A Direct Classical Trajectory Study of HCl Elimination from the 193 nm Photodissociation of Vinyl Chloride

Abstract

Direct AM1 with specific reaction parameters (AM1-SRP) trajectory calculations were performed to investigate the photodissociation of vinyl chloride at 193 nm. Marked differences were found between the trajectories run from the transition states to the products for the four-center (4C) and three-center (3C) dissociation channels. The average internal energy of HCl is found to be about 2.5 times larger for the 4C channel. The calculated translational and HCl vibrational distributions, especially those obtained with a quasi-classical normal-mode sampling method, are in good agreement with the experimental data. The results are consistent with a concerted but nonsynchronous 3C mechanism, producing a lifetime for vinylidene to acetylene isomerization in line with the experimental observations. The theoretical HCl rotational distributions are in reasonable agreement with experiment, although they do not support the experimental interpretation of Lin et al. [J. Chem. Phys. 2001, 114, 160], who attributed low-J and high-J components to the 4C and 3C channels, respectively.