Theoretical and experimental studies of the electrochemistry of p-aminophenol on a golden electrode

The geometric parameters, vibrational frequencies, and thermochemical values of p-quinonimine (p-AQ) and p-aminophenol (p-AP) were computed ab initio (IIF) and by the density functional theory (DFT) method with the 6-31G(d, p) basis set. Cyclic voltammetry with a golden electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.728 V. The standard electrode potentials of half reactions for p-QI and p-AP were calculated using the free energies and solvation energies of p-QI, p-AP, p-benzoquinone (p-BQ), and hydroquinone (p-HQ). The results showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.743 V at the B3LYP/6-31G(d, p) level and 0.755 V at the HF/6-31G(d, p) level. The standard electrode potentials computed at the B3LYP/6-31G(d, p) and HF/6-31G(d, p) levels were close to their experimental values. The article is published in the original.