KINETICS AND MECHANISM OF REACTION BETWEEN METHYLCOBALAMIN AND MERCURIC-CHLORIDE

The reaction between the organometallic compound methylcobalamin and mercuric chloride has been studied at several temperatures by ultraviolet-visible spectrophotometric and electron capture gas chromatographic methods. The mechanism of the reaction is shown to involve a transfer of a methyl group as a carbanion from base on" methylcobalamin to mercuric chloride and the activation parameters have been determined. The initial product is methylmercury rather than dimethylmercury. Where mercuric chloride is in excess no dimethylmercury can be detected as a product of the reaction. This mechanistic study is related to the environmentally important process of mercury methylation leading to the occurrence of toxic methylmercury species under natural conditions. © 1978."