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dc.contributor.authorWyer, Martin
dc.contributor.otherQueen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))en
dc.date2008-01-31 13:47:24.044en
dc.date.accessioned2008-02-01T17:57:34Z
dc.date.available2008-02-01T17:57:34Z
dc.date.issued2008-02-01T17:57:34Z
dc.identifier.urihttp://hdl.handle.net/1974/1009
dc.descriptionThesis (Master, Chemistry) -- Queen's University, 2008-01-31 13:47:24.044en
dc.description.abstractThe chemical fate of organophosphorus pesticides is influenced by several factors, one being the chemistry of their aquatic environment. Dissolved metal ions have been shown in several instances to promote the hydrolysis of organophosphorus pesticides, with various reasons forwarded as to the intimate mechanism of metal ion promoted hydrolysis. Several postulates have suggested metal ion co-ordination of Lewis sites to be an important factor in promoting the reaction. In view of this, the study herein reports on the promoted hydrolysis of diazinon at various pH’s in the presence of several metal ions including Hg2+, Cu2+, Cd2+ and Ag+. The observed 1H and 31P NMR data indicated complexation of Cu2+ and Ag+ with diazinon through the formation of a six-membered ring (chelate), via co-ordination at both nitrogen and sulfur Lewis base sites. In contrast, NMR results with Hg2+ indicated Hg2+ ion promoted hydrolysis of diazinon through co-ordination at sulfur alone, possibly through stronger binding to the altered transition state than the reactant state. Another possibility would entail lowering of the pKa of H2O on metal complexation, thus facilitating nucleophilic attack. Electrospray ionization mass spectrometry (ESI-MS) substantiated the proposed metal ion complexation. In the case of Cu2+ and Ag+, complexation between diazinon and metal ions was observed at given m/z ratios, while subsequent MS/MS analysis of the complexed ions revealed co-ordination at both S and N sites by Cu2+ and Ag+. No complexation between diazinon and Hg2+ was observed in ESI-MS; however Hg2+ was shown to complex the hydrolytic product O,O diethyl phosphorothioic acid, presumably through sulfur. Hydrolysis of diazinon was studied at several pH’s at 22oC in the presence of Hg2+, Cu2+, Cd2+ and Ag+, by following spectrophotometrically the appearance of 2-isopropyl-6-methylpyrimidin-4-ol. Kinetic data showed Hg2+, Cu2+ and Ag+ to be extremely effective in neutral-to-mildly acidic conditions, with a reduced effect in the presence of Cd2+. Smaller rate enhancements were also observed at slightly lower pH of 4.0. Possible factors include; 1) Competing acid hydrolysis involving protonation at one heterocyclic N of diazinon (N-3). 2) The dominant nature of the HgCl2 species at pH 4.0. 3) Metal speciation.en
dc.format.extent12478480 bytes
dc.format.mimetypeapplication/pdf
dc.languageenen
dc.language.isoenen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectOrganophosphorus pesticideen
dc.subjectMetal ionen
dc.subjectHydrolysisen
dc.subjectDiazinonen
dc.titleMetal ion promoted hydrolysis of the organophosphorus pesticide diazinonen
dc.typeThesisen
dc.description.degreeMasteren
dc.contributor.supervisorBuncel, Erwinen
dc.contributor.departmentChemistryen


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