A DFT study on kinetics of the gas phase reactions of CH3CH2OCF3 with OH radicals and Cl atoms

Abstract

A theoretical study on the mechanism and kinetics of the gas phase reactions of CH3CH2OCF3 (HFE-263) with the OH radicals and Cl atoms have been performed using meta-hybrid density functional MPWB1K method and 6-31+G(d,p) basis set. Energetics are further refined by calculating the energy of the species with a high level G2(MP2) method. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels. The hydrogen abstraction from CH2 group is found to be the dominant reaction channel for reaction with OH radicals, whereas hydrogen abstraction from CH3 group is the dominant channel for Cl atoms, especially at higher temperature. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CH3CH2OCF3 and radicals generated by hydrogen abstraction, CH3CHOCF3 and CH2CH2OCF3 are reported for the first time. The calculated bond dissociation energies for CH bonds are in good agreement with experimental results. The rate constants of the two reactions are determined for the first time in a wide temperature range of 250–1000K. The G2(MP2) calculated rate constant values are 0.52×10−13 and 0.77×10−12cm3molecule−1s−1, respectively for reactions with OH radicals and Cl atoms at 298K.