title: Infrared spectral identification of the Criegee intermediate (CH3)2COO.
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+ O2in a flow reactor and detected with a step-scan Fourier-transform spectrometer. The four observed bands near 1424, 1368, 1040, and 887.4 cm-1provide 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 × 10-10cm3molecule-1s-1for 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.
authors: Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001, Ta-Hsueh Road, Hsinchu 30010, Taiwan.
authors: Yi-Ying
authors: YY
authors: Wang
authors: Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001, Ta-Hsueh Road, Hsinchu 30010, Taiwan.
authors: Chao-Yu
authors: CY
authors: Chung
authors: Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001, Ta-Hsueh Road, Hsinchu 30010, Taiwan.
authors: Yuan-Pern
authors: YP
authors: Lee