Ozonolysis of $α$-pinene and $β$-pinene: Kinetics and mechanism

A combined quantum-chemical and RRKM/ME (ME—master equation) approach is employed to investigate the structures, energetics, and kinetics of intermediate and stable species, and the yields of stabilized carbonyl oxides and OH radicals from the $α$-pinene and $β$-pinene ozonolysis reactions. The cycloaddition of $O3$ is highly exothermic, with the reaction energies of 55.1 and $51.1kcalmol−1$ for $α$- and $β$-pinenes, respectively. Cleavage of primary ozonides yields carbonyl oxides with the barrier height of $12.2–17.5kcalmol−1$⁠. For the prompt reactions of carbonyl oxides from $α$- and $β$-pinene ozonolysis, H migration to hydroperoxides represents the dominant pathway over ring closure to dioxiranes. The kinetic calculations indicate a significant portion of stabilization for $α$- and $β$-carbonyl oxides. The yields of stabilized carbonyl oxides are estimated to be 0.34 for $α$-pinene and 0.22 for $β$-pinene. The applicability of theoretical methods for investigation of oxidation reactions of large hydrocarbon molecules is demonstrated.