Mechanisms of gas-phase and liquid-phase ozonolysis

Abstract

Generalized valence bond (GVB) and configuration interaction (Cl) calculations using an extensive basis [double f plus polarization functions (DZd)] have been carried out on peroxymethylene (H₂COO, often referred to as carbonyl oxide or as the Criegee intermediate), dioxirane, and dioxymethylene (OCH₂O). The ab initio thermochemical results are combined with existing thermochemical data to analyze possible modes of ozonolysis. The predicted heat of formation of peroxymethylene is 29.1 kcal, indicating that the dissociation of the primary ozonide to form peroxymethylene biradical and formaldehyde is 9 kcal endothermic. The ring state, dioxirane, is predicted to be 36 kcal below peroxymethylene with dioxymethylene lying 15 kcal above the ring state. Gas-phase experimental results are shown to be consistent with the predicted thermochemistry. In addition, solution-phase results on the stereospecificity of ozonolysis are shown to be consistent with a biradical intermediate.

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