Question

Why does a carbocation experiences a greater stabilizing effect from hyperconjugation than a radical?

Answer 1

A carbocation stabilizes by hyperconjugation by overlapping of a C-H orbital with two electrons, with an p orbital as follows.

A radical stabilizes by hyper conjugation by the overlap of a C-H orrbital with two electrons and a p orbital with one electron.

In the first scenario, the carbocation hyperconjugates using the bonding orbital of lower energy. In the second scenario, the radical hyperconjugates by filling two electrons in the bonding orbital and one in the antibonding, which is of higher energy. Thus, carbocations achieve a greater stability from hyperconjugation.