Mechanisms of Ozonation of N-(1,3-Dimethylbutyl)-N′-Phenyl-p-Phenylenediamine

Abstract

The ozonation products of a common rubber antiozonant, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (HPPD), have been separated by liquid chromatography and identified by mass spectrometry. Three principal mechanisms appear to govern the ozonation of HPPD. Amine oxide formation leads to observed nitrosoaryl and nitroaryl products. Side-chain oxidation leads to several low molecular weight products, including some that contain an amide moiety. Nitroxide radical formation leads to a nitrone that is the most abundant ozonation product; a dinitrone is also formed. Ozonation of HPPD occurs mainly with degradation of the alkyl portion of the molecule. The results of this study are consistent with a combined “scavenger-protective film” theory of antiozonant protection of rubber compounds.