Electrochemical Reduction of 1,6-Dihalohexanes at Carbon Cathodes in Dimethylformamide
作者:Mohammad S. Mubarak、Dennis G. Peters
DOI:10.1021/jo00108a034
日期:1995.2
Cyclic voltammograms for the reduction of 1,6-dibromo-, 1,6-diiodo-, 1-bromo-6-chloro-, and 1-chloro-6-iodohexane at glassy carbon electrodes in dimethylformamide containing tetramethylammonium perchlorate exhibit single irreversible waves that correspond to the reductive cleavage of carbon-bromine or carbon-iodine bonds. When large-scale controlled-potential electrolyses of either 1,6-dibromo- or 1,6-diiodohexane are performed at reticulated vitreous carbon, the principal products are n-hexane (30-45%), 1-hexene (28-34%), 1,5-hexadiene (6-16%), and cyclohexane (<7%), with n-dodecane being another significant species obtained from 1,6-diiodohexane. Because a carbon-chlorine bond is not directly reducible, 1-bromo-6-chloro- and 1-chloro-5-iodohexane give rise mainly to 1-chlorohexane (47-64%), 6-chloro-1-hexene (20-33%), and 1,12-dichlorododecane (2-25%). From these product distributions, and with the aid of experiments done in the presence of deuterium-labeled reagents, we conclude that the electrolytic reduction of 1,6-diiodo- and 1-chloro-6-iodohexane involves both radical and carbanion intermediates, whereas only carbanionic pathways are important for electrolyses of 1,6-dibromo- and 1-bromo-6-chlorohexane.