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Article: Kinetics and mechanism of propachlor reductive transformation through nucleophilic substitution by dithionite

TitleKinetics and mechanism of propachlor reductive transformation through nucleophilic substitution by dithionite
Authors
KeywordsActivation barriers
Chloroacetanilide herbicides
Dechlorination products
Dithionite
Ethanesulfonic acid
Issue Date2011
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/chemosphere
Citation
Chemosphere, 2011, v. 85 n. 9, p. 1438-1443 How to Cite?
AbstractChloroacetanilide herbicides are extensively used in the control of weeds and have widely resulted in nonpoint contamination of groundwater and soil resources. In the attempt to achieve better remediation for herbicide-contaminated resources, we investigated the reductive transformation of propachlor through nucleophilic substitution by dithionite (S2O42-). Results showed that propachlor underwent rapid dechlorination in the presence of dithionite. The reaction was of second-order kinetics and strongly influenced by pH and temperature. At pH 7.0 and temperature 308K, the rate constant of propachlor dechlorination was estimated at 123.4±0.7M -1h -1. Within the pH range tested (3.0-9.5), higher pH promoted the ionization of dithionite, resulting in a more active nucleophilic reagent of S2O42- to enhance the propachlor transformation rate. Similarly, higher reaction temperature overcame the activation barrier of steric hindrance in propachlor structure and accelerated the excitation of dithionite, in which higher rate constants of propachlor reductive dechlorination were obtained. Dechlorination was found to be the first and necessary step of propachlor nucleophilic substitution by dithionite. Sulfur nucleophile substituted compounds, including propachlor dithionite, propachlor ethanesulfonic acid (ESA), and hydroxyl propachlor, were identified as the dechlorination products of propachlor, indicating bimolecular nucleophilic substitution (S N2) as the mechanism for propachlor transformation initiated by dithionite. © 2011 Elsevier Ltd.
Persistent Identifierhttp://hdl.handle.net/10722/150627
ISSN
2015 Impact Factor: 3.698
2015 SCImago Journal Rankings: 1.536
ISI Accession Number ID
Funding AgencyGrant Number
National Natural Science Foundation of China40801086
Research Grants Council of Hong Kong
General Research Fund SchemeHKU 716809E
Funding Information:

This study was funded by the National Natural Science Foundation of China (40801086) and the Research Grants Council of Hong Kong and its General Research Fund Scheme (HKU 716809E).

References
Grants

 

DC FieldValueLanguage
dc.contributor.authorLiu, CSen_US
dc.contributor.authorShih, Ken_US
dc.contributor.authorWei, Len_US
dc.contributor.authorWang, Fen_US
dc.contributor.authorLi, FBen_US
dc.date.accessioned2012-06-26T06:06:15Z-
dc.date.available2012-06-26T06:06:15Z-
dc.date.issued2011en_US
dc.identifier.citationChemosphere, 2011, v. 85 n. 9, p. 1438-1443en_US
dc.identifier.issn0045-6535en_US
dc.identifier.urihttp://hdl.handle.net/10722/150627-
dc.description.abstractChloroacetanilide herbicides are extensively used in the control of weeds and have widely resulted in nonpoint contamination of groundwater and soil resources. In the attempt to achieve better remediation for herbicide-contaminated resources, we investigated the reductive transformation of propachlor through nucleophilic substitution by dithionite (S2O42-). Results showed that propachlor underwent rapid dechlorination in the presence of dithionite. The reaction was of second-order kinetics and strongly influenced by pH and temperature. At pH 7.0 and temperature 308K, the rate constant of propachlor dechlorination was estimated at 123.4±0.7M -1h -1. Within the pH range tested (3.0-9.5), higher pH promoted the ionization of dithionite, resulting in a more active nucleophilic reagent of S2O42- to enhance the propachlor transformation rate. Similarly, higher reaction temperature overcame the activation barrier of steric hindrance in propachlor structure and accelerated the excitation of dithionite, in which higher rate constants of propachlor reductive dechlorination were obtained. Dechlorination was found to be the first and necessary step of propachlor nucleophilic substitution by dithionite. Sulfur nucleophile substituted compounds, including propachlor dithionite, propachlor ethanesulfonic acid (ESA), and hydroxyl propachlor, were identified as the dechlorination products of propachlor, indicating bimolecular nucleophilic substitution (S N2) as the mechanism for propachlor transformation initiated by dithionite. © 2011 Elsevier Ltd.en_US
dc.languageengen_US
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/chemosphereen_US
dc.relation.ispartofChemosphereen_US
dc.subjectActivation barriersen_US
dc.subjectChloroacetanilide herbicidesen_US
dc.subjectDechlorination productsen_US
dc.subjectDithioniteen_US
dc.subjectEthanesulfonic aciden_US
dc.titleKinetics and mechanism of propachlor reductive transformation through nucleophilic substitution by dithioniteen_US
dc.typeArticleen_US
dc.identifier.emailLiu, CS: cecsliu@hku.hken_US
dc.identifier.emailShih, K: kshih@hku.hk-
dc.identifier.authorityShih, K=rp00167en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1016/j.chemosphere.2011.08.023en_US
dc.identifier.pmid21893332-
dc.identifier.scopuseid_2-s2.0-82455210778en_US
dc.identifier.hkuros205546-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-82455210778&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume85en_US
dc.identifier.issue9en_US
dc.identifier.spage1438en_US
dc.identifier.epage1443en_US
dc.identifier.isiWOS:000298459000004-
dc.publisher.placeUnited Kingdomen_US
dc.relation.projectSorption of Perfluorochemicals on Sediments and Sludge of Hong Kong-
dc.identifier.scopusauthoridLi, FB=24484830300en_US
dc.identifier.scopusauthoridWang, F=54789258400en_US
dc.identifier.scopusauthoridWei, L=54789202400en_US
dc.identifier.scopusauthoridShih, K=14072108900en_US
dc.identifier.scopusauthoridLiu, CS=48861430400en_US
dc.identifier.citeulike9773885-

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