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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Friedel–Crafts alkylation of benzene with propyl chloride

This is a question from my textbook: Why does the alkylation of benzene with 1-chloropropane give (propan-2-yl)benzene and not (propan-1-yl)benzene? The book shows the reaction with chloromethane ...
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277 views

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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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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159 views

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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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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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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2k views

How do we check octet rule in resonance structures?

For example, this carbon has an incomplete octet: Can we say this is because C has configuration $\mathrm{1s^2 2s^2 2p^2}$ and hence here its just forming 3 bonds whereas it should form 4 to make it $...
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293 views

Nucleophile substitution in nonclassical carbocation

In nucleophilic substitution of exo-2-norbornyl brosylate, carbocation formation is the rate determining step and the carbocation formed is: (in equilibrium) After forming carbocation, the ...
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1answer
153 views

Is this rearrangement in carbocation possible?

Generally, in the following type of reactions, positive charge on $\alpha$-Carbon causes ring expansion, but in the following example positive charge is formed on $\beta$-Carbon and the cation is ...
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1answer
56 views

Rearrangement considerations in feasibility of SN1 in given reactants

I have been asked to compare the feasibility of Unimolecular Nucleophilic Substitution ($\mathrm{S_N1}$) in the following question. I have received instruction that the reaction will be feasible only ...
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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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180 views

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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Carbocation ring expansion jump

is the given rearrangement possible {major product}? from cyclo butane derivative to cyclohexane derivative.
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What is the order of stability of the following carbocations?

What is the order of stability of the following carbocations? I think that it is clear thatt the first two are more stable than the last 2 as they involve resonance in ring, i.e. the mesomeric ...
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If alkyl-substituted alkenes are more stable, how does one explain their increased addition reactivity?

My understanding is that in alkyl-substituted alkenes there is hyperconjugation between $𝜎(\ce{C−X})$ and $𝜋^∗(\ce{C=C})$. I also have read that more alkyl-substituted alkenes are many folds more ...
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Chirality in carbocations

The following compound is a carbocation. Clearly, the given compound does not have any element of symmetry. The compound is non planar due to the presence of ethyl group. Thus it must be chiral. But ...
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44 views

Does 2,2-dimethylpropan-1-ol give a positive Lucas test?

I learnt that the Lucas test involves the formation of a carbocation and it gives a positive test based on the stability of the carbocation formed, and hence primary alcohols do not show turbidity (...
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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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63 views

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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283 views

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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96 views

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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196 views

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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Is the Friedel-Crafts alkylation of benzene with cyclopropenyl chloride feasible?

Is the Friedel-Crafts alkylation of benzene with cyclopropenyl chloride according to the following scheme feasible? Would the attack of the benzene towards the cycopropylium take place? I am ...
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1answer
210 views

Stability of carbocations

We know that if a structure has all equivalent resonance structures, then it will be highly stabilised. So then why benzylic carbocation is more stable than other cyclic allylic carbocations, though ...
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1answer
866 views

Isn't the mechanism of aqueous sodium hydroxide and 1-bromobutane involves both heterolytic bond fission and attacking by a nucleophile?

What is involved in the mechanism of the reaction between aqueous sodium hydroxide and 1-bromobutane? A. attack by a nucleophile on a carbon atom with a partial positive charge B. heterolytic bond ...
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35 views

What is the order of stability of the cyclobutyl and cyclopropyl carbocations?

I know about the exceptional stability of Cyclopropylmethyl carbocation. In some books it is given that cyclopropyl and cyclobutyl carbocations are highly unstable due to their high strain. That ...
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202 views

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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142 views

Migratory aptitude of substituents for carbonation rearrangement in Pinnacol Pinnacolone rearrangment

Generally, the observed migratory aptitude for carbocation rearrangement is (as given in various books) : $$\ce{H- > Ph- >CH_3-}$$ But the fact is that the carbocation at the benzylic carbon ...
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1answer
245 views

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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880 views

Esterification with tertiary alcohol

I saw a different mechanism for esterification of tertiary alcohol in a book. They say that first the $\ce{OH}$ is protonated and it leaves to form the tertiary carbocation. Then the oxygen's lone ...
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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?