Reactivity of natural phenols in radical reactions

Activation enthalpies and energies and the rate constants of reactions with peroxyl, alkyl, and thiyl radicals (76 reactions) were calculated for a group of natural antioxidants (19 monohydroxy and polyhydroxy phenols). The calculation was performed with the use of the model of a radical abstraction reaction as the intersection of two parabolic potential curves. The results of the calculation were compared with experimental data: the average discrepancy in the activation energies of the reactions RO ₂ ^? + ArOH was 0.8 kJ/mol. Interatomic distances in the reaction centers of the transition states of the test reactions were calculated. Factors affecting the reactivity of these compounds are discussed.