Pressure-Dependent Stabilization of Carbonyl Oxides from Alkene Ozonolysis (Invited Presentation)

Carbonyl oxides (Criegee Intermediates) have gained renewed interest since an efficient source from gem-diiodoalkanes was perfected. However, the dominant atmospheric source is thought to be the stabilization of highly vibrationally excited species resulting from the extremely exothermic addition of ozone to alkenes. We have long studied the pressure dependence of this process, including prompt production of OH radicals as well production of the intermediates themselves. Here we use highly sensitive nitrate anion chemical ionization mass spectrometry to probe the pressure dependence of carbonyl oxide stabilization via the formation of sulfuric acid vapor from the reaction between carbonyl oxides and sulfur dioxide. OH radicals produced from ozonolysis also convert sulfur dioxide to sulfuric acid vapor and so we measure the ratio of sulfuric acid production with and without an OH radical scavenger to infer the ratio of OH and stabilized carbonyl oxide production. We studied pressure dependence between 30 and 900 torr of nitrogen for the reactions of ozone with a series of symmetrical trans alkenes (butene though tetradecene), 2,3 dimethyl-2-butene (tetramethylethylene) and the monoterpenes a-pinene, 3-carene, limonene, and beta-pinene.