Polar effect and geometry of the transition state in the reactions of ozone with C-H bonds of polar molecules

A large body of experimental data on the reactions of ozone with C-H bonds of polar molecules in the liquid and gas phases is analyzed in the framework of the intersecting parabolas model. The reactions are considered as the abstraction reaction O₃ + RH → HOOO^. + R^.. The contribution from the polar effect to the activation energy of such reactions is calculated. This contribution is ?6.8 kJ/mol for the reactions of ozone with aliphatic alcohols, and is ?8.1, ?11.7, ?6.8, and ?2.2 kJ/mol for the reactions of ozone with ketones, ethers, 1,3-dioxolanes, and 1,3-dioxanes, respectively. The contribution is insignificant in the reactions of ozone with aldehydes. The interatomic distances in the transition state of these reactions r ^#(C…H) and r ^#(O…H) and the angle between the C…H and O…H bonds are calculated. For the reactions in polar solvents, the contribution from solvation to the activation energy is calculated. In most of the systems considered, this contribution is insignificant (from ?1 to ?3 kJ/mol). The reactions involving ozone are compared to the reactions of peroxy radicals with the same classes of compounds.