Mechanistic study on the oxidation of sulfacetamide by aqueous alkaline diperiodatoargentate(III)

Oxidation of sulfacetamide (SUL), a sulfonamide drug by alkaline diperiodatoargentate(III) (DPA), a powerful oxidizing agent at 298 K and at a constant ionic strength of 0.50 mol/dm³, has been carried out spectrophotometrically at 360 nm. The results indicate that 3 mol of DPA consumed 1 mol of SUL (3:1). The oxidation product has been separated and characterized by IR and NMR spectral studies. The reaction is first order in [DPA] and has less than unit order in [SUL]. The rate constants increased with an increase in alkali concentration and decreased with increase in [IO ₄^-]. Ionic strength and dielectric constant of the medium had negligible effect on the reaction rate. A mechanism has been proposed which explains the observed orders and experimental observations. Monoperiodatoargentate(III) (MPA) has been considered as the active species for the title reaction. The reaction proceeds through a SUL:MPA complex which decomposes in a slow step to give the p-hydroxylamine benzenesulfonamide and Ag(I) species. Further oxidation in the subsequent fast steps yeilds nitroso and nitro derivative of benzenesulfonamide, each transformation consuming 1 mol of MPA. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed, and thermodynamic quantities are also determined. The probable active species of oxidation have been identified.