Kinetics of bimolecular decay of α‐tocopheroxyl free radicals studied by ESR

The kinetics of bimolecular decay of alpha-tocopheroxyl free radicals (T) was studied by ESR mainly in ethanol and heptanol solvents. A second-order kinetic law was observed during the whole course of reaction (-d[T]/dt = 2k[T]2) and the following rate constants were determined with good accuracy in the temperature range 281-321 K: ethanol: log(2k) = 8.2 +/- 0.5--(6.6 +/- 0.7 kcal/mol)/(2.3RT) M-1.s-1; heptanol: log(2k) = 6.1 +/- 0.4--(4.3 +/- 0.6 kcal/mol)/(2.3RT) M-1.s-1. The global rate constant clearly increases with solvent polarity.