UNT Theses and Dissertations - 272 Matching Results

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An NMR study of 2-ethyl-1-butyllithium and of 2-ethyl-1-butyllithium/lithium 2-ethyl-1-butoxide mixed aggregates

Description: A 1H, 13C, and 6Li NMR study of 2-ethyl-1-butyllithium indicated that 2-ethyl-1-butyllithium exists only as a hexameric aggregate over the entire temperature range of 25 to - 92.1 ° C in cyclopentane. Reacting 2-ethyl-1-butyllithium with 2-ethyl-1-butanol resulted in alkyllithium/lithium alkoxide mixed aggregates, apparently of the form Ra(RO)bLia+b. A multinuclear, variable temperature NMR study of samples with O:Li ratios of 0.2 and 0.4 showed, in addition to the alkyllithium, the formation o… more
Date: May 2001
Creator: Ferreira, Aluisio V. C.
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Thermodynamic Properties of Nonelectrolyte Solutes in Ternary Solvent Mixtures

Description: The purpose of this dissertation is to investigate the thermodynamic properties of nonelectrolyte solutes dissolved in ternary solvent mixtures, and to develop mathematical expressions for predicting and describing that behavior in the solvent mixtures. Thirty-four ternary solvent systems were studied containing either alcohol (1-propanol, 2-propanol, 1-butanol, and 2-butanol), alkane (cyclohexane, heptane, and 2,2,4-trimethylpentane) or alkoxyalcohol (2-ethoxyethanol and 2-butoxyethanol) cosol… more
Date: August 1999
Creator: Deng, Tʻai-ho
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Experimental and Theoretical Studies of Polycarbocyclic Compounds

Description: Part I. Diels-Alder cycloadditions of 1,2,3,4,9,9-hexachloro-1α,4α,4aα,8aβ-tetrahydro-l,4-methanonaphthalene (32) and 1,2,3,4,9,9-hexachloro-lα,4α,6,7- tetrahydro-l,4-methanonaphthalene (33) to 4-methyl- and 4-phenyl-l,2,4-triazoline-3,5-dione [MTAD and PTAD, respectively] and to N-methylmaleimide (NMM) have been studied. The structures of several of the resulting cycloadducts were determined by X-ray crystallographic methods. The observed stereoselectivity of each of these Diels-Alder reaction… more
Date: May 1998
Creator: Shukla, Rajesh, 1964-
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Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study

Description: The focus of this research is to explore the molecular-level interactions between reactive metal surfaces and aqueous environments by combined ultra-high vacuum/electrochemistry (UHV-EC) methodology. The objectives of this work are to understand (1) the effects of sulfate ions on the passivity of metal oxide/hydroxide surface layer, (2) the effects of sulfur-modification on the evolution of metal oxide/hydroxide surface layer, and (3) the effects of sulfur adsorbate on cation adsorption at meta… more
Date: May 1998
Creator: Lin, Tien-Chih, 1966-
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Ligand Substitution Studies in the Tetracobalt Cluster Co₄(CO)₁₀([mu]₄-PPh₂) and Synthesis and Reactivity Studies in the Fe₂Pt and FeCo₂ Mixed-metal Clusters

Description: The kinetics of ligand substitution for CO in Co4(CO)10(mu4-PPh2) , 1, have been investigated for the ligands P(OMe)3, P(OEt)3, PPh2H, P(0-i-Pr)3, P(n-Bu)3, PPh3, P(i-Pr)3, and PCy3 over a wide temperature range.
Date: August 1991
Creator: Don, Ming-jaw
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The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos

Description: The purpose of this study was to determine the factors affecting the acid degradation of chrysotile asbestos (Mg_3Si_2O_5(OH_4)) . Millions of tons of asbestos have found use in this country as insulative or ablative material. More than 95 percent of the asbestos in use is of the chrysotile variety. The remaining 5 percent is composed of various types of fibrous amphiboles. The inhalation of asbestos can lead to several diseases in humans. Asbestosis, lung cancer and mesothelioma are the most c… more
Date: May 1993
Creator: Ingram, Kevin D. (Kevin Dean)
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Spectrofluorometric and Solubility Studies of Polycyclic Aromatic Hydrocarbons in Hydrogen Bonded Binary Solvent Mixtures

Description: The purpose of this dissertation is to investigate the behavior of polycyclic aromatic hydrocarbons (PAHs) in binary solvent systems and determine and/or develop predictive mathematical expressions for describing solutions in which hydrogen-bonding occurs.
Date: May 1997
Creator: Powell, Joyce R., 1968-
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Solution Studies of the Structures and Stability of Mixed Lithium Alkoxide/Alkvllithium Aggregates

Description: New one- and two-dimensional NMR techniques were used to elucidate the solution structures of these complex mixtures. The system, lithium tert-butoxide/tert-butyllithium, was studied as a model system with O/Li ratios varying from 0/1 to 1/1. It was found that at low O/Li ratios, a single mixed tetrameric aggregate was formed. At higher O/Li ratios, mixed hexameric species were formed. Two other systems, lithium isopropoxide/iso-propyllithium and lithium n-propoxide/n-propyllithium were also st… more
Date: December 1992
Creator: DeLong, George T. (George Thomas)
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Syntheses of Antimetabolites

Description: In these studies several different types of antimetabolites were synthesized, and their biological effects were examined in various assay systems. More extensive investigations were done in microbial systems in which many of the compounds proved to be inhibitory to growth, and attempts were made to determine the mode of biochemical action by adding supplements of the appropriate natural metabolite.
Date: January 1970
Creator: Clifton, George Gil
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Discontinuous Thermal Expansions and Phase Transformations in Crystals at Higher Temperatures

Description: The purpose of this investigation is to make more detailed studies of transformations. Fourteen compounds have been examined by high temperature X-ray diffraction for this purpose. The investigations have been carried out in such a way as to reveal: 1. the existence of transformations, 2. the influence of polarizability on thermal expansion, 3. the anisotropy of expansion, and 4. the discontinuity of thermal expansion.
Date: 1967
Creator: Hsu, Yuan Tsun
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Thermochemical investigations of crystalline solutes in non-electrolyte solutions: Mathematical representation of solubility data and the development of predictive solubility equations in systems with specific and non-specific interactions.

Description: Understanding the thermodynamic properties of multicomponent mixtures is of critical importance in many chemical and industrial applications. Experimental measurements become progressively difficult as the number of solution components increases -- producing the need for predictive models. Problems in development of predictive models arise if the mixture has one or more components that interact through molecular complexation or association. Experimental solubilities of anthracene and pyrene di… more
Date: May 2008
Creator: Zvaigzne, Anita Ilze
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Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model

Description: Several studies were done to illustrate the versatillity of the Abraham model in mathematically describing the various solute-solvent interactions found in a wide range of different chemical and biological systems. The first study focused on using the solvation model to construct mathematical correlations describing the minimum inhibitory concentration of organic compounds for growth inhibition towards the three bacterial strains Porphyromonas gingivalis, Selenomonas artemidis, and Streptococc… more
Date: May 2009
Creator: Mintz, Christina
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Substitution Chemistry of the Cobalt Complexes [Co₂(CO)₆(PhC≡CR) (R=Ph, H) and PhCCo₃(CO)₉] with the Diphosphine Ligands [Bis(diphenylphosphino)maleic Anhydride (BMA) and (Z)-Ph₂PCH=CHPPh₂]. Reversible Chelate-to-Bridge Diphosphine Ligand Exchange, Phosphorus-Carbon Bond Cleavage and Phosphorus-Carbon Bond Formation

Description: The tricobalt cluster PhCCo3(CO)9 (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in the presence of added Me3NO to give the diphosphine-substituted cluster PhCCo3(CO)7(bma) (2). Cluster 2 is unstable in solution, readily losing CO to afford Co3(CO)6[(μ2-η2/η1-C(Ph)C=C(PPh2)C(O)OC(O)](μ2-PPh2) (3) as the sole observed product. VT-31P NMR measurements on cluster 2 indicate that the bma ligand functions as both a chelating and a bridging ligand. At … more
Date: December 1994
Creator: Yang, Kaiyuan
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Diphosphine Ligand Activation Studies with Organotransition-Metal Compounds

Description: Thermolysis of CoRu(CO)7(m -PPh2) (1) in refluxing 1,2-dichloroethane in the presence of the diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the new mixed-metal complexes CoRu(CO)4(μ -P-P)(μ -PPh2) [where P-P = bma (3); bpcd (6)], along with trace amounts of the known complex CoRu(CO)6(PPh3)(μ -PPh2) (4). The requisite pentacarbonyl intermediates CoRu(CO)5(μ -P-P)(μ -PPh2) [where P-P = bma (2); bpcd (5)… more
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Date: December 2000
Creator: Wang, Jiancheng
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Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines

Description: The second order rate constants for nucleophilic substitution by methoxide of (Z)- and (E)-O-methylbenzohydroximoyl fluorides [C6H4C(F)=NOCH3] with various substituents on the phenyl ring [p-OCH3 (1h, 2h), p-CH3 (1g, 2g), p-Cl (1f, 2f), p-H (1e, 2e), (3,5)-bis-CF3 (1i, 2i)] in 90:10 DMSO:MeOH have been measured. A Hammett plot of these rate constants vs σ values gave positive ρ values of 2.95 (Z isomer) and 3.29 (E isomer). Comparison of these rates with methoxide substitution rates for Ometh… more
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Date: December 2001
Creator: Dolliver, Debra D.
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Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks

Description: A group of azabiphenyl complexes and supramolecules, and their reduced and oxidized forms when possible, were characterized by cyclic voltammetry and electronic absorption spectroscopy. The oxidized and reduced species, if sufficiently stable, were further generated electrochemically inside a specially designed quartz cell with optically transparent electrode, so that the spectra of the electrochemically generated species could be taken in situ. Assignments were proposed for both parent and pro… more
Date: August 1995
Creator: Yang, Lei
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Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field

Description: Metal and oxide interactions are of broad scientific and technological interest in areas such as heterogeneous catalysis, microelectronics, composite materials, and corrosion. In the real world, such interactions are often complicated by the presence of interfacial impurities and/or high electric fields that may change the thermodynamic and kinetic behaviors of the metal/oxide interfaces. This research includes: (1) the surface hydroxylation effects on the aluminum oxide interactions with coppe… more
Date: December 2001
Creator: Niu, Chengyu
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Reduction Pathways in Cyclopentadienyl Rhenium Dicarbonyl Dibromide Deriviatives and Indenyl Rhenium Tricarbonyl: Synthesis, Structure, and Reactivity of Anionic Cyclopentadienyl Rhenium Complexes. Ring Attack vs. Metal-Halogen Exchange

Description: The reactions of diagonal and lateral Cp'Re(CO)2Br2 (where Cp' = n5-C5H5, n5-C5Me5) and (n5-CgH7)Re(CO)3 with reducing agents have been examined. Hydride reduction at -78 °C is observed to occur at the Cp ring in both CpRe(CO)2Br2 isomers, affording a thermally unstable [(n4 -C5Hg)Re(CO)2Br2]- complex. The product of hydride ring attack has been characterized by low-temperature IR and 1H NMR measurements in addition to 13C NOE and heteronuclear 2D NMR measurements. Reaction of lateral CpRe(CO)2… more
Date: December 1989
Creator: Lee, Sang Woo, 1952-
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Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography

Description: Waste-to-energy has become an attractive alternative to landfills. One concern in this development is the release of pollutants in the combustion process. The binder enhanced d-RDF pellets satisfy the requirements of environmental acceptance, chemical/biological stability, and being storeable. The acid gas emissions of combusting d-RDF pellets with sulfur-rich coal were analyzed by ion chromatography and decreased when d-RDF pellets were utilized. The results imply the possibility of using d-RD… more
Date: August 1988
Creator: Jen, Jen-Fon
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Chromatographic and Spectroscopic Studies on Aquatic Fulvic Acid

Description: High Performance Liquid Chromatography (HPLC) was used to investigate the utility of this technique for the analytical and preparative separation of components of aquatic fulvic acids (FA). Three modes of HPLC namely adsorption, anion exchange and reversed phase were evaluated. Aquatic fulvic acids were either extracted from surface water and sediment samples collected from the Southwest of the U.S., or were provided in a high purity form from the USGS. On the adsorption mode, a major fraction… more
Date: August 1986
Creator: Chang, David Juan-Yuan
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Studies of Solvent Displacement from Solvated Metal Carbonyl Complexes of Chromium, Molybdenum, and Tungsten

Description: Flash photolysis techniques were applied to studies of solvent displacement by Lewis bases (L) from solvated metal carbonyl complexes of Cr, Mo, and W. On the basis of extensive studies of the reaction rate laws, activation parameters , and linear-free-energy-relationships, it was concluded that the mechanisms of solvent displacement reactions depend on the electronic and steric properties of the solvents and L, as well as the identities of the metal atoms. The strengths of solvent-metal bondin… more
Date: August 1990
Creator: Zhang, Shulin
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Raman Studies of Molecular Dynamics and Interactions in Liquids

Description: In order to explore the N-H stretching region of aliphatic amines, we performed a study of the Raman spectrum of n-propylamine at various concentrations in cyclohexane. Statistical analysis provided evidence of a second symmetric stretching vibration, which we were able to assign to nonhydrogen bonded NH2 groups. To obtain additional evidence on the existence of monomers in n-propylamine and to further study hydrogen bonding and Fermi resonance in aliphatic amines, we extended the investigation… more
Date: May 1984
Creator: Friedman, Barry R. (Barry Richard)
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