Prev. Article Next Article Table of Contents

Article

The Energetics of the Hydrogenolysis, Dehydrohalogenation, and Hydrolysis of 4,4‘-Dichloro-diphenyl-trichloroethane from ab Initio Electronic Structure Theory

Supporting Info

Eric J. Bylaska,* David A. Dixon,^† and Andrew R. Felmy

Fundamental Sciences, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352

Edoardo Aprà and Theresa L. Windus

William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352

Chang-Guo Zhan

Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 907 Rose Street, Room 501B, Lexington, Kentucky 40536

Paul G. Tratnyek

OGI School of Science & Engineering, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, Oregon 97006-8921

J. Phys. Chem. A, 2004, 108 (27), pp 5883–5893

DOI: 10.1021/jp0312316

Publication Date (Web): June 10, 2004

Corresponding author. Email: Eric.Bylaska@pnl.gov.

†

Current address: Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0036.

Abstract

Electronic structure methods were used to calculate the aqueous reaction energies for hydrogenolysis, dehydrochlorination, and nucleophilic substitution by OH^- of 4,4‘-DDT. Thermochemical properties ΔH_f° (298.15 K), S° (298.15 K, 1 bar), ΔG_S (298.15 K, 1 bar) were calculated by using ab initio electronic structure calculations, isodesmic reactions schemes, gas-phase entropy estimates, and continuum solvation models for a series of DDT type structures (p−C₆H₄Cl)₂−CH−CCl₃, (p−C₆H₄Cl)₂−CH−CCl₂•, (p−C₆H₄Cl)₂−CH−CHCl₂, (p−C₆H₄Cl)₂−CCCl₂, (p−C₆H₄Cl)₂−CH−CCl₂OH, (p−C₆H₄Cl)₂−CH−CCl(O), and (p−C₆H₄Cl)₂−CH−COOH. On the basis of these thermochemical estimates, the overall aqueous reaction energetics of hydrogenolysis, dehydrochlorination, and hydrolysis of 4,4‘-DDT were estimated. The results of this investigation showed that the dehydrochlorination and hydrolysis reactions have strongly favorable thermodynamics in the standard state, as well as under a wide range of pH conditions. For hydrogenolysis with the reductant aqueous Fe(II), the thermodynamics are strongly dependent on pH, and the stability region of the (p−C₆H₄Cl)₂−CH−CCl₂•_(aq) species is a key to controlling the reactivity in hydrogenolysis. These results illustrate the use of ab initio electronic structure methods to identify the potentially important environmental degradation reactions by calculation of the reaction energetics of a potentially large number of organic compounds with aqueous species in natural waters.