Density functional theory thermal rate constant calculation of hydrogen abstraction reactions of trans-cyc-CF2CF2CF2CHFCHF and cyc-CF2CF2CF2CHFCH2 with OH radicals

Abstract

The bimolecular hydrogen abstraction rate constants of the reactions trans-cyc-CF2CF2CF2CHFCHF + OH and cyc-CF2CF2CF2CHFCH2 + OH are investigated. The stationary points on the potential energy surface of the reaction are found at the KMLYP/6-311+g(d,p). To have more reliable energies obtained, single point calculations are done by the same method along with two distinct basis sets; 6-311++G(3df,2p) and aug-cc-pVTZ. Furthermore, the energies of the stationary points are calculated at the levels M05-2X/6-31+G(d,p)//MG3S and MPWB1K/6-31+G(d,p)//MG3S for the purpose of comparison. The ro-vibrational properties calculated at KMLYP/6-311+G(d,p) are employed in the semiclassical transition state theory to compute the rate constants at the temperature range of 200–2000 K. We found that the rate constants computed via the barrier heights at M05-2X and MPWB1K are in more accordance with the experimental results than the ones at the DFT level KMLYP. The atmospheric lifetime of trans-cyc-CF2CF2CF2CHFCHF and cyc-CF2CF2CF2CHFCH2 are estimated by the level M05-2X to be 1.21 years and 3.59 years, respectively.