SUBSTITUTED THIOBISPHENOLS AS ANTIOXIDANTS - CORRELATION BETWEEN ANTIOXIDANT ACTIVITIES AND C-13 CHEMICAL-SHIFTS

The antioxidant activities of ten thiobisphenols were evaluated by an oxygen-absorption method at 60 degrees C in tetralin and determination of peroxide values at 160 degrees C in paraffin. For the 4,4'-thiobisphenols, alkyl groups ortho to the phenolic hydroxyl groups increased the induction period compared to that of other thiobisphenols for both oxidation of tetralin and paraffin. The data on electrochemical oxidation potentials that were determined by linear-sweep voltammetry and the C-13 nuclear magnetic resonance chemical shifts (delta) of these compounds were associated with antioxidant activities. In particular, the activities exhibited during the induction period closely correlated with the C-13 chemical shifts of ipso carbon of the OH substituent.