Structure, torsional potentials, and thermodynamic properties ΔHof298, So298, and Cp(T) of chloro-dimethyl ethers: CH2ClOCH3, CHCl2OCH3, and CCl3OCH3. Density functional and ab initio calculations

Document Type

Article

Publication Date

6-7-2001

Abstract

Thermochemical properties of oxygenated chlorocarbons are important in studies on oxidation and kinetics of chlorocarbons and in Cl initiated kinetic studies on oxidation of hydrocarbons. Enthalpy, ΔHof298, entropy, S298, and heat capacities, Cp(T), from 300 to 1500 K are determined for three chloro-dimethyl ethers by density functional and ab initio calculation methods. Molecular structures and vibration frequencies are determined at the B3LYP/6-31G(d,p) density functional calculation level, with single point calculations for energy at the B3LYP/6-311+G(3df,2p), QCISD(T)/6-31G(d,p), and CBS-Q//B3LYP/6-31G(d,p) levels of calculation (abbreviated as CBSQ//B3**). Enthalpies of formation are determined at each calculation level using the ΔHrxn(298) and known enthalpies of other reactants in each of seven different working reactions. Contributions to entropy and heat capacity from internal rotation of the chloro-dimethyl ethers are also determined. Evaluation of data from three isodesmic schemes, and the energies of rotational conformers, result in ΔHof298 values for CH2ClOCH3 of -55.42 ± 0.91, for CHCl2OCH3 of -62.28 ± 2.10, and for CCl3OCH3 of -63.11 ± 2.26 kcal/mol at the CBS-Q//B3** level. We determine enthalpy, entropy, and Cp(T) terms for the three mono-oxygenated carbon chlorine groups, where enthalpy values for use in group additivity are C/Cl/H2/O (-20.90), C/C12/H/O (-28.23), and C/Cl3/O (-28.69 kcal/mol), respectively. © 2001 American Chemical Society.

Identifier

0035821937 (Scopus)

Publication Title

Journal of Physical Chemistry A

External Full Text Location

https://doi.org/10.1021/jp0029562

ISSN

10895639

First Page

5420

Last Page

5430

Issue

22

Volume

105

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