Intramolecular homolytic displacements. Part 22. Polar effects in the homolytic induced decompositions of allyl peroxides

Abstract

The products of the decomposition of allyl peroxides 1–5, initiated by tert-butyl peracetate, in three solvents—cyclohexane, dimethyl malonate and benzene—were analysed. The formation of epoxides proved the existence of an homolytic induced decomposition of the unsaturated peroxides by a chain process involving a free radical addition to the double bond and an intramolecular homolytic substitution on the peroxide linkage. The balance of the reaction's products indicated a second way of degradation of the peroxides: allylic hydrogen abstraction followed by the breaking of the peroxide bond by β-elimination. The relative ratios of the products generated by the eliminated alkoxy radicals YO˙ and of the different epoxides produced in these reactions showed the influence of the polar factors in the various steps of the homolytic induced decomposition: i.e. hydrogen abstraction to the solvent or to the peroxide and addition to the double bond.