# Comparing the stabilities of allylic, benzylic, and tertiary radicals

Which is the most stable free radical among the given species?
(1) $$\ce{CH2=CH-CH2^.}$$ (allyl radical)
(2) $$\ce{C6H5-CH2^.}$$ (benzyl radical)
(3) $$\ce{(H3C)3C^.}$$ (t-butyl radical)
(4) $$\ce{C2H5^.}$$ (ethyl radical)

The book claims the answer to be the allyl radical, option 1. But how can we definitely say that the allylic free radical is more stable, compared to the benzyl radical (option 2) which is also resonance-stabilised, or the tertiary radical (option 3) which has more hyperconjugative donation from α-hydrogen atoms?

• I just want to say your book is correct. In simple words in this case benzyl free radical has resonance but the mesomeric effect is not transmitted to the free radical simply because it does not have a LONE PAIR of electrons. And besides Benzene has a -I effect thus further withdrawing the electrons and making the free radical unstable. (Coz obviously it needs electrons) Jan 2 '20 at 5:51