POTENTIALS AND REACTIONS OF SOME ELECTROGENERATED RADICALS

Organic molecules bearing a potential leaving group can be reduced ind irectly by mediators such as anion radicals of aromatic compounds with cleavage of a sigma-bond and formation of a radical and the leaving g roup. The radical moiety can react further with the mediator by coupli ng or reduction. Both types of reactions may be of preparative value, even if the regioselectivity of the coupling reaction is less than des irable. The relatively low regioselectivity may be counterbalanced by the possibility of obtaining substitutions in ''unusual'' positions. T he competition between coupling and reduction of the radical by mediat ors can serve as a measure of the reduction potential of the radical. A method has been developed for an estimation of reduction and standar d potentials of different types of short-lived radicals such as alkyl, allyl, benzyl, and acyl radicals. The knowledge of these potentials i s useful for predicting whether ionic or radical products may be expec ted in a given reaction.