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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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Which Carbocation is most stable among the three? [on hold]

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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Carbocation stability with respect to different groups attached [on hold]

Out of $\alpha$-methoxy ($\ce {-OR}$), $\alpha$-hydroxy ($\ce {-OH}$) and $\alpha$-amino groups ($\ce {-NH2}$) attached to a positively-charged carbon which will produce the more stabilizing effect?
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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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Why does charge separation decrease stability of resonances forms?

Why is an resonance form with negative and positive formal charges in its atoms, lets say +1 and -1, less stable than an resonance form with just positive or negative formal charges, lets say just +1 ...
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For fluorine as group, effectiveness +M>-I or -I>+M(is F electron donating or withdrawing?)

When fluorine is bonded with carbon of benzene ring, It can act like an +M(electron donating mesomeric) group and -I(inductive) group. +M depends on the successful delocalisation of fluorine's p ...
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1answer
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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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2answers
512 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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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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1answer
67 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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36 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
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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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1answer
80 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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Tautomerism in phenyl substituted compounds

Why doea phenyl substituted compounds have more enol content? For example, in almost all benzyl glyoxals and diarylmethanes, the enol content range up to a 100% I tried to see the effect of ...
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Arranging these aromatic amines according to their basic character

The problem asks to arrange theses amines in an increasing order of their basic character. Clearly 2 is less basic than 1, because $NO_2$ is a strong $e^-$ withdrawing group and it is going to show ...
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1answer
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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
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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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Main resonance structures of the conjugate base of a 1,3-diketone

In a textbook I read that the main resonance structures of the conjugate base of a 1,3-diketone are as follows: But why can't it be something like this is unclear to me: I need help with ...
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1answer
135 views

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 have seen somewhere. My approach - Since ...
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151 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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Is Ring Expansion possible in the given carbocation [duplicate]

In the following carbocation, is ring expansion from 3 membered ring to 4 membered ring possible? : https://i.stack.imgur.com/tVsn0.jpg My approach - The given carbocation is highly stabilised by ...
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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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3answers
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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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1answer
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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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1answer
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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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1answer
35 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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1answer
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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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1answer
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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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2answers
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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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2answers
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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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1answer
42 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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Resonance structures for acyl imidazole

I was asked to draw the four resonance structures of the acyl imidazole boxed in the picture. I'm not too confident with drawing resonance structures, so i'm really not sure if the answer i came up ...
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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 ...
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1answer
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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
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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 ...
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2answers
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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, ...
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1answer
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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. ...
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1answer
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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 ...
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1answer
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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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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[...
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1answer
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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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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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1answer
228 views

Comparison of acidic strength between nitric acid and nitrous acid

These are the structures of nitric acid and nitrous acid respectively: To compare acid strength, we compare the stability of the corresponding conjugate base. Here conjugate bases are nitrate and ...
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SO3-2 Lewis structure

so I was trying to draw SO3-2 Lewis structure and when I looked it up on the internet I found it different to the one I've drawn This is the one I found on the internet, mine was without a double ...
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2answers
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What is the most “important” resonance structure of SCN⁻?

Numerous online references say that $\ce{SCN-}$ has two resonance structures: I am wondering why this structure is not also possible? I expect structure 3 to be rare because of the high formal ...
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1answer
571 views

Stability of resonance structure

My book states- " the one that has ...less separation of opposite charges ,...., more dispersal of charge is more stable than others" Aren't 'less separation ' and 'more dispersal' opposite to each ...
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Question about resonance structures [duplicate]

I stumbled upon an exercise asking to draw the resonance structure of $\ce{SO4^{2-}}$. We can choose between the resonance structures by calculating the formal charges and by checking which one gives ...
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Which is the most acidic hydrogen in vitamin C

I thought it would be the lower first $\ce{-OH}$ because it's close to the double bond with oxygen, so I thought there would be more electron withdrawal from the oxygen atom due to its ...
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1answer
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Will the carboxylate groups of the citrate anion undergo hydrogen bonding?

The citrate anion of trisodium citrate has three carboxylate groups. I am concerned with whether or not there will be hydrogen bonding in water, with hydroxyl groups of other ions or alcohols. It has ...
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Rules to identify the most stable resonance structures

While studying resonance from this Chemistry LibreTexts article, I found the rules to follow in order to decide which structure is the most stable. Among them: The structure with the least number of ...
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Comparing Basicity of Aniline Derivatives

Why is 4-hydroxyaniline more basic than 2-hydroxyaniline? Hydroxyl is an electron donating group, and their resonance structures suggest that they both isolate a negative formal charge on the carbon ...