THE KINETICS OF THE REACTIONS OF C7F15OC2H5 (HFE-7500) WITH OH AND Cl RADICALS: THEORETICAL INVESTIGATIONS

The potential energy surface for the hydrogen abstraction reaction from HFE-7500 (C7F15OC2H5) by OH radical is investigated by hybrid meta density functional theory methods. The geometries for the reactants, van der Waals complexes, saddle-points and products for the title reaction is optimized by using M06-2X density functional method along with the standard 6-31+G(d,p) basis set. The vibrational frequencies of the optimized geometries are also computed at the M06-2X/6-31+G(d,p) level. To obtain more accurate estimations for electronic energies, single-point calculations are performed by the M05-2X, M06-2X, MPWB1K and BB1K methods along with the larger MG3S basis set. The computed energies are slightly sensitive to the DFT electronic structure calculation method. Transition state theory is used to compute the thermal rate constants over the temperature range 200-2000 K. The rate coefficients computed by using M05-2X/MG3S and MPWB1K/MG3S are in more agreement with the available experimental data. According to the present computed rate coefficients, the atmospheric half-life of the C7F15OC2H5 is estimated to be 0.3 years.