Theoretical investigations on kinetics, mechanism and thermochemistry of the gas phase reactions of CHF2OCF2CHF2 with OH radicals

Abstract

Theoretical investigations were carried out on the mechanism, kinetics and thermochemistry of the gas-phase reactions between CHF2CF2OCHF2 and OH radical using the high level ab initio G2(MP2) and hybrid density functional MPWB1K/6-31+G(d,p) methods. Two most stable conformers of CHF2CF2OCHF2 are identified and the energy difference between them is found to be only 0.3kcalmol−1. Both of them are considered for rate coefficient calculations in our study and the contribution from each of the conformers is found to be quite significant in the temperature range of our study. The rate coefficients are determined for the first time in a wide range of temperature 250–1000K. The calculated total rate coefficient value kOH=1.01×10−15cm3molecule−1s−1 is in reasonably good agreement with the experimental value of kOH=2.36×10−15cm3molecule−1s−1 at 298K. The heats of formation for CHF2CF2OCHF2 and CHF2CF2OCF2 and CF2CF2OCHF2 radicals are estimated to be −359.64, −305.43 and −306.88kcalmol−1, respectively. The bond dissociation energies of the two C–H bonds are CHF2CF2OC(–H)F2: 106.3kcalmol−1 and C(–H)F2CF2OCHF2: 104.8kcalmol−1. The atmospheric lifetime of CHF2OCF2CHF2 is estimated to be around 35years.