Gibbs free energies of formation of PCDDs: Evaluation of estimation methods and application for predicting dehalogenation pathways

Ching L.I. Huang, B. Keith Harrison, Jeffry Madura, Jan Dolfing

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)

Abstract

Gibbs free energies of formation for the ideal gas, liquid phase, and species in solution were estimated for 75 polychlorinated dibenzo-p-dioxins (PCDDs) at 298.15 K and 100,000 Pa. These values were used to calculate standard redox potentials, with H2 as the electron donor. Owing to the lack of experimental thermodynamic data for the involved chemical species, the standard-state ideal gas enthalpies of formation were evaluated by several semiempirical methods including the Modified Neglect of Diatomic Differential Overlap (MNDO). Austin Model 1 (AM1), and MNDO-Parametric Method 3 (PM3). Three different implementations of Benson's group additivity method for estimation of ideal gas enthalpies of formation were also evaluated. As a result the evaluation, the CHETAH program based on Benson's group additive method was chosen for ideal gas enthalpy of formation calculations. Entropies, vapor pressure, and aqueous solubility were calculated by existing methods in order to complete the thermodynamic cycle Calculated redox potentials indicate that chlorodioxins, including 2,3,7,8-tetrachlorodioxin, can serve as electron acceptors in anaerobic environments, at least from a thermodynamic perspective.

Original languageEnglish
Pages (from-to)824-836
Number of pages13
JournalEnvironmental Toxicology and Chemistry
Volume15
Issue number6
DOIs
Publication statusPublished - 1 Jun 1996
Externally publishedYes

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