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

Journal Article · Thu Nov 25 00:00:00 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 Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1001095
• Report Number(s): PNNL-SA-73300; ISSN 1520-5215; JPCAFH; 25709; KC0303020; TRN: US201101%%831
• Journal Information: Journal of Physical Chemistry A, 114(46):12269-12282, Vol. 114, Issue 46; ISSN 1089-5639
• Country of Publication: United States
• Language: English

Related Subjects

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