Vibrational mode-specific dynamics of the F - + CH 3 CH 2 Cl multi-channel reaction.

We investigate the mode-specific dynamics of the ground-state, C-Cl stretching ( v 10 ), CH 2 wagging ( v 7 ), sym-CH 2 stretching ( v 1 ), and sym-CH 3 stretching ( v 3 ) excited F - + CH 3 CH 2 Cl( v k = 0, 1) [ k = 10, 7, 1, 3] → Cl - + CH 3 CH 2 F (S N 2), HF + CH 3 CHCl - , FH⋯Cl - + C 2 H 4 , and Cl - + HF + C 2 H 4 (E2) reactions using a full-dimensional high-level analytical global potential energy surface and the quasi-classical trajectory method. Excitation of the C-Cl stretching, CH 2 stretching, and CH 2 /CH 3 stretching modes enhances the S N 2, proton abstraction, and FH⋯Cl - and E2 channels, respectively. Anti -E2 dominates over syn -E2 (kinetic anti -E2 preference) and the thermodynamically-favored S N 2 (wider reactive anti -E2 attack angle range). The direct (a) S N 2, (b) proton abstraction, (c) FH⋯Cl - + C 2 H 4 , (d) syn -E2, and (e) anti -E2 channels proceed with (a) back-side/backward, (b) isotropic/forward, (c) side-on/forward, (d) front-side/forward, and (e) back-side/forward attack/scattering, respectively. The HF products are vibrationally cold, especially for proton abstraction, and their rotational excitation increases for proton abstraction, anti -E2, and syn -E2, in order. Product internal-energy and mode-specific vibrational distributions show that CH 3 CH 2 F is internally hot with significant C-F stretching and CH 2 wagging excitations, whereas C 2 H 4 is colder. One-dimensional Gaussian binning technique is proved to solve the normal mode analysis failure caused by methyl internal rotation.