Infrared spectral identification of the Criegee intermediate (CH3)2COO

Yi-Ying Wang; Chao-Yu Chung; Yuan-Pern Lee

doi:10.1063/1.4964658

Infrared spectral identification of the Criegee intermediate (CH₃)₂COO

J Chem Phys. 2016 Oct 21;145(15):154303. doi: 10.1063/1.4964658.

Authors

Yi-Ying Wang¹, Chao-Yu Chung¹, Yuan-Pern Lee¹

Affiliation

¹ Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001, Ta-Hsueh Road, Hsinchu 30010, Taiwan.

PMID: 27782495
DOI: 10.1063/1.4964658

Abstract

Criegee intermediates are carbonyl oxides that play critical roles in the ozonolysis of alkenes in the atmosphere. So far, the infrared spectra of only the simplest Criegee intermediates CH₂OO and CH₃CHOO are reported. We report the transient infrared spectrum of the next member (CH₃)₂COO, produced from ultraviolet irradiation of a mixture of (CH₃)₂CI₂ + O₂ in a flow reactor and detected with a step-scan Fourier-transform spectrometer. The four observed bands near 1424, 1368, 1040, and 887.4 cm^-1 provide definitive identification of (CH₃)₂COO. The observed vibrational wavenumbers and rotational contours agree with those predicted with quantum-chemical calculations; contributions of the hot bands from excited states of the low-lying torsional modes are significant. The rapid decay yields an estimate of the rate coefficient ∼1.6 × 10^-10 cm³ molecule^-1 s^-1 for the self-reaction of (CH₃)₂COO. The direct IR detection of (CH₃)₂COO should prove useful for field measurements and laboratory investigations of related Criegee mechanism.