Theoretical study of the reactions CF₃CH₂OCHF₂ + OH/Cl and its product radicals and parent ether(CH₃CH₂OCH₃) with OH

Abstract

A dual-level direct dynamic method is employed to study the reaction mechanisms of CF3CH2OCHF2 (HFE-245fa2; HFE-245mf) with the OH radicals and Cl atoms. Two hydrogen abstraction channels and two displacement processes are found for each reaction. For further study, the reaction mechanisms of its products (CF3CH2OCF2 and CF3CHOCHF2) and parent ether CH3CH2OCH3 with OH radical are investigated theoretically. The geometries and frequencies of all the stationary points and the minimum energy paths (MEPs) are calculated at the B3LYP/6-311G(d,p) level. The energetic information along the MEPs is further refined at the G3(MP2) level of theory. For reactions CF3CH2OCHF2 + OH/Cl, the calculation indicates that the hydrogen abstraction from --CH2-- group is the dominant reaction channel, and the displacement processes may be negligible because of the high barriers. The standard enthalpies of formation for the reactant CF3CH2OCHF2, and two products CF3CH2OCHF2 and CF3CHOCHF2 are evaluated via group-balanced isodesmic reactions. The rate constants of reactions CF3CH2OCHF2 + OH/Cl and CH3CH2OCH3 + OH are estimated by using the variational transition state theory over a wide range of temperature (200-2000 K). The agreement between the theoretical and experimental rate constants is good in the measured temperature range. From the comparison between the rate constants of the reactions CF3CH2OCHF2 and CH3CH2OCH3 with OH, it is shown that the fluorine substitution decreases the reactivity of the C--H bond.

Exploring the Reactivity of Hydrofluoropolyethers toward OH through a Cost-Effective Protocol for Calculating Multiconformer Transition State Theory Rate Constants

“…The electronic partition function is evaluated as where ϵ n is the electronic energy of the n th level and ω n is the correspondent degeneracy of that level. For the OH electronic partition function, we have included the two electronic states ( 2 Π 3/2 and 2 Π 1/2 ) resulting from the 139.7 cm –1 splitting of the 2 Π ground state. , Accordingly, the electronic partition function for the OH radical can be written − as , where c is the speed of light. For a single conformer structure, its overall rate constant (conformer-specific rate constant) can then be calculated as a sum over the n H individual reaction paths where σ i is the reaction path symmetry number and n H is the total number of hydrogen atoms in the molecule ranging from n H = 2 for R = CF 2 H to n H = 14 for R = CH 2 CH 2 CH 3 and CH­(CH 3 ) 2 .…”

Symmetric Ethers as Bioderived Fuels: Reactivity with OH Radicals

“… a The data are compiled from Luo, Zhou et al, Shang et al, Yang et al, Serinyel et al, Thion et al., and Cai et al …”

“…The rate parameters were taken as analogous to the C−H primary sites of n-alkane + OH reactions as given by Sivaramakrishnan and Michael. The data are compiled from Luo, 40 Zhou et al, 29 Shang et al, 41 Yang et al, 42 Serinyel et al, 10 comparable branching ratios but with a slight T dependence. In line with Cai et al, 5 we observed that the contribution of the α(2°) channel decreases with increasing alkyl chain length in dialkyl ethers and thus an increase in the number of sites where hydrogen atoms can be abstracted.…”

AN INSILCO STUDY OF 1,1-DIFLUORO-2-METHOXYPROPANE REACTION MECHANISM WITH THE BROMINE MONOXIDE (BrO) RADICAL

“…Thus, the presence of an atom of Br, Cl, I etc. in an atmosphere is a chemical set back to ozone layer (Deka and Mishra, 2014;Laszlo et al, 1997;Wofsy et al, 1975;Yang et al, 2007).…”