Electron-transfer processes: The electrochemical reduction of N,N-dimethyl- and p-cyanobenzene-sulfonamide

Abstract

The redox behavior of N,N-dimethyl-and p-cyanobenzenesulfonamide has been studied in dimethylformamide by electroanalytical methods. The tertiary sulfonamide is reduced in successive one-electron steps to give first its stable radical anion and then its dianion. The latter species is unstable and rapidly decomposes by sulfur-nitrogen bond cleavage to give dimethylamide anion and p-cyanobenzenesulfinate ion. One-electron reduction of the sulfinate to its stable dianion radical occurs at the applied potential and completes the reduction pathway. The reduction pathway for the primary sulfonamide is potential dependent. At the potential of the first cathodic wave, the primary sulfonamide is reduced irreversibly to its radical anion. This species undergoes nitrogen-hydrogen bond cleavage and affords hydrogen and the conjugate base of the primary sulfonamide as products. The base is then reduced to its stable dianion radical at more negative potential. Reduction of the primary sulfonamide at the potential of the second cathodic wave gives its dianion, a species which rapidly undergoes decomposition by nitrogen-sulfur bond cleavage to give amide anion and p-cyanobenzenesulfinate. Subsequent chemical and electrochemical reactions involving these species and the primary sulfonamide formally give p-NCC6H4SO2NH−2 as the principal product in an overall two-electron step.