Molecular Structure of Substituted Phenylamine α-OMe- and α-OH-p-Benzoquinone Derivatives. Synthesis and Correlation of Spectroscopic, Electrochemical, and Theoretical Parameters

Thirteen C6 para-substituted anilinebenzoquinones derived from perezone (PZ) (2-(1,5-dimethyl-4-hexenyl)-3-hydroxy-5-methyl-1,4-benzoquinone) were prepared to analyze the effect of the substituents on quinone electronic properties. The effect of a hydrogen bond between the α-hydroxy and carbonyl C4−O4 groups was determined in perezone derivatives by substituting electron-donor and electron-acceptor groups such as −OMe, −Me, −Br, and −CN and comparing the −OH (APZs) and −OMe (APZms) derivatives. Reduction potentials of these compounds were measured using cyclic voltammetry in anhydrous acetonitrile. The typical behavior of quinones, with or without α-phenolic protons, in an aprotic medium was not observed for APZs due to the presence of coupled, self-protonation reactions. The self-protonation process gives rise to an initial wave, corresponding to the irreversible reduction reaction of quinone (HQ) to hydroquinone (HQH2), and to a second electron transfer, attributed to the reversible reduction of perezon...