Theoretical studies on the mechanism and kinetics of the hydrogen abstraction reactions from C4F9OC2H5 (HFE-7200) by OH and Cl radicals

Abstract

Abstract The potential energy surfaces for the hydrogen abstraction reactions from C 4 F 9 OC 2 H 5 by OH (reaction R A ) and Cl (reaction R B ) radicals are investigated theoretically by density functional theory methods. The stationary points including reactants, saddle-points and products of the title reactions are optimized by using M06-2X density functional method along with the standard 6-31 + G(d,p) basis set. The vibrational frequencies are computed at the same level of theory. More accurate energies are estimated by single-point calculations at the M05-2X/MG3S, M06-2X/MG3S, MPWB1K/MG3S, BB1K/MG3S and KMLYP/6-311 + + G(2d,2p) levels of theory. The computed barrier heights are slightly sensitive to the DFT method. Conventional transition state theory employing the tunneling for Eckart potential barrier is used to compute the thermal rate coefficients in the temperature range from 200 to 2000 K. The rate coefficients computed by using M05-2X/MG3S and MPWB1K/MG3S are in more agreement with the available experimental data. On the basis of the present computed rate coefficients, the atmospheric lifetime of the C 4 F 9 OC 2 H 5 is estimated to be about 0.5 year.