Final-State-Resolved Dynamics of the OH + CH3OH Reaction from Full-Dimensional Quasi-Classical Trajectory Simulations.

State-resolved dynamics of the OH + CH3OH hydrogen-abstraction reaction, OH + CH3OH → CH2OH + H2O (R1) and OH + CH3OH → CH3O + H2O (R2), has been investigated using full-dimensional quasi-classical trajectory (QCT) calculations on a recently developed high-accuracy potential energy surface (PES). Selective single-quantum excitation of five vibrational modes of CH3OH and rotational excitation of the OH radical were considered over a collision-energy range from 1 to 20 kcal/mol. Product internal state distributions and energy partitioning were analyzed by the normal-mode analysis (NMA) method. The calculations show that both channels gradually approach a direct mechanism at high collision energies, with most of the available energy partitioned into product relative translation. Distinct product-state distributions are observed for the two channels and are closely related to transition-state geometrical relaxation and kinematic constraints. Excitation of different reactant modes leads to pronounced mode-specific effects. Rotational excitation mainly induces stereodynamical steering effects, while torsional excitation promotes energy transfer into low-frequency bending modes through intramolecular vibrational redistribution (IVR). More importantly, excitation of the high-frequency O-H and C-H stretching modes reveals strong anharmonic coupling and transient mode mixing in the transition-state region. In particular, the nominal spectator C-H stretching modes actively participate in the reaction dynamics and significantly enhance the vibrational excitation of the H2O product. These results provide further insight into mode-specific energy flow and nonstatistical dynamics in polyatomic hydrogen-abstraction reactions.