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Questions tagged [carbocation]

Carbocations are species bearing a positive charge on carbon. They are intermediates generally formed during organic reactions, which can be stabilised by various electronic effects. Less stable carbocations are capable of undergoing rearrangements to form more stable carbocations in the course of a reaction.

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Stability of the alkenyl and phenyl cations

One reason often cited for why alkenyl and phenyl halides do not undergo nucleophilic substitution by the $\ce {S_N1}$ mechanism is that the formation of the alkenyl and phenyl cations involve a ...
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Mechanism of ring formation of an epoxide under acidic aqueous conditions

I am trying to figure out the mechanism of this reaction: I think the $\ce{H+}$ will first attack the oxygen of the epoxide and another $\ce{OH-}$ will be added to the most substituted carbocation, ...
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Is isobutyl chloride or ethyl chloride more reactive in an SN1 reaction?

Compare the rate of $\mathrm{S_N1}$ reaction in the following compounds: We see that both compounds form primary carbocations. However, there is more hyperconjugation in the second compound as ...
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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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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 a tertiary carbocation rearrange to another tertiary carbocation?

I strongly believe that a carbocation should not rearrange to another if there are no immediate benefits(like a Greedy Algorithm). The doubt hit me while solving this question. The answer mentioned ...
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Stability of carbocation

While comparing the stability, as the $\ce{CH3}$ group is electron donating, the first structure should be more stable due to this reason. But apparently the second one is more stable. Is there ...
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Stability of methoxy-methyl and tropylium carbocations

Which is expected to be more stable: methoxy-methyl carbocation $(\ce{CH3-O-CH2+})$ or tropylium $(\ce{C7H7+})$ cation? I think because oxygen would donate its lone pair so there will be complete ...
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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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Stability of carbocation on doubly bonded carbon [duplicate]

What can be said about the stability of the following carbocation? I think that it would have something to do with hybridisation as, clearly one carbon is sp hybridised and the other is sp2. Can ...
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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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Number of products on dehydrobromination

Question: The total number of alkene products possible from the dehydrobromination of 3-bromo-3-cyclopentylhexane using alcohol KOH is : This question was asked here before but I am getting more ...
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Effect of solvent polarity on SN1 reactions of different charge types

On the topic of the ionisation mechanism (i.e. $\mathrm{S_N1}$), Carey & Sundberg (2007) discuss the effect of polarity of solvent on the rate of $\mathrm{S_N1}$ reactions of different charge ...
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Stability of tertiary carbocation [duplicate]

Our teacher told us that a carbocation connected to 3 cyclopropane rings is among the most stable carbocations. But I am unable to understand how, as resonance (the most important factor governing ...
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Is 1-(1-Methyl cyclopropyl) carbocation [1] as stable as Cyclopropyl Methyl Carbocation[2]

Does the extra Methyl group interfere with the exceptional stability of Cyclopropyl Methyl Carbocation?
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Accounting for Vinylic Carbocation instability [closed]

I read that due to geometrical constraint, positive carbons in an aryl carbocation exhibit sp^2 hybridization instead of sp^1. The empty p-orbital is forced into a hybridized position via geometrical ...
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Can an EWG behave as an EDG and vice versa?

Can an Electron Withdrawing Group(EWG)(like NO2, F, Cl, OH, etc.) behave as a Electron Donating group(EDG) in a compound where a carbocation is present in order to stabilise it? Does the position ...
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Major product of isomerization reaction

I am trying to come up with a logical mechanism for the following transformation, where 2-methylenecyclobutan-1-ol is converted to cyclopentanone under acidic conditions: What I have tried to do was ...
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Hydride shift in carbocation [closed]

I was practising some problems on hydride shift and got stuck in this particular question. I wanted to know if hydride shift would take place in this particular case and which carbon would get the ...
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1answer
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Why doesn't cyclopropyl methyl carbocation stabilises itself by ring expansion? [duplicate]

I have been taught that ring expansion stabilises smaller cyclic compounds to a great extent. So why does cyclopropyl methyl carbocation shows such type of resonance rather than expanding its ring ...
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Ring Expamsion And Final Structure

[If you don't like to read the question just look at the 3 pictures the first one has the carbocation which have to be stabilised by ring expansions the other 2 are my predicted structure so please ...
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Which of the following is most likely to undergo hydride shift?

For the following question the answer is given as option (a) . However both,option (a) and (c) has alpha H atoms and both will form 3° carbocations after rearrangement. So what makes (a) more ...
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The delocalised nature of hyperconjugation

I have always thought I understood hyperconjugation well until recently, in my post on Regioselectivity of bromination of alkenes, I began to question my understanding of this concept. ...
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IUPAC name of C₆(CH₃)₆²⁺

What is the correct IUPAC name (or least incorrect one, if the current rules can't precisely describe that) of the interesting species $\ce{[C6(CH3)6]^{2+}}$ (which is extensively discussed here), ...
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Which is more stable Ethyl carbocation or Neopentyl carbocation?

As per my knowledge, hyperconjugation is more dominating over inductive effect, so due to three alpha hydrogen ethyl carbocation should be more stable. In some books, while solving questions I ...
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How is more than one pinacolone is possible?

This question came in one of my school tests. They had given us an unsymmetrical pinacol i.e 1,1-diphenyl-2-methylpropane-1,2-diol and asked us whether it will give only one pinacolone or not. ...
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Can a stable vinylic carbocation be formed?

Is it possible to prepare/form a vinylic primary carbocation? Will it be stable (low energy) or not?
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Can a six member ring expand to achieve octet completion to stabilize a carbocation?

(Probably unnecessary background: I came up with this carbocation while predicting the major product of $\ce{NaNO2/HCl}$ with 1-(methylamine)cyclohexan-1-ol) Will the following carbocation ...
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1answer
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Why is the initial carbocation not formed adjacent to the phenyl moiety?

I know that after rearrangement the carbocation is more stable, but we should protonate the compound first where the carbocation it is more stable, i.e. adjacent to the phenyl group. Why do they ...
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230 views

Why do vinylic carbocations generally not undergo hydride rearrangement from neighbouring sp3 carbon to get more stability?

Why do vinylic carbocations generally not undergo hydride rearrangement from neighbouring sp3 carbon to get more stability? According to me, a rearrangement would lead to an allylic carbocation, ...
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Can an organic compound undergo ring contraction to give more stable carbocation? [duplicate]

Throughout my journey in organic chemistry I’ve only seen ring expansions by a compound in order to attain more stability, but yesterday I thought about the following reaction. I feel that ring ...
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Determining the stereochemistry of the product(s) when an alkyl shift in a carbocation generates a chiral carbon

Consider this carbocation: We know that this carbocation would immediately rearrange - by a methyl shift - to form the more stable carbocation. Now, notice that the migration will produce a chiral ...
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Ring expansion of two fused rings to a larger ring

I saw the following reaction mechanism in paper Tetrahedron Lett. 1976, 17 (33), 2869–2872.: I'm not able to understand the following parts: How did the conversion of 27 to 29 take place? I've never ...
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Acid Catalysed Ring Expansion – Mechanism?

Ring expansion of vinyl cyclobutane - Could someone please help me with a detailed mechanism for the above conversion? It is the acid-catalyzed rearrangement of 4,7,7-trimethylbicyclo[3.2.0]hept-3-...
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Are allylic three degree alcohols oxidized by the Jones' reagent via a classical carbocation intermediate?

I know the mechanism for Jones' oxidation is (picture from Organic Chemistry by Clayden): and it proceeds through a chromate ester. And in general we understand that the Jones' reagent $\ce{H2CrO4}$ ...
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Can inductive effect be the sole driving force for carbocation rearrangement?

I've been taught that a carbocation mainly rearranges because of: increasing degree (1 to 2, 1 to 3, or 2 to 3) +M stabilization ring expansion (in an exceptional case, ring contraction as well). ...
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NGP mechanism vs the simple carbocation mechanism

Question: Predict the product of: ($\ce{C^*}$ is a $\ce{C^14}$ carbon) My attempt: I simply assumed the super-leaving group $\ce{-OTs^-}$ would leave, forming a primary ethylbenzene ...
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Carbocation rearrangement involving three membered rings

Question: Taking into account of various carbocations and, as well as the rules governing mechanisms of carbocation rearrangements, which reaction is most likely to occur during the given reaction? ...
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Which is more stable out of the given carbocation?

I have read in Solomon's Fryhle that +I effect of D is more than H but here in this problem it is given that (CH3)3C+ is more stable. How is it possible when Deuterium enriches the electron density ...
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Is this carbocation rearrangement possible? [closed]

Is this rearrangement possible in carbocations?
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Carbon atoms which carbocation and carboanion are BOTH less stable then arene/vinyl

I'm trying to come up with a compound class in which iodine atom would be a bad leaving group both whether it leaves or takes charge with it (I know that $\ce{I^+}$ on its own would be horrible ...
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Carbocation stability order 3

I have come to an example which suggests that +M effect of -OH is better than =O . How is that possible? Here is the picture with their Hydride affinities (in Kcal/mol) I think -OH should have ...
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Why doesn't the carbocation form on the carbon that is attached to the ethyl group in this reaction?

Why doesn't the carbocation form on the carbon that is attached to the ethyl group in this reaction? Subsequently, why doesn't the $\ce{Cl-}$ attack the carbon that is attached to the ethyl group? Is ...
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Nucleophilic Substitution rate comparison 1-bromobutane and 2-bromo-2-methylpropane with NaOH

I want to ask a question about the hydrolysis of haloalkanes to form alcohols. I have been presented with a flowchart diagram of possible reactions of haloalkanes below: Now, I have been presented ...
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Inductive effect in cyclic compounds vs open-chained compounds

Consider the two carbocations. Which one is more stable? I think it should be the open-chained one as it has 2 more H atoms than the cyclic one, so polarity will be greater; but I suspect that there ...
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Stability of canonical forms

Which of the following ions is more stable? Use resonance to explain your answer. When we have to compare stability of resonance structures we generally check for the following features in the ...
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What happens to the t-butyl cation in the TFA deprotection of a t-butyl ester?

I am a first-year chemistry graduate student and I am currently learning how to synthesize proteins. I have reached a stage in the process where I need to deprotect a carboxylic acid moiety protected ...
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Carbocation formation in electrophilic addition of hydrogen halides to alkenes

Question: My attempt: I made the carbocation on the carbon labelled $1$ because I think that the positive charge would be slightly more stable on $1$ compared to $2$ due to the inductive effect of $\...
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What is the reaction mechanism of nitrogen leaving from diazo compounds?

When a diazo compound is formed, and then a nucleophile is added to the mixture. Will nitrogen gas leave first or will the nucleophile have to "do" a substitution reaction? What I mean is will the ...
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Why does a carbocation undergo covalent bonding with, say, chloride, rather than ionic bonding, like what occurs between Na+ and Cl-?

I've been trying to look for an answer for a while but I can't find one. Why does a carbocation accept an electron pair from a nucleophile and form a covalent bond rather than just accepting one ...