PULSE-RADIOLYSIS STUDY OF OXIDATION REACTIONS OF SULFACETAMIDE IN AQUEOUS-SOLUTIONS

The one-electron oxidation of sulphacetamide by specific oxidizing rad icals such as N3., Br2.-, Cl2.-, Tl2+ and SO4.- in the pH range 2-9.2 has been studied employing pulse radiolysis technique. The semi-oxidiz ed species formed exhibits a pK(a) at pH 5.4 indicating the presence o f two conjugate acid-base forms whose spectral and kinetic features ha ve been evaluated. Reaction of OH radicals with sulphacetamide resulte d in the formation of a transient which in neutral and alkaline soluti ons decayed by first-order kinetics (k = 1.7 x 10(4) s-1) to yield the semi-oxidized species. The latter, formed both by decay of OH-adduct, as well as directly, has been observed to react rapidly with the biol ogical antioxidant ascorbic acid (k(ASC+SA) = 1.9 x 10(5) dm3 mol-1 at pH 9.2) forming the ascorbate radical. The effect of oxygen on the de cay behaviour of the OH-adduct and semi-oxidized species has also been investigated.