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.