Free Energies for Degradation Reactions of 1,2,3-Trichloropropane from ab initio Electronic Structure Theory

Journal Article · Thu Nov 25 04:00:00 EST 2010 · Journal of Physical Chemistry A, 114(46):12269-12282

DOI:https://doi.org/10.1021/jp105726u· OSTI ID:1001095

Bylaska, Eric J; Glaesemann, Kurt R; Felmy, Andrew R; Vasiliu, Monica; Dixon, David A; Tratnyek, P G

Electronic structure methods were used to calculate the gas-phase and aqueous phase reaction energies for reductive dechlorination (i.e. hydrogenolysis), reductive Beta-elimination, dehydrochlorination, and nucleophilic substitution by OH- of 1,2,3-trichloropropane. The thermochemical properties Delta Hof(298.15K), So(298.15K,1 bar), and Delta GS(298.15K, 1 bar) were calculated by using ab initio electronic structure calculations, isodesmic reactions schemes, gas-phase entropy estimates, and continuum solvation models for 1,2,3-trichloropropane and several likely metabolites. On the basis of these thermochemical estimates, together with a Fe(II)/Fe(III) chemical equilibrium model for natural reducing environments, all of the reactions studied were predicted to be very favorable in the standard state and under a wide range of pH conditions. The most favorable reaction was reductive Beta-elimination (Delta Gorxn ≈ -32 kcal/mol), followed closely by reductive dechlorination (Delta Gorxn ≈ -27 kcal/mol), dehydrochlorination (Delta Gorxn ≈ -27kcal/mol), and nucleophilic substitution by OH- (Delta Gorxn ≈ -25 kcal/mol). For both reduction reactions studied, it was found that the first electron-transfer step, yielding the intermediate CH2-CHCl-CH2Cl , and CH2Cl-CH-CH2Cl species, was not favorable in the standard state (Delta Gorxn ≈ +15 kcal/mol) and was predicted to occur only at relatively high pH values. This result suggests that reduction by natural attenuation is unlikely.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1001095
• Report Number(s): PNNL-SA-73300; 25709; KC0303020
• Journal Information: Journal of Physical Chemistry A, 114(46):12269-12282, Journal Name: Journal of Physical Chemistry A, 114(46):12269-12282 Journal Issue: 46 Vol. 114; ISSN 1089-5639; ISSN 1520-5215; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
DECHLORINATION
ELECTRON TRANSFER
ELECTRONIC STRUCTURE
ENTROPY
Electronic Structure Theory
Environmental Molecular Sciences Laboratory
METABOLITES
NATURAL ATTENUATION
PH VALUE
SOLVATION
aqueous phase reaction energies
calculations
gas-phase
thermochemical