Electrochemical reduction of (1R,2r,3S,4R,5r,6S)-hexachlorocyclohexane (Lindane) at carbon cathodes in dimethylformamide

Direct reduction of Lindane (1R,2r,3S,4R,5r,6S-hexachlorocyclohexane, 1) at carbon cathodes in dimethylformamide (DMF) containing 0.10 M tetra-n-butylammonium tetrafluoroborate (TBABF4) has been explored by means of cyclic voltammetry and controlled-potential (bulk) electrolysis. Cyclic voltammograms for reduction of 1 at a glassy carbon electrode exhibit two cathodic peaks at −1.40 V and −2.10 V as well as an anodic peak at −1.93 V; the first cathodic peak is attributed to reduction of 1 itself, whereas the second cathodic peak is due to reduction of chlorobenzene that is derived from 1. Controlled-potential (bulk) electrolyses conducted with reticulated vitreous carbon electrodes held at −1.70 or −2.20 V reveal that reduction of 1 is essentially a six-electron process that affords benzene as major product (80–100% yield) along with small amounts of chlorobenzene (3–10% yield). To account for these products, a mechanism is proposed that is supported by the results of theoretical computations based on density functional theory.