Acyloxyl radical pair intermediate for the initial stage of the thermal decomposition of diacyl peroxide: a density functional study

To examine the reaction mechanism for the thermal reorganization, or more specifically the oxygen scrambling, in diacyl peroxide, we have carried out a hybrid density functional study using formyl peroxide as a model compound. The B3LYP calculations suggest that the oxygen scrambling in diacyl peroxide is most likely to occur via a σ-acyloxyl radical pair species: the competitive pathways of the [3,3]- and [1,3]-sigmatropic shifts are highly improbable. Thus, the mechanism for the thermal oxygen scrambling in diacyl peroxide should be completely different from those for the carbon counterparts of diacyl peroxide (the Cope and Claisen rearrangement).