Abstract

Criegee intermediates (CI), yielded from the ozonolysis of unsaturated hydrocarbons, are short-lived reactive intermediates that are found abundant in earth’s atmosphere. The reactivity of Criegee intermediates with water molecules has aroused great interests as the reaction with water vapor is one of the dominant atmospheric reactions of CIs. Many studies have been carried out on the simplest CI CH2OO, while the reactions of larger CIs with water are seldomly discovered. Moreover, the understanding of influence of the environmental water network on the CI-water reaction has has remained still elusive. In this study, We firstly reveal the reaction pathways of a larger CI anti-CH3CHOO with adaptive Quantum mechanical/Molecular mechanical (QM/MM) model integrated with our recently developed MBE(3)-OSV-MP2 theory. The comparison of the NVT trajectories of CH2OO and anti-CH3CHOO is made in the current poster, revealing that the loop structure is not a premise for the beginning of both loop-structure and step-wise reactions. Moreover, we study the impact of the hydrogen-bonding network on the reaction of CIs through high-level electron density and energy computations. The electrostatic effect of the solvent environment and the electron transfer through the hydrogen bonding system promote the difference in the electronegativity between the center carbon of CI and its nearest oxygen atom from water, which enhances the probability of the C-O bond formation. In addition, we investigate the impact of the reaction-favorable loop structure appearing in 88% of the beginning of the CI-water reactions. The results show that it is equivalent to the combination of 1) the electron transfer effect through the hydrogen bonding chain which benefits the C-O bond formation and 2) a hydrogen bond composed of the CI terminal oxygen and a water chain, where the hydrogen bond is strengthened by the cooperativity effect brought by the water chain. These two effects contribute to the substantial reduction in the energy barrier of the CI-water reaction. The research is of profound significance for it brings deeper understanding of the reactivity of Criegee intermediates in the presence water, as well as the mechanism of the CI-water reaction in a complex solvent environment.