Antioxidant effectiveness of dehydrogenated p-phenylene diamines through NMR calculations

NMR shifts of N-phenyl-N’-alkyl-p-phenylenediamines (PPD) in vacuum were evaluated by B3LYP calculations using GIAO method. According to our previous studies, the Molar Antioxidant Effectiveness (AEM) of PPD antioxidants correlates with NMR chemical shifts of the amine nitrogen between aromatic rings (N_A), the side aliphatic chain nitrogen (N_B) and its neighboring tertiary carbon atom (C_T) as well as of the hydrogens bonded to them. Our results indicate that the above mentioned chemical shifts correlate with increasing reactivity of dehydrogenated PPD antioxidants at these sites as well.