Bromide oxidation and bromine reduction in propylene carbonate (PC) + 1 M LiClO4 was investigated voltammetrically using polycrystalline platinum rotating disc electrode. The corresponding voltammograms were compared to those of iodide oxidation and HCl decomposition. The oxidation 2Br(-) --> Br-2 + 2e(-) was found to proceed through two steps, which are caused by the formation of a stable intermediate Br-3(-) ion. The stability constant of tri-bromine ion was estimated to be 10(5.5) M. The diffusion coefficient of Br- ion in this solution was determined to be 3.41 X 10(-6) cm(2) s(-1). In the case of bromine reduction, a time dependence of the shape of the voltammogram was observed, which showed that one is dealing with a direct bromination of PC. (C) 2003 Elsevier Science B.V. All rights reserved.