Direct Ab initio dynamics study on the reaction of CH3CHF2 (HFC-152a) with the Cl atom.

A direct ab initio dynamics method is used to investigate the hydrogen-abstraction reaction CH(3)CHF(2)+Cl. One transition state is located for alpha-H abstraction, and two are identified for beta-H abstraction. The potential-energy surface (PES) is obtained at the G3(MP2)//MP2/6-311G(d, p) level. Furthermore, the rate constants of the three channels are evaluated by using canonical variational transition-state theory (CVT) with small-curvature tunneling (SCT) contributions over a wide temperature range of 200-2500 K. The dynamic calculations show that the reaction proceeds mainly by alpha-H abstraction over the whole temperature range. The calculated rate constants and branching ratios are both in good agreement with the available experimental values.