Thermochemistry of Fluorinated Dimethyl and Ethyl Methyl Ethers and Corresponding Radical Species

Document Type

Article

Publication Date

4-9-2020

Abstract

Standard enthalpies of formation (?fH°298), standard entropies (S°(T)), and heat capacities (Cp(T)) are calculated for dimethyl and ethyl methyl fluorinated ethers, both the parent and related radical species. The parent and radical species are utilized to determine carbon-hydrogen, carbon-fluorine, carbon-carbon, and carbon-oxygen bond dissociation energies (C-H, C-F, C-C, and C-O BDEs). The ?fH°298 and BDEs are calculated using a variety of error-canceling isogyric and/or isodesmic reactions at the MN15/cc-pVTZ, CBS-QB3, and CBS-APNO levels of theory. ?fH°298 calculations from the MN15 functional for these ether species are shown to have consistency with the CBS-QB3 and CBS-APNO composite methods with our recommended ideal gas phase ?fH°298 values from the average of these two composite methods. C-F BDE values are shown to range overall between 111 and 128 kcal mol-1, the C-H BDEs are in the 93-106 kcal mol-1 range, the C-O BDEs are in the 83-107 kcal mol-1 range, and the C-C BDEs are in the 88-101 kcal mol-1 range. It is observed that as the number of fluorine atom substitutions increases, the C-H BDEs also increase. The number of fluorine atom substitutions on the carbon atom where the C-F bond is being broken has a larger influence than that of the total number of fluorine atom substitutions in the species. Optimized geometry parameters, moments of inertia, vibrational frequencies, and single bond internal rotor potentials are calculated at the MN15/cc-pVTZ level for contributions to entropy and heat capacities. Calculated thermochemical properties for CF-C-O-C, C-CF-O-C, and C-C-O-CF (i.e., 1-fluoroethyl methyl ether, 2-fluoroethyl methyl ether, and ethyl fluoromethyl ether) are utilized to develop fluorinated group additivity values (C/C/F/H2, C/C/F/H/O, and C/F/H2/O) for use in the group additivity (GA) method (as well as several carbon-hydrogen bond increment groups corresponding to radical formation). This work is of value in the development of detailed chemical kinetic mechanisms for use in atmospheric chemistry.

Identifier

85084116504 (Scopus)

Publication Title

Journal of Chemical and Engineering Data

External Full Text Location

https://doi.org/10.1021/acs.jced.9b01034

e-ISSN

15205134

ISSN

00219568

First Page

1594

Last Page

1616

Issue

4

Volume

65

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