The kinetics of tetramethylethene ozonolysis: decomposition of the primary ozonide and subsequent product formation in the condensed phase.
We report data from real-time FTIR temperature programmed reaction spectroscopy on a cryogenic zinc selenide window revealing the intermediates from ozonation of 2,3-dimethyl-2-butene (TME). We have found convincing evidence of a 1,2,3-trioxolane (the primary ozonide, POZ), which decomposes at 185 K to yield a 1,2,4-trioxolane product (the secondary ozonide, SOZ). Computational infrared spectra confirmed the presence of the POZ and SOZ. The barrier height for POZ decomposition, determined experimentally, was found to be 13.8 +/- 1.0 kcal mol(-1), and the A factor calculated with RRKM theory based on density functional reactant and transition state frequencies was found to be 4.16 x 10(13) s(-1). The TME SOZ has not previously been observed without the presence of a polyethylene surface. SOZ formation kinetics from the reaction of the POZ decomposition products along with the competing reaction pathways were examined with computational chemistry calculations using DFT. These calculations confirm our experimental observation of SOZ formation.
Epstein
Scott A
SA
Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Donahue
Neil M
NM