Question

Sort the following free radicals according to their stability in increasing order.

• A. $\mathrm{Methyl}\mathrm{Carbocation}$
• B. $\mathrm{Primary}\mathrm{Carbocation}$
• C. $\mathrm{Tertiary}\mathrm{Carbocation}$
• D. $\mathrm{Secondary}\mathrm{Carbocation}$

Answer 1

Stability order of carbocations: Methyl < 1^o < 2^o < 3⁰

These species display stability as a function of increasing substitution at the central carbon. This expectation is borne out by experimental measurements. Presumably replacement of a hydrogen atom by an alkyl group creates the possibility for hyperconjugative stabilization of the free radical in the same way it does for the carbocation.