Based on chem. and phys. evidence, a single electron transfer (SET) mechanism for the generation of dihalocarbene from haloform and sodium hydroxide is suggested. 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 the carbon-carbon double bond. The primary electron donor in this reaction is CX3- (X = halo) and the main electron acceptor is the haloform present in excess.

Key words: REACTION MECHANISM, HALIDE, CHLOROFORM, CARBENE, ELECTRON TRANSFER, HALOHYDROCARBON, SINGLE ELECTRON TRANSFER REACTION