Mechanism of the antioxidant action of dialkyl sulfoxides

The main inhibiting action of dialkyl sulfoxides in the autoxidation of hydrocarbons derives from their ability to form sulfenic acids on thermal decomposition. The sulfenic acids are extremely active radical scavengers, the rate constant of the reaction of sulfenic acid and peroxy radicals being at least 10 7 l.mole −1 · S −1 at 60°C. In the AIBN‐initiated oxidation of tetralin in the presence of sulfoxides one peroxy radical is scavenged per molecule of sulfenic acid. This inhibition can be described kinetically as a reduction of the rate of initiation by an amount equal to the rate of decomposition of the sulfoxide.