Spectroscopic studies of solvent effects on the kinetics of hydrogen abstraction from 2,4,6-tri-t-butylphenol by 2,2-diphenyl-1-picrylhydrazyl free radical

Abstract

The rate of hydrogen abstraction from 2,4,6-tri-t-butylphenol varies appreciably with the solvent. It is suggested that this is a function primarily of the hydrogen-bonding ability of the solvent, which competes with the free radical for interaction with the phenol. A poor correlation is obtained between log (rate constant) and i.r. shift, the latter representing enthalpy of hydrogen bond formation between solvent and phenol. However, an excellent correlation is obtained between log (rate constant) and n.m.r. chemical shift, which gives a measure not only of the enthalpy but also of the extent of hydrogen bonding.