Aqueous photochemistry of syringic acid as a model for the environmental photochemical behaviour of humic substances

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dc.contributor.authorDallin, Erin
dc.contributor.supervisorWan, Peter
dc.contributor.supervisorKrogh, Erik
dc.date.accessioned2007-10-09T17:07:40Z
dc.date.available2007-10-09T17:07:40Z
dc.date.copyright2007en_US
dc.date.issued2007-10-09T17:07:40Z
dc.degree.departmentDepartment of Chemistry
dc.degree.levelMaster of Science M.Sc.en_US
dc.description.abstractThe aqueous photochemistry of 4-hydroxy-3,5-dimethoxybenzoic acid (syringic acid) has been studied as a model humic substance in order to better understand the reactions that compounds of this type undergo in the natural environment. Syringic acid was chosen since it has been identified as a component of humic substances in the environment and bears many of chemical moieties found in structures of this type. In addition, there has been speculation that humic substances are responsible for some of the production of halomethanes that are released into the environment. Photolysis of these compounds in marine and estuarine waters may be responsible for the release of halomethanes which are known stratospheric ozone depleters. Photochemical product studies of syringic acid and related compounds along with UV-Vis spectrometry, laser flash photolysis and membrane introduction mass spectrometry were carried out in aqueous solutions to study its photochemical transformations. Syringic acid was found to form methanol at a 0.01 quantum yield upon its photolysis in basic solution. Other major photoproducts included 3-methoxygallic acid and 3,5-dimethoxybenzoic acid. Chloromethane was identified as a minor photoproduct in chloride enriched solution by following its production via membrane introduction mass spectrometry. The proposed mechanism for the formation of these photoproducts involves an initial photoprotonation of the benzene ring, resulting in a carbocation that can facilitate the nucleophilic attack by water or chloride, to produce methanol or chloromethane, respectively. The formation of 3,5-dimethoxybenzoic acid is via a novel pathway that involves the loss of the hydroxy group from the aromatic ring after the photoprotonation.en_US
dc.identifier.urihttp://hdl.handle.net/1828/240
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjecthumic substancesen_US
dc.subjectsyringic aciden_US
dc.subjectozone depletionen_US
dc.subjectchloromethaneen_US
dc.subjectphotochemistryen_US
dc.subjectphotoprotonationen_US
dc.subject.lcshUVic Subject Index::Sciences and Engineering::Chemistry::Chemistry, Organicen_US
dc.titleAqueous photochemistry of syringic acid as a model for the environmental photochemical behaviour of humic substancesen_US
dc.typeThesisen_US

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