Criegee intermediates (CIs) are the key intermediates in the ozonolysis reactions of alkenes, which are important in tropospheric oxidation. CIs are the precursors of OH radicals in the ozonolysis reactions of alkenes, and they react with many important atmospheric species such as SO2, NO2, O3, and water, which lead to the secondary organic aerosol (SOA) formation. While several CIs have recently been synthesized from photolysis of iodoalkanes in the presence of O2, no unambiguous observation of CIs has been made previously in the ozonolysis reactions of alkenes. This work is the first time direct observation of the gas-phase Criegee intermediate in the ozone and alkene reaction system. (CH3)2COO has been directly detected in the ozone and tetramethylethylene (TME) reaction using vacuum ultraviolet (VUV) photoionization mass spectrometry coupled with a fast flow reactor. Photoionization efficiency (PIE) curve has identified CI, its isomers, its decomposition products, and other products in this reaction. Chemical reaction kinetics and modeling have been carried out in the short time range of tens of milliseconds, which provides detailed reaction mechanism of the early steps of the alkene ozonolysis reaction. This study of the TME ozonolysis reaction could open a door to exploring many other Criegee intermediates in the atmospheric ozonolysis reactions of alkenes.

Direct characterization of Criegee intermediate in ozonolysis reaction of alkene

248th National Meeting (2014)

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