which is stabler
a)aryrl carbocation
b)vinyl cabocation
For the aryl carbocation , there are 2 reso structure posible for it and there even no hyperconjugation for vinyl carbocation.So aryl must be stabler
But in the most recognised book "SOLOMNS" by the use of ots(oxytosyl group,one of the best leaving group) vinyl carbocation is formed but aryl is not,which suggests vinyl is stabler
1no . vinyl is definitely less stable than benzyl .
OTs is a very good leaving group . this will depend on the Nucleophile. this would not have happened with out the attack of a nucleophile I feel.
1In the literature Vinyl and Aryl (Please note Aryl is different from Benzyl) carbocations are grouped together. Both these are generally not stabilized and hence vinyl and aryl halides donot undergo SN1 reactions.
No hyperconjugation is possible in Aryl carbocation because the sp2 orbital without electron is not in the same plane as the C-H bond on the next carbon.
1another in favour of vinyl
in the formation of aryl from benzene there is loss of aromaticity,so large energy is required
but vinyl is formed from ethene (no such loss of aromaticity)therefore
vinyl is stabler
19aryl cation( more commonly phenyl cation) is much less stable than the vinyl cation....the former involves loss of aromaticity of the highly stable ring !!