Gas-Phase Ozonolysis of Selected Olefins: The Yield of Stabilized Criegee Intermediate and the Reactivity toward SO2

The gas-phase reaction of ozone with olefins represents an important path for the conversion of unsaturated hydrocarbons in the atmosphere. The current interest is focused on the formation of stabilized Criegee intermediates (sCI) and possible further reactions of sCI. We report results from the ozonolysis of 2,3-dimethyl-2-butene (TME), trans-2-butene and 1-methyl-c-yclohexene (MCH) carried out in an atmospheric pressure flow tube at 293 +/- 0.5 K and RH = 50% using chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry to detect H2SO4 produced from SO2 oxidation by sCI. The yields of sCI were found to be in good agreement with recently observed data: 0.62 +/- 0.28 (TME), 0.53 +/- 0.24 (trans-2-butene) and 0.16 +/- 0.07 (MCH). The rate coefficients for sCI + SO2 from our experiment, (0.9-7.7) X 10(-13) cm(3) molecule(-1) s(-1), are within the range of recommendations from indirect determinations as given so far in the literature. Our study helps to assess the importance of sCI in atmospheric chemistry, especially for the oxidation of SO2 to H2SO4.