Question

Order of stability of vinyl, allyl, tertiary radicals is :

• A. tertiary, vinyl, allyl
• B. vinyl, tertiary, allyl
• C. tertiary, allyl, vinyl
• D. allyl, tertiary, vinyl

Answer 1

Answer: (D)

The stability of alkyl free radicals is not influenced by inductive effect because they have no charge (difference from carbonium and carbanions).
So, they are stabilised by hyperconjugation (no bond resonance).
The relative order of stability of common free radical.
Tri phenylmethyl $>$ benzyl $>$ allyl $>$ tert. $>$ sec. $>$ pri.$>$ methyl $>$ venyl.