On NMR prediction of the antioxidant effectiveness of heterocyclic nitrogen compounds and substituted amines in styrene-butadiene rubber

Structures of 13 heterocyclic nitrogen compounds and substituted tertiary amines were optimized and their NMR shifts were evaluated by B3LYP calculations. The relation between experimental values of Molar Antioxidant Effectiveness (AEM) in styrene-butadiene rubber at various temperatures and calculated NMR chemical shifts of nitrogens and hydrogens bonded to them was investigated. AEM values are negatively affected by additional non-nitrogen heteroatoms. Only the molecules containing nitrogen atoms with NMR chemical shifts under −277 ppm are usable as antioxidants.