Which of the following carbocations is the most stable?

A $CH X_{3} X^{+}$
B $CH X_{3} CH X_{2} X^{+}$
C $C X_{6} H X_{5} - CH X_{2} X^{+}$
D $CH X_{2} = CH X^{+}$

Answer: C

The benzyl cation is stabilised by delocalisation of the positive charge into the benzene ring through resonance. The other cations have no such delocalisation: the methyl and ethyl cations are only weakly stabilised and the vinyl cation is destabilised.

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Which of the following carbocations is the most stable?

Answer: C

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