Autoxidation activity of substituted styrenes (aryl alkenes) and their product formation were studied in the temperature range of 65-125 degrees C using cumene or chlorobenzene as solvent. It was observed that higher reaction temperatures, inert solvent, electron donating substituents, and bulky sterical groups at a-, ortho- and para-positions promoted radical formation of epoxides and led to C=C oxidative cleavage. in contrast, electron accepting substituents and using cumene as the solvent favored the formation of oligomeric peroxides. The relative activity of all investigated styrenes could be correlated to the linear free energy (LFE) relation and the ionization potential. For a-substituted styrenes and ring substituted a-methylstyrenes LFE correlation for the reactivity of aryl alkenes and formation of epoxides was found to depend on the polar and steric factors. A general pathway for product formation by autoxidation of aryl alkenes has been proposed.