The physical chemistry of Criegee intermediates in the gas phase

Abstract

Carbonyl oxides, also known as Criegee intermediates, are key intermediates in both gas phase ozonolysis of unsaturated hydrocarbons in the troposphere and solution phase organic synthesis via ozonolysis. Although the study of Criegee intermediates in both arenas has a long history, direct studies in the gas phase have only recently become possible through new methods of generating stabilised Criegee intermediates in sufficient quantities. This advance has catalysed a large number of new experimental and theoretical investigations of Criegee intermediate chemistry. In this article we review the physical chemistry of Criegee intermediates, focusing on their molecular structure, spectroscopy, unimolecular and bimolecular reactions. These recent results have overturned conclusions from some previous studies, while confirming others, and have clarified areas of investigation that will be critical targets for future studies. In addition to expanding our fundamental understanding of Criegee intermediates, the rapidly expanding knowledge base will support increasingly predictive models of their impacts on society.

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.…”

Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study

“…In addition to providing additional sources of hydroxyl radicals at night, it also produces organic compounds that can then lead to the formation of aerosols and particulates. [1][2][3][4][5][6] Therefore, understanding the mechanism and kinetics of the elementary ozonolysis reactions is fundamentally important to atmospheric chemistry and kinetic models.…”

“…[1][2][3][4][5][6] Hot CIs have sufficient internal energies to undergo prompt H-migration and/or ring-closure, leading to formations of OH radicals and/or organic acids/esters, respectively. 7 Cold CIs, in contrast, have insufficient internal energies to undergo fast unimolecular reactions, 7 and thus, their lifetimes are much longer than those of hot CIs.…”