Computational Insights into the CH3 Cl+OH Chemical Reaction Dynamics at the Air-Water Interface.

The reaction of methyl chloride with the hydroxyl radical OH is an important process in the troposphere. The kinetics of this reaction has been thoroughly studied in the gas phase, both experimentally and theoretically, but little is known about the effect of water on this reaction. In particular, investigating the reaction mechanism at the air-water interface is key in order to better understand the role of cloud water droplets and aerosols on the overall oxidation capacity of the troposphere. In this work, we have implemented a "rare event" approach combined to QM/MM (quantum mechanics and molecular mechanics) molecular dynamics simulations to investigate the dynamics of the H-abstraction reaction CH3 Cl+OH→CH2 Cl+H2 O at the air-water interface. For comparison, high-level ab initio calculations for the reaction mechanism in the gas phase are also reported and accurate kinetic constants at different temperatures are provided.