Investigation on redox mechanism of p-aminophenol in non-aqueous media by FT-IR spectroelectrochemistry

The electrochemical character of p-aminophenol in non-aqueous media was investigated by cyclic voltammetry (CV). Two couples of redox peaks and two shoulder peaks are observed in cyclic voltammogram. By in situ FT-IR spectroelectrochemistry, several IR absorption peaks, 1518, 1256, 1210; 1610, 1503, 1272; 1664, 1649, 1595, 1287 cm−1, corresponding to OHC6H4NH2; (OHC6H4NH2)+ and dimer; (OHC6H4NH2)2+ and C6H4ONH, are observed. Based on cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) techniques, we can track the changes of each species during electrochemical process. The results indicate that p-AP is oxidized in two-step one-electron transfer, and moreover, amino group is first oxidized than the hydroxyl group. The final oxidized product is quinonimine, and meanwhile the formation of dimer is detected. The dimer can be oxidized at more positive potential to form the final oxidation product (quinonimine) and reduced at more negative potential to form a new reduction product. By calculating relative energy, three possible structures of the dimer are proposed.