Kinetics of the reduction of hexachloroethane by juglone in solutions containing hydrogen

Hexachloroethane was converted to tetrachloroethene and unknown products in solutions containing juglone and hydrogen sulfide. Measured rates of disappearance in solutions containing hydrogen sulfide alone were approximately a factor of 10 slower than rates containing micromolar concentrations of juglone and hydrogen sulfide. Electrochemically-reduced juglone was unreactive with respect to hexachloroethane reduction. Reaction of hexachloroethane with polysulfides produced in the reaction of elemental sulfur with hydrogen sulfide in the experimental solutions also could not account for the rate observed in solutions containing juglone and hydrogen sulfide. Evidence is provided to indicate the reaction of hexachloroethane with the Michael addition product of hydrogen sulfide and juglone. No conclusions can be drawn from the present results as to whether the reaction mechanism is a one- or a two-electron transfer. This study points out the importance of the geochemistry of sulfur and organic matter in the transformation of halogenated alkane pollutants in reducing environments.