FORMATION AND SPECTROSCOPIC INVESTIGATION OF 2 HEXACHLOROBORNANES FROM 6 ENVIRONMENTALLY RELEVANT TOXAPHENE COMPONENTS BY REDUCTIVE DECHLORINATION IN SOIL UNDER ANAEROBIC CONDITIONS

Six pure polychlorinated bornanes isolated from technical toxaphene, n amely, Parlar 32 (toxicant B), Parlar 42a (toxicant A(1)), Parlar 42b (toxicant A(2)), Parlar 49a, Parlar 56, and Parlar 59, as well as the technical mixture were investigated as to their fate in a loamy silt u nder anaerobic conditions by laboratory studies taking 4 or 6 months. All test substances shared the geminal dichloro group in the C-2 posit ion and, additionally, one chlorine atom each in the C-5(endo) and C-6 (exo) 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 gro up in the C-2 position, preferentially from the endo-position. The dec hlorination rate was in the order of nonachlorobornanes > octachlorobo rnanes > heptachlorobornanes. While the two monodechlorination product s formed from Parlar 32 underwent no further transformation, those pro ducts with additional geminal dichloro groups lost further chlorine at oms from exactly these groups. Finally, all six compounds formed two v ery stable end-metabolites in different ratios, which have been isolat ed and identified as 2-exo,5-endo,6-exo,8c,9b,10a- and 2-endo,5-endo,6 -exo, 8c,9b,10a-hexachlorobornane. Additionally, one of these end-meta bolites was identified as the major product of the degradation of tech nical toxaphene after 6 months.