Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Abstract

The Criegee intermediates, carbonyl oxides proposed by Criegee in 1949 as key intermediates in the ozonolysis of alkenes, play important roles in many aspects of atmospheric chemistry. Because direct detection of these gaseous intermediates was unavailable until recently, previous understanding of their reactions, derived from indirect experimental evidence, had great uncertainties. Recent laboratory detection of the simplest Criegee intermediate CH2OO and some larger members, produced from ultraviolet irradiation of corresponding diiodoalkanes in O2, with various methods such as photoionization, ultraviolet absorption, infrared absorption, and microwave spectroscopy opens a new door to improved understanding of the roles of these Criegee intermediates. Their structures and spectral parameters have been characterized; their significant zwitterionic nature is hence confirmed. CH2OO, along with other products, has also been detected directly with microwave spectroscopy in gaseous ozonolysis reactions of ethene. The detailed kinetics of the source reaction, CH2I + O2, which is critical to laboratory studies of CH2OO, are now understood satisfactorily. The kinetic investigations using direct detection identified some important atmospheric reactions, including reactions with NO2, SO2, water dimer, carboxylic acids, and carbonyl compounds. Efforts toward the characterization of larger Criegee intermediates and the investigation of related reactions are in progress. Some reactions of CH3CHOO are found to depend on conformation. This perspective examines progress toward the direct spectral characterization of Criegee intermediates and investigations of the associated reaction kinetics, and indicates some unresolved problems and prospective challenges for this exciting field of research.

Investigation of potential interferences in the detection of atmospheric RO<sub><i>x</i></sub> radicals by laser-induced fluorescence under dark conditions

“…The sCI yield for molecules which give internal OH production has been determined to be 15 % for α-pinene, 27 % for limonene, and 58 % for isoprene Donahue et al, 2011;Newland et al, 2015b). The chemistry of the sCI is diverse and is subject to recent research that has been summarized in recent reviews (Taatjes et al, 2014;Lee, 2015). The sCI can decompose and form OH like the excited CI, but its lifetime is often long enough that it can also react with other molecules, for example SO 2 or water vapour (Mauldin III et al, 2012;Vereecken et al, 2012Vereecken et al, , 2014.…”

High resolution quantum cascade laser spectroscopy of the simplest Criegee intermediate, CH2OO, between 1273 cm−1 and 1290 cm−1

“…However, direct detection of CIs only became feasible after Welz et al 2 produced CIs efficiently by the reaction of an iodoalkyl radical with O 2 : e.g., CH 2 I + O 2 → CH 2 OO + I. According to recent studies, [3][4][5] CIs play an important role in atmospheric chemistry, being responsible for the oxidation of SO 2 , NO 2 , organic and inorganic acids, alkenes, and water vapor, 2,[6][7][8][9][10][11][12][13][14][15][16][17][18][19] the formation of OH radicals [20][21][22][23] and aerosols. Furthermore, significant structure-dependent chemistry of CIs has also been observed.…”

Direct Measurements of Unimolecular and Bimolecular Reaction Kinetics of the Criegee Intermediate (CH3)2COO

“…[2][3] The reaction kinetics of carbonyl oxides has been the subject of increasingly intense study [4][5][6] since the discovery that carbonyl oxides can be easily prepared via the reactions of α-iodoalkyl radicals with O 2 . [7][8] The reactions of the simplest carbonyl oxide, CH 2 OO, have been most extensively investigated.…”