Halocarbons produced by natural oxidation processes during degradation of organic matter

Keppler, Frank; Eiden, Ralf; Niedan, V.; Pracht, Jens; Schöler, H. F.

doi:10.1038/35002055

Cited by 330 publications

(299 citation statements)

References 20 publications

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“…[18][19][20][21][22] Having been so extensively studied, by both experimental [23][24][25][26][27] and computational [28][29][30][31][32][33][34][35][36] means, lends this class of reactions to be an outstanding starting position for benchmarking and refining new computational methods and techniques. In particular, the chloride/methyl chloride reaction is a strong candidate as a prototype reaction as it has been quite extensively studied in order to understand the exact nature of the transition state in the gas and condensed phases.…”

Section: Introductionmentioning

confidence: 99%

Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl− attack on CH3Cl

Kuechler

York

2014

The Journal of Chemical Physics

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The nucleophilic attack of a chloride ion on methyl chloride is an important prototype S N 2 reaction in organic chemistry that is known to be sensitive to the effects of the surrounding solvent. Herein, we develop a highly accurate Specific Reaction Parameter (SRP) model based on the Austin Model 1 Hamiltonian for chlorine to study the effects of solvation into an aqueous environment on the reaction mechanism. To accomplish this task, we apply high-level quantum mechanical calculations to study the reaction in the gas phase and combined quantum mechanical/molecular mechanical simulations with TIP3P and TIP4P-ew water models and the resulting free energy profiles are compared with those determined from simulations using other fast semi-empirical quantum models. Both gas phase and solution results with the SRP model agree very well with experiment and provide insight into the specific role of solvent on the reaction coordinate. Overall, the newly parameterized SRP Hamiltonian is able to reproduce both the gas phase and solution phase barriers, suggesting it is an accurate and robust model for simulations in the aqueous phase at greatly reduced computational cost relative to comparably accurate ab initio and density functional models. © 2014 AIP Publishing LLC. [http://dx

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Section: Introductionmentioning

confidence: 99%

Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl− attack on CH3Cl

Kuechler

York

2014

The Journal of Chemical Physics

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“…The TCA production in absence of CPO suggests that an abiotic formation might also occur. Indeed, Keppler et al (2000) showed that an abiotic formation of volatile halocarbons occurs in soil.…”

Section: Introductionmentioning

confidence: 99%

Formation of chloroacetic acids from soil, humic acid and phenolic moieties

2003

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The mechanism of formation of chloroacetates, which are important toxic environmental substances, has been controversial. Whereas the anthropogenic production has been well established, a natural formation has also been suggested. In this study the natural formation of chloroacetic acids from soil, as well as from humic material which is present in soil and from phenolic model substances has been investigated. It is shown that chloroacetates are formed from humic material with a linear relationship between the amount of humic acid used and chloroacetates found. More dichloroacetate (DCA) than trichloroacetate (TCA) is produced. The addition of Fe 2þ , Fe 3þ and H 2 O 2 leads to an increased yield. NaCl was added as a source of chloride. We further examined the relationship between the structure and reactivity of phenolic substances, which can be considered as monomeric units of humic acids. Ethoxyphenol with built-in ethyl groups forms large amounts of DCA and TCA. The experiments with phenoxyacetic acid yielded large amounts of monochloroacetate (MCA). With other phenolic substances a ring cleavage was observed. Our investigations indicate that chloroacetates are formed abiotically from humic material and soils in addition to their known biotic mode of formation.

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“…Metals such as Fe are often the key cofactors in the reaction centers of haloperoxidative enzymes (Sundaramoorthy et al, 1995). In addition, abiotic (non-enzymatic) metal-catalyzed chlorination of aliphatic and aromatic substrates has been documented in natural systems (Keppler et al, 2000;Schoeler and Keppler, 2002;Fahimi et al, 2003;Holmstrand et al, 2006) and as part of biomimetic synthetic schemes in the laboratory (Delaude and Laszlo, 1990;Walker et al, 1997).…”

Section: Summary and Implications For The Formation Of Different CL Omentioning

confidence: 99%

“…In addition to these non-specific natural chlorination products, individual chlorinated metabolites have been isolated from soil fungi and lichen for decades (Yosioka et al, 1968;Turner and Aldridge, 1983;Wijnberg, 1998;Gribble, 2003). Abiotic (nonenzymatic) chlorination has also been shown to occur naturally and is thought to be catalyzed by metal ions in the low-pH soil environment (Keppler et al, 2000;Schoeler and Keppler, 2002;Fahimi et al, 2003;Holmstrand et al, 2006). This evidence collectively indicates that terrestrial Cl undergoes complex biogeochemical transformations.…”

Section: Introductionmentioning

confidence: 99%

X-ray spectromicroscopic investigation of natural organochlorine distribution in weathering plant material

Leri

Marcus

Myneni

2007

Geochimica et Cosmochimica Acta

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Halocarbons produced by natural oxidation processes during degradation of organic matter

Cited by 330 publications

References 20 publications

Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl− attack on CH3Cl

Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl− attack on CH3Cl

Formation of chloroacetic acids from soil, humic acid and phenolic moieties

X-ray spectromicroscopic investigation of natural organochlorine distribution in weathering plant material

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