Kinetics and mechanism of the chain reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-dimethylhydroquinone

The kinetics of the reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-dimethyl-1,4-hydroquinone in chlorobenzene was studied at 298.2 and 340 K. The reaction occurs by a chain mechanism with a chain length of ∼102−103 units, depending on temperature and reactant concentrations. The orders of reaction with respect to components and the rate constants (or estimated values) were determined for all of the elementary steps at 298.2 and 340 K. The experimental data were compared with the results obtained previously for the reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-di-tert-butyl-1,4-hydroquinone. The nature of substituents in hydroquinone exerts a strong effect on the kinetic parameters of this new class of chain reactions. The effect of the final product, 2,5-dimethylquinone, on the reaction kinetics at 298.2 and 340 K was studied, and it was found that 2,5-dimethylquinone additives has only a weak inhibiting effect. The rate constant of the reaction of 2,5-dimethylquinone with semiquinone radicals, which were produced from 4-hydroxydipheny-lamine, was estimated: k −2 ∼ 104−105 l mol−1 s−1.