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.