Gaussian M-062x/6-31+g (d,p) Calculation of Standard Enthalpy, Entropy and Heat Capacity of Some Fluorinated Alcohol’s and Its Radicals at Different Temperatures

Hebah Abdel-Wahab,Joseph Bozzelli

doi:10.11648/j.ajpc.20200904.13

Abstract

Thermochemical properties of fluorinated alcohols are needed for understanding their stability and reactions in the environment and in thermal process. Structures and thermochemical properties of these species were determined by the Gaussian M-062x/6-31+g (d,p) calculation. Contributions of entropy, S°298, and heat capacities, Cp(T) due to vibration, translation, and external rotation of the molecules were calculated based on the vibration frequencies and structures obtained from the M-062x/6-31+g (d,p) density functional method. Potential barriers are calculated using M-062x/6-31+g (d,p) density functional method and are used to calculate rotor contributions to entropy and heat capacity using integration over energy levels of rotational potential. Enthalpies of formation for 19 ﬂuorinated ethanol and some radicals were calculated with a popular ab initio and density functional theory methods: the Gaussian M-062x/6-31+g (d,p) via several series of isodesmic reactions. The recommended ideal gas phase ΔHf298 ° (kcal mol−1) values calculated in this study are the following: -101.74 ± 0.72 for CH2FCH2OH; -113.51 ±1.39 for CH3CHFOH; -50.66 ± 0.75 for C•HFCH2OH; -56.05±0.62 for CH2FCH•OH; -45.00±1.31 for CH2FCH2O•; -59.61±1.20 for CH2•CHFOH; -67.99± 1.29 for CH3CF•OH; -58.76±1.20 for CH3CHFO•; -154.12±1.72 for CH2FCHFOH; -155.26±1.67 for CF2HCH2OH; -174.53±1.54 for CH3CF2OH; -104.07 ± 1.45 for CH2FC•FOH; -105.63±1.74 for C•HFCFHOH; -99.08±1.57 for CH2FCHFO•; -102.34±1.74 for CHF2C•HOH; -102.23±1.57 for C•F2CH2OH; -98.86±1.57 for CHF2CH2O•; -119.41±1.74 for CH2•CF2OH; -110.56±1.62 for CH3CF2O•. Entropies (S298° in cal mol−1 K−1) were estimated using the M-062x/6-31+g (d,p) computed frequencies and geometries. Rotational barriers were determined and hindered internal rotational contributions for S298°- 1500°, and Cp(T) were calculated using the rigid rotor harmonic oscillator approximation, with direct integration over energy levels of the intramolecular rotation potential energy curves.

Highlights

Fluorinated hydrocarbons used as refrigerants, in polymers, heat exchange fluids, and as solvents
[1] Fluorinated hydrocarbons exist as compounds ranging from pure to oxidized intermediates resulting from oxidation in the environment
It’s a Global-hybrid meta-GGA density functional approximation, GGA, generalized gradient approximation, in which the density functional depends on the up and down spin densities and their reduced gradient, meta GGA, in which the functional depends on the up and down spin kinetic energy densities, hybrid GGA, a combination of GGA with Hartree-Fock exchange, hybrid meta GGA, a combination of meta GGA with Hartree-Fock exchange [21]

Summary

Introduction

Fluorinated hydrocarbons used as refrigerants, in polymers, heat exchange fluids, and as solvents. They are present in the atmosphere, lithosphere, and hydrosphere. Because of their less adverse effects on the stratospheric ozone layer, they are used in place of greenhouse gases. [1] Fluorinated hydrocarbons exist as compounds ranging from pure to oxidized intermediates resulting from oxidation in the environment. In order to study their reactivity in biological systems, lifetimes, and in the environment, it’s critical to understand the chemical and thermodynamic properties of fluorocarbons and their breakdown intermediates. In 2016 Hang Wang studied thermodynamic properties of fluorinated methanol using CBS-QB3, M06, M06-2X, WB97X, W1U, B3LYP, CBS-APNO and G4 Calculations.

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Results

Conclusion