Theoretical investigation of the reaction of CF(3)CHFOCH(3) with OH radical.

A direct ab initio dynamics method was used to study the mechanism and kinetics of the reaction CF(3)CHFOCH(3) + OH. Two reaction channels, R1 and R2, were found, corresponding to H-abstraction from a CH(3) group and a CHF group, respectively. The potential energy surface (PES) information was obtained at the G3(MP2)//MP2/6-311G(d,p) level. The standard enthalpies of formation for the reactant (CF(3)CHFOCH(3)) and products (CF(3)CHFOCH(2) and CF(3)CFOCH(3)) were evaluated via isodesmic reactions at the same level. Furthermore, the rate constants of two channels were calculated using the canonical variational transition state theory (CVT) with small-curvature tunneling (SCT) contributions over a wide temperature range of 200-3000 K. The dynamic calculations demonstrate that reaction R1 dominates the overall reaction when the temperature is lower than 800 K whereas reaction R2 becomes more competitive in the higher temperature range. The calculated rate constants and branching ratios are both in good agreement with the available experimental values.