most stable cation?

Please see the following two cations. I have proposed the following resonance structures. Please let me know if I have missed something. Thank you.
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Does hyperconjugation into sigma-star explain methylamine's increased basicity relative to ammonia?

The inductive effect with the polarisation of the C-N bond obviously plays a role in stabilising the positive charge of the conjugate acid. But given the similar electronegativities for C and H, CH3 ...
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Stability order of carbocations [duplicate]

These are some of the most stable carbocations, but what is the relative stability order between them. According to me it should be: C>D>B>A........ I came to this conclusion because both C and D ...
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105 views

Why does delocalization lead to stability? [duplicate]

If the electrons are relatively more stable when they are delocalized than when they are localized between two atoms, then why do we have bonds formed in the first place? Forming of bonds between two ...
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Compare stability of the given carbocation

Give the order of stability of the given carbocations. Usually stability is determined by studying effects taking place in the carbocation. All are resonating and there is no diff in inductive effect....
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271 views

Which Carbocation is most stable among the three? [closed]

According to me the answer should be (C) as that Carbocation will be stablized by resonance with Chlorine. I have read that resonance is the biggest deciding factor about the stability of a ...
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Basicity of nitrogen in amide versus basicity of nitrogen in aniline

I was wondering that how can we compare the basicity of nitrogen in amide to the nitrogen in aniline as in both structures the lone pair on nitrogen is in conjugation as shown below, Can someone help ...
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225 views

Determining the more acidic proton in cyclopenta-1,3-diene

I am in the David Klein textbook in Chapter 3 going over rule 2 of finding the more acidic proton: if the electron pair in the conjugated base is delocalized, then the conjugate base is more stable, ...
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Do non-classical carbanions exist?

There are some non-classical carbocations, such as the 2-norbornyl cation, in which the positive charge is heavily delocalised. Have non-classical carbanions also been discovered? I have not seen any ...
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Sigma electron movement in resonance forms

I have come across an example in my textbook, which shows resonance structures for the bromonium ion. However, I am confused as to why the sigma bond electrons "move" to get the tertiary carbocation ...
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442 views

Which has more enol content?

According to me, resonance in {a} is more effective than {b}. And for monocyclic ketones, enol has very less content. I say {1} has lesser enol than {2}. Which is right?
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Which is most stable resonance structure of 4-nitrophenoxide ion?

According to my coaching module the first structure is more stable. Why is this so? I feel both must be approximately equally stable since negative charge is on oxygen in both cases. Would someone ...
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Resonance in benzene: creation of current

I am a student. I recently studied resonance in Benzene. I know that π electrons in Benzene are involved in resonance this means the electrons somewhat move in the process of resonance. I have a ...
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410 views

How does hyperconjugation explain the stability of alkenes?

The more the number of alpha hydrogens, the higher is the stability of alkenes, because the more the number of hyperconjugative structures. Why is this so? Has it got something to do with the ...
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108 views

Resonance structure and stability

Does the existence of resonance structures always translate as stability? I've been taught that resonance structures generally "spread out" charge in order to compensate for deficiency or excess of ...
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Stability order of methy benzyl cations?

I know that meta position shown no resonance effect and hyperconjugation effect . So According to the order given I guess Hyperconjugating effect is taken into account as -CH3 has no Resonance effects....
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249 views

Are p‐xylylene and fulvene aromatic?

Are the following structures aromatic? I have not seen this type of question anywhere so I do not know the answer. This is just a problem that has been roaming around in my head that I may ...
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What is the most stable structure amongst the keto-enol tautomers of pentane-2,4-dione?

I was assigned the following question and I cannot decide which is the correct answer. Which is the most stable structure? (a) pentane-2,4-dione (b) 4-hydroxypent-4-en-2-one (c) (Z)-4-...
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Is steric inhibition of resonance, or of protonation, dominant in 0-substituted anilines?

There's a question about inhibition of resonance: Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine? If you look at Martin's answer he says that CH3 is ...
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Why do electron donating groups decrease the acidity of aromatic carboxylic acids?

If we look at the resonance structures of benzoate anion, we would see that some amount of positive charge is present on the ring and this charge can get delocalised on the ring, like this: Now, if ...
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Is ortho-nitro benzoic acid more acidic than formic acid?

We know that the Electron Donating effect of the benzene ring in benzoic acid makes it less acidic than formic acid! And we also now that whenever an ortho substituent is present in benzoic acid ...
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Is delocalisation of non-bonding electrons into the benzene ring possible in case of conjugate base of benzoic acid? [duplicate]

If we take a look at conjugate base of benzoic acid it is as given below: Now my question is: Is delocalisation of non bonding electrons(in the carboxylate part) into the benzene ring possible? ...
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How far-reaching is the effect of conjugation?

Due to conjugation, it is possible for 1,4-addition, or conjugate addition, to occur. I was thinking, since conjugation and resonance effects do no diminish with distance, unlike inductive effects, ...
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Electrophilic aromatic substitution of napthalene

It is known that the $\alpha$-position (or 1-position) for napthalene is the preferable position for substitution to occur at. However, I am getting two different explanations as to why this is the ...
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Why carbonyl groups are strong benzene deactivating group for electrophillic aromatic substitution?

In carbonyl group there is a resonance avaibility and also due to inductive effect it can also withdraw electron from benzene ring . As, resonance(e- donating chracter) dominates than Inductive effect ...
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How does the 1.5 bond order of ozone contribute to its instability?

I'm confused as to why ozone is so unstable? I've been told it's because it has a fractional bond order. However, this doesn't make sense to me. Don't fractional bond orders mean resonance and doesn't ...
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Why do most carboxylic acids have high pKa (~5) in spite of having a conjugate base ion that is stabilized by resonance?

This is from my textbook: Carboxylic acids owe their acidity ($\mathrm pK_\mathrm a$ of about $5$) to the resonance-stabilized carboxylate anions formed by deprotonation. Why are they such weak ...
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Why can't negative charge on a carbon have resonance with a neighboring alcohol?

In these resonance forms of a conjugate base of ascorbic acid, why can't the electrons on the negatively charged carbon in the third form be used to form a double bond with the alcohol and thus ...
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How to calculate the resonance energy of thiophene?

How to calculate the Resonance energy of Thiophene? I know how to calculate the resonance energy of Benzene. I am applying same procedure for thiophene, too. (Wikipedia: Resonance energy) The values ...