Pulse radiolytic studies on the reactions of some oxidizing and reducing radicals with sulfanilamide in aqueous medium

Abstract

The reactions of the primary radicals of water radiolysis such as e aq −, H atom, OH radical and some oxidizing radicals like Cl 2 − and N 3 . with sulfanilamide (SA) have been studied under different conditions. SA reacts with OH radical at pH 7 to form an adduct which decays following second order kinetics. This adduct gets converted into a radical cation in acidic solutions below pH 4. Cl 2 − and N 3 . also oxidize SA to form this radical cation which gets deprotonated to anilino type radical with a p K a of 6.8. The hydrated electron and H atom react with SA with diffusion controlled rate constants, 9.4 × 10 9 dm 3 mol −1 s −1 and 2.1 × 10 9 dm 3 mol −1 s −1 respectively. The e aq − and H attact the −SO 2NH 2 group of the side chain when SA is in neutral form and the resulting species with absorption maximum at 385 nm (ε at 385 nm = 87 m 2 mol −1 at pH 7) subsequently forms NH 3 as one of the radiolytic products with G(NH 3) = 3.4. This is supported by the observation that when SA is in protonated form at pH 0.5, this transient is not produced and there is no ammonia formation.