AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Reaction of Criegee Intermediates with Organic Acids in the Condensed Phase
SHOUMING ZHOU, Shira Joudan, Matthew Forbes, Jonathan Abbatt, University of Toronto, Toronto, Canada
Abstract Number: 278 Working Group: Aerosol Chemistry
Abstract It is believed that gas-phase Criegee intermediates (CIs) play a role in the degradation of unsaturated species in the atmosphere, and in the formation of free radicals, oxygenated organics and secondary organic aerosol (SOA). Gas-phase CIs can also efficiently oxidize SO2, leading to the production of H2SO4. Following direct observations of the smallest CIs (e.g. CH2OO) in the gas-phase, studies on the chemistry of CIs have gained increased attention. Due to their biradical nature, the CIs could also be important oxidants in the condensed phase. However, studies on the multiphase reactions of CIs are very limited.
In this presentation, we will present our recent work on the oxidation of a highly unsaturated model organic - squalene (C30H50, with 6 C=C double bonds in the molecule) with ambient levels of ozone. Using direct analysis in real time-mass spectrometry (DART-MS), high molecular weight products from the heterogeneous reaction with ozone were observed, which are attributed to the CI reaction with acids. To confirm this reaction in the condensed phase, squalene was mixed with a saturated fatty acid (i.e. palmitic acid) or a perfluorinated acid (i.e. perfluorotetradecanoic acid) prior to oxidation. The degradation of the organic acids under ozonolysis conditions was confirmed by HPLC-MS/MS analysis. The effect of relative humidity on this heterogeneous reaction was investigated. The reaction products and mechanism will be discussed.