Irradiation of 3, 4-dibromobiphenyl (BpBr2) in acetonitrile resulted in the formation of 4- bromobiphenyl (BpBr) and 3-bromobiphenyl (3-BpBr) in a ratio of 7.6±0.1 up to 22% conversion of starting material. The dependence of the reciprocal of the quantum yield (1 Φ) upon 1 BpBr 2 is linear. Reduction of BpBr2 with lithium di-tert-butylbiphenylide generates a 3.6: 1.0 ratio of BpBr to 3-BpBr, while photohyrodebromination of BpBr2 in the presence of ...