ELECTROCHEMICAL REDUCTION OF NITROBENZYL HALIDES IN ACETONITRILE

The electrochemical reduction of nitrobenzyl chlorides and bromides has been studied in acetonitrile solution. Electrochemical and spectroscopic methods show that the reduction of a nitrobenzyl halide is initially a one-electron process which gives the corresponding anion radical. In the case of an anion radical of either o- or p-nitrobenzyl halide, halide ion is rapidly lost to give the neutral nitrobenzyl radical. Although the principal pathway for the reaction of the nitrobenzyl radical is dimerization, a small amount of the product of hydrogen atom abstraction is also observed. The subsequent reduction of the corresponding dinitrobibenzyl and nitrotoluene to the dianion and the anion radical, respectively, completes the overall two-electron process. Decomposition of an anion radical of either m-nitrobenzyl chloride or m-nitrobenzyl bromide occurs more slowly than in the case of the ortho and para isomers. Although the short-term chronoamperometric and cyclic voltammetric results are consistent with a reaction pathway involving hydrogen atom abstraction and m-nitrotoluene formation, controlled-potential coulometry indicates that less than 40% of the theoretical amount of m-nitrotoluene is actually present. No other products, including a dimer, could be found electrochemically or by gas chromatography. © 1969, American Chemical Society. All rights reserved.