MNDO calculations of the effects of substitution on antioxidant activity of phenols and Vitamin E

MNDO calculations are reported for the O-H bond dissociation energy in phenol and -OH, -CH₃, and -NH₂ substituted phenols. The phenol dissociation energy agrees well with the experimental result, as does the change due to a para -OH group; the agreement is less good for methyl substitution. The effect of rotating the O-H substituent out of the benzene plane is explored and analyzed, and the calculations are related to corresponding effects in Vitamin E chemistry.