Thermochemical properties, rotation barriers, and group additivity for unsaturated oxygenated hydrocarbons and radicals resulting from reaction of vinyl and phenyl radical systems with O 2

Document Type

Article

Publication Date

3-17-2005

Abstract

Oxidation of unsaturated and aromatic hydrocarbons in atmospheric and combustion processes results in formation of linear and cyclic unsaturated, oxygenated-hydrocarbon intermediates. The thermochemical parameters Δ fH° 298, S° 298 and C pf298(T) for these intermediates are needed to understand their stability and reaction paths in further oxidation. These properties are not available for a majority of these unsaturated oxy-hydrocarbons and their corresponding radicals, even via group additivity methods. Enthalpy, entropy, and heat capacity of a series of 40 oxygenated and non-oxygenated molecules, or radicals corresponding to hydrogen atom loss from the parent stable molecules are determined in this study. Enthalpy (Δ fH° 298 in kcal mol -1) is derived from the density function calculations at the B3LYP/6-311g(d,p) calculated enthalpy of reaction (ΔH° rxn,298) and by use of isodesmic (work) reactions. Estimation of error in enthalpy (Δ fH° 298), from use of computational chemistry coupled with work reactions analysis, is presented using comparisons between the calculated and literature enthalpies of reaction. Entropies (S° 298) and heat capacities (C pf298(T)) were calculated using the B3LYP/6-311G(d,p) determined frequencies and geometries. Potential barriers for internal rotors in each molecule were determined and used (in place of torsion frequencies) to calculate contributions to S and C p(T) from the hindered rotors. Twenty-six groups for use in group additivity (GA) are also developed. © 2005 American Chemical Society.

Identifier

15944421174 (Scopus)

Publication Title

Journal of Physical Chemistry A

External Full Text Location

https://doi.org/10.1021/jp046285+

ISSN

10895639

First Page

2233

Last Page

2253

Issue

10

Volume

109

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