Degradation of Chlorinated Compounds

Wischnak, Catrin; Müller, Rudolf

doi:10.1002/9783527620951.ch10

Cited by 4 publications

(2 citation statements)

References 141 publications

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“…The production of halogenated hydrocarbons for use as herbicides, pesticides, refrigerants, or solvents has given rise to environmental concerns due to their toxicity and possible role as carcinogenic agents . A possible route for bioremediation of contaminated soils and waters − involves the action of the haloalkane dehalogenase enzyme − ,− present in, for instance, the bacterium Xanthobacter autotrophicus GJ10.…”

Section: Introductionmentioning

confidence: 99%

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase S_N2 Reaction of Acetate Ion with 1,2-Dichloroethane

Valero

Song

Gao

et al. 2008

J. Chem. Theory Comput.

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Diabatic models are widely employed for studying chemical reactivity in condensed phases and enzymes, but there has been little discussion of the pros and cons of various diabatic representations for this purpose. Here we discuss and contrast six different schemes for computing diabatic potentials for a charge rearrangement reaction. They include (i) the variational diabatic configurations (VDC) constructed by variationally optimizing individual valence bond structures and (ii) the consistent diabatic configurations (CDC) obtained by variationally optimizing the ground-state adiabatic energy, both in the nonorthogonal molecular orbital valence bond (MOVB) method, along with the orthogonalized (iii) VDC-MOVB and (iv) CDC-MOVB models. In addition, we consider (v) the fourfold way (based on diabatic molecular orbitals and configuration uniformity), and (vi) empirical valence bond (EVB) theory. To make the considerations concrete, we calculate diabatic electronic states and diabatic potential energies along the reaction path that connects the reactant and the product ion-molecule complexes of the gas-phase bimolecular nucleophilic substitution (SN2) reaction of 1,2-dichloethane (DCE) with acetate ion, which is a model reaction corresponding to the reaction catalyzed by haloalkane dehalogenase. We utilize ab initio block-localized molecular orbital theory to construct the MOVB diabatic states and ab initio multi-configuration quasidegenerate perturbation theory to construct the fourfold-way diabatic states; the latter are calculated at reaction path geometries obtained with the M06-2X density functional. The EVB diabatic states are computed with parameters taken from the literature. The MOVB and fourfold-way adiabatic and diabatic potential energy profiles along the reaction path are in qualitative but not quantitative agreement with each other. In order to validate that these wave-function-based diabatic states are qualitatively correct, we show that the reaction energy and barrier for the adiabatic ground state, obtained with these methods, agree reasonably well with the results of high-level calculations using the composite G3SX and G3SX(MP3) methods and the BMC-CCSD multi-coefficient correlation method. However, a comparison of the EVB gas-phase adiabatic ground-state reaction path with those obtained from MOVB and with the fourfold way reveals that the EVB reaction path geometries show a systematic shift towards the products region, and that the EVB lowest-energy path has a much lower barrier. The free energies of solvation and activation energy in water reported from dynamical calculations based on EVB also imply a low activation barrier in the gas phase. In addition, calculations of the free energy of solvation using the recently proposed SM8 continuum solvation model with CM4M partial atomic charges lead to an activation barrier in reasonable agreement with experiment only when the geometries and the gas-phase barrier are those obtained from electronic structure calculations, i.e., methods i–v. These comparis...

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Section: Introductionmentioning

confidence: 99%

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase S_N2 Reaction of Acetate Ion with 1,2-Dichloroethane

Valero

Song

Gao

et al. 2008

J. Chem. Theory Comput.

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“…The accurate opportunity for biodegradation of perchloroethylene, maximum chlorinated congeners and hexachlorobenzene is only reductive dechlorination (Wischnak and Müller 2008). Due to diverse redox conditions, prevailing because of halophyte roots that donate oxygen, a wetland is basically a metabolically strong technical ecosystem (Stottmeister et al 2003).…”

Section: Discussionmentioning

confidence: 99%

Screening of Wetland Plants Subjected to Stress From Polychlorinated Biphenyls Contaminated Soils

Khalid

Hashmi

Jamil

et al. 2021

Preprint

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Soil pollution due to electric and electronic waste (e-waste) has become a major problem that is degrading environment and drawing worldwide attention. PCBs are widespread and have potential health risk so their removal from the environment has become an international priority. Phytoremediation is considered as highly accepted and good method for treatment of contaminated soils. Current study was conducted to investigate the abilities of several promising wetland plants to degrade and dechlorinate PCBs and demonstrate their advantages in disappearance of polychlorinated biphenyls. The soils samples were collected from PCB-contaminated sites at Layyari, Karachi Pakistan. Under both floody and dry condition plants including Alternanthera sessilis (L.), Bacopa moneiri (L.) Pennell, Centella asiatica (L.) Urban, Juncus articulatus L., Cyperus arenarius Retz were grown. For dechlorination of PCBs three treatments were set up in a fully randomized layout of greenhouse pots. Soil from those pots was extracted and further analyzed by Gas chromatography equipped with a 63Ni electron capture detector. The detection limits of PCBs ranged from 0.009 to 0.082 µg/kg. In total PCBs degradation ratio was 22.44% while in high chlorinated PCBs almost 15.26% of the high polychlorinated biphenyls were removed from the soil after 2 month in the wetland planted soil, while only 4.64% was removed in the drowned control and 6.54% in the unplanted control. Present study concludes that this method only has high efficiency in removal of low chlorinated biphenyls, while low efficiency even nothing in removal of high components.

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Strategies to Improve PAH Bioavailability: Addition of Surfactants, Ozonation and Application of Ultrasound

Tiehm

Stieber

2001

Treatment of Contaminated Soil

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Degradation of Chlorinated Compounds

Cited by 4 publications

References 141 publications

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase S_N2 Reaction of Acetate Ion with 1,2-Dichloroethane

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase S_N2 Reaction of Acetate Ion with 1,2-Dichloroethane

Screening of Wetland Plants Subjected to Stress From Polychlorinated Biphenyls Contaminated Soils

Strategies to Improve PAH Bioavailability: Addition of Surfactants, Ozonation and Application of Ultrasound

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Degradation of Chlorinated Compounds

Cited by 4 publications

References 141 publications

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase SN2 Reaction of Acetate Ion with 1,2-Dichloroethane

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase SN2 Reaction of Acetate Ion with 1,2-Dichloroethane

Screening of Wetland Plants Subjected to Stress From Polychlorinated Biphenyls Contaminated Soils

Strategies to Improve PAH Bioavailability: Addition of Surfactants, Ozonation and Application of Ultrasound

Contact Info

Product

Resources

About

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase S_N2 Reaction of Acetate Ion with 1,2-Dichloroethane

Perspective on Diabatic Models of Chemical Reactivity as Illustrated by the Gas-Phase S_N2 Reaction of Acetate Ion with 1,2-Dichloroethane