Dual photo- and electro-chemical activation of m-chloronitrobenzene and m-bromonitrobenzene in acetonitrile solution leads to halide loss through a photo-ECE mechanism. This proceeds via absorption of visible light by the radical anions [X-C6H4NO2].-, which is followed by fragmentation forming the .C6H 4NO2 aryl radical. The latter reacts with the solvent system forming nitrobenzene which is further reduced at the electrode with the generation of [C6H5NO2].-. Reduction of m-iodonitrobenzene leads to iodide loss without the need for irradiation. However, this process is accelerated by visible light. In contrast the dual activation of p-cyanonitrobenzene, p-dinitrobenzene, phenyl 4-nitrophenyl sulfone, methyl 4-nitrophenyl sulfone, phenyl 4-nitrophenyl sulfoxide or methyl 4-nitrophenyl sulfoxide failed to induce the leaving of any substituent suggesting that the process may be selective to halo-compounds.
