Formation and Spectroscopic Investigation of Two Hexachlorobornanes from Six Environmentally Relevant Toxaphene Components by Reductive Dechlorination in Soil under Anaerobic Conditions

Six pure polychlorinated bornanes isolated from technical toxaphene, namely, Parlar 32 (toxicant B), Parlar 42a (toxicant A1), Parlar 42b (toxicant A2), Parlar 49a, Parlar 56, and Parlar 59, as well as the technical mixture were investigated as to their fate in a loamy silt under anaerobic conditions by laboratory studies taking 4 or 6 months. All test substances shared the geminal dichloro group in the C-2 position and, additionally, one chlorine atom each in the C-5endo and C-6exo positions, respectively. Reductive dechlorination was the major reaction leading to a sequential removal of a chlorine atom from each geminal dichloro group. Generally, in the first step of transformation, all six compounds lost a chlorine atom from the geminal dichloro group in the C-2 position, preferentially from the endo-position. The dechlorination rate was in the order of nonachlorobornanes > octachlorobornanes > heptachlorobornanes. While the two monodechlorination products formed from Parlar 32 underwent no further tra...