Chain mechanisms for the dehydro-bromination of ring-substituted α-bromoacetophenones in alcohols

Ring substituted α-bromoacetophenones undergo efficient photodecomposition upon ultraviolet irradiation in alcohol solvents. The process involves chain reactions mediated by the ketyl radicals derived by hydrogen abstraction from the alcohols. It is suggested that two chain reactions involving hydrogen and electron transfer may be taking place concurrently. Competitive studies lead to relative rate constants for the reactions of ketyl radicals with ring-substituted α-bromoacetophenones.