Latest content added for UNT Digital Library Partner: UNT Librarieshttps://digital.library.unt.edu/explore/partners/UNT/browse/?sort=default&fq=untl_collection:UNTETD&fq=str_degree_discipline:Chemistry2014-08-22T18:00:56-05:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Partner: UNT LibrariesAn NMR study of 2-ethyl-1-butyllithium and of 2-ethyl-1-butyllithium/lithium 2-ethyl-1-butoxide mixed aggregates2007-09-25T21:26:08-05:00https://digital.library.unt.edu/ark:/67531/metadc2807/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2807/"><img alt="An NMR study of 2-ethyl-1-butyllithium and of 2-ethyl-1-butyllithium/lithium 2-ethyl-1-butoxide mixed aggregates" title="An NMR study of 2-ethyl-1-butyllithium and of 2-ethyl-1-butyllithium/lithium 2-ethyl-1-butoxide mixed aggregates" src="https://digital.library.unt.edu/ark:/67531/metadc2807/small/"/></a></p><p>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 of four mixed aggregates, one of them probably an octamer. Higher O:Li ratio samples showed the formation of several other mixed aggregates. Mixing 2-ethyl-1-butyllithium with independently prepared lithium 2-ethyl-1-butoxide formed the same mixed aggregates formed by in situ synthesis of lithium alkoxide. Lithium 2-ethyl-1-butoxide also exists as aggregates in cyclopentane.</p>Thermodynamic Properties of Nonelectrolyte Solutes in Ternary Solvent Mixtures2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279275/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279275/"><img alt="Thermodynamic Properties of Nonelectrolyte Solutes in Ternary Solvent Mixtures" title="Thermodynamic Properties of Nonelectrolyte Solutes in Ternary Solvent Mixtures" src="https://digital.library.unt.edu/ark:/67531/metadc279275/small/"/></a></p><p>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) cosolvents. Approximately 2500 experimental measurements were performed. Expressions were derived from the Combined Nearly Ideal Multiple Solvent (NIMS)/Redlich-Kister, the Combined Nearly Ideal Multiple Solvent (NIMS)/Bertrand, Acree and Burchfield (BAB) and the Modified Wilson models for predicting solute solubility in ternary solvent (or even higher multicomponent) mixtures based upon the model constants calculated from solubility data in sub-binary solvents. Average percent deviation between predicted and observed values were less than 2%, documenting that these models provide a fairly accurate description of the thermodynamic properties of nonelectrolyte solutions. Moreover, the models can be used for solubility prediction in solvent mixtures in order to find the optimum solvent composition for solubilization or desolubilization of a solute. From a computational standpoint, the Combined Nearly Ideal Multiple Solvent/Redlich-Kister equation is preferred because the needed model constants can be calculated with a simple linear regressional analysis. Model constants for the Modified Wilson equation had to be calculated using a reiterative trial-and-error method. The C++ program for the Modified Wilson equation applied to ternary and heptanary solvent mixtures is attached.</p>Experimental and Theoretical Studies of Polycarbocyclic Compounds2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279238/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279238/"><img alt="Experimental and Theoretical Studies of Polycarbocyclic Compounds" title="Experimental and Theoretical Studies of Polycarbocyclic Compounds" src="https://digital.library.unt.edu/ark:/67531/metadc279238/small/"/></a></p><p>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 reactions was further investigated via application of theoretical methods. Thus, semiempirical (AMI) and ab initio molecular orbital calculations were used to calculate relative energies. Ab initio calculations were employed to perform frontier molecular orbital analyses of diene-dienophile interactions.</p>Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc278914/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc278914/"><img alt="Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study" title="Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study" src="https://digital.library.unt.edu/ark:/67531/metadc278914/small/"/></a></p><p>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 metal surfaces.</p>Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279113/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279113/"><img alt="Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces" title="Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces" src="https://digital.library.unt.edu/ark:/67531/metadc279113/small/"/></a></p><p>This study was intended to provide a fuller understanding of the surface chemical processes which result in the corrosion of ferrous materials.</p>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 Clusters2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279335/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279335/"><img alt="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" title="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" src="https://digital.library.unt.edu/ark:/67531/metadc279335/small/"/></a></p><p>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.</p>The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279343/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279343/"><img alt="The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos" title="The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos" src="https://digital.library.unt.edu/ark:/67531/metadc279343/small/"/></a></p><p>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 common afflictions associated with asbestos inhalation, and they may occur up to 40 years after the initial exposure. It has previously been reported that if more than 50 percent of the magnesium is removed from a chrysotile sample its carcinogenicity is reduced to nil. Several inorganic acids were studied to determine their ability to leach magnesium from chrysotile. It was found that the ability to leach magnesium was dependent upon the acidic anion in addition to the concentration of the acid. The ordering of the efficiency of the acids in their ability to remove magnesium from chrysotile was found to be HCl > H_2SO_4 > H_3PO_4 > HNO_3. Predictive equations were developed to allow the calculation of the amount of magnesium removed under various acid concentrations as a function of time and acid species. The effects of temperature and dissolved spectator cations upon the degradation process were also examined. There was no major effect on the amount of magnesium removed as a function of spectator cation concentration. An infrared method was also developed to allow the determination of the percent degradation of a chrysotile sample directly. The shifts in the positions of three silicate stretching peaks (1068 cm^-1, 948 cm^-1 and 715 cm^-1) and one magnesium oxygen stretching peak (415 cm"1) as a function of the percent magnesium removed were correlated to allow this determination.</p>Survey of the Solid State Conformation of Calix[4]arenes2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc278942/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc278942/"><img alt="Survey of the Solid State Conformation of Calix[4]arenes" title="Survey of the Solid State Conformation of Calix[4]arenes" src="https://digital.library.unt.edu/ark:/67531/metadc278942/small/"/></a></p><p>The characteristics of seventy-six calix[4]arene crystal structures derived from the Cambridge Crystallographic Database are presented. This survey is a discussion of the
inter and intramolecular effects on the solid state cavity shape and molecular recognition ability of the compounds. In addition to this survey, four new calix[4]arene crystal structures are presented. The conformational characteristics
of these four calixarenes are determined by a complicated array of inter and intramolecular interactions in the crystal packing.</p>Conformational Analogs of Some Phytoactive Compounds2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279187/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279187/"><img alt="Conformational Analogs of Some Phytoactive Compounds" title="Conformational Analogs of Some Phytoactive Compounds" src="https://digital.library.unt.edu/ark:/67531/metadc279187/small/"/></a></p><p>In an effort to determine if there is a specific conformational structure which is most effective at the appropriate active physiological site, the synthesis of a group of sterically restricted analogs was undertaken. A portion of the polymethylene carbon skeleton of glutaric acid was replaced by selected aromatic carbons in benzenedicarboxylic acids to produce a series of ridged conformers, and the relative plant growth regulating properties of these derivatives were determined.</p>Spectrofluorometric and Solubility Studies of Polycyclic Aromatic Hydrocarbons in Hydrogen Bonded Binary Solvent Mixtures2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279188/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279188/"><img alt="Spectrofluorometric and Solubility Studies of Polycyclic Aromatic Hydrocarbons in Hydrogen Bonded Binary Solvent Mixtures" title="Spectrofluorometric and Solubility Studies of Polycyclic Aromatic Hydrocarbons in Hydrogen Bonded Binary Solvent Mixtures" src="https://digital.library.unt.edu/ark:/67531/metadc279188/small/"/></a></p><p>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.</p>Solution Studies of the Structures and Stability of Mixed Lithium Alkoxide/Alkvllithium Aggregates2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279031/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279031/"><img alt="Solution Studies of the Structures and Stability of Mixed Lithium Alkoxide/Alkvllithium Aggregates" title="Solution Studies of the Structures and Stability of Mixed Lithium Alkoxide/Alkvllithium Aggregates" src="https://digital.library.unt.edu/ark:/67531/metadc279031/small/"/></a></p><p>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 studied at low O/Li ratios.</p>Syntheses of Antimetabolites2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279358/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279358/"><img alt="Syntheses of Antimetabolites" title="Syntheses of Antimetabolites" src="https://digital.library.unt.edu/ark:/67531/metadc279358/small/"/></a></p><p>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.</p>Layered Double Hydroxides and the Origins of Life on Earth2007-09-25T21:32:17-05:00https://digital.library.unt.edu/ark:/67531/metadc2766/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2766/"><img alt="Layered Double Hydroxides and the Origins of Life on Earth" title="Layered Double Hydroxides and the Origins of Life on Earth" src="https://digital.library.unt.edu/ark:/67531/metadc2766/small/"/></a></p><p>A brief introduction to the current state of research in the Origins of Life field is given in Part I of this work. Part II covers original research performed by the author and co-workers. Layered Double Hydroxide (LDH) systems are anion-exchanging clays that have the general formula M(II)xM(III)(OH)(2x+2)Y, where M(II) and M(III) are any divalent and trivalent metals, respectively. Y can be nearly any anion, although modern naturally occuring LDH systems incorporate carbonate (CO32-), chloride (Cl-), or sulfate (SO42-) anions. Intercalated cobalticyanide anion shows a small yet observable deviation from local Oh symmetry causing small differences between its oriented and non-oriented infrared spectra. Nitroprusside is shown to intercalate into 2:1 Mg:Al LDH with decomposition to form intercalated ferrocyanide and nitrosyl groups of an unidentified nature. The [Ru(CN)6]4- anion is shown to intercalate into layered double hydroxides in the same manner as other hexacyano anions, such as ferrocyanide and cobalticyanide, with its three-fold rotational axis perpendicular to the hydroxide sheets. The square-planar tetracyano-nickelate(II), -palladate(II), and platinate(II) anions were intercalated into both 2:1 and 3:1 Mg:Al layered double hydroxides (LDH). The basal spacings in the 2:1 hosts are approximately 11 Å, indicating that the anions are inclined approximately 75 degrees relative to the hydroxide layers, while in the 3:1 hosts the square-planar anions have enough space to lie more nearly parallel to the LDH cation layers, giving basal spacings of approximately 8 Å. It has been found that the LDH Mg2Al(OH)6Cl catalyzes the self-addition of cyanide, to give in a one-pot reaction at low concentrations an increased yield of diaminomaleonitrile and in addition, at higher ($0.1M) concentrations, a purple-pink material that adheres to the LDH. We are investigating whether this reaction also occurs with hydrotalcite itself, what is the minimum effective concentration of cyanide, and what can be learned about the products and how they compare with those reported at high HCN concentrations in the absence of catalyst.</p>Synthesis and Alkali Metal Extraction Properties of Novel Cage-Functionalized Crown Coronands and Cryptands2014-03-24T20:07:29-05:00https://digital.library.unt.edu/ark:/67531/metadc277666/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc277666/"><img alt="Synthesis and Alkali Metal Extraction Properties of Novel Cage-Functionalized Crown Coronands and Cryptands" title="Synthesis and Alkali Metal Extraction Properties of Novel Cage-Functionalized Crown Coronands and Cryptands" src="https://digital.library.unt.edu/ark:/67531/metadc277666/small/"/></a></p><p>A novel crown ether precursor was developed in which a rigid 4-oxahexacyclo (5.4.1.26.3,10.05,9.08,11) dodecyl cage moiety ("cage functionality") was incorporated.</p>Discontinuous Thermal Expansions and Phase Transformations in Crystals at Higher Temperatures2014-03-24T20:07:29-05:00https://digital.library.unt.edu/ark:/67531/metadc277668/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc277668/"><img alt="Discontinuous Thermal Expansions and Phase Transformations in Crystals at Higher Temperatures" title="Discontinuous Thermal Expansions and Phase Transformations in Crystals at Higher Temperatures" src="https://digital.library.unt.edu/ark:/67531/metadc277668/small/"/></a></p><p>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.</p>Synthesis and characterization of molecules for electron transfer research.2007-09-25T21:23:46-05:00https://digital.library.unt.edu/ark:/67531/metadc2683/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2683/"><img alt="Synthesis and characterization of molecules for electron transfer research." title="Synthesis and characterization of molecules for electron transfer research." src="https://digital.library.unt.edu/ark:/67531/metadc2683/small/"/></a></p><p>Dimethoxynaphthalene (donor) and quinone (acceptor) have been chosen as a suitable redox pair and are bonded to either permethylated silane chains or corresponding permethylated alkyl chains to form Acceptor-(Bridge)-Donor molecules. The idea that the s-delocalization phenomenon of silane chains may greatly facilitate ET reactions will be tested. The starting material for the donor precursor, 4-(1,4-dimethoxynaphthyl)bromocyclohexane, was 1,4-naphthoquinone. After methylation and bromination, the Grignard reagent of the resulting bromide was reacted with cyclohexanedione, mono ethylene ketal. The resulting alcohol was changed to the donor precursor through the following functional group transformation steps: dehydration, hydrogenation, deketalization and bromination. 1,4-Dibenzyloxybromobenzene, the precursor for the acceptor, was synthesized from 1,4-hydroquinone through bromination and benzylation. The connection of the two precursors and either permethylated silane chains or permethylated alkyl chains will give the final target molecules for ET research. Progress on this is included.</p>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.2010-09-10T01:20:16-05:00https://digital.library.unt.edu/ark:/67531/metadc28369/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc28369/"><img alt="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." title="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." src="https://digital.library.unt.edu/ark:/67531/metadc28369/small/"/></a></p><p>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 dissolved in binary systems containing one or more alcohols were measured in order to address this problem. Alcohols examined in this study were: 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 3-methyl-1-butanol, and 1-octanol. In binary solvent mixtures containing only a single self-associating alcoholic solvent, the alkane cosolvents studied were: n-hexane, n-heptane, n-octane, 2,2,4-trimethylpentane, cyclohexane, methylcyclohexane, tert-butylcyclohexane. Predictive solubility equations were developed using mobile order theory. This approach differs from classical solution models by representing hydrogen bonding with a probability term rather than with expressions derived from stepwise equilibria or expressions to represent hypothetical solution aggregates. Results were compared with the predicted solubilities found from using expressions developed using the Kretschmer-Wiebe and Mecke-Kempter approaches for modeling associated solutions. It was found that the mobile order approach provided reasonably accurate predictions for the solute solubilities in the systems studied. The limitations and applications for mathematical methods of representing experimental isothermal solubility data were also studied for 72 systems. Two possible descriptive forms for this mathematical representation were suggested based on the various nearly ideal binary solvent (NIBS) and modified Wilson models.</p>Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model2010-09-10T01:20:16-05:00https://digital.library.unt.edu/ark:/67531/metadc28373/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc28373/"><img alt="Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model" title="Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model" src="https://digital.library.unt.edu/ark:/67531/metadc28373/small/"/></a></p><p>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 Streptococcus sobrinus. The next several studies expand the practicallity of the Abraham model by predicting free energies of partition in chemical systems. The free energy studies expand the use of the Abraham model to other temperatures and properties by developing correlations for the enthalpies of solvation of gaseous solutes of various compounds dissolved in water, 1-octanol, hexane, heptane, hexadecane, cyclohexane, benzene, toluene, carbon tetrachloride, chloroform, methanol, ethanol, 1-butanol, propylene carbonate, dimethyl sulfoxide, 1,2-dichloroethane, N,N-dimethylformamide, tert-butanol, dibutyl ether, ethyl acetate, acetonitrile, and acetone. Also, a generic equation for linear alkanes is created for use when individual datasets are small. The prediction of enthalpies of solvation is furthered by modifying the Abraham model so that experimental data measured at different temperatures can be included into a single correlation expression. The temperature dependence is directly included in the model by separating each coefficient into an enthalpic and entropic component. Specifically, the final study describes the effects of temperature on the sorption coefficients of organic gases onto humic acid. The derived predicted values for each research study show a good correlation with experimental values.</p>Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si2010-09-10T01:20:16-05:00https://digital.library.unt.edu/ark:/67531/metadc28421/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc28421/"><img alt="Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si" title="Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si" src="https://digital.library.unt.edu/ark:/67531/metadc28421/small/"/></a></p><p>NiSi is an attractive material in the production of CMOS devices. The problem with the utilization of NiSi, is that there is no proper method of cleaning the oxide on the surface. Sputtering is the most common method used for the cleaning, but it has its own complications. Dry cleaning methods include the reactions with radicals and these processes are not well understood and are the focus of the project. Dissociated NF3 and NH3 were used as an alternative and XPS is the technique to analyze the reactions of atomic fluorine and nitrogen with the oxide on the surface. A thermal cracker was used to dissociate the NF3 and NH3 into NFx+F and NHx+H. There was a formation of a NiF2 layer on top of the oxide and there was no evidence of nitrogen on the surface indicating that the fluorine and hydrogen are the reacting species. XPS spectra, however, indicate that the substrate SiO2 layer is not removed by the dissociated NF3 and NiF2 growth process. The NiF2 over layer can be reduced to metallic Ni by reacting with dissociated NH3 at room temperature. The atomic hydrogen from dissociated ammonia reduces the NiF2 but it was determined that the atomic hydrogen from the ammonia does not react with SiO2.</p>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 Formation2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279206/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279206/"><img alt="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" title="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" src="https://digital.library.unt.edu/ark:/67531/metadc279206/small/"/></a></p><p>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 -97 °C, 31P NMR analysis of 2 reveals a Keq of 5.7 in favor of the bridging isomer. The bridged bma cluster 2 is the only observed species above -50°C. The solid-state structure of 2 does not correspond to the major bridging isomer observed in solution but rather the minor chelating isomer. The conversion of 2 to 3 followed first-order kinetics, with the reaction rates being independent of the nature of the reaction solvent and strongly suppressed by added CO, supporting a dissociative loss of CO as the rate-determining step. The activation parameters for CO loss were determined to be ΔH≠ = 29.9 ± 2.2 kcal/mol and ΔS≠ = 21.6 ± 6 eu.</p>Diphosphine Ligand Activation Studies with Organotransition-Metal Compounds2007-09-25T21:16:32-05:00https://digital.library.unt.edu/ark:/67531/metadc2665/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc2665/"><img alt="Diphosphine Ligand Activation Studies with Organotransition-Metal Compounds" title="Diphosphine Ligand Activation Studies with Organotransition-Metal Compounds" src="https://digital.library.unt.edu/ark:/67531/metadc2665/small/"/></a></p><p>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)] have been prepared by separate routes and studied for their conversion to CoRu(CO)4(μ -P-P)(μ -PPh2). The complexes 2/3 and 5/6 have been isolated and fully characterized in solution by IR and NMR spectroscopy. The kinetics for the conversion of 2→3 and of 5→6 were measured by IR spectroscopy in chlorobenzene solvent. On the basis of the first-order rate constants, CO inhibition, and the activation parameters, a mechanism involving dissociative CO loss as the rate-limiting step is proposed. The solid-state structure of CoRu(CO)4(μ -bma)(μ -PPh2) (3) reveals that the two PPh2 groups are bound to the ruthenium center while the maleic anhydride π bond is coordinated to the cobalt atom. Thermolysis of the cluster Ru3(CO)12 with the bis(phosphine)hydrazine ligand (MeO)2PN(Me)N(Me)P(OMe)2 (dmpdmh) in toluene at 75°C furnishes the known clusters Ru4(CO)12[μ -N(Me)N(Me)] (9) and Ru3(CO)11[P(OMe)3] (10), in addition to the new cluster Ru3(CO)10(dmpdmh) (8) and the phosphite-tethered cluster Ru3(CO)9[μ -P(OMe)3] (11). The simple substitution product Ru3(CO)10(dmpdmh), a logical intermediate to clusters 9-11, was synthesized by treating Ru3(CO)12 and dmpdmh with Me3NO in CH2Cl2 at room temperature, and independent thermolysis reactions using cluster 8 were shown to yield clusters 9-11. The tetrahedrane cluster FeCo2(CO)9(μ3-S) reacts with the redox-active ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) to give the disubstituted cluster FeCo2(CO)7(bpcd)(μ3-S) as the sole product. This diphosphine-substituted cluster contains a cobalt-bound, chelating bpcd ligand. The solid-state structure has been unequivocally established by X-ray diffraction analysis. Cyclic voltammetric studies on FeCo2(CO)7(bpcd)(μ3-S) reveal the presence of two quasireversible redox responses assigned to the 0/1- and 1-/2- redox couples. The orbital composition of these redox couples has been examined by carrying out extended Hückel MO calculations on the model complex FeCo2(CO)7(H4-bpcd)(μ3-S), with the results being compared to related cluster compounds.</p>Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines2007-09-25T22:40:16-05:00https://digital.library.unt.edu/ark:/67531/metadc3017/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc3017/"><img alt="Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines" title="Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines" src="https://digital.library.unt.edu/ark:/67531/metadc3017/small/"/></a></p><p>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 Omethylbenzohydroximoyl bromide [C6H4C(Br)=NOCH3] and Omethylbenzohydroximoyl chloride [C6H4C(Cl)=NOCH3] reveal an element effect for the Z isomers of Br:Cl:F(1e) = 2.21:1.00:79.7 and for the E isomers of Cl:F(2e) = 1.00:18.3. With the p-OCH3-imidoyl halides the following element effects are found: Br:Cl:F(1h) = 2.78:1.00:73.1 for the Z isomer and Br:Cl:F(2h) = 1.97:1.00:12.1 for the E isomer. Measurement of activation parameters revealed ∆S≠ = -17 eu for 1e and ∆S≠ = -9.9 eu for 2e. Ab initio calculations (HF/6-31+G*, MP2/6-31+G*//HF/6-31+G*, B3LYP/6- 31+G*//HF/6-31+G*, HF-SCIPCM/6-31+G*//HF/6-31+G*) were performed to define the reaction surface. These calculations demonstrate a relatively large barrier for nucleophilic attack in relation to halogen loss and support the experimental findings that this reaction proceeds by an addition-elimination mechanism (AN# + DN). The imidoyl fluorides have been used to synthesize highly functionalized O-methyloximes by reaction with enolate anions derived from malononitrile, ethyl cyanoacetate, and diethyl malonate. Acid-catalyzed isomerization of compounds containing the O-methyloxime moiety have been investigated with ab initio calculations (HF/6-31+G*, MP2/6- 31+G*//HF/6-31+G*, B3LYP/6-31+G*//HF/6-31+G*). Barriers for rotation around the C-N bond following protonation have been calculated. The calculated barriers are discussed in relation to an isomerization mechanism of protonation-rotation versus a nucleophilic catalysis.</p>The preparation and characterization of thermo-sensitive colored hydrogel film and surfactant-free porous polystyrene three-dimensional network.2007-09-25T23:00:40-05:00https://digital.library.unt.edu/ark:/67531/metadc3019/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc3019/"><img alt="The preparation and characterization of thermo-sensitive colored hydrogel film and surfactant-free porous polystyrene three-dimensional network." title="The preparation and characterization of thermo-sensitive colored hydrogel film and surfactant-free porous polystyrene three-dimensional network." src="https://digital.library.unt.edu/ark:/67531/metadc3019/small/"/></a></p><p>Polymer hydrogel films change their properties in response to environmental change. This remarkable phenomenon results in many potential applications of polymer hydrogel films. In this thesis colored thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel film was prepared by firstly synthesizing polymer latex and secondarily crosslinking the nanoparticles and casting the polymers onto glass. The shape-memory effect has been observed when changing the environmental temperature. The temperature-dependent of turbidity of polymer hydrogel film was measured by HP UVVisible spectrophotometer. This intelligent hydrogel might be used in chemomechanical systems and separation devices as well as sensors. Polymer adsorption plays an important role in many products and processes. In this thesis, surfactant-free three-dimensional polystyrene (PS) nanoparticle network has been prepared. The infrared spectroscopy and solubility experiment are performed to prove the crosslinking mechanism, also the BET method was used to measure the adsorption and desorption of polystyrene network. The BET constant (C) is calculated (C=6.32). The chemically bonded polymer nanoparticle network might have potential applications as catalyst or used for chromatographic columns.</p>Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279396/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279396/"><img alt="Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks" title="Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks" src="https://digital.library.unt.edu/ark:/67531/metadc279396/small/"/></a></p><p>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 product electronic spectra. Species investigated included a range of Ru(II) and Pt(II) complexes, as well as catenanes and their comparents. Using the localized electronic model, the electrochemical reduction can be in most cases assigned as azabiphenyl-based, and the oxidation as transition metal-based. This is consistent with the fact that the azabiphenyl compounds have a low lying π* orbital. The electronic absorption spectra of the compounds under study are mainly composed of π —> π* bands with, in some cases, charge transfer bands also.</p>Synthesis, structure and redox reactivity of Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂)2014-03-26T18:36:44-05:00https://digital.library.unt.edu/ark:/67531/metadc279408/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279408/"><img alt="Synthesis, structure and redox reactivity of Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂)" title="Synthesis, structure and redox reactivity of Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂)" src="https://digital.library.unt.edu/ark:/67531/metadc279408/small/"/></a></p><p>The tricobalt cluster PhCCo₃(CO)₉ (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic thioanhydride (bta) with added Me₃NO to yield PhCCo₃(CO)₇(bta) (2), which upon heating overnight yields Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂) (3). Cluster (3) has been isolated and characterized by FT-IR and ³¹P NMR spectroscopy. Structural determination of the cluster has been demonstrated by X-ray diffraction analysis. Cluster (3) is analogous to the cluster synthesized by Richmond and coworkers. The redox properties of (3) have been examined by cyclic voltammetry and the data are reported within.</p>The Determination of the Constants in the System of Methyl Alcohol, Formic Acid, Methyl Formate and Water2011-03-08T17:55:33-06:00https://digital.library.unt.edu/ark:/67531/metadc31301/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc31301/"><img alt="The Determination of the Constants in the System of Methyl Alcohol, Formic Acid, Methyl Formate and Water" title="The Determination of the Constants in the System of Methyl Alcohol, Formic Acid, Methyl Formate and Water" src="https://digital.library.unt.edu/ark:/67531/metadc31301/small/"/></a></p><p>Problems presented in this paper concern the chemical equilibrium of methyl alcohol, formic acid, and methyl formate when combined.</p>Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field2007-09-25T22:57:57-05:00https://digital.library.unt.edu/ark:/67531/metadc3039/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc3039/"><img alt="Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field" title="Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field" src="https://digital.library.unt.edu/ark:/67531/metadc3039/small/"/></a></p><p>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 copper adlayers, and (2) effects of high electric fields on the interface of thin aluminum oxide films and Ni3Al substrate. X-ray photoelectron spectroscopy (XPS) studies and first principles calculations have been carried out to compare copper adsorption on heavily hydroxylated a- Al2O3(0001) with dehydroxylated surfaces produced by Argon ion sputtering followed by annealing in oxygen. For a heavily hydroxylated surface with OH coverage of 0.47 monolayer (ML), sputter deposition of copper at 300 K results in a maximum Cu(I) coverage of ~0.35 ML, in agreement with theoretical predictions. Maximum Cu(I) coverage at 300 K decreases with decreasing surface hydroxylation. Exposure of a partially dehydroxylated a-Al2O3(0001) surface to either air or 2 Torr water vapor results in recovery of surface hydroxylation, which in turn increases the maximum Cu(I) coverage. The ability of surface hydroxyl groups to enhance copper binding suggests a reason for contradictory experimental results reported in the literature for copper wetting of aluminum oxide. Scanning tunneling microscopy (STM) was used to study the high electric field effects on thermally grown ultrathin Al2O3 and the interface of Al2O3 and Ni3Al substrate. Under STM induced high electric fields, dielectric breakdown of thin Al2O3 occurs at 12.3 } 1.0 MV/cm. At lower electric fields, small voids that are 2-8 A deep are initiated at the oxide/metal interface and grow wider and deeper into the metal substrate, which eventually leads to either physical collapse or dielectric breakdown of the oxide film on top.</p>The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers2011-01-06T06:55:18-06:00https://digital.library.unt.edu/ark:/67531/metadc30454/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc30454/"><img alt="The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers" title="The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers" src="https://digital.library.unt.edu/ark:/67531/metadc30454/small/"/></a></p><p>Two aluminum spherical mirrors with radii of 203.2 mm and radii of curvature also of 203.2 mm have been used to construct a tunable Fabry-Perót type resonator operational at frequencies as low as 500 MHz. The resonator has been incorporated into a pulsed nozzle, Fourier transform, Balle-Flygare spectrometer. The spectrometer is of use in recording low J transitions of large asymmetric molecules where the spectra are often greatly simplified compared to higher frequency regions. The resonators use is illustrated by recording the rotational spectra of bromobenzene and iodobenzene. In related experiments, using similar equipment, the pure rotational spectra of four isotopomers of SrS and all three naturally occurring isotopomers of the actinide-containing compound thorium monoxide have been recorded between 6 and 26 GHz. The data have been thoroughly analyzed to produce information pertaining to bond lengths and electronic structures.</p>Substitution chemistry of the cobalt complexes RCCo3(CO)9 (R = H, CHO) with the diphosphine ligand: 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Syntheses, X-ray structures and reactivity.2007-09-25T22:57:37-05:00https://digital.library.unt.edu/ark:/67531/metadc3043/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc3043/"><img alt="Substitution chemistry of the cobalt complexes RCCo3(CO)9 (R = H, CHO) with the diphosphine ligand: 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Syntheses, X-ray structures and reactivity." title="Substitution chemistry of the cobalt complexes RCCo3(CO)9 (R = H, CHO) with the diphosphine ligand: 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Syntheses, X-ray structures and reactivity." src="https://digital.library.unt.edu/ark:/67531/metadc3043/small/"/></a></p><p>The reaction between the tetrahedrane cluster RCCo3(CO)9{R = CHO (1), H (3)} and the redox-active diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3- dione (bpcd) leads to the replacement of two CO groups and formation of RCCo3(CO)7(bpcd) {R = CHO (2), H (4)}. Clusters 2 and 4 are thermally unstable and readily transform into the new P-C bond cleavage cluster 5. All three clusters 2, 4, and 5 have been isolated and fully characterized in solution by IR and 31P NMR spectroscopy. VT 31P NMR data indicate that the bpcd ligand in RCCo3(CO)7(bpcd) is fluxional at 187 K in THF. Clusters 2, 4, and 5 have been structurally characterized by X-ray diffraction analyses.</p>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 Exchange2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc332212/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332212/"><img alt="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" title="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" src="https://digital.library.unt.edu/ark:/67531/metadc332212/small/"/></a></p><p>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)2Br2 with either MeLi or PhLi affords both Cp-ring attack and metalhalogen exchange, [CpRe(CO)2Br]- (1) while t-BuLi reacts exclusively via metal-halogen exchange. diag-CpRe(CO)2Br2 reacts with the above lithium reagents to yield the same metal-halogen exchange anion. Analogous reactions using diag- and lat-Cp*Re(CO)2Br2 (where Cp* = n5-CgMe5) afford only the corresponding rhenium metal-halogen exchange anion, [Cp*Re(CO)2Br] (2). The molecular structures of 1-[Li/15-Crown-5] and 2-PPP were established by X-ray crystallography. 1-[Li/15-Crown-5] crystallizes in the monoclinic space group P21 with a = 10.860(4) A, b = 13.116(5) A, c = 7.417(3) A, B = 105.26(3)0, V = 1018.7(3) A3 , and Z = 2. 2-PPP crystallizes in the orthorhombic space group Pbca with a = 20.646(5) A, b = 17.690(5) A, c = 17.553(3) A, and z = 8. Solution FT-IR studies of 2 in THF reveal the presence of only solvent-separated ion pairs when the gegencation is Li+, K+, or PPP+ from -70 °C to room temperature. 2-Na at room temperature displays a 39:61 mixture of carbonyl oxygen-sodium and solvent-separated ion pairs, respectively. These ion pairs reveals a reversible temperature-dependent equilibrium. The equilibrium constant has been determined by IR band shape analysis over the temperature range -70 °C to room temperature and values of AH and AS are reported. The reaction of the ring-attacked complex, diag-[(n4-C5H6)Re(CO)2Br2]- with PPh3, P(OPh)3, or Me3CNC leads to the formation of the CpRe(CO)2L. Treatment of [Cp'Re(CO)2Br]- with methyltriflate, TFA, and magic ethyl yields the corresponding diag-Cp'Re(CO)2Br(R) (R = CH3, H, C2H5) complexes based on in situ IR analysis. All of these functionalized complexes decomposed in solution over a period of days to give Cp'Re(CO)3 as the only isolable product (20-30 %). The reaction of the [Cp,Re(C0)2Br]- with Bu3SnH at 60 °C leads to the formation of diag-Cp'Re(CO)2(SnBu3)2, which was also synthesized independently by the deprotonation of diag-Cp'Re(CO)2H2 with Et3N in the presence of Bu3SnBr at room temperature. The reaction of Cp'Re(CO)2Br2 with Bu3SnH at room temperature was discovered to afford the dihydride in excellent yield and, thus represents an improved synthetic route for the synthesis of diag-Cp'Re(CO)2H2. The hydride reduction of (n5-CgH7)Re(CO)3 at room temperature leads to the immediate formation of [(n5-CgH7)Re(CO)2H]- complex, which has been characterized by IR analysis and 1H and 13C NMR spectroscopy.</p>Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331848/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331848/"><img alt="Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography" title="Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography" src="https://digital.library.unt.edu/ark:/67531/metadc331848/small/"/></a></p><p>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-RDF pellets to substitute for sulfur-rich coal as fuel, and also substantiate the effectiveness of a binder, calcium hydroxide, in decreasing emissions of SOx.
In order to perform the analysis of the combustion sample, sampling and sample pretreatment methods prior to the IC analysis and the first derivative detection mode in IC are investigated as well. At least two trapping reagents are necessary for collecting acid gases: one for hydrogen halides, and the other for NOx and SOx. Factors affecting the absorption of acid gases are studied, and the strength of an oxidizing agent is the main factor affecting the collection of NOx and SOx. The absorption preference series of acid gases are determined and the absorption models of acid gases in trapping reagents are derived from the analytical results. To prevent the back-flushing of trapping reagents between impingers when leak-checking, a design for the sampling train is suggested, which can be adopted in sample collections. Several reducing agents are studied for pretreating the sample collected in alkali-permanganate media. Besides the recommendation of the hydrogen peroxide solution in EPA method, methanol and formic acid are worth considering as alternate reducing agents in the pretreatment of alkaline-permanganate media prior to IC analysis. The first derivative conductivity detection mode is developed and used in IC system. It is efficient for the detection and quantification of overlapping peaks as well as being applicable for non-overlapping peaks.</p>Chromatographic and Spectroscopic Studies on Aquatic Fulvic Acid2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331734/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331734/"><img alt="Chromatographic and Spectroscopic Studies on Aquatic Fulvic Acid" title="Chromatographic and Spectroscopic Studies on Aquatic Fulvic Acid" src="https://digital.library.unt.edu/ark:/67531/metadc331734/small/"/></a></p><p>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 of aquatic fulvic acid was isolated on a semipreparative scale and subjected to Carbon-13 NMR and FAB Mass Spectroscopy. Results indicated that (1) The analyzed fraction of fulvic acid contains more aliphatic than aromatic moieties; (2) Methoxy, carboxylic acids, and esters are well-defined moieties of the macromolecule; (3) Phenolic components of the macromolecules were not detected in the Carbon-13 NMR spectrum possibly because of the presence of stable free radicals. Results of the anion exchange mode have shown that at least three types of acidic functionalities in aquatic fulvic acid can be separated. Results also indicated that aquatic fulvic acid can be progressively fractionated by using subsequent modes of HPLC. Results of reversed phase mode have shown that (1) The fractionation of aquatic fulvic acid by RP-HPLC is essentially controlled by the polarity and/or pH of the carrier solvent system; (2) Under different RP-HPLC conditions aquatic fulvic acid from several locations are fractionated into the same major components; (3) Fulvic acid extracted from water and sediment from the same site are more similar than those extracted from different sites; (4) Cationic and anionic ion pair reagents indicated the presence of amphoteric compounds within the polymeric structure of fulvic acid. Each mode of HPLC provided a characteristic profile of fulvic acid. The results of this research provided basic information on the behavior of aquatic fulvic acids under three modes of HPLC. Such informations are prerequisite for further investigation by spectroscopic methods.</p>Studies of Solvent Displacement from Solvated Metal Carbonyl Complexes of Chromium, Molybdenum, and Tungsten2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331992/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331992/"><img alt="Studies of Solvent Displacement from Solvated Metal Carbonyl Complexes of Chromium, Molybdenum, and Tungsten" title="Studies of Solvent Displacement from Solvated Metal Carbonyl Complexes of Chromium, Molybdenum, and Tungsten" src="https://digital.library.unt.edu/ark:/67531/metadc331992/small/"/></a></p><p>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 bonding interactions, varying from ca. 7 to 16 kcal/mol, and the bonding "modes" of solvents to metals are sensitive to the structures of the solvent molecules and the identities of the metal centers. The results indicate dissociative desolvation pathways for many arene solvents in (solvent)Cr(CO)_5 (solvent = benzene, fluorobenzene, toluene, etc.) complexes, and are consistent with competitive interchange and dissociative pathways for (n-heptane)M(CO)_5. Different types of (arene)-Cr(CO)_5 interactions were suggested for chlorobenzene (CB) vs. fluorobenzene and other non-halogenated arenes, i.e. via σ-halogen-Cr bond formation in the CB solvate vs. π-arene-Cr bond formation through "isolated" double bonds in solvates of the other arenes. The data also indicate the increasing importance of interchange pathways for solvent displacement from the solvates of Mo and W vs. that of Cr.</p>Raman Studies of Molecular Dynamics and Interactions in Liquids2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc332034/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332034/"><img alt="Raman Studies of Molecular Dynamics and Interactions in Liquids" title="Raman Studies of Molecular Dynamics and Interactions in Liquids" src="https://digital.library.unt.edu/ark:/67531/metadc332034/small/"/></a></p><p>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 to the analysis of the Raman spectrum of this compound over an extended range of temperature in the neat liquid phase. This study corroborated our finding that the peak previously assigned to the symmetric stretching mode of hydrogen bonded amines is actually composed of two bands. Furthermore, trends in both the resolved band parameters and the Fermi resonance analysis were tabulated, allowing one to monitor the change in the N-H valence region with concentration and temperature.</p>Thermal and Flash Photolysis Studies of Ligand-Exchange Reactions of Substituted Metal Carbonyl Complexes of Cr and Mo2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc332097/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332097/"><img alt="Thermal and Flash Photolysis Studies of Ligand-Exchange Reactions of Substituted Metal Carbonyl Complexes of Cr and Mo" title="Thermal and Flash Photolysis Studies of Ligand-Exchange Reactions of Substituted Metal Carbonyl Complexes of Cr and Mo" src="https://digital.library.unt.edu/ark:/67531/metadc332097/small/"/></a></p><p>Thermal and flash photolysis studies of ligand-substitution reactions of cis-(pip)(L)M(CO)_4 by L' (pip = piperidine; L, L' = CO, phosphines, phosphites; M = Cr, Mo) implicate square-pyramidal [(L)M(CO)_4], in which L occupies a coordination site in the equatorial plane, as the reactive species. In chlorobenzene (= CB) solvent, the predominant species formed after flash photolysis and a steady-state intermediate for the thermal reaction is cis—[(CB)(L)M(CO)_4], for which rates of CB-dissociation increase with increasing steric demands of coordinated L. Rates of CB-dissociation from trans-[(CB)(L)M(CO)_4] intermediates, formed after photolysis but not thermally, exhibit no observable dependence on the steric properties of the coordinated L.</p>The Photolytic Ozonation of Organics in Aqueous Solutions2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc332180/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332180/"><img alt="The Photolytic Ozonation of Organics in Aqueous Solutions" title="The Photolytic Ozonation of Organics in Aqueous Solutions" src="https://digital.library.unt.edu/ark:/67531/metadc332180/small/"/></a></p><p>The aim of the investigation described in this work is to gain a better understanding of the processes involved in the oxidation of organic compounds by photolytic ozonation in a laboratory scale reactor. The results and discussions are presented in Chapter III. This chapter contains four parts. In the first part, mass transfer efficiency and the calculation of the mass transfer coefficient, KLa, as well as the ozone decomposition rate constant, KD, are presented and compared with those obtained by other investigators. The second part deals with the kinetics of the photolysis of 2,2',4,4',6,6'-hexachlorobiphenyl both in purified and natural lake water. Mathematical expressions and a discussion of the possible reaction processes involved are given. Kinetic models of ozonation and photolytic ozonation in purified and natural lake water are developed and discussed in part three. Rate constants are calculated from experimental data and used to predict values of substrate destruction with a mathematical model. The fourth part of this chapter deals with the identification of products from the photolysis, ozonation and photolytic ozonation of 2,2'4,4',6,6'-hexachlorobiphenyl. The products are isolated and identified using combined gas chromatography and mass spectroscopy, and reaction mechanisms are suggested.</p>Synthesis and Structure of Polynitro- and Polymenthylpolycyclic "Cage" Monomers and Polymers2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc332109/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332109/"><img alt="Synthesis and Structure of Polynitro- and Polymenthylpolycyclic "Cage" Monomers and Polymers" title="Synthesis and Structure of Polynitro- and Polymenthylpolycyclic "Cage" Monomers and Polymers" src="https://digital.library.unt.edu/ark:/67531/metadc332109/small/"/></a></p><p>The objective of this study was to synthesize and characterize new energetic polycyclic "cage" compounds.
As part of a program involved in the synthesis of new polynitropolycyclic compounds, 2,6-dinitro-5-methoxy-
7-carbomethoxypentacyclo[5. 3 .0 . 0* • * . CP • i ° . 0* •8]decane has been synthesized. This is a model system which can be used to study (1) the effect of nitro substitution on the photolability of carbon-carbon double bonds and (2) to develop methods for avoiding Haller-Bauer cleavage in cage /3-keto esters when synthesizing polynitro-substituted cage compounds.</p>The Preparation, Properties, and Reactions of Silenes, Silenoids, and 2-Silanobornenes2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc332166/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc332166/"><img alt="The Preparation, Properties, and Reactions of Silenes, Silenoids, and 2-Silanobornenes" title="The Preparation, Properties, and Reactions of Silenes, Silenoids, and 2-Silanobornenes" src="https://digital.library.unt.edu/ark:/67531/metadc332166/small/"/></a></p><p>The reaction of chlorodimethylvinylsilane with tertbutyllithium was investigated in the presence of several conjugated dienes. In all cases except with 2,5-dimethylfuran, [2+4] cycloadducts of a silene intermediate are obtained in hydrocarbon solvents. The presence of THF in the reaction mixture suppresses the formation of cycloadducts in favor of 1,3-disilacyclobutanes. In the reaction of dimethylethoxyvinylsilane or dimethylmethoxyvinylsilane with tert-butyllithium the main product is the 1,1-dimethyl2-neopentyl-4-(dimethylalkoxysilyl)silacyclobutane. It is concluded that lithium chloride elimination to give silene intermediates occurs in hydrocarbon solvents. In the presence of strong Lewis bases or when the leaving group on silicon is an alkoxy group, the addition reaction giving a-lithiosilanes occurs and products arising from their coupling reactions are obtained.</p>(4+2)-Cycloaddition Reactions of Ketenes; Pyranones2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331498/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331498/"><img alt="(4+2)-Cycloaddition Reactions of Ketenes; Pyranones" title="(4+2)-Cycloaddition Reactions of Ketenes; Pyranones" src="https://digital.library.unt.edu/ark:/67531/metadc331498/small/"/></a></p><p>This study deals with the (4+2)-cycloaddition reactions of 4-π electron compounds with ketenes. Chloroketenes were generated in situ from the corresponding chlorinated acid chlorides in the presence of the ketenophiles. Chloro-, dichloro- and diphenylketenes reacted with 1-methoxy-3-trimethylsiloxy-l,3-butadiene, and 2,4-bis(trimethylsiloxy)-1,3-pentadiene to yield the corresponding dihydropyrans. The dihydropyrans yielded substituted 4-pyranones on hydrolysis.</p>Molecular Dynamics and Interactions in Liquids2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331452/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331452/"><img alt="Molecular Dynamics and Interactions in Liquids" title="Molecular Dynamics and Interactions in Liquids" src="https://digital.library.unt.edu/ark:/67531/metadc331452/small/"/></a></p><p>Various modern spectroscopies have been utilized with considerable success in recent years to probe the dynamics of vibrational and reorientational relaxation of molecules in condensed phases. We have studied the temperature dependence of the polarized and depolarized Raman spectra of various modes in the following dihalomethanes: dibromomethane, dichloromethane, dichloromethane-d2, and bromochloromethane. Among other observed trends, we have found the following: Vibrational dephasing times calculated from the bend) and (C-Br stretch) lineshapes are of the same magnitude in CI^B^. The vibrational dephasing time of [C-D(H) stretch] is twice as long in CD2Cl2 as in CH-^C^, and the relaxation time of (C-Cl stretch) is greater in CI^C^ than in CD2CI2. Isotropic relaxation times for all three stretching vibrations are significantly shorter in C^BrCl than in CI^C^ or CI^B^. Application of the Kubo model revealed that derived modulation times are close to equal for equivalent vibrations in the various dihalomethanes. Thus, the more efficient relaxation of the A^ modes in CE^BrCl can be attributed almost entirely to the broader mean squared frequency perturbation of the vibrations in this molecule.</p>Regulation of Lactobacillic Acid Formation in Lactobacillus Plantarum2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331446/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331446/"><img alt="Regulation of Lactobacillic Acid Formation in Lactobacillus Plantarum" title="Regulation of Lactobacillic Acid Formation in Lactobacillus Plantarum" src="https://digital.library.unt.edu/ark:/67531/metadc331446/small/"/></a></p><p>Cyclopropanation of the unsaturated fatty acid moieties of membrane phospholipids is a commonly observed phenomenon in a number of bacterial systems. The cyclopropane fatty acids are usually synthesized during and after the transition from exponential growth to stationary phase, or under such environmental conditions as acidic culture pH, low oxygen tension or high salt concentrations. S-Adenosylmethionine, the ubiquitous methyl group donor, provides the methylene bridge carbon in the reaction catalyzed by cyclopropane fatty acid synthase. Also formed in the reaction is S-adenosylhomocysteine, a potent inhibitor of cyclopropane fatty acid synthase, which is degraded by S-adenosylhomocysteine nucleosidase. This work provides evidence for at least two modes of regulation of lactobacillic acid synthesis, the cyclopropane fatty acid formed from cis-vaccenic acid (cis-11,12-octadecenoic acid), in Lactobacillus piantarum.</p>The Nature of Intermediates Produced Through Ligand-Substitution Reactions of Octahedral Metal Carbonyls2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331634/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331634/"><img alt="The Nature of Intermediates Produced Through Ligand-Substitution Reactions of Octahedral Metal Carbonyls" title="The Nature of Intermediates Produced Through Ligand-Substitution Reactions of Octahedral Metal Carbonyls" src="https://digital.library.unt.edu/ark:/67531/metadc331634/small/"/></a></p><p>Pulsed laser time-resolved ligand-substitution photochemistry for (DTO)W(CO)4, (DTN)W(CO)4, and (NP)Mo(CO)4 (DTO = 2,2,7,7-tetramethyl-3,6-diathiaoctane; DTN = 2,2,8,8- tetramethyl-3,7-diathianonane; NP = l-diethylamino-2- diphenylphosphinoethane) proceeds via initial fission of the W-S and Mo-P bonds, affording Cs and C4v five-coordinate intermediates for DTN and NP but largely Cs for DTO. The rates of reaction of these intermediates, via chelate ring closure and competitive bimolecular interaction with Lewis bases (= L, alkylphosphines and alkyl phosphites) for the Cs intermediates and via bimolecular interaction of L with the C4v intermediates, together with activation parameters for these processes have been determined. The rates of interactions at the Cs intermediates are significantly faster than at the C4v intermediates.</p>Reactions of Chloroketenes with Ketene Acetals2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331644/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331644/"><img alt="Reactions of Chloroketenes with Ketene Acetals" title="Reactions of Chloroketenes with Ketene Acetals" src="https://digital.library.unt.edu/ark:/67531/metadc331644/small/"/></a></p><p>The first objective of this investigation was to conduct a systematic study into the reactions of chloroketenes with ketene acetals. The second objective was to explore the synthetic utility of these reaction products and offer a rational explanation for these reaction products.</p>The Study of Low Temperature Silene Generation2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331711/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331711/"><img alt="The Study of Low Temperature Silene Generation" title="The Study of Low Temperature Silene Generation" src="https://digital.library.unt.edu/ark:/67531/metadc331711/small/"/></a></p><p>The reactions of tert-butyl-, sec-butyl-, and n-butyllithium with dimethylfluorovinylsilane include addition to the double bond to give both silene and silenoid intermediates, fluorine substitution, and a novel vinyl substitution. For the tert-butyllithium reaction, product stereochemistry and trapping experiments using both cyclopentadiene and methoxytrimethylsilane show that silenes are not formed in THF. In hexane about 67% of the 1,3-disilacyclobutanes obtained arise from silene dimerization while 33% are formed by silenoid coupling. In hexane the order of reactivity for addition, t-Bu > sec-Bu > n-Bu, is opposite that for fluorine substitution. The vinyl substitution is most significant with secondary alkyllithium reagents including the tert-butyllithium adduct to dimethylfluorovinylsilane and with sec-butyllithium itself. Evidence for the formation of vinyllithium or ethylene in the process could not be obtained.</p>Pressure Effects on Electric Field Spectra of Molecular Rydberg States2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331713/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331713/"><img alt="Pressure Effects on Electric Field Spectra of Molecular Rydberg States" title="Pressure Effects on Electric Field Spectra of Molecular Rydberg States" src="https://digital.library.unt.edu/ark:/67531/metadc331713/small/"/></a></p><p>Electric field studies, electrochromism, were used to obtain excited-state data for analogous divalent sulfur compounds. The sulfides investigated were dimethyl sulfide and small cyclic sulfides including the three to six member ring compounds. The excited-state dipole moments and polarizabilities are reported for the first s, p, and d Rydberg absorption bands which occur in the near vacuum ultraviolet region from 230 to 170 nm. The excited-state data are interpreted in terms of the particular excited-state (s, p, or d) for the molecules and the bending differences due to the presence of the ring and the number of atoms in the ring. The next section describes the use of electrochromism to investigate the pressure effect of argon, carbon tetrafluoride and sulfur hexafluoride on the spectra for molecular Rydberg states.</p>Synthesis and Reactions of Some N-Nitrosamines2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331690/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331690/"><img alt="Synthesis and Reactions of Some N-Nitrosamines" title="Synthesis and Reactions of Some N-Nitrosamines" src="https://digital.library.unt.edu/ark:/67531/metadc331690/small/"/></a></p><p>Nucleophiles react with the α-acetoxy derivative of α-hydroxybenzylbenzylnitrosamine at the carbonyl carbon of the acetoxy moiety followed by fragmentation to the very same intermediates formed by oxidative metabolism. Since α-acetoxybenzylbenzylnitrosamine has been shown to be able to acylate nucleophiles and since the nucleic acids are nucleophiles, then it is possible that this compound may cause mutations by an acylation pathway instead of or in addition to the more common alkylation pathway. The data in Part I of this dissertation should be considered in any further biological investigations of N,N-dialkylnitrosamine induced mutagenesis or carcinogenesis. The study of the synthesis, reactions, mutagenicity, and the possible correlation to compound liposolubility of cyclic N-nitrosamines was also investigated.</p>Studies on Human Plasma Lecithin:Cholesterol Acyltransferase: Physical and Chemical Characterization and Coupled Spectrophotometric Enzyme Assay2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331696/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331696/"><img alt="Studies on Human Plasma Lecithin:Cholesterol Acyltransferase: Physical and Chemical Characterization and Coupled Spectrophotometric Enzyme Assay" title="Studies on Human Plasma Lecithin:Cholesterol Acyltransferase: Physical and Chemical Characterization and Coupled Spectrophotometric Enzyme Assay" src="https://digital.library.unt.edu/ark:/67531/metadc331696/small/"/></a></p><p>The physico-chemical properties of lecithin:cholesterol acyltransferase were investigated. The amino acid composition analysis showed a relatively high content of glutamic acid, aspartic acid, glycine and leucine. The spectrophotometric titration of phenolic groups in the enzyme showed a large increase in absorbance at 295 nm with an apparent pK of about 12.0. The largest change in molar ellipticity at 222 nm was also observed above pH 11. Circular dichroism studies revealed that human lecithin:cholesterol acyltransferase has a relatively high content of β-pleated sheet structure (48%) with 20% α-helix, and 32% remaining structure. Human lecithin:cholesterol acyltransferase has a high extinction coefficient at neutral pH. Microsequencing of the amino terminal residues of the enzyme revealed a hydrophobic character. Inactivation of lecithin:cholesterol acyltransferase activity was observed using diisopropylfluorophosphate with a stoichiometry of 1 mole of diisopropylphosphate incorporated per mole of enzyme. This suggests the involvement of a serine residue in the active site of the enzyme, possibly for the formation of an acyl-intermediate. A new quicker assay method for lecithin:cholesterol acyltransferase was developed. This assay involved coupling reaction with acyl CoA synthetase, ΡΡᵢ-dependent phosphofructokinase, aldolase, triosephosphate isomerase and α-glycerol-3-phosphate dehydrogenase monitoring a change in the absorbance or fluorescence intensity due to the oxidation of NADH. The activity of each coupling enzyme was accurately determined to establish the optimum assay condition for lecithin:cholesterol acyltransferase. The coupled enzyme assay for lecithin:cholesterol acyltransferase by spectrofluorometry showed a significant change in relative fluorescence intensity whereas a UV absorption spectroscopy method showed no significant absorbance change for the initial rate of lecithin:cholesterol acyltransferase reaction.</p>GC/MS Analysis of Chlorinated Organic Compounds in Municipal Wastewater After Chlorination2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331677/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331677/"><img alt="GC/MS Analysis of Chlorinated Organic Compounds in Municipal Wastewater After Chlorination" title="GC/MS Analysis of Chlorinated Organic Compounds in Municipal Wastewater After Chlorination" src="https://digital.library.unt.edu/ark:/67531/metadc331677/small/"/></a></p><p>A study has been conducted for the qualitative and Quantitative analysis of chlorinated organic compounds in water. The study included the adaptation of Amberlite XAD macroreticular resin techniques for the concentration of municipal wastewater samples, followed by GC/MS analysis. A new analytical method was developed for the determination of volatile halogenated organics using liquid-liquid extraction and electron capture gas chromatography. And, a computer program was written which searches raw GC/MS computer files for halogen-containing organic compounds.</p>Synthesis of Anthracyclines Related to Adriamycin2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331548/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331548/"><img alt="Synthesis of Anthracyclines Related to Adriamycin" title="Synthesis of Anthracyclines Related to Adriamycin" src="https://digital.library.unt.edu/ark:/67531/metadc331548/small/"/></a></p><p>This dissertation reports the preparation of several types of anthraquinones structurally related to adriamycin. It describes the synthesis of two types of 2-aminoquinizarin compounds. It also presents two new syntheses of a heterocyclic tetracyclic ring system, similar to the aglicone ring system of adriamycin. A series of 2-aminoquinizarins was prepared by adding several primary amines to quinizarin. Quinizarin was shown to be essentially inert toward secondary amines. Several secondary amine adducts with quinizarin have been prepared, however, by treating the bis-boroacetate ester of quinizarin with the amines. Both types of 2-aminoquinizarin compounds exhibit outstanding potential for possessing antineoplastic activity, and several have been submitted to the National Cancer Institute for testing in their screening program for antineoplastic agents.</p>Silenes and Silenoids in the Chemistry of Cyclopentadienylsilanes2014-08-22T18:00:56-05:00https://digital.library.unt.edu/ark:/67531/metadc331302/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc331302/"><img alt="Silenes and Silenoids in the Chemistry of Cyclopentadienylsilanes" title="Silenes and Silenoids in the Chemistry of Cyclopentadienylsilanes" src="https://digital.library.unt.edu/ark:/67531/metadc331302/small/"/></a></p><p>Evidence is presented that apparent silene products obtained from the metalation of cyclopentadienyldimethyl - chlorosilane either with tert-butyl1ithium or with methylenetriphenylphosphorane actually arise from the metalated starting material, a silenoid, rather than from a silafulvene intermediate. Trimethylmethoxysi1ane is shown to be an effective trap for dimethylsilafulvene. A new dimethylsilafulvene precursor, bis(dimethylmethoxysi1yl) cyclopentadiene, which gives high yields of dimethyldimethoxysi1ane and the silafulvene at temperatures as low as 240°C is reported.</p>