A pulse radiolysis study of salicylic acid and 5-sulpho-salicylic acid in aqueous solutions

Abstract

Reactions of H, OH, e aq - and some one-electron oxidants have been studied with salicylic acid and 5-sulpho-salicylic acid in aqueous solutions. Rate constants for the reaction of e aq - with these compounds were of the order of 10 9 dm 3 mol −1 s −1 and this reaction led to the formation of reducing radicals which could transfer electron to methyl viologen. Other one-electron reductants were not able to reduce these compounds. OH radicals reacted with these compounds by addition pathway with very high rate constants (>10 10 dm 3 mol −1 s −1) while O − radical anions could oxidize these molecules to give phenoxyl type of radicals. Amongst the one-electron oxidants, only N 3 and SO 4 − could oxidize salicylic acid while 5-sulpho-salicylic acid could be oxidized only by SO 4 − radicals indicating that while one-electron reduction potential for semi-oxidized SA may be<1.33 V vs. NHE (the E o1 for N 3 radical), it is more than 1.33 V vs. NHE for semi-oxidized SSA species.