One-electron reduction of nitrobenzyl halides produces the anion radicals, which subsequently undergo dehalogenation to form nitrobenzyl radicals. The rate constants for these processes have been studied by pulse radiolysis in aqueous alcoholic solutions. a-Substitution with a methyl group increases the rate of dehalogenation by weakening the C-X bond. On the other hand, substitution with a tert-butyl group was found to decrease the rate of dehalogenation considerably. Since the tert-butyl is not expected to increase the C-X bond dissociation energy, it is concluded that its effect is a result of steric interaction, which rotates the C-X bond toward the ring plane and thus decreases the overlap between this bond and the ring T system and slows down the transfer of the electron. Other related compounds have also been examined.

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