On the dehydrogenation of N,N′-substituted p-phenylenediamine antioxidants: II. N-Phenyl-N′-(α-methylbenzyl)-p-phenylenediamine (SPPD)

Using B3LYP/6-31G* treatment, the optimal geometries, electronic structures and IR spectra of N-phenyl-N′-(α-methylbenzyl)-p-phenylenediamine antioxidant (SPPD) and of its double dehydrogenated oxidation products have been obtained. Experimental IR spectra of SPPD sample heated on air at 140 °C correspond to the double dehydrogenated SPPD structure with the phenyl–NC ketimine double bond and not to its N,N′-dehydrogenated quinonediimine-type counterpart as supposed in the literature. This finding supports the idea of preferential dehydrogenation at N-bonded tertiary carbon atom in comparison with the amine nitrogen bonded to two phenyl rings.