The Electronic Structure and Homolytic Dissociation of Dibenzoyl Peroxide

Abstract
The conformations and electronic structures of dibenzoyl peroxide (BPO) and the benzoyloxyl radical (PhCOO) were elucidated by means of closed-shell and restricted open-shell SCF MINDO/3 calculations. The dihedral angle of BPO between the two PhCOO planes was predicted to be 115°, and the barrier to the trans form of BPO was estimated to be very small. The ground state of the PhCOO radical was predicted to be of the ∑-type. The non-planar conformation of PhCOO was more stable (2 kcal/mol) than the planar one. The variation in the radical-pair property of the lowest state of acetyl peroxide during the homolytic dissociation process was estimated by the analysis of the two-configuration wavefunctions. The substituent effect on the rate of the homolytic dissociation of BPO was discussed in terms of the electronic structures of substituted BPO.