Protection Mechanisms of p-Phenylenediamine-Type Antiozonants

Abstract

The relative ozonation rate constants for p-phenylenediamines have been estimated from the linear correlation of the ozonation rate constants with the ionization potentials (Figure 1). The efficient antiozonants were found to have relatively lower ionization potentials, but not too low to react with the atmospheric molecular oxygen. The bond dissociation enthalpies (BDEs) of the N—H bonds of p-aminodiphenylamine and related derivatives were found to be about 80 kcal/mol, suggesting that the p-aminodiphenylamines are not only efficient antiozonants, but are also efficient antioxidants. Efficient antiozonants should also be efficient antioxidants to quench the reactive radical intermediates formed during the degradation.