ELECTRON-TRANSFER REACTIONS OF 2,2'-THIODIETHANOIC ACID IN AQUEOUS-SOLUTIONS - A PULSE-RADIOLYSIS STUDY

OH radicals are observed to react with 2,2'-thiodiethanoic acid in aqueous solutions containing a high concentration of HClO4 by an inner-sphere electron transfer reaction mechanism to form solute dimer (lambda(max) = 520 nm) radical cations at high solute concentrations. The stability constant for the dimer radical cation has been determined to be 68 dm3 mol-1 at 25-degrees-C. The decay kinetics of solute dimer radical cation is discussed in detail and deprotonation of the solute radical cation is found to be the rate-determining step. The solute dimer radical cations are able to undergo electron transfer reactions with Br- and form a transient band (lambda(max) = 385 nm) which is assigned to a bromine-solute adduct.