Phenolic antioxidants: Effect of o-benzyl substituents

Abstract

A previous study showed that a substituent with an α-hydrogen atom on an o-position of a phenolic antioxidant enhances the antioxidative activity. The α-hydrogen atom can stabilize a phenoxy radical and is finally moved to the phenoxy radical to regenerate a new phenol. In this study, new o-substituted phenolic antioxidants, having such hydrogen atom(s), are molecularly-designed. They include o-benzyl-substituted phenols having a methyl, methoxy, phenyl, or halogen group on the o- or p- positions of the benzyl substituent and also a methylene group activated by two phenyl groups. As expected, almost all new phenols exhibited high activities, trapping 3-4 peroxy radicals and having radical-trapping rate constants of 1.5 or more times higher than that of BHT.