Dechlorination of hexachlorobiphenyl by using potassium-sodium alloy.

2,2',4,4',5,5'-Hexachlorobiphenyl (HCB) was dechlorinated with potassium-sodium (K-Na) alloy under an inert gas atmosphere. Solvent effect was observed in the reaction. Dechlorination yields in benzene and cyclohexane were 99.9998%, and 99.99996%, respectively. The reaction was exothermic and proceeded at room temperature. In benzene, trace amounts of polychlorinated biphenyls (PCBs) as products by stepwise dechlorination and polychlorinated quarterphenyls as product of Wurtz-Fittig reaction were detected as reaction intermediate. Reaction products were biphenyl, cyclohexylbenzene, and dicyclohexyl. In cyclohexane, there were no products of Wurtz-Fittig reaction. Dechlorination at para-position preferred to that at ortho-position, judging from analysis of PCBs as intermediates of stepwise dechlorination.