Reaction of Ozone with p-Phenylene-Diamine and Related Compounds

An improved method for measuring the relative rates of reaction of materials with ozone is given. This method is used to evaluate the reactivities of new antiozonants. The similar reactivities of isomeric N-alkyl-p-phenylenediamines indicate that antiozonants may in large measure be active as a result of the physical nature of the ozone and antiozonant (and possibly rubber) reaction product. Proton magnetic resonance spectroscopy was used to evaluate the types of products formed on the ozonation of p-phenylenediamines. These results are compared with previously reported infrared work. Evidence for a one electron oxidation of p-phenylenediamines with ozone is also presented. This evidence is not conclusive. A correlation of the HOMO energies of N-substituted p-phenylenediamines with the reactivities of p-phenylenediamines towards ozone is attempted. Although a rather broad correlation is noted, an exact correlation is not found. On the basis of these results, it is felt that the reaction between phenylenediamines and ozone may be free radical in nature. But the general type of substitution on the phenylenediamine alters the products that are formed and possibly changes the rate-determining step of the reaction.