Formation of halide-ions on one-electron reduction of halogenated nitroimidazoles in aqueous solution. A radiolytic study.

Reactions of e-aq, (CH3)2COH and CO.2- with a series of halogenated nitroimidazoles (ArNO2) results predominantly in the formation of their one-electron reduced species (ArNO.2-), the properties of which are consistent with those of other nitroimidazole radical anions. Further, one-electron reduction of ArNO2 ultimately leads to production of halide ion (X-); G(X-) = 1.2 to 2.2. In the presence of either the nitroxyl free radical, norpseudopelletierine-N-oxyl (NPPN), or oxygen the yield of X- is reduced and 'residual' yields of X- were observed, G(X-) = 0.08 to 0.43. From the results it is suggested that less than or equal to 10 per cent of the yield of reducing species results in the production of X- and an imidazolyl-type radical and that the majority of the yield of X- results from subsequent reactions of ArNO.2- (e.g. bimolecular reactions).