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Explorations with Polycarbocyclic Cage Compounds
A variety of novel cage-functionalized pyridyl containing crown ethers have been prepared for use in selective alkali metal complexation studies. A highly preorganized, cage-functionalized cryptand also has been designed and has been synthesized for use as a selective Li+ complexant. The alkali metal picrate extraction profiles of these cage-functionalized crown ethers also have been studied. Novel cage-functionalized diazacrown ethers have been prepared for selective alkali metal complexation studies. Alkali metal picrate extraction experiments have been performed by using this new class of synthetic ionophores to investigate the effects of cage-annulation and the influence of N-pivot lariat sidearms upon their resulting complexation properties. Novel pyridyl containing calix[4]arene receptors were prepared. Analysis of their respective 1H NMR and 13C NMR spectra suggests that calix[4]arene moieties in the ligand occupy the cone conformation. The complexation properties of these host molecules were estimated by performing a series of alkali metal picrate extraction experiments. An optically active cage-functionalized crown ether which contains a binaphthyl moiety as the chiral unit was prepared. The ability of the resulting optically active crown ether to distinguish between enantiomers of guest ammonium ions (i.e., phenylethylamonium and phenylglycinate salts) in transport experiments was investigated. Hexacyclo[11.2.1.02,12.05,10.05,15.010,14]hexadeca-6,8-diene-4,11-dione was prepared from hexacyclo[7.4.2.01,9.03,7.04,14.06,15] pentadeca-10,12-diene-2,8-dione. Unanticipated …
Date:
August 1999
Creator:
Chong, Hyun-Soon
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Performance of Silicon Based Sensor and its Application in Silver Toxicity Studies
The silicon based sensor is able to detect part per trillion ionic silver in 0.0098% hydrofluoric acid based on the open circuit potential (OCP) measurement. The OCP jump of 100 ppt ionic silver solution is up to 120 mV. The complex agent can effectively suppress the ionic silver concentration and suppress the OCP signal. The ability of complex agent to suppress the OCP signal depends on the formation constant of the complex with silver. The complex adsorbed on the sensor surface induces a second OCP jump, the height of the second jump depends on the formation constant of the complex. The MINEQL chemical equilibrium modeling program is used to calculate the ionic silver concentration when complex agent presents, a discrepancy is found between the MINEQL simulation result and the OCP signal of the silicon based sensor. The toxicity of ionic silver to C. dubia is studied parallel to the OCP signal of silicon based sensor. Less toxicity is found when the complex agent is present similar to the OCP signal. Another discrepancy is found between the MINEQL simulation and the toxicity test when MINEQL simulation is used to predict and control the ionic silver concentration. The data from both biosensor …
Date:
August 2000
Creator:
Peng, Haiqing
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Diffusion Barriers/Adhesion Promoters. Surface and Interfacial Studies of Copper and Copper-Aluminum Alloys
The focus of this research is to study the interaction between copper and the diffusion barrier/adhesion promoter. The behavior of copper sputter-deposited onto sputter-cleaned tantalum nitride is investigated. The data show that copper growth on tantalum nitride proceeds with the formation of 3-D islands, indicating poor adhesion characteristics between copper and Ta0.4N. Post-annealing experiments indicate that copper will diffuse into Ta0.4N at 800 K. Although the data suggests that Ta0.4N is effective in preventing copper diffusion, copper's inability to wet Ta0.4N will render this barrier ineffective. The interaction of copper with oxidized tantalum silicon nitride (O/TaSiN) is characterized. The data indicate that initial copper depositions result in the formation a conformal ionic layer followed by Cu(0) formation in subsequent depositions. Post-deposition annealing experiments performed indicate that although diffusion does not occur for temperatures less than 800 K, copper "de-wetting" occurs for temperatures above 500 K. These results indicate that in conditions where the substrate has been oxidized facile de-wetting of copper may occur. The behavior of a sputter-deposited Cu0.6Al0.4 film with SiO2 (Cu0.6Al0.4/SiO2) is investigated. The data indicate that aluminum segregates to the SiO2 interface and becomes oxidized. For copper coverages less than ~ 0.31 ML (based on a Cu/O …
Date:
August 2000
Creator:
Shepherd, Krupanand Solomon
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Stereochemical Elucidation Of The Tetrahydro [2.2]paracyclophane System
The purpose of this investigation is to study the Birch reduction products of [2.2lparacyclophane and of [2.2]paracyclophane- 2-carboxylic acid. The tetrahydro Birch reduction product of [2.2]paracyclophane is shown to be dl stereoisomer, with the olefins of the upper deck only partially overlapping with the olefins of the lower deck. This stereochemical elucidation is accomplished by means of a complete proton nmr analysis of the tetraepoxide derivative. A proposed mechanism supported by VB (valence bond) and MO (molecular orbital) theories for this Birch reduction process is presented.
Date:
August 1975
Creator:
Song, Ban-Huat
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Separation of Transition Metal Ions by HPLC, Using UV-VIS Detection
HPLC has been used and can quickly determine several ions simultaneously. The method of determination described for transition metals [Cr(III), Fe(III), Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Mn(II)] and [Ca(II), Pb(II)] using HPLC with UV-VIS detection is better than the PAR complexation method commonly used. The effects of both eluent pH and detector wavelength were investigated. Results from using different pHs and wavelengths, optional analytical conditions for the separation of [Ni(II), Co(II), Cu(II)], [Cr(III), Fe(III), Ca(II), Ni(II), Cu(II)], and [Ca(II), Zn(II), Pb(II)] in one injection, respectively, are described. The influence of adding different concentrations of Na_2EDTA solvent to the sample is shown. Detection limits, linear range, and the comparisons between this study and a post-column PAR method are given.
Date:
August 1987
Creator:
Lien, Wan-Fu
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Synthesis, Structure, and Solution Dynamics of Co₄(CO)₈(dmpe)(mu₄-PPh)₂
Reaction of the tetracobalt cluster Co4(CO)10(t 4-PPh)2 with 1,2-bis(dimethylphosphino)ethane (dmpe) affords the bis-substituted cluster Co4(CO)8(dmpe)(t 4-PPh)2. The bidentate dmpe ligand is shown to bind to the cluster in a chelating fashion by IR, NMR, and X-ray diffractions analyses. The fluxional nature of the ancillary carbonyl groups has been studied by variable temperature 13C NMR measurements which reveal two distinct carbonyl scrambling pathways. The stability of the phosphine-ligated cluster has been examined using in situ Cylindrical Internal Reflection (CIR) Spectroscopy. The effect of the dmpe ligand on the cluster polyhedron will be discussed with respect to the observed crystallographic and spectroscopic results
Date:
May 1990
Creator:
Schulman, Cheryl Lutins
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Trace Elemental Analysis of Ashes in the Combustion of the Binder Enhanced d-RDF by Inductively Coupled Plasma Atomic Emission Spectroscopy
Incineration is an attractive solution to the problems of disposing of municipal solid wastes and supplying energy. Because up to 25 percent of the waste in refuse-derived-fuel systems is ash, the physical and chemical characteristics of ash become more and more important for its potential impacts and methods suitable for their disposal. Trace elements concentration in ash is of great interest because of its relationship to regulatory criteria under the Resource Conservation and Recovery Act (RCRA) regarding toxicity and hazards. The applications of a microwave oven sample dissolution method has been tested on a variety of standard reference materials, with reproducible and accurate results. Fourteen trace elements, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl, V, and Zn, from the dissolved ash samples were determined by inductively coupled plasma atomic emission spectrometry.
Date:
November 1988
Creator:
Tai, Chia-Hui
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Synthesis and Reactivity of Bis(silyl)acetylenes
Six bis(silyl)acetylenes with the following varied silicon substituents were prepared: I (Me, Me); II (H, H); III (Cl, H); IV (Cl, Cl); V (OMe, H); VI (OMe, OMe). While I and II may be prepared by the reaction of dilithio- or bis(bromomagnesium)-acetylide with appropriate chlorosilane, similar reactions designed to give III - VI give oligomers, YMe_2Si(C≡C-SiMe_2)_nY, VII, Y = Cl, OMe, as the major products indicating that the acetylenic functionality on silicon activates the chlorosilane toward nucleophilic substitution. Compounds III and IV were prepared by free radical chlorination of II. Methanolysis of III and IV gave quantitative yields of V and VI, respectively. In the presence of mineral acid, VI readily cyclized to give high yields of the cyclic siloxane octamethyl-4,9-dioxa-3,5,8,10-tetrasila-cyclodeca-1,6-diyne, VIII, and the analogous triyne, IX. It was determined that V and VI could be prepared directly from II in high yield by methanolysis with palladium catalyst. Vaska's complex also accomplished the conversion. I attempted to prepare bis(ethoxydimethylsilyl)acetylene by using of Wilkinson 's catalyst for hydrosilylation with acetaldehyde. The principal product of this reaction was 1-(dimethylsilyl)-3,5,5-trimethyl-4-oxa-3-silacyclopent-1-ene, XI.
Date:
May 1987
Creator:
Albanesi, Todd E. (Todd Edward)
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Ion Chromatography of Soluble Cr(III) and Cr(VI)
Ion chromatography coupled with a conductivity detector was used to investigate the analysis of Cr(III) and Cr(VI) in aqueous samples. An IC methodology for Cr(III) was developed using a cation column and an eluent containing tartaric acid, ethylenediamine, and acetonitrile at pH 2.9. The detection limit of this method can reach 0.1 ppm level with good precision. Several operational parameters were evaluated during the regular use of the method. Comparison of the IC method with AA method showed good agreement between the two methods. The anion exchange column was used for Cr(VI) determination. The best results were obtained with an eluent containing sodium gluconate, borate buffer, glycerin, and acetonitrile. The retention time for the Cr207 2 - sample was 11 min. and the calibration curve was linear between 1.0 and 100 ppm.
Date:
August 1988
Creator:
Huang, Julie Shiong-Jiun
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Elemental Analysis of Brainstem in Victims of Sudden Infant Death Syndrome
A brainstem-related abnormality in respiratory control appears to be one of the most compelling mechanisms for sudden infant death syndrome (SIDS). The elements calcium, copper, iron, potassium, magnesium, sodium, phosphorus, sulfur, and zinc were analyzed by inductively coupled plasma atomic emission spectroscopy in the brainstem of 30 infants who died from SIDS and 10 infants who died from other causes (control). No differences were found between SIDS and control for any element except for more calcium in the SIDS group. A multivariate analysis of the data failed to group the majority of SIDS and control subjects in different clusters. Further research is required to determine the biological significance of the higher calcium found in the SIDS group.,
Date:
December 1988
Creator:
Oquendo, Javier
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
An NMR Investigation of Aryl Mercury Compounds
A variable temperature ^13 C and ^199 Hg NMR study has been conducted for diphenyl-, bis(o-tolyl)-, bis(m-tolyl)-, and bis(2, 6-xylyl)mercury in dimethyl sulfoxide and 1,1,2,2 tetrachloroethane; ^13 C T1 relaxation times are reported as a function of temperature. Barriers to rotation of the aryl rings are obtained. Chemical shifts and couplings in CDCl_3 are given for bis(p-tolyl)-, bis(2, 5-xylyl)-, bis(mesityl)-,phenyl(o-tolyl)-, phenyl(m-tolyl)mercury, and the compounds listed above. The steric interactions of these aryl mercury compounds are discussed.
Date:
May 1987
Creator:
Rowland, Keith E. (Keith Edward)
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Detector Comparison for Simultaneous Determination of Organic Acids and Inorganic Anions
The research reported here is a study of detector systems to determine those most suited for simultaneous organic acid, inorganic anion determination. Comparisons are made on the basis of detection limits and sensitivities for conductivity, UV/Vis, photoconductivity, and derivative conductivity detection systems. The investigation was made using a constant chromatographic system with the only variable component being the detector system. Eluant optimization conditions for each detector are reported along with tables reporting detection limits and sensitivities for each detector system. Various chromatograms are also shown to provide a visual comparison between detector results.
Date:
August 1988
Creator:
Pannell, Daniel K. (Daniel Kirk)
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Syntheses and the Structures of Polymethylpolycyclic and Polycyclic "Cage" Molecules
The structures of Diels-Alder cycloaddition of cyclopentadiene to 2,6-dimethyl-p-benzoquinone and methylcyclopentadiene to 2,6-dimethyl-p-benzoquinone were assigned by analysis of 1-D and 2-D proton and carbon-13 NMR spectra. The structures of the cycloadduct of methylcyclopentadiene to 2,6-dimethyl-p-benzoquinone and that of the corresponding intramolecular [2+2] photocyclization product were also obtained by single crystal X-ray structural analysis. As the second part of the study, a new polycyclic "cage" molecule, a substituted trishomocubane isomer, was synthesized. In this synthesis, reductive bond cleavage followed by Dieckmann condensation was employed. Wolff-Kishner reduction then was used to convert a β-keto ester "cage" molecule to the corresponding carboxylic acid. A compound that possesses twofold symmetry was isolated from reaction product mixture. The structure of this compound has been established by single crystal X-ray crystallography.
Date:
May 1989
Creator:
Zhao, Dalian
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A Reinvestigation of the Kinetics and Mechanism of Ligand Exchange in Mu-(2,2,8,8-Tetramethyl-3, 7-Dithianonane)-Decacarbonylditungsten(0)
This student is interested in reinvestigating the kinetics and mechanism of the bridged compound in l,2-dichloroethane with triisopropyl phosphite and in finding the reasons why the values of competition ratio k₋₂ /k₃ in this reaction are so large.
Date:
August 1988
Creator:
Liao, Jing-Piin
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Manufacturer [Sic] of Densified-Refuse Derived Fuel (d-RDF) Pellets and Methods for the Determination of d-RDF Pellet Densities
There are 150 million tons of Municipal Solid Waste (MSW) annually produced in the United States, which is approximately equivalent to 150 million barrels of oil. MSW production is inexhaustible, and is increasing on an annual per capita basis of approximately three per cent. After controlling the moisture and adding a binder, the combustible portion of MSW was converted to pellets. The objects of this project were to 1) evaluate the binder, 2) prepare the pellets, and 3) evaluate the pellets with regard to density. The manufacture of pellets was conducted at the Naval Air Station, Jacksonville, Florida. The evaluation of the binders and the pellets was done at North Texas State University (NTSU). There were three procedures for measuring the density. The first, using water displacement, was from the American Society for Testing and Material (ASTM). The second, using wax coating, was also from ASTM. The third, using sharply-cut cylindrical pellets, was developed at NTSU.
Date:
December 1986
Creator:
Attili, Bassam Saleem
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Static and Flow Properties of Dilute Polymer Solutions
Small weight percentages of certain high-molecular weight polymers added to liquids in turbulent flow through conduits can result in dramatic friction reduction. Although many current and potential uses of the drag reduction phenomenon exist, there is a fundamental problem: drag reduction efficacy decreases rapidly with flow time due to the mechanical degradation in flow of the added polymer. In this thesis study, dilute aqueous solutions of polyacrylamide were tested under turbulent flow conditions in an attempt to determine where mechanical degradation in flow occurs.
Date:
August 1991
Creator:
Whang, Kyu-ho
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Investigation of Substituent Effects of 2-Substituted Silaethylenes
This investigation is concerned with determining whether a carbon substituent or a silicon substituent on the carbon terminus of a silicon-carbon double bond has a more stabilizing effect. Two different 2-substituted silaethylenes were generated at the same time by pyrolyzing 1, 1-dimethyl-2-neopentyl-4- (dimethylalkoxysilyl) silacyclobutanes in a nitrogen flow system. The results of these pyrolyses, both neat and in the presence of a trapping reagent, show that the silaethylene with a silicon substituent on the carbon terminus was favored approximately two to one over the silaethylene with a carbon substituent. This datum, along with other observations and hypotheses discussed, leads to the suggestion that the silicon substituenton the carbon terminus of the silaethylene bond has a more stabilizing effect than the carbon substituent.
Date:
December 1980
Creator:
Snyder, Walter David
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Determination of Halogens in Organic Compounds by Using Sodium Fusion-Ion Chromatography Method
A sodium fusion-Ion chromatographic method for determination of fluorine, chlorine, bromine, and iodine in organic compounds is described. Seventeen organic halogen compounds and eleven mixtures were decomposed by Na fumes at 280-290°C for one hour or longer. The absorbing solutions were injected for ion chromatographic analysis using electrochemical and conductometric detectors. The arrangement of the apparatus includes the placement of the electrochemical and conductometric detectors. This method provides a mechanism providing for complete analysis for all four halogens in one ion chromatographic sample injection. Reproducibility is excellent and liquid sample handling is mentioned.
Date:
August 1983
Creator:
Wang, Chung-Yu
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Synthesis and 2-D NMR Analysis of a New Phenyl-Substituted Polycyclic Compound
Diels-Alder [4+2] cycloaddition of a mixture of 1- and 2 methylcyclopentadiene to 2-phenyl-g.-benzoquinone affords a mixture of four nd cycloadducts. A single, isomerically pure cycloadduct was isolated by careful column chromatography. Stereospecific reduction of this material with sodium borohydride and cerium(III) chloride 'affords a single, isomerically pure tricyclic diol. The structures of the cycloadduct and this tricyclic diol, established via analysis of their one- and two-dimensionial NMR spectra, were shown to be (1-methyl-5-phenyltricyclo[6.2.1.02,7]undec a-4,9 diene-3,6-dione and 1-methyl-5-phenyltricyclo[6.2.1.0 2 ,7 ]undeca-4,9-diene t.&A-3-=.a-6-diol), respectively. Intramolecular [2+2] photocyclization of this tricyclic diol afforded the corresponding cage diol, 3-methyl-7phenylpentacyclo[5.4.0.0 2 ,6 .03 , 1 0 .05, 9 ]undecane-.exogxa-8,11-diol. Oxidation of this cage diol with pyridinium chlorochromate in dry dichloromethane afforded a single, isomerically pure cage hydroxyketone, 3-methyl-7 phenylpentacyclo[5.4.02,6.03,l .1519]undecane-xA-8-ol-II-one, whose structure was established by single crystal X-ray crystallographic methods.
Date:
May 1991
Creator:
Tsay, Fuh-Rong
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Raman Studies of Conformational Energies and Hydrogen Bonding in Alcohols
The conformational energy differences have been determined for ethylene glycol, 2- chloroethanol, and 2,2- dichloroethanol in the neat liquid, DMSO, and H20 with Raman spectroscopy. Spectra in the 0-H valence region were utilized to determine the energy difference between interand intramolecularly hydrogen bonded species. It was found that the solvent effect on the relative stabilities of the gauche and trans rotamers of the alcohols differ significantly. The results also indicate that, unlike ethylene glycol, there is significant intramolecular hydrogen bond formation in the halogenated alcohols in the neat liquid phase. Stronger intramolecular hydrogen bond formation was observed in dichloroethanol than in 2-chloroethanol.
Date:
August 1982
Creator:
Maleknia, Simindokht
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Regulation of Pyridine Nucleotide Metabolism in Saccharomyces cerevisiae
The levels of total nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), and their redox states were determined as the function of growth in S. cerevisiae. Cells growing in a medium containing 0.8% glucose exhibit two phases of exponential growth, utilizing glucose and ethanol, respectively. The NAD pool is 50% reduced during both stages of growth while the NADP pool is 67% reduced in glucose growth and 48% reduced in ethanol growth. The NAD/NADP ratio is constant during growth on glucose and a two-fold increase in the NAD/NADP ratio occurs upon exhaustion of glucose. The increased ratio is maintained during growth on ethanol. This alteration in the regulation of the relative levels of NAD and NADP may be due to a change in the regulation of NAD kinase and/or NADP phosphatase activities. These changes may be related to the redox state of the NADP pool.
Date:
May 1976
Creator:
Ting, Haung-yu
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Reactivity of Five-Coordinate Intermediates Derived from (Chelate) Tetracarbonylmetal (0) Complexes
The reactivity of the [(Phen)Cr(CO)_3] intermediate with phosphines and phosphites (L) has been investigated through ligand-competition studies. This intermediate possesses virtually no ability to discriminate among L. The agreement between reactivity data for the thermal and photochemically-generated intermediates indicates that the same intermediate is produced via each process. Pulsed laser flash photolysis of (n^2-NP)M(CO)_4 (I) (M = Cr, Mo; NP = 1-diethylamino-2-diphenylphosphinoethane) in the absence and presence of P (OPr-i)_3 (L) in 1,2-dichloroethane and chlorobenzene induces unimolecular ring-opening to afford [(n^1-NP)M(CO)_4] (II), in which the bidentate ligand is coordinated through P. Reaction of this intermediate takes place through competitive ring-reclosure and attack at (II) by L to afford (I) and cis-(n^1-NP) (L)M(CO)_4.
Date:
December 1983
Creator:
Mansour, Saber E. (Saber El-Sayed)
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Conformation-Activity Studies of Pyrethroid Alcohols
The synthesis and insecticidal activity of certain alcohols (hydroxymethyldibenzofurans, hydroxymethyldibenzothiophenes and some of their ⍺-cyano derivatives), esterified with trans-chrysanthemic acid, were investigated. The preparation of these planar alcohol moieties was undertaken to study conformation-activity effects in insecticides of the pyrethroid type. The synthesis of final ester products employed two methods. One was the direct condensation of the appropriate alcohol with chrysanthemic acid chloride in the presence of pyridine. The other involved the in situ formation of the cyanohydrin from the appropriate aldehyde and subsequent condensation with chrysanthemic acid chloride in the presence of a phase transfer reagent. Insecticidal activity is to be tested at rates of 0.001, 0.01, 0.1, 10, 100, and 1000 ppm. Fenvalerate is used as the standard against Diabrotica undecimpuntata (spotted cucumber beetles).
Date:
August 1984
Creator:
Tu, Huai-Tsu
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Precipitation of Strontium Sulfate in Gels
The growth of strontium sulfate precipitate by diffusion in various gels was studied by using optical transmission and confocal microscopies, scanning and transmission electron microscopies, and energy dispersive X ray fluorescence. Pure silica gel, pure agarose gel and the silica/agarose mixed gel at pH 7 - 10 were used throughout the present study. Precipitate morphology is sensitive to pH and to the nature of the growth medium. The morphology was observed as a function of time. The lack of change is presumably because of rapid depletion of the limiting reagent after the very beginning of precipitation. The problem of separating strontium sulfate precipitate from the gel medium is discussed.
Date:
December 1991
Creator:
Lee, Ya
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library