A laser flash photolysis study of the intramolecular photoisomerization and reduction of dibenzo-p-dioxins

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dc.contributor.authorSasaki, Ryan Roeen_US
dc.date.accessioned2024-08-15T18:19:07Z
dc.date.available2024-08-15T18:19:07Z
dc.date.copyright2002en_US
dc.date.issued2002
dc.degree.departmentDepartment of Chemistry
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractThe mechanistic details of the photoisomerization and reduction of four dibenzo­ p-dioxins 33, 39, 40 and 41 are reported. The dibenzo-p-dioxin ring system is common to chlorinated dioxins, which are known to be some of the most toxic compounds ever synthesized. Although chlorinated dioxins have dechlorination (typically via C-C1 bond homolysis) as an important photochemical reaction channel, we have recently shown that photoisomerization of the dibenzo-p-dioxin ring system is a significant reaction channel. Therefore, the kinetic details of the photoisomerization and subsequent reaction of the 2,2'-biphenylquinones would add further insight into the photochemical reactivity of these compounds. For this purpose, laser flash photolysis and conventional kinetic measurements are used to study the parent compound 33 and three derivatives, 39, 40 and 41. It is shown that laser flash photolysis is able to kinetically resolve the growth of the 2,2'-biphenylquinone from its assumed spiroketone precursor, whereas the reduction of the 2,2'-biphenylquinone can be followed conveniently by UV-Vis spectrophotometry. The effects of pH have shown an acid catalysed effect on both the formation and disappearance of the 2,2'-biphenylquinones. Studies in different solvents and solvent isotope effects have illustrated the solvent participation in the reduction of the 2,2'­ biphenylquinones. Electron-donating substituents has been shown to decrease the lifetimes of both the spiroketone and the biphenylquinone. The results of this thesis support a mechanism for the photochemical degradation of dibenzo-p-dioxins.
dc.format.extent75 pages
dc.identifier.urihttps://hdl.handle.net/1828/19574
dc.rightsAvailable to the World Wide Weben_US
dc.titleA laser flash photolysis study of the intramolecular photoisomerization and reduction of dibenzo-p-dioxinsen_US
dc.typeThesisen_US

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