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

Options

A. `+ R` effect of `- CH_3` groups
B. `- R` effect of `- CH_3` groups
C. Hyperconjugation
D. `-1` effect of `- CH_3` groups

Answer

C

Explanation

`underset(9 alpha - H-"atoms")underset("Tertiary butyl carbocation")(H_3C-underset(o+)overset(CH_3)overset(|)(O)-CH_3) " " underset(5 alpha -H" atoms")underset("Secondary butyl carbocation")(H_3C -overset(o+)(C)H-CH_3-CH_3)`
A Tertiary butyl carbocation has 9 alpha hydrogen atoms whereas secondary butyl carbocation has 5 alpha hydrogen atoms.
So when morc number of `alpha - H` atoms is present, more will be the hyperconjugation effect hence more will be the stability of carbocation.
Thus tertiary butyl carbocation is more stable than a secondary butyl carbocation due to hyperconjugation