Dechlorination of hexachlorobiphenyl by using potassium sodium alloy

2,2',4,4',5,5'-Hexachlorobiphenyl (HCB) was dechlorinated with potassium-so dium (K-Na) alloy under an inert gas atmosphere. Solvent effect was observe d in the reaction. Dechlorination yields in benzene and cyclohexane were 99 .9998% and 99.99996%, respectively. The reaction was exothermic and proceed ed at room temperature. In benzene, trace amounts of polychlorinated biphen yls (PCBs) as products by stepwise dechlorination and polychlorinated quart erphenyls as product of Wurtz-Fittig reaction were detected as reaction int ermediate. Reaction products were biphenyl, cyclohexylbenzene, and dicycloh exyl. In cyclohexane, there were no products of Wurtz-Fittig reaction. Dech lorination at para-position preferred to that at ortho-position, judging fr om analysis of PCBs as intermediates of stepwise dechlorination. (C) 2000 E lsevier Science Ltd. All rights reserved.