Unimolecular Decay of the Dimethyl-Substituted Criegee Intermediate in Alkene Ozonolysis : Decay Time Scales and the Importance of Tunneling

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Drozd , G T , Kurten , T , Donahue , N M & Lester , M I 2017 , ' Unimolecular Decay of the Dimethyl-Substituted Criegee Intermediate in Alkene Ozonolysis : Decay Time Scales and the Importance of Tunneling ' , Journal of Physical Chemistry A , vol. 121 , no. 32 , pp. 6036-6045 . https://doi.org/10.1021/acs.jpca.7b05495

Title: Unimolecular Decay of the Dimethyl-Substituted Criegee Intermediate in Alkene Ozonolysis : Decay Time Scales and the Importance of Tunneling
Author: Drozd, Greg T.; Kurten, Theo; Donahue, Neil M.; Lester, Marsha I.
Contributor: University of Helsinki, Department of Chemistry
Date: 2017-08-17
Language: eng
Number of pages: 10
Belongs to series: Journal of Physical Chemistry A
ISSN: 1089-5639
URI: http://hdl.handle.net/10138/318333
Abstract: We used the steady-state master equation to model unimolecular decay of the Criegee intermediate formed from ozonolysis of 2,3-dimethyl-2-butene (tetramethylethylene, TME). Our results show the relative importance and time scales for both the prompt and thermal unimolecular decay of the dimethyl-substituted Criegee intermediate, (CH3)(2)COO. Calculated reactive fluxes show the importance of quantum mechanical tunneling for both prompt and thermal decay to OH radical products. We constrained the initial energy distribution of chemically activated (CH3)(2)COO formed in TME ozonolysis by combining microcanonical rates k(E) measured experimentally under collision-free conditions and modeled using semiclassical transition-state theory (SCTST) with pressure dependent yields of stabilized Criegee intermediates measured with scavengers in flow-tube experiments. Thermal decay rates under atmospheric conditions k(298 K, 1 atm) increase by more than 1 order of magnitude when tunneling is included. Accounting for tunneling has important consequences for interpreting pressure dependent yields of stabilized Criegee intermediates, particularly with regard to the fraction of Criegee intermediates formed in the zero-pressure limit.
Subject: GAS-PHASE OZONOLYSIS
VOLATILE ORGANIC-COMPOUNDS
WATER-VAPOR
PRESSURE-DEPENDENCE
CARBONYL OXIDES
ATMOSPHERIC IMPLICATIONS
SULFUR-DIOXIDE
OH
KINETICS
OZONE
114 Physical sciences
116 Chemical sciences
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