The effects of the position of a second nitroaromatic group (ortho vs para vs meta) during reduction of run benzenes were analysed Cyclic voltammetric experiments in acetonitrile solution revealed that ortho-meta- and para-dinitrobenzenes show two reversible reduction processes An Electrochemical-Electron Spin Resonance (E-ESR) study showed that the corresponding radical anions of the ortho and para derivatives electrogenerated during the first electron transfer uptake remain the same even after the second monoelectronic process increasing their intensity due to the presence of a comproportionation process (A(2-) + A -> 2A (-)) For the case of the meta derivative the electrogenerated radical anion at the first reduction peak is consumed at the second reduction step forming a secondary radical species During the electrochemical study of methyl 3 5-dinitrobenzoate two successive and reversible electron processes were also observed however in this case a very rare biradical dianion structure was found The use of ESR-spectroelectrochemistry shed some light on controversial aspects of nitroaromatic reduction especially concerning the second and further waves These results were corroborated and interpreted with quantum chemical calculations of the molecular and electronic structures electron affinities and spin densities As a result electrochemical mechanisms are presented and discussed (C) 2010 Elsevier Ltd All rights reserved