Theoretical model of the alpha dissociation of electronically excited molecules of carbonyl compounds

A theoretical model of the a dissociation of the C-C bond in molecules of c arbonyl compounds (the Norrish reaction I) is developed. It is shown that t he high probability of C-C bond dissociation in carbonyl compounds results from a great difference in the energies of n pi* states of a molecule and t he benzoyl radical being formed, This explains the difference in directions of the photodecomposition of carbonyl and other compounds, for example, hy drocarbons. The decomposition probability crucially depends on the orbital nature of the state and energy of the bond being dissociated. A criterion i s established for a carbonyl compound to be an efficient photosensitizer of polymerization. The absorption spectrum of the benzoyl radical is recorded . It is shown that our theoretical model adequately explains the available experimental data.