Electrochemical reduction of 4,4 '-(2,2,2-trichloroethane-1,1-diyl)bis(chlorobenzene) (DDT) and 4,4 '-(2,2-dichloroethane-1,1-diyl)bis(chlorobenzene) (DDD) at carbon cathodes in dimethylformamide

摘要

In dimethylformamide containing tetramethylammonium tetrafluoroborate, cyclic voltammograms for reduction of 4,4'-(2,2,2-trichloroethane-1,1-diyl)bis(chlorobenzene) (DDT) at a glassy carbon cathode exhibit five waves, whereas three waves are observed for the reduction of 4,4'-(2,2-dichloroethane-1,1-diyl)bis(chlorobenzene) (DDD). Bulk electrolyses of DDT and DDD afford 4,4'-(ethene-1,1-diyl)bis(chlorobenzene) (DDNU) as principal product (67-94%), together with 4,4'-(2-chloroethene- 1,1-diyl)bis(chlorobenzene) (DDMU), 1-chloro-4-styrylbenzene. and traces of both 1,1-diphenylethane and 4,4'-(ethane-1, l-diyl)bis(chlorobenzene) (DDO). For electrolyses of DDT and DDD, the coulometric n values are essentially 4 and 2, respectively. When DDT is reduced in the presence of a large excess of D2O, the resulting DDNU and DDMU are almost fully deuterated, indicating that reductive cleavage of the carbon-chlorine bonds of DDT is a two-electron process that involves carbanion intermediates. A mechanistic scheme is proposed to account for the formation of the various products.