Question

Which among the following will be most stable radical?

• A. $CH_2= \dot{C}H$
• B. $H_2C = CH-\dot{C}H_2$
• C. Benzyl radical
• D. Cyclohexene radical

Answer 1

Answer: (C)

C

Answer 2

Radical stability increases with resonance and hyperconjugation. The vinyl radical (A) is least stable due to the unpaired electron on an sp2 carbon. The allyl radical (B) is resonance stabilized. The benzyl radical (C) is highly resonance stabilized by delocalization into the aromatic ring. Option D, a cyclohexene radical, is also resonance stabilized but to a lesser extent than the benzyl radical. Therefore, the benzyl radical is the most stable.