On the Proton-Coupled Electron Transfer of Urazole Derivatives in pH-Unbuffered Protic and Aprotic Solutions: The Substituent Effect

Abstract

Proton-coupled electrochemical oxidation of some urazole derivatives has been investigated in pH-unbuffered N,N-dimethylformamide as an aprotic solvent to understand the role of substituent of the urazole on the electrode process. The redox chemistry of urazole is easily influenced by the presence of trace basic or acidic impurities of solvent. The voltammetric responses of the urazole derivatives affected by impurities are completely depended on the electron-donating/withdrawing properties of the functional groups. Further in the following of our previous research on the electrochemical reduction of 4-(4-nitrophenyl) urazole, the electroreduction has been examined and compared in aqueous buffered solutions and the solutions with limited concentration of proton. The mechanistic pathways display a number of similarities and differences regarding the number of involved electrons, electrode processes, reduction peaks and reversibility of the electrode processes. The mechanism of the electron transfer was surveyed in a variety of pH ranges.