Boosting effect of ortho-propenyl substituent on the antioxidant activity of natural phenols

摘要: Seven new antioxidants derived from natural or synthetic phenols have been designed as alternatives to BHT and BHA antioxidants. Influence of various substituents at the ortho, meta para positions aromatic core on bond dissociation enthalpy ArO-H was evaluated using a DFT method B3LYP/6-311++G(2d,2p)//B3LYP/6-311G(d,p). This prediction highlighted ortho-propenyl group best substituent decrease (BDE) value. The rate constants hydrogen transfer these DPPH radical in non-polar non-protic solvent measured were found be agreement with BDE calculations. For o-propenyl derivatives 2-tert-butyl-4-methylphenol, BHA, creosol, isoeugenol di-o-propenyl p-cresol, fewer radicals trapped by single phenol molecule, i.e. lower stoichiometric number. Reaction mechanisms involving evolution primary phenoxyl ArO are proposed rationalise effects.