Mechanism of the electrochemical reduction of sulfur dioxide in non-aqueous solvents

The results of the spectroscopic and electrochemical study of SO2 solutions and of polythionite solutions (i.e. solutions where SO2 is reduced chemica lly) in HMPA, allowed us to build a model describing the reduction of SO2 i n non-aqueous solvents. Simulations and adjustments of this model to the ex perimental data led to the determination of the parameters of the reactions . This mechanism is shown to explain the observations for all solutions, bo th in semi-infinite diffusion and in thin layer conditions, and it also des cribes the composition of any polythionite solution. The model also explain s the reduction of SO2 in other non-aqueous solvents. The analysis of the m echanism shows that the stability and electroactivity of the species involv ed can be related to their structure. (C) 1999 Elsevier Science S.A. All ri ghts reserved.