INFLUENCE OF POLAR SUBSTITUENTS ON THE ANTIOXIDANT PROPERTIES OF PARA-VINYL PHENOLS AND ON THE STABILIZATION OF THE CORRESPONDING PHENOXY RADICALS

Phenols 1 substituted in the para position by vinyl groups bearing different combinations of thioether and cyano substituents in the beta positions were synthesized. The determination of their efficiency as antioxidants led to the following order of reactivity: RS,RS much greater than RS,CN > CN,CN. The analysis of the ESR spectra of analogous phenoxy radicals 4 indicates however a different order for the radical stabilization: RS,CN > RS,RS much greater than CN,CN. This behavior is explained by a charge or electron transfer in the transition state as the main factor governing the reactivity. Relative stabilizations of the phenoxy radicals are easily explained according to the captodative concept.