Decomposition of diacyl peroxides. Part VIII. Mechanism of thermal decomposition of cyclopropaneacetyl peroxide
Abstract
The thermal decomposition of cyclopropaneacetyl peroxide in CCl4 has been studied in detail. Major products of the decomposition at 55° were cyclopropylmethyl cyclopropaneacetate, cyclopropylmethyl cyclopropaneacetyl carbonate, 1,1,1,3,5-pentachloropentane, and carbon dioxide. A tracer study with [18O]carbonyl labelled peroxide indicated that there was no oxygen scrambling in the original peroxide while there was oxygen scrambling both in the resulting carbonate formed via carboxy-inversion and in the ester. The carbonate did not give the ester under the conditions employed for the decomposition of the peroxide. On the basis of the 18O and other studies, radical cage recombination is suggested for the formation of the ester and a cyclic mechanism is ruled out. The distribution of 18O in the carbonate is explained by the assumption of transient formation of a common intermediate prior to both the radical and carboxy-inversion processes. Thermal decomposition of the carbonate to give the ester was also studied and this proceeds by acyl–oxygen bond fission.