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Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 124-128). Also available for download via the World Wide Web; free to University of Oregon users.

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Previous investigations involving the behaviour of cis-4a,5,8,8a-tetrahydro-1,4-naphthoquinone and its derivatives in solution under UV irradiation raised the question of what role, if any, the ground state conformations of these molecules play in a) the type of photochemical behaviour the substrate exhibits and b) the product distribution in cases where more than one product is formed. In addition, it has never been established experimentally just what the geometric requirements for the various reactions encountered in this series are. Such requirements usually provide insights into the geometry of the transition state itself. In the solid state, the initial conformation of molecules of any given substrate can be accurately determined by single crystal X-ray diffraction methods. Furthermore, since the crystal lattice usually resists any gross changes in conformation during the course of a reaction, it follows that most reactions in the crystalline state will occur from the ground state conformation of the substrate. By studying these reactions in the solid state and correlating the results with the X-ray data, it was hoped that the questions raised as well as others e.g. concentration effects could be answered. Eleven substrates were chosen for the investigation. They were all prepared by the Diels Alder addition of a diene to a quinone. By slow crystallization all substrates with the exception of 6,7-dimethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 2 and 2,3,4aβ,5α,8α,8aβ-hexamethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 10, gave crystals suitable for single crystal X-ray structure determination. Relevant X-ray data of nine of these substrates and five of the solid state photoproducts are reported. In the solid state, 5α,8α-dimethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 1, 6,7-dimethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 2, and the parent compound 4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 3, did not undergo the photochemical intramolecular hydrogen abstraction they undergo in solution. Instead, they dimerized stereospecifically to their respective centrosymmetric dimers when irradiated with UV light below their respective eutectic temperatures. This is rationalized in terms of a parallel alignment of the C(2), C(3) double bonds of adjacent monomers and short intermolecular centre-to-centre separation (≤4.040Å) of these double bonds. Five of the substrates, namely, 6,7-diphenyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 4, 2,3-dimethyl-1, 4-4aβ, 9aβ~tetrahydro-9,10-anthraquinone, 6,4aβ,8aβ-dicyano-6,7-dimethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 7, 2,3,4aβ,6,7,8aβ-hexamethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 9 and 2,3,4aβ,5β,8β,8aβ- hexamethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 11 have intermolecular double bond contacts exceeding 4.1Å and did not undergo dimerization in the solid state. Instead, upon UV irradiation, they formed tricyclic enone alcohols derived from intramolecular abstraction by oxygen of the C(8) hydrogen which lies in the plane of the C(1)=0(1) carbonyl group. Substrates 9 and 11, in addition, each gave a tricyclic diketone resulting from the abstraction of one of the C5 hydrogens by C2. The geometric requirements, the geometries of the transition states and intermediates and the factors governing the modes of closure of the biradical intermediates in both of these hydrogen abstraction reactions and their implications for other hydrogen abstractions such as the Norrish Type II are discussed. One substrate, namely, 4aβ,8aβ-dicyano-5α,8α-dimethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 8, which lacks short intermolecular double bond contacts and has its C(8) hydrogen out of plane and far removed from the C(1)=0(1) group neither dimerized nor gave hydrogen abstraction products when irradiated in the solid state. Instead, it gave an oxetane resulting from an intramolecular [π2+ π2] addition of C(1)=0(1) to the C(6)=C(7) double bond. The intermolecular double bond contact here was 3.20Å. Lastly, 2,3,6,7-tetramethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 5, and 2,3,4aβ5α,8α,8aβ-hexamethyl-4aβ,5,8,8aβ-tetrahydro-1,4-naphthoquinone, 10, failed to react when irradiated in the solid state. The reason for this is not clear but the possibility of deexcitation via excimer formation and subsequent dissociation is raised. / Science, Faculty of / Chemistry, Department of / Graduate

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A systematic literature search on the system Na2O-ZrO2-SiO2 is presented which reveals inconsistencies on the number and identity of the ternary phases. New X-ray diffraction data are presented for Na2ZrSiO5, Na2ZrSi2O7 and Na2ZrSi4O11; these data are substantiated by good agreement with data calculated from single-crystal work. The unit-cell parameters were redetermined. The compounds Na2ZrSi4O11 and Na4Zr2Si10O31 have now been successfully synthesised by solid state reaction, although the latter could not be prepared phase-pure; these phases had previously only been synthesised hydrothermally. The subsolidus compatibility relations at 1000oC have been reassessed, taking into account the two phases mentioned above, which have not featured in any previously published phase diagram. The addition of dopants, such as calcia, magnesia or yttria, as the oxide, carbonate etc., into solid solution with zirconia are known to stabilise the cubic phase to room temperature. A comparative trial is reported of the physical properties of these powders produced using either organic or inorganic gel-processing routes; the organic route consistently provided powders with greater thermal stability and surface area, which should lead to a more sinterable product, therefore this method was extended to include lanthanide oxide dopants. The incorporation of these dopants has been previously reported, but long sintering times at elevated temperatures were necessary; the organic precursor route described above successfully produced cubic zirconia more rapidly and at much reduced temperatures. The gelation tendencies of the lanthanide dopants are discussed. The binary system ZrO2-SnO2 was investigated at various temperatures; at 1000oC one metastable phase, zirconium stannate, which was observed previously but was poorly characterised, has been studied by X-ray diffraction techniques; new unit-cell parameters and X-ray diffraction data are presented; these data have been substantiated by agreement with calculated data. This phase has now been shown, by various techniques, to exsolve to two distinct phases with average compositions 90ZrO210SnO2 and 82SnO218ZrO2. The monoclinic zirconia solid-solution has been proven by the influence of this inclusion of tin oxide on the physical properties of pure monoclinic zirconia. A discussion of the crystallography of zirconium titanate, which is isostructural with zirconium stannate, is also reported. The extent of solid solubility of tin oxide in zirconium titanate has been determined at 1000, 1350, 1500 and 1550oC; the compositions in this single-phase region are known as zirconium tin titanates and are used as microwave dielectric resonators. A large metastable region of ZrO2-TiO2 solid solution was noted at 1000oC which is similar to data previously published. At 1350oC, the extent of solid solution in the ternary region was also as previously published, but a vast increase in solid-solubility was noted at higher temperatures. A comparison of the dielectric properties of pellets produced by mixed oxide sintering and gel-processing is reported.

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Thesis (Ph. D.)--State University of New York at Binghamton, Chemistry Department, 2006. / Includes bibliographical references.

Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 35-36). Also available via the World Wide Web in PDF format.