Photochemical reactions of chlorobenzene derivatives in benzene

Abstract

U.v. irradiation of a variety of substituted chlorobenzenes in benzene gives the corresponding biphenyls, accompanied in some cases by products of reductive dechlorination. m-Chlorofluorobenzene and p-bromochlorobenzene react with selective replacement of the heavier halogen. Isomer ratios have been measured for the photochemical phenylation of anisole with chloro-, bromo-, and iodo-benzenes. The excited singlet state of the chloro-compound is implicated in the mechanism of these reactions. Chloronitrobenzenes, which are photostable in benzene, are slowly reduced to nitrobenzene on irradiation in ethanol.