Carbon tetrachloride dechlorination by the bacterial transition metal chelator pyridine-2,6-bis(thiocarboxylic acid)

A reaction pathway is proposed to explain the formation of end products dur ing defined chemical reactions between carbon tetrachloride (CCl4) and eith er metal complexes of pyridine-2,6-bis(thiocarboxylic acid) (PDTC) or pure cultures of Pseudomonas stutzeri KC. The pathway includes one-electron redu ction of CCl4 by the Cu(II):PDTC complex, condensation of trichloromethyl a nd thiyl radicals, and hydrolysis of a labile thioester intermediate. Produ cts detected were carbon dioxide, chloride, carbonyl sulfide, carbon disulf ide, and dipicolinic acid. Spin-trapping and electrospray MS/MS experiments gave evidence of trichloromethyl and thiyl radicals generated by reaction of CCl4 with PDTC and copper. Experiments testing the effects of transition metals showed that dechlorination by PDTC requires copper and is inhibited by cobalt but not by iron or nickel. PDTC was shown to react stoichiometri cally rather than catalytically without added reducing equivalents. With ad ded reductants, an increased turnover was seen along with increased chlorof orm production.