Isotopic and Optical Studies of the Decomposition of Crystalline Dibenzoyl Peroxide

Mass spectral analysis of volatile products from thermolysis or photolysis of a solid solution of dibenzoyl peroxide (BPO) and 4.4′-dideutero BPO shows that most phenyl benzoate is formed intramolecularly, while most biphenyl is formed intermolecularly, presumably by radical-molecule reactions. The strong visible dichroism in uv-irradiated BPO crystals appears to be due to selective scattering of light polarized along 010], not to the selective absorption which would have indicated an oriented product with a strong visible chromophore. Thermal development of the dichroism may be due to radical chain reactions. Studies on selective decarboxylation of BPO molecules using plane polarized light are discussed in terms of the birefringence of crystalline BPO.