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 ...

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Is the phenyl cation or ethynylium more stable?

I recently gave an exam and I received an interesting question to which I believe the answer is wrong. Given two compounds, a benzene molecule with carbocation at one of its constituting carbon atoms ...
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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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Dehydration of primary, secondary & tertiary alcohols

Rate of dehydration when given compounds are treated with conc. H2SO4 is According to me the answer should be $R > Q > S > P$ but my textbook solution gives the answer as R > Q > P > S ...
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Stability between Tropylium and Tri cyclopropyl methyl carbocation

Why is Tropylium less stable than Tri cyclopropyl methyl carbocation? Tri cyclopropyl methyl carbocation undergoes sigma-tropic rearrangement whereas Tropylium is highly stable due to conjugated ...
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1answer
50 views

Formation of Tropylium carbocation

I've read that Tropylium carbocation is formed by the ring expansion of benzyl carbocation. But in benzyl carbocation, the $\ce{C}$ atoms in the benzene ring are $sp^2$ hybridized i.e. $120^\circ$ is ...
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1answer
26 views

Formation of thermodynamic product from 1,4-addition

Question: The temperature is high enough for formation of the thermodynamic product. Now, there are two possibilities: Starting with the top double bond 2 Or, starting from the bottom double ...
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1answer
49 views

Carbocation Stability

A homework question I was given asked me to identify the most stable carbocation between these 4. I was able to narrow it down to either the trifluoromethylcyclohexane carbocation or the ...
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33 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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1answer
65 views

Dependence of carbocation stability with respect to the length of alkyl group

Which carbocation is more stable, the ethyl carbocation or n-propyl carbocation? What is the effect of alkyl group length on the stability of a carbocation?
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Thermodynamic and kinetic products - carbocation stability

The professor wants to know which is the thermodynamic product and which is the kinetic product. He says there are only two products - the two on the right that result from the ...
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1answer
234 views

Why are tertiary carbocations so stable?

Today our lecturer provided this data to illustrate the relative stability of carbocations. \begin{array}{|c|c|c|c|c|} \hline \text{Substrate} & \ce{t-BuBr} & \ce{i-PrBr} & \ce{EtBr} ...
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Is an ethyl shift possible in the reaction of 2-chloro-N,N-diethylbutan-1-amine with an hydroxyl ion?

What is the major product of the following reaction? $$\ce{(CH3CH2)2N-CH2-CHCl-CH2CH3 ->C[{}^{-}OH]}\qquad ?$$ Please see the option of problem 3 in the image below: My initial thought was ...
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1answer
77 views

Why does fluorine stabilise a carbocation?

I have read that halogens have a stonger -I (inductive effect) than +M (mesomeric effect),then why do they stabilise a carbocation instead of destabilising it? I asked this doubt to my teacher and he ...
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1answer
67 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
304 views

Stability of carbocations: CF3+ vs CH3+

Is $\ce{CF_3+}$ more stable than $\ce{CH_3+}$? In $\ce{CF_3+}$, there is $\ce{C-F}$ back bonding that increases stability of the carbocations. But -I effect of $\ce{F}$ dominates +R effect and this ...
3
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38 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 ...
3
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0answers
57 views

Influence of neighboring fluorine and hydroxyl on carbocation

Which of the 2-fluorobutan-3-yl and butan-2-ol-3-yl carbocations will be more stable? I know that fluorine has a greater electron-withdrawing inductive effect, but what about the resonance effect of ...
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0answers
22 views

Stability order

The stability order of $\ce{(CH3)3C+ > (C6H5)H2C+}$ ,its the same for free radicals too. Why is it like that, because the phenyl is resonance stabilized ,it should provide more stability. I ...
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1answer
211 views

Do vinyl cations adopt a classical or non-classical structure?

Whilst reading this question today, I remembered something that I had seen previously here. In the second linked question, @Martin provided a reference to suggest that vinyl cations actually adopt a ...
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2answers
716 views

Which of the following is the more stable carbocation?

Which of the following is the more stable carbocation? I thought the 1st carbocation would be the more stable one as the pi-electron density of phenyl group can overlap with the vacant orbital on ...
2
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1answer
124 views

Confused about carbocation stability

For which element 'X' is the carbocation $\ce{CH3-X-CH2+}$ the most stable? A. X = S B. X = N C. X = O I thought since oxygen is the most electronegative among the options, it would create the ...
2
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1answer
132 views

Stability of carbocation intermediates: secondary alkane versus primary allyl?

Say I have the following carbocations: The first is secondary; the second is resonance stabilized, but primary. Which is more stable and why? I've been looking around in my textbooks and haven't ...
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1answer
92 views

How can I- be both a nucleophile and a weak base?

I am just confused as to how $\ce{I-}$ cannot attract $\ce{H+}$, but it can attack a carbocation. It is sharing electrons in both cases, so what is the difference?
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1answer
122 views

Cyclopentyl to cyclohexyl carbocation rearrangement

Here is my problem. The mechanism seems pretty straightforward, but I am having trouble converting the cyclopentane to a cyclohexane. During a synthesis problem, does the starting material add the ...
2
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1answer
74 views

How can I predict the product of the reaction of a substituted tetrahydrofuran with HI?

Well, this looks like a pretty straight forward question. But I am getting stuck at the point when preference is being given to the less stable 1° carbocation to form the product. Or am I writing an ...
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154 views

SN1 reactivity order

The question is to compare the SN1 reactivity for the following compounds. According to me it should be like R>S>Q>P. But the correct answer is Q>P>R>S. How can a lone pair donating into a vacant p ...
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1answer
274 views

Stability of a carbocation, in part of camphor synthesis

Can someone explain to me why there is a rearrangement reaction of carbocation 1 to carbocation 2? To me the second carbocation appears to be less stable than the first because it is less substituted. ...
22
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1answer
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What is a non-classical carbocation?

What is a non-classical carbocation? How is it different from a classical carbocation? I am confused as I have come across this term many times on Chem.SE but there seems to be nothing for my ...
3
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1answer
88 views

Does the carbocation rearrangement in a SN1 reaction specify a change in degree?

I am asked to determine whether the following process is likely to involve a carbocation rearrangement or not: I think it is possible through the rearrangement given above (though the ...
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2answers
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Why are tertiary carbocations the most reactive, if they're already stable?

This may seem silly, but doesn't it seem weird for a compound that's stable (in this context, the tertiary carbocation) to be the most reactive? I mean, wouldn't it be the least, given that it's ...
5
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1answer
243 views

Ring expansion from a given cyclic carbocation

How will the cyclobutane ring behave in the following case? I initially thought there would be ring expansion to a five membered ring so that there may be less angle strain and a secondary ...
3
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1answer
953 views

Benzylic and allylic carbocation stability order [closed]

Most books I have read stop at this order : Benzylic > Allylic > Tertiary > secondary > primary However If I want to compare tertiary, secondary and primary benzylic and Allylic carbocations what ...
3
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Are carbocation intermediates in equilibrium?

So for the reaction of $\ce{H_2O}$ with an alkyl ethene, in the presence of $\ce{D^+}$ ions, forms two possible carbocations: $\ce{ R-CHD-CH2^+}$ and $\ce{R-CH^+-CH2D}$ The major product formed is ...
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1answer
250 views

Mechanism for acid-catalyzed dehydration of 2,3-dimethylcyclopentanol

How do you get from 2,3-dimethylcyclopentanol to 1,2-dimethylcyclopent-1-ene? I know the -OH group leaves as water (being protonated by acid) forming a carbocation. Then the weak nucleophile (water) ...
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Which carbocation is more stable, the ethyl- or 1-propyl-carbocation?

$\ce{C2H5+ vs \ C3H7+}$ There are two conflicting trends here. Inductive effect of ethyl will be higher than that of methyl so carbocation attached to ethyl (3 carbons in total) should be more ...
3
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1answer
223 views

Carbocation Rearrangement Due To Ring Strain And Back Bonding

Today our teacher told us that the following carbocation rearrangement occurs due to back bonding.I could not really follow what he meant.Can someone please explain what is actually happening during ...
8
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3answers
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Addition of HBr to Vinyl bromide

The addition of $\ce{HBr}$ to $\ce{CH2=CHBr}$ produces $\ce{CH3-CHBr2}$. Why is this so? According to me, halogens have a stronger $-I$ effect than a $+M$ effect (for example a halogen substituent on ...
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2answers
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Can Hydride Shift and Methyl shift happen one after another in a carbocation?

Can hydride shift be followed by methyl shift for stabilizing a carbocation? In case both is possible which will occur first?
16
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1k views

Carbocation stability order

I was wondering whether the following order (from here) is correct: In the first inequality, why did 9 hyperconjugations dominated resonance effect of benzene ring? In the last inequality ...
3
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1answer
47 views

What makes E1 more favourable than SN1?

Each goes through a carbocation intermediate which is enormously reactive so what would promote attack towards a proton (E1) rather than towards the carbocation for substitution. Besides an increase ...
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2answers
867 views

How does a carbocation have a positive charge?

When an alkene bonds with an H+ ion, the electron pair from the pi bond goes towards a new dative covalent bond with the hydrogen ion, leaving, on one side of the old double bond, a carbon bonded to ...
4
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1answer
226 views

Carbocation rearrangement in alkene addition reaction

This is a question from my textbook: Determine a step-wise $S_N1$ mechanism for the overall reaction: The solution shows the following carbocation rearrangement after Bromine leaves in the ...
5
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2answers
3k views

Why cyclopropylmethyl carbocation is more stable Benzyl carbocation?

I know in tri cyclopropylmethyl carbocation the hybridization of carbocation will be pushed to $sp^2$ but how? Can someone explain this to me by drawing resonance structures for tri cyclopropyl methyl ...
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Are carbocations that bad?

My professor has an anti-fetish for carbocations. In any mechanism that we draw with a carbocation, the maximum earnable credit is automatically halved. In any case, he draws all mechanisms involving ...
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1answer
113 views

Rearrangements; Carbocations; E1 Mechanism

If the leaving of the leaving group creates a secondary carbocation, and a tertiary carbocation has the possibility of being formed through a 1,2 methyl shift: 1) Will the methyl shift? I'm guessing ...
4
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1answer
2k views

Instability of vinylic and arylic carbocations

I have checked the net a lot and read quite a few books, but I still am not able to understand why vinylic and arylic carbocations are so unstable. Can someone please help For arylic carbocation, the ...
6
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3answers
965 views

Stability of cyclobutyl methyl carbocation

I know that cyclopropyl methyl carbocation is exceptionally stable compared to say, benzyl carbocation. But I want to know how stable is cyclobutyl methyl carbocation compared to say, ...
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6answers
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Will bridged compounds undergo SN1 reaction?

$\mathrm{S}_{\mathrm{N}}1$ reaction involves only one molecule in the rate determining step. So, the molecule which undergoes $\mathrm{S}_{\mathrm{N}}1$ reaction should be stable when it forms a ...
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Why does carbocation stability increase in the order 1°, 2°, 3°?

I'm reading about $\:\mathrm{S_N1}$ and $\:\mathrm{S_N2}$ reaction mechanisms. 1° carbocations are unstable to the point of not having been observed in solution, ever. 2° are more stable, and 3° ...
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1answer
645 views

Resonance in carbocation derived from allenes

During a reaction if addition on one of the $\pi$ bonds of an allene(containing even number of $\pi$ bonds like $\ce {H2C=C=CH2}$) takes place then a carbocation is formed. To decide the position of ...