10.1021/jp102177v.s001 Scott A. Epstein Scott A. Epstein Neil M. Donahue Neil M. Donahue Ozonolysis of Cyclic Alkenes as Surrogates for Biogenic Terpenes: Primary Ozonide Formation and Decomposition American Chemical Society 2010 Primary Ozonide Formation reaction spectroscopy Cyclic Alkenes decomposition pathways Additional computations TPRS barrier height ozonide decomposition barrier heights POZ decomposition Entropic differences DFT decomposition products 298 K enthalpic variations DecompositionAlkene ozonolysis reactions ozonide decomposition Biogenic Terpenes barrier heights decomposition spectra POZ decomposition controls 2010-07-22 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Ozonolysis_of_Cyclic_Alkenes_as_Surrogates_for_Biogenic_Terpenes_Primary_Ozonide_Formation_and_Decomposition/2750167 Alkene ozonolysis reactions proceed through an unstable intermediate, the primary ozonide (POZ). POZ decomposition controls the complex mechanism. We probe the kinetics of primary ozonide decomposition using temperature programmed reaction spectroscopy (TPRS), revealing primary ozonide decomposition barrier heights of 9.1 ± 0.4, 9.4 ± 0.4, and 11.9 ± 1.2 kcal mol<sup>−1</sup> for cyclohexene, 1-methyl-cyclohexene, and methylene-cyclohexane, respectively. We compare experimental decomposition spectra with spectral predictions using density functional theory (DFT) to reveal decomposition products resembling vinyl-hydroperoxides and dioxiranes. We do not find evidence of secondary ozonides. Additional computations with DFT, scaled with the TPRS barrier height, yield barrier heights ranging from 9.4 to 12.1 kcal mol<sup>−1</sup> for the four competing decomposition pathways of the 1-methyl-cyclohexene POZ. Entropic differences were minimal, indicating that POZ decomposition branching is controlled purely by enthalpic variations. These kinetic computations were used to calculate a hydroxyl radical yield for 1-methyl-cyclohexene ozonolysis of 0.85 at 298 K.