Theoretical study for the CH3OCF2CF2OCHO + Cl reaction

The reaction of CH3OCF2CF2OCHO with Cl atom has been investigated theoretically by direct dynamics method. The BB1K hybrid functional in conjunction with the 6-31 + G(d,p) basis set has been used to optimize the geometries for the stationary points and explore the potential energy surface of the reaction. Four rotation conformers (RC1-4) of CH3OCF2CF2OCHO are identified, and they are all considered in the kinetic calculation. For each conformer, there are two kinds of H-abstraction channels and one displacement channel, and the latter one should be negligible due to involving much higher energy barrier than the former two. The individual rate constants for each H-abstraction channel are evaluated by the improved canonical variational transition-state theory with a small-curvature tunneling correction. The overall rate constant is evaluated by the Boltzmann distribution function, and a fitted four-parameter rate constant expression is obtained over a wide temperature range of 200–2,000 K. The agreement between the calculated and available experimental value at 296 K is good. The contribution of each conformer to the title reaction is discussed with respect to the temperature. In addition, because of the lack of available experimental data for the species involved in the reactions, the enthalpies of the formation (ΔH f,298°) for the reactant and its product radicals are predicted via isodesmic reaction at the BB1K/6-31 + G(d,p) level.