Comprehensive Investigations of the Cl + CH ₃ OH → HCl + CH ₃ O/CH ₂ OH Reaction: Validation of Experiment and Dynamic Insights

Abstract

Cl+CH 3 OH → HCl+CH 3 O/CH 2 OH is a prototypical multiple-channel reaction. Experimentally, ample dynamical and kinetic information is available, but there are still many uncertainties concerning the reaction mechanism. Theoretical investigations are rare due to the absence of a potential energy surface (PES), which has greatly hindered our understanding of the reaction dynamics. Using a machine-learning approach, an accurate full-dimensional PES for the title reaction based on tens of thousands of high-level ab initio data is reported. Comprehensive dynamical calculations were performed on the PES using quasi-classical trajectories, and the results provide insights into the reaction kinetics and dynamics. The calculated non-Arrhenius rate coefficients are consistent with the experimental data, attributable to a complex-forming mechanism at low temperatures. At high energies, the reaction is dominated by a direct mechanism, which results in dominant forward scattering via a stripping mechanism augmented by less prominent sideways and backward scattering via a rebound mechanism. At collision energies of 5.6 and 8.7 kcal/mol, the measured product translational energy and ro-vibrational state distributions of HCl are well reproduced. In addition, mode specificity is revealed and rationalized by the sudden vector projection model. This work sheds valuable light on the microscopic mechanism and dynamics of this prototypical multichannel reaction.

First-Principles Reaction Dynamics beyond Six-Atom Systems

“…Furthermore, the vibrationally resolved HF rotational distributions are also in excellent qualitative or even semiquantitative agreement with experiment, as shown in Figure 5 , as well. Li and co-workers 35 , 71 achieved similar accuracy for the rotational distributions in the case of the F/Cl + CH 3 OH reactions, showcasing again the remarkable performance of the current state-of-the-art of the field.…”

Quantitative Dynamics of the N2O + C2H2 → Oxadiazole Reaction: A Model for 1,3-Dipolar Cycloadditions

“…All dynamically relevant regions should be well described by the PES. Following our previous strategy, 36 , 44 − 48 the ranges of configurations and energies were first inspected. Then, different grids with appropriate coordinates were used in different regions to sample dynamically relevant configurations.…”

“…This approach has succeeded in fitting accurate PESs for many polyatomic reactions with up to 7 atoms, for instance, OH + CH 4 52 and F/Cl + CH 3 OH. 44 , 48 …”

Benchmark ab initio stationary-point characterization of the complex potential energy surface of the multi-channel Cl + CH3NH2 reaction

“…The F/Cl + CH 3 OH reactions have been investigated recently by several experimental and theoretical groups. [19][20][21][22][23] The present study aims to combine the functional groups of NH 3 and CH 4 and investigates the reaction pathways of the Cl + CH 3 NH 2 multichannel reaction. The H-abstraction channels of this reaction forming HCl and CH 2 NH 2 or CH 3 NH were investigated in a joint experimentalÀtheoretical study in 2003.…”