Kinetics and dynamics study of the Cl( 2 P) + CH 3 OH reaction based on an analytical potential energy surface

• Published in: Physical chemistry chemical physics : PCCP 2023-04, Vol.25 (15), p.10678-10688
• Main Authors: Rangel, Cipriano, Espinosa-Garcia, Joaquin
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/D3CP00224A

The reaction of chlorine atoms with methanol plays a central role in atmospheric and combustion processes and is a prototype of multi-channel reaction with two paths, HCl( , ) + CH OH (R1) and HCl( , ) + CH O (R2). In order to understand the kinetics and dynamics of the title reaction, using a valence-bond (VB) strategy we developed a new full-dimensional potential energy surface, named PES-2023, fitted to high-level calculations. Given that the (R2) path shows a noticeable barrier height, 12.7 kcal mol , while the (R1) path presents a submerged transition state with respect to the reactants, the latter is the kinetically favoured path on which most experimental kinetics and dynamics studies have focused. The PES-2023 surface presents a smooth and continuous behavior and is free of spurious features. Quasi-classical trajectory calculations were performed on this surface in order to shed light on the reaction kinetics and dynamics. The thermal rate constants in the temperature range 200-1000 K are practically independent of temperature, reproducing recent experimental evidence, although the experimental kinetics isotope effects are not well simulated. In the dynamics study the product distribution energy and the HCl( , ) product roto-vibrational energy reasonably simulate the experimental data, where only the = 0 and = 1 vibrational states are populated, 80-20%, respectively. We found that both HCl( ) vibrational states present similar forward scattering distributions, associated with a stripping mechanism. This theoretical result contrasts with some of the previous experimental measurements. Finally, PES-2023 was compared with a recent and accurate full-dimensional surface based on a different strategy, a molecular orbital (MO) based surface, fitted to a very large number of points, concluding that both surfaces present similar behaviour, where some kinetics and dynamics properties are better reproduced by one surface and other properties by the other.