Efficient Factors on the Hydrolysis Reaction Rate of Some Para-Aminophenol Derivatives in Acidic pHs

Abstract

Electrochemical oxidation of some p-aminophenol derivatives (1–5) in acidic solutions has been investigated both experimentally and theoretically to provide insight into the influence of some factors on the hydrolysis reaction rate. The result of this work shows that the electrogenerated p-quinoneimines participate in the hydrolysis reaction and are converted to the p-benzoquinone. The hydrolysis reaction rate strongly depends on the structure of the p-aminophenols and solution's pH. In this work, the observed homogeneous rate constants of hydrolysis (kobshyd) of p-quinoneimines were determined using digital simulation technique. The effect of different parameters such as: change of Gibbs free energy (ΔG) of the electrochemical oxidation of para-aminophenol derivatives (1–5), charge of reaction site, N–C4 bond order (Wiberg Bond Indices, WBIs) and the nature of substituted group, on the hydrolysis rate constant were also studied. All calculations were performed using Density Functional Theory (DFT) both BP86 and B3LYP levels of theory and 6-311G (p,d) basis set. The results showed that the N–C4 bond order and charge on the reaction site play significant roles in hydrolysis reaction's rate.