REDUCTIVE DECHLORINATION OF CARBON-TETRACHLORIDE BY COBALAMIN(II) IN THE PRESENCE OF DITHIOTHREITOL - MECHANISTIC STUDY, EFFECT OF REDOX POTENTIAL AND PH

A mechanistic study of the reductive dechlorination of carbon tetrachl oride by vitamin B-12 (cyanocobalamin) in the presence of dithiothreit ol was conducted as a function of redox potential and pH. The solution redox potential decreased both with an increase in the total concentr ation of dithiothreitol present and with an increase in pH. The pseudo -first-order rate constant of carbon tetrachloride disappearance incre ased with decreasing redox potential. The predominant cobalt species p resent under the reaction conditions was cobalamin(II) (vitamin B-12r) , as confirmed by spectrophotometric analysis, suggesting a one-electr on reduction of vitamin B-12 and the involvement of two vitamin B-12 m olecules per reacting carbon tetrachloride molecule. This study illust rates the role of Co(II) in reductive dechlorination by vitamin B-12.