Question

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following ?

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• A. Hyperconjugation
• B. $+R$ effect of $-C{H}_3$ groups
• C. $-R$ effect of $-C{H}_3$ groups
• D. $-I$ effect of $C{H}_3$ groups

Answer 1

The correct option is A Hyperconjugation

Tertiary carbocations are stable due to inductive effect (+I effect of alkyl groups) and hyperconjugation.

Tert. butyl carbocation has greater number of $9\alpha -H$ in comparison to sec butyl carbocation which has only $5\alpha -H$. This increases hyperconjugation which results to its greater stability.