Thermochemical Properties and Bond Dissociation Energies for Fluorinated Methanol, CH3-xFxOH, and Fluorinated Methyl Hydroperoxides, CH3-xFxOOH: Group Additivity

Document Type

Article

Publication Date

9-8-2016

Abstract

Oxygenated fluorocarbons are routinely found in sampling of environmental soils and waters as a result of the widespread use of fluoro and chlorofluoro carbons as heat transfer fluids, inert materials, polymers, fire retardants and solvents; the influence of these chemicals on the environment is a growing concern. The thermochemical properties of these species are needed for understanding their stability and reactions in the environment and in thermal process. Structures and thermochemical properties on the mono- to trifluoromethanol, CH3-xFxOH, and fluoromethyl hydroperoxide, CH3-xFxOOH (1 ≤ x ≤ 3), are determined by CBS-QB3, CBS-APNO, and G4 calculations. Entropy, S°298, and heat capacities, Cp(T)'s (300 ≤ T/K ≤ 1500) from vibration, translation, and external rotation contributions are calculated on the basis of the vibration frequencies and structures obtained from the B3LYP/6-31+G(d,p) density functional method. Potential barriers for the internal rotations are also calculated from this method and used to calculate hindered rotor contributions to S°298 and Cp(T)'s using direct integration over energy levels of the internal rotational potentials. Standard enthalpies of formation, ΔfH°298 (units in kcal mol-1) are CH2FOOH (-83.7), CHF2OOH (-138.1), CF3OOH (-193.6), CH2FOO• (-44.9), CHF2OO• (-99.6), CF3OO• (-153.8), CH2FOH (-101.9), CHF2OH (-161.6), CF3OH (-218.1), CH2FO• (-49.1), CHF2O• (-97.8), CF3O• (-150.5), CH2F• (-7.6), CHF2• (-58.8), and CF3• (-112.6). Bond dissociation energies for the R-OOH, RO-OH, ROO-H, R-OO•, RO-O•, R-OH, RO-H, R-O•, and R-H bonds are determined and compared with methyl hydroperoxide to observe the trends from added fluoro substitutions. Enthalpy of formation for the fluoro-hydrocarbon oxygen groups C/F/H2/O, C/F2/H/O, C/F3/O, are derived from the above fluorinated methanol and fluorinated hydroperoxide species for use in Benson's Group Additivity. It was determined that fluorinated peroxides require interaction terms O/CH2F/O, O/CHF2/O, and O/CF3/O, as opposed to the common (O/C/O) group in hydrocarbons, resulting from interactions of the peroxide oxygen with the fluorines. Hydrogen bond dissociation increment (HBI) groups are also developed.

Identifier

84986300594 (Scopus)

Publication Title

Journal of Physical Chemistry A

External Full Text Location

https://doi.org/10.1021/acs.jpca.6b05293

e-ISSN

15205215

ISSN

10895639

First Page

6998

Last Page

7010

Issue

35

Volume

120

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