Ozonolysis of alpha-pinene and beta-pinene: Kinetics and mechanism

摘要

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 a-pinene and beta-pinene ozonolysis reactions. The cycloaddition of O-3 is highly exothermic, with the reaction energies of 55.1 and 51.1 kcal mol(-1) for alpha- and beta-pinenes, respectively. Cleavage of primary ozonides yields carbonyl oxides with the barrier height of 12.2 - 17.5 kcal mol(-1). For the prompt reactions of carbonyl oxides from a- and beta-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 alpha- and beta-carbonyl oxides. The yields of stabilized carbonyl oxides are estimated to be 0.34 for a-pinene and 0.22 for beta-pinene. The applicability of theoretical methods for investigation of oxidation reactions of large hydrocarbon molecules is demonstrated. (c) 2005 American Institute of Physics.