Which of the following free radicals is most stable?


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Correct Answer: B. 2
Carbon-centered radicals follow the same rules of stability as carbocations: the greater number of alkyl groups directly connected to a carbon atom, the greater the stabilization. Of the choices, B and D have the greater substitution around the radical carbon center (2o). B, however, can also be described as an allylic radical; the pi system of a double bond stabilizes an adjacent radical through resonance. Remember that delocalizing the radical is a stabilizing effect.

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