One-Electron-Transfer Reaction of the Couple SO2/SO2(1-) in Aqueous Solutions. Pulse Radiolytic and Cyclic Voltammetric Studies

Article abstract of DOI:10.1021/j100290a063

Rate constants for one-electron reduction of SO2 by several radicals and for reduction of several compounds by SO2(1-) radicals were determined by pulse radiolysis at pH 1.SO2 is reduced by the (CH3)2COH radicals with k = 2.1E9/M*s and by viologen radicals and certain porphyrin Π-radical anions with k ca. 1E8 - 1E9/M*s.The SO2(1-) radical reduces compounds which have reduction potentials more positive than -0.28 V.The rate constants for these reductions vary from ,1E7 to>1E9/M*s and depend on the redox potentials of the compounds and on other propeties such as charge and self-exchange rate.The reduction potentials for SO2 and for he porphyrins were determined by cyclic voltametry under identical conditions.These production potentials were used along with the rate constants and previously reported self-exchange rates to estimate the self-exchange rate for the couple SO2/SO2(1-) radical in acidic solutions.The calculated values were found to vary over many orders of magnitude, similar to the situation reported before for the O2/O2(1-) couple.