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Reductive outer-sphere single electron transfer is an exception rather than the rule in natural and engineered chlorinated ethene dehalogenation.
Environ. Sci. Technol. 51, 9663-9673 (2017)
Chlorinated ethenes (CEs) such as perchloroethylene, trichloroethylene and dichloroethylene are notorious groundwater contaminants. Although reductive dehalogenation is key to their environmental and engineered degradation, underlying reaction mechanisms remain elusive. Outer-sphere reductive single electron transfer (OS-SET) has been proposed for such different processes as Vitamin B 12 -dependent biodegradation and zerovalent metal-mediated dehalogenation. Compound-specific isotope effect ( 13 C/ 12 C, 37 Cl/ 35 Cl) analysis offers a new opportunity to test these hypotheses. Defined OS-SET model reactants (CO 2 radical anions, S 2- -doped graphene oxide in water) caused strong carbon (ε C = -7.9‰ to -11.9‰), but negligible chlorine isotope effects (ε Cl = -0.12‰ to 0.04‰) in CEs. Greater chlorine isotope effects were observed in CHCl 3 (ε C = -7.7‰, ε Cl = -2.6‰), and in CEs when the exergonicity of C-Cl bond cleavage was reduced in an organic solvent (reaction with arene radical anions in glyme). Together, this points to dissociative OS-SET (SET to a σ∗ orbital concerted with C-Cl breakage) in alkanes compared to stepwise OS-SET (SET to a π∗ orbital followed by C-Cl cleavage) in ethenes. The nonexistent chlorine isotope effects of chlorinated ethenes in all aqueous OS-SET experiments contrast strongly with pronounced Cl isotope fractionation in all natural and engineered reductive dehalogenations reported to date suggesting that OS-SET is an exception rather than the rule in environmental transformations of chlorinated ethenes.
Impact Factor
Scopus SNIP
Web of Science
Times Cited
Times Cited
Scopus
Cited By
Cited By
Altmetric
6.198
1.889
18
26
Anmerkungen
Besondere Publikation
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Publikationstyp
Artikel: Journalartikel
Dokumenttyp
Wissenschaftlicher Artikel
Schlagwörter
Stable-isotope Fractionation; Ratio Mass-spectrometry; Transformation Pathways; Carbon-tetrachloride; Vinyl-chloride; Granular Iron; Dechlorination; Mechanisms; Trichloroethene; Degradation
Sprache
Veröffentlichungsjahr
2017
HGF-Berichtsjahr
2017
ISSN (print) / ISBN
0013-936X
e-ISSN
1520-5851
Zeitschrift
Environmental Science & Technology
Quellenangaben
Band: 51,
Heft: 17,
Seiten: 9663-9673
Verlag
ACS
Verlagsort
Washington, DC
Begutachtungsstatus
Peer reviewed
Institut(e)
Institute of Groundwater Ecology (IGOE)
POF Topic(s)
20403 - Sustainable Water Management
Forschungsfeld(er)
Environmental Sciences
PSP-Element(e)
G-504390-001
PubMed ID
28727446
WOS ID
WOS:000410255800027
Scopus ID
85028953919
Erfassungsdatum
2017-09-28