Cyclic,voltammetry and controlled-potential electrolysis have been employed to examine the electrochemical reduction of methyl 2-bromomethylbenzoate at carbon cathodes in dimethylformamide (DMF) containing tetramethylammonium tetrafluoroborate (TMABF(4)). A cyclic voltammogram for the reduction of the substrate exhibits one irreversible cathodic wave with a peak potential of -1.45 V vs. SCE, which is due to the two-electron cleavage of the benzylic carbon-bromine bond. The corresponding reductive peak current also increases incrementally with the amount of water in DMF. Bulk electrolyses of methyl 2-bromomethylbenzoate have been carried out at -1.85 V vs. SCE with different concentrations of water in the solvent. The reduction process involves carbanion intermediates to afford various products including phthalide, which is generated via intramolecular cyclization that is affected by the presence of water. Detailed mechanism for the electrochemical reaction is proposed and further studied by isotope incorporation experiment. (C) 2013 The Electrochemical Society. All rights reserved.