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Electrochemical reduction of alkyl halides at vitreous carbon cathodes in dimethylformamide

1986; Elsevier BV; Volume: 198; Issue: 1 Linguagem: Inglês

10.1016/0022-0728(86)90030-6

2590-2954

James A. Cleary, Mohammad S. Mubarak, Kenneth L. Vieira, Mark R. Anderson, Dennis G. Peters,

Marine Toxins and Detection Methods

At vitreous carbon electrodes in dimethylformamide which contains tetramethylammonium perchlorate, cyclic voltammograms for 1-iododecane, 1-bromodecane, and 2-bromooctane consist of one irreversible reduction wave signaling formation of the alkyl carbanion, whereas voltammograms for 2-iodooctane, t-butyl bromide, and t-butyl iodide reveal stepwise generation of the alkyl radical and carbanion. Large-scale electrolysis of 1-iododecane at reticulated vitreous carbon yields decane, eicosane, 1-decene, and 1-decanol; the first two compounds arise, respectively, from reaction of decyl carbanions with a proton donor and with unreduced alkyl iodide, whereas the last two species are produced via chemical attack of hydroxide ion on 1-iododecane. Reduction of 1-bromodecane results in production of decane, 1-decene, and 1-decanol, but little or no eicosane is seen. Electrolysis of 2-bromooctane gives octane, 1-octene, 2-octene, 2-octanol, and 7,8-dimethyltetradecane, the last species probably being formed by coupling of 2-octyl radicals; the other compounds are derived from the 2-octyl carbanion. Although products obtained upon reduction of 2-iodooctane are identical with those from 2-bromooctane, both radicals and carbanions (the relative amounts of which are potential dependent) are involved in the formation of products from the secondary alkyl iodide. A combination of reactions involving t-butyl radicals and t-butyl carbanions is responsible for production of isobutane, isobutylene, and 2,2,3,3-tetramethylbutane during electrolyses of t-butyl bromide.