Temperature-Dependent\nKinetics of the Reactions of\nthe Criegee Intermediate CH<sub>2</sub>OO with Aliphatic Aldehydes

Criegee intermediates, formed by alkene ozonolysis in\nthe troposphere,\ncan react with volatile organic compounds (VOCs). The temperature-dependent\nkinetics of the reactions between the Criegee intermediate CH<sub>2</sub>OO and three aliphatic aldehydes, RCHO where R = H, CH<sub>3</sub>, and C<sub>2</sub>H<sub>5</sub> (formaldehyde, acetaldehyde,\nand propionaldehyde, respectively), have been studied using a laser\nflash-photolysis transient absorption spectroscopy technique. The\nexperimental measurements are supported by <i>ab initio</i> calculations at various composite levels of theory that characterize\nstationary points on the reaction potential and free energy surfaces.\nAs with other reactions of CH<sub>2</sub>OO with organic carbonyls,\nthe mechanisms involve 1,3-dipolar cycloaddition at the C=O group,\nover submerged barriers, leading to the formation of 1,2,4-trioxolane\nsecondary ozonides. The bimolecular rate constants of all three reactions\ndecrease with increasing temperature over the range 275–335\nK and are characterized by equations of Arrhenius form: <i>k</i>(<i>T</i>) = (7.1 ± 1.5) × 10<sup>–14</sup>exp((1160 ± 60)/<i>T</i>), (8.9 ± 1.7) ×\n10<sup>–15</sup>exp((1530 ± 60)/<i>T</i>), and\n(5.3 ± 1.3) × 10<sup>–14</sup>exp((1210 ± 70)/<i>T</i>) cm<sup>3</sup> s<sup>–1</sup> for HCHO, CH<sub>3</sub>CHO, and C<sub>2</sub>H<sub>5</sub>CHO, respectively. Based\non estimated concentrations of CH<sub>2</sub>OO, the reactions with\naldehydes are unlikely to play a significant role in the atmosphere.