Single electron transfer mechanism in the generation of dihalocarbene from haloform

Abstract

Based on chemical and physical evidences, a single electron transfer (SET)mechanism for the reaction of generating dihalocarbene from haloform and sodium hydroxide is suggested. It is proved that no equilibrium exists between the carbenoid-trihalocarbanion and dihalocarbene, and the halogen-exchange brought about by trihalomethyl and dihalomethyl radicals formed via the single electron transfer process occurs prior to the addition of carbene to carbon-carbon double bond. The primary electron donor in this reaction is CX_3~- and the main electron acceptor is the haloform present in excess.