An Elusive Intermediate Gets Caught

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Science  13 Jan 2012:
Vol. 335, Issue 6065, pp. 178-179
DOI: 10.1126/science.1217165

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The Criegee intermediates (CIs) are central to understanding the reactions of ozone with unsaturated compounds (see the figure) (1). These reactions contribute directly to the oxidation of hydrocarbons in the lower atmosphere, are important sources of hydroxyl radicals, atmospheric organic acids, and carbonyl compounds, and can lead to the generation of secondary aerosols. On the local scale, these secondary aerosols contribute to the low visibility and health problems associated with photochemical smog, while on the global scale, their formation has crucial implications for climate change (2). Yet despite their central importance in these processes, little is known about the reactivity of CIs. On page 204 of this issue, Welz et al. report direct kinetic measurements of several reactions involving the simplest CI (3).