Infrared identification of the Criegee intermediates syn- and anti-CH3CHOO, and their distinct conformation-dependent reactivity

• Type of Material: Article
• Authors: Hui-Yu Lin, National Chiao Tung University; Yu-Hsuan Huang, National Chiao Tung University; Xiaohong Wang, Emory University; Joel Bowman, Emory University; Henryk Witek, National Chiao Tung University; Yoshifumi Nishimura, National Chiao Tung University; Yuan-Pern Lee, National Chiao Tung University
• Language: English
• Date: 2015-05-11
• Publisher: Nature Publishing Group: Nature Communications
• Publication Version: Final Published Version
• Copyright Statement: © 2015, Nature Publishing Group, a division of Macmillan Publishers Limited
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1038/ncomms8012
• Title of Journal or Parent Work: Nature Communications
• ISSN: 2041-1723
• Volume: 6
• Start Page: 7012
• End Page: 7012
• Grant/Funding Information: Y.P.L. and H.A.W. thank the Ministry of Science and Technology (grants number MOST103-2745-M-009-001-ASP and MOST102-2113-M-009-015-MY3); Ministry of Education, Taiwan (‘Aim for the Top University Plan’ of National Chiao Tung University) for support; and the National Center for High-Performance Computing for computer time.; X.W. thanks NASA for financial support (NNX12AF42G from the NASA Astrophysics Research and Analysis programme).; J.M.B. thanks the US Department of Energy (DE-FG02-97ER14782).
• Research Categories: Chemistry, General; Environmental Sciences

Abstract

The Criegee intermediates are carbonyl oxides that play critical roles in ozonolysis of alkenes in the atmosphere. So far, the mid-infrared spectrum of only the simplest Criegee intermediate CH2OO has been reported. Methyl substitution of CH2OO produces two conformers of CH3CHOO and consequently complicates the infrared spectrum. Here we report the transient infrared spectrum of syn- and anti-CH3CHOO, produced from CH3CHI + O2 in a flow reactor, using a step-scan Fourier-transform spectrometer. Guided and supported by high-level full-dimensional quantum calculations, rotational contours of the four observed bands are simulated successfully and provide definitive identification of both conformers. Furthermore, anti-CH3CHOO shows a reactivity greater than syn-CH3CHOO towards NO/NO2; at the later period of reaction, the spectrum can be simulated with only syn-CH3CHOO. Without NO/NO2, anti-CH3CHOO also decays much faster than syn-CH3CHOO. The direct infrared detection of syn- and anti-CH3CHOO should prove useful for field measurements and laboratory investigations of the Criegee mechanism.