Electrochemical oxidation of some N-(4-aminophenyl) and N-(4-hydroxyphenyl)benzenesulfonamide derivatives (BS1-BS6) has been investigated over a wide range of pH and different concentrations by cyclic voltammetry technique. In addition, to gain a better understanding of the electrochemical behavior of these compounds, their oxidation been compared with the oxidation of some compounds such as: p-phenylenediamine (PDA), 4,4′ -sulfonyldianiline (DSA) (dapsone) and p-aminophenol (PAP). The results show that the oxidation potential as well as the oxidation mechanism of these compounds are pH dependent and change with changing pH. Our data display that electrochemically generated quinoneiminesulfonamide (QI) quinonediiminesulfonamide (QDI) are unstable in acidic and alkaline solutions and participate in following chemical processes such as hydroxylation and/or dimerization reactions. In this work, different mechanisms for their oxidation at different pH have been proposed for sulfonamides BS1-BS6. Furthermore, in this research, the adsorption behavior of these compounds and their oxidation products under conditions that are relatively similar to the human body were investigated and discussed. Our data show that BS1-BS6 sulfonamides have an adsorption-diffusion control process, and furthermore, the adsorption activity of N-(4-hydroxyphenyl)-sulfonamides is higher than that of N-(4-aminophenyl) sulfonamides. Also, Pourbaix diagrams were drawn for sulfonamides BS1-BS6 and the predominant species were identified at different pH.
