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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12
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1answer
193 views

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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150 views

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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1answer
233 views

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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0answers
75 views

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 ...
2
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1answer
343 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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0answers
22 views

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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0answers
78 views

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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1answer
69 views

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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164 views

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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1answer
55 views

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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1answer
61 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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1answer
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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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47 views

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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1answer
132 views

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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1answer
665 views

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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2answers
188 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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1answer
100 views

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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1answer
834 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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0answers
191 views

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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2answers
764 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, ...
14
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2answers
786 views

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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0answers
281 views

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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269 views

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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2answers
60 views

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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1answer
1k 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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1answer
166 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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1answer
309 views

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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1answer
305 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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1answer
749 views

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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0answers
150 views

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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3answers
4k views

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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1answer
640 views

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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1answer
182 views

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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1answer
61 views

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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2answers
172 views

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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1answer
2k views

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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2answers
1k views

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 ...
6
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2answers
410 views

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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1answer
138 views

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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0answers
3k views

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 ...
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1answer
402 views

Why do the unsaturated ketones have C-O bond weaker than saturated ketones? How it is related to resonance structures?

I am studying Infrared Spectroscopy and the book says that unsaturated ketones have a carbonyl group which has weaker bond because it's more single-bond character than single bond because it has these ...
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2answers
4k views

How many resonance structures does the oxalate ion have?

I have drawn the Lewis structure of the oxalate ion, and I see that two oxygens are double bonded to the carbons. When finding the resonance structures, I said there are 2, but the exam solutions ...
9
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2answers
4k views

Participation of Pi-bonds and lone pairs in resonance

Below is a quote from Klein's Organic Chemistry 3rd edition: Here is the bottom line: Whenever an atom possesses both a π bond and a lone pair, they will not both participate in resonance However, ...
9
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1answer
941 views

How does conjugation affect reactivity?

From this topic on MOs of butadiene vs ethene, it is clear that when two ethene molecules are combined to extend the conjugate chain, the HOMO is raised in energy and the LUMO is lowered in energy. ...
3
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1answer
5k views

Is an antiaromatic compound more stable than a non-aromatic compound because of more conjugation?

(image from a LibreTexts page (archive link)) It is shown that the antiaromatic compound is more stable than the non aromatic compounds 2 and 3 because of a more conjugated system. Here's the exact ...
5
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1answer
252 views

Is planarity really necessary for conjugation?

If we look at the $\ce{ClO4-}$ anion, the chlorine atom in it is sp3 hybridised. Hence, it has a tetrahedral structure in which conjugation shouldn't be possible, but while explaining the acidic ...
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58 views

Do amides oxidize to double-bonds?

Do amides from primary or secondary amines ever oxidize to a double-bond on the nitrogen? For example, like from an $\mathrm{R \bbox[yellow]{\color{red}{-}}(NH)-(C=O)-R'}$ to an $\mathrm{ R \bbox[...
9
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1answer
4k views

Most basic nitrogen in Adenine

I need to find the most basic site of Adenine: The $\ce{NH2}$ group and $\ce{NH}$ cant be strong base as electrons are delocalised. This leaves us with $1,7,3$. I thought that electron density on $1,...
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0answers
170 views

Is Argus lab accurate?

I was trying to calculate the resonance energy of benzene by using Argus Lab. These values are weird and very different from the experimental data. I have two questions regarding them. What is the ...

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