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Direct production of OH radicals upon CH overtone activation of (CH3)(2)COO Criegee intermediates

Liu, Fang, Beames, Joseph M. and Lester, Marsha I. 2014. Direct production of OH radicals upon CH overtone activation of (CH3)(2)COO Criegee intermediates. Journal of Chemical Physics 141 (23) , 234312. 10.1063/1.4903961

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Abstract

Ozonolysis of alkenes, a principle non-photolytic source of atmospheric OH radicals, proceeds through unimolecular decay of energized carbonyl oxide intermediates, known as Criegee intermediates. In this work, cold dimethyl-substituted Criegee intermediates are vibrationally activated in the CH stretch overtone region to drive the 1,4 hydrogen transfer reaction that leads to OH radical products. IR excitation of (CH3)2COO reveals the vibrational states with sufficient oscillator strength, coupling to the reaction coordinate, and energy to surmount the effective barrier (≤ 16.0 kcal mol−1) to reaction. Insight on the dissociation dynamics is gleaned from homogeneous broadening of the spectral features, indicative of rapid intramolecular vibrational energy redistribution and/or reaction, as well as the quantum state distribution of the OH X2Π (v = 0) products. The experimental results are compared with complementary electronic structure calculations, which provide the IR absorption spectrum and geometric changes along the intrinsic reaction coordinate. Additional theoretical analysis reveals the vibrational modes and couplings that permit (CH3)2COO to access to the transition state region for reaction. The experimental and theoretical results are compared with an analogous recent study of the IR activation of syn-CH3CHOO and its unimolecular decay to OH products

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: American Institute of Physics (AIP)
ISSN: 0021-9606
Last Modified: 30 Jan 2020 15:30
URI: http://orca.cf.ac.uk/id/eprint/72849

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