REDUCTIVE TRANSFORMATION OF TRICHLOROETHENE BY COBALAMIN - REACTIVITIES OF THE INTERMEDIATES ACETYLENE, CHLOROACETYLENE, AND THE DCE ISOMERS

The transformations of acetylene, chloroacetylene, 1,1-dichloroethene (DCE), and cis- and trans-DCE mediated by cobalamin in the presence of titanium(III) citrate were investigated at pH 8 and 22 degrees C. Ace tylene quantitatively reacted to ethene via vinylcobalamin as the prop osed intermediate. Chloroacetylene reacted to acetylene and vinyl chlo ride. Proposed intermediates are ethynylcobalamin and vinylcobalamin, respectively. The principal initial reaction of chloroacetylene formed ethynylcobalamin which decomposed to acetylene. The proposition for e thynyl- and vinylcobalamin formation is based on fitting reaction mode ls to kinetic data. Kinetic modeling suggests half-lives for ethynyl- and vinylcobalamin of 1.4 and 251 h, respectively. 1,1-Dichloroethene reacted to approximately 20% volatiles (ethene, ethane, vinyl chloride , and acetylene) and 80% unidentified nonvolatile products. cis- and t rans-DCE transformed slowly and produced small yields of vinyl chlorid e, ethene, and ethane.