Electron paramagnetic monitoring of free phenoxyl radicals in benzene-
toluene (1 : 1) solution has been used to study the temperature depend
ence of the equilibrium (a), for which the equilibrium constant, K-1 i
s [GRAPHICS] mol(-1). The entropy change value is about 30 J K-1 mol(-
1) in excess of the absolute entropy of the molecular rotor evolving a
bout each of the C-S bonds in the thiobis(phenol) 1, thus denoting the
enhancement by solute-solvent interactions. As well as using the enth
alpy change to account for the stability of the generated phenoxyls, a
nd/or the ability of hydrogen cession by phenols, the entropy change m
ust also be measured when evaluating the antioxidant behaviour of this
type of molecule, as its influence on the Gibbs free energy change is
shown to be relevant.