UNT Libraries - 622 Matching Results

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Baeyer-Villiger Oxidation of 1,7- & 1,9-dibromopentacyclo[,6.03,10.05,9]undecane-8,11-dione

Description: Baeyer-Villiger oxidation of 1,9-dibromopentacyclo[,6.03,10.05,9]undecane-8,11-dione (1,9-dibromo-PCU-8,11-dione) was performed by using an excess amount of m-chloroperbenzoic acid (3 equivalents) and resulted in the formation of the corresponding monolactone. The reaction would not proceed to the dilactone stage. The structure of the reaction product was established unequivocally via single crystal X-ray diffraction. Baeyer-Villiger oxidation of 1,9-dibromo-PCU-8,11-dione using ceric ammonium nitrate (CAN) was also performed and afforded a mixture of lactones. Only one of these lactones, which also contained an alkene functionality, could be isolated and characterized. 1,7-dibromo-PCU-8,11-dione was also reacted with CAN, yielding the mono-lactone, which has also been characterized.
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Date: May 2004
Creator: Akinola, Adeniyi O.

Barbituric Acids. VII. 5-alkyl-derivatives of 5-ethoxy-barbituric Acid

Description: A great deal of research has been devoted in recent years to the search for new drugs for the treatment of epilepsy and related convulsive disorders. This emphasis is occasioned by the fact that no one drug is effective for all patients, and also by the fact that the toxicity of a drug varies considerably from one patient to another. Among the most effective drugs are certain members of the hydantoin and barbituric acid series. For some time there has been in progress in this laboratory an investigation of members of these two series in which a hetro atom attached directly to the hetrocyclic nucleus is introduced into the side chain at position five of these two series.
Date: January 1955
Creator: Hyde, Harold Wayne

Barbituric Acids. VIII. 5-substituted-5-(1-pyrrolidyl)barbituric Acids

Description: The purpose of this investigation then was the preparation of a series of 5-substituted-5-(1-pyrrolidyl)barbituric acids in which R would consist of alkyl groups ranging in size from methyl to amyl, and other groups such as phenyl and benzyl. These compounds are to be tested elsewhere for hypnotic and anticonvulsant activity.
Date: 1957
Creator: Compton, Ross Davis

Barbituric Acids. V. 5-substituted-mercapto Derivatives of 5-isoamylbarbituric Acid

Description: Since no mention has been found in the literature of any 5-substituted mercapto-5-alkyl derivatives of barbituric acid, it was thought to be of interest to prepare a series of compounds containing sulfur attached directly to the barbituric acid nucleus. 5-substituted mercapto-5-isoamylbarbituric acids were chosen as representative of barbituric acids in which the alkyl group has a fairly high molecular weight.
Date: August 1952
Creator: Peterson, Paul Eugene

Base Effects on the Thermal Decomposition of Sec-butyllithium Solutions

Description: The pyrolysis of sec-butyllithium in solution was studied in an attempt to understand the loss of stereo-specificity and the atypical kinetics that have been reported. Additionally, the effect of added lithium alkoxides was studied to determine their effects on the highly reactive sec-butyllithium substrate.
Date: June 1966
Creator: Adams, George Michael

Biological Applications of a Strongly Luminescent Platinum (II) Complex in Reactive Oxygen Species Scavenging and Hypoxia Imaging in Caenorhabditis elegans

Description: Phosphorescent transition metal complexes make up an important group of compounds that continues to attract intense research owing to their intrinsic bioimaging applications that arise from bright emissions, relatively long excited state lifetimes, and large stokes shifts. Now for biomaging assay a model organism is required which must meet certain criteria for practical applications. The organism needs to be small, with a high turn-over of progeny (high fecundity), a short lifecycle, and low maintenance and assay costs. Our model organism C. elegans met all the criteria. The ideal phosphor has low toxicity in the model organism. In this work the strongly phosphorescent platinum (II) pyrophosphito-complex was tested for biological applications as a potential in vivo hypoxia sensor. The suitability of the phosphor was derived from its water solubility, bright phosphorescence at room temperature, and long excited state lifetime (~ 10 µs). The applications branched off to include testing of C. elegans survival when treated with the phosphor, which included lifespan and fecundity assays, toxicity assays including the determination of the LC50, and recovery after paraquat poisoning. Quenching experiments were performed using some well knows oxygen derivatives, and the quenching mechanisms were derived from Stern-Volmer plots. Reaction stoichiometries were derived from Job plots, while percent scavenging (or antioxidant) activities were determined graphically. The high photochemical reactivity of the complex was clearly manifested in these reactions.
Date: December 2015
Creator: Kinyanjui, Sophia Nduta

Biological Inhibitors

Description: Four isosteric series of plant growth-regulating compounds were prepared. Using an Avena sativa coleptile assay system, derivatives in series I and IV inhibited segment elongation to a greater degree than did comparable derivatives in series II and III.
Date: December 1971
Creator: Sargent, Dale Roger

Bonding Studies in Group IV Substituted n,n-dimethylanilines

Description: The purpose of the present work is to study the effects of the trimethylsilyl and trimethylgermyl substituents on the N,N-dimethylamino ring system. Both ground and excited state interactions were studied and their magnitudes determined. The experimental data were then used in conjunction with molecular orbital calculations to differentiate among, and determine the importance of, d-p bonding, hyperconjugation or polarization of the trimethylsilyl group on the ground and excited state bonding.
Date: December 1971
Creator: Drews, Michael James

Boron Nitride by Atomic Layer Deposition: A Template for Graphene Growth

Description: The growth of single and multilayer BN films on several substrates was investigated. A typical atomic layer deposition (ALD) process was demonstrated on Si(111) substrate with a growth rate of 1.1 Å/cycle which showed good agreement with the literature value and a near stoichiometric B/N ratio. Boron nitride films were also deposited by ALD on Cu poly crystal and Cu(111) single crystal substrates for the first time, and a growth rate of ~1ML/ALD cycle was obtained with a B/N ratio of ~2. The realization of a h-BN/Cu heterojunction was the first step towards a graphene/h-BN/Cu structure which has potential application in gateable interconnects.
Date: August 2011
Creator: Zhou, Mi

Brainstem Lipids' Relationship to Death

Description: Previous work relating postmortem findings with cause of death have focused on the vitreous portion of the body. This research investigated the link between phospholipids in the brainstem and cause of death. The lipids were extracted by the Folch extraction method and then separated by High Performance Thin Layer Chromatography. These techniques gave excellent separation and resolution. Results showed no link between cause of death and the type of lipids found in the brainstem after death.
Date: December 1982
Creator: Schrynemeeckers, Patrick J.

Calcium Aluminates Synthesis, Characterization, and Hydration Behavior

Description: The hydration behavior of the calcium aluminates as a function of the glass content, the curing temperature, and the water-solid ratio was investigated. In order to keep them from influencing the results, the free-lime content and the surface area of all samples were kept constant, whenever possible. Samples were hydrated with a water-solid ratio of 10/1 for periods of 1 to 90 days. Three curing temperatures were studied; 2°C, 25°C, and 50°C. Samples were hydrated in tightly sealed polyethylene containers to prevent reactions with atmospheric carbon dioxide. The hydration was followed by X-ray diffraction and thermal analysis. Only two samples, Hexacalcium Tetra-alumino Magnesium Silicate and Tricalcium Magnesium Dialuminate, were successfully prepared in an amorphous form. These compounds were used to investigate the effect of glass content on the hydration behavior. Results indicate that when the glass content is increased a corresponding increase is found in the percent combined water. Samples hydrated at 25°C were influenced by changes in the glass content to a greater degree than were those hydrated at either 2°C or 50°C. The effect of the water-solid ratio on the hydration behavior of the calcium aluminates was studied using the compounds; Hexacalcium Tetra-Alumino Magnesium Silicate/ and Dodecacalcium Hepta-Aluminate. In general, samples that were hydrated with large water-solid ratios reacted more completely than did those hydrated with small water-solid ratios. The presence of sufficient water to theoretically hydrate the samples to completion did not guarantee that the sample would do so. The curing temperature influenced the hydration behavior to a greater degree than did the glass content or the water-solid ratio. Increasing the curing temperature not only increased the rate of hydration, but, in some cases, also changed the hydration products.
Date: December 1984
Creator: Griffin, Joseph George

Calcium Silicates: Glass Content and Hydration Behavior

Description: Pure, MgO doped and B2C3 doped monocalcium, dicalcium, and tricalcium silicates were prepared with different glass contents. Characterization of the anhydrous materials was carried out using optical microscopy, infrared absorption spectroscopy, and X-ray powder diffraction. The hydration of these compounds was studied as a function of the glass contents. The hydration studies were conducted at 25°C. Water/solid ratios of 0.5, 1, 10, and 16 were used for the various experiments. The hydration behavior was monitored through calorimetry, conductometry, pH measurements, morphological developments by scanning electron microscopy, phase development by X-ray powder diffraction, and percent combined water by thermogravimetry. A highly sensitive ten cell pseudo-adiabatic microcalorimeter was designed and constructed for early hydration studies. Conductometry was found to be of great utility in monitoring the hydration of monocalcium silicate and the borate doped dicalcium silicates.
Date: August 1987
Creator: Zgambo, Thomas P. (Thomas Patrick)

A Carbon-13 and Lithium-6 NMR Study of Alkyllithium Compounds

Description: A variable temperature 13C and 6Li NMR study has been conducted for 6Li-enriched ethyl-, n-propyl-, isopropyl-, n-butyl-, isobutyl-, t-butyl--, isopentyl-, 2-ethylbutyl-, and n-hexyllithium in cyclopentane. Significant differences in the 13C NMR parameters are observed as a function of the alkyl group and temperature. These changes are compared to the 6Li spectra and explained in terms of the aggregates present. 13C-6Li coupling is readily observed in both the 13 6 C and Li spectra of compounds which contain branching at either the alpha or beta carbons of the alkyl group. This coupling has been used to identify the aggregates present in solution and to identify the fluxional behavior of these aggregates.
Date: December 1983
Creator: Jensen, Randy M.

Carbon Nanostructure Based Donor-acceptor Systems for Solar Energy Harvesting

Description: Carbon nanostructure based functional hybrid molecules hold promise in solarenergy harvesting. Research presented in this dissertation systematically investigates building of various donor-acceptor nanohybrid systems utilizing enriched single walled carbon nanotube and graphene with redox and photoactive molecules such as fullerene, porphyrin, and phthalocyanine. Design, synthesis, and characterization of the donor-acceptor hybrid systems have been carefully performed via supramolecular binding strategies. Various spectroscopic studies have provided ample information in terms of establishment of the formation of donor-acceptor hybrids and their extent of interaction in solution and eventual rate of photoinduced electron and/or energy transfer. Electrochemical studies enabled construction of energy level diagram revealing energetic details of the possible different photochemical events supported by computational studies carried out to establish the HOMO-LUMO levels in the donor acceptor systems. Transient absorption studies confirmed formation of charge separated species in the donor-acceptor systems which have been supported by electron mediation experiments. Based on the photoelectrochemical studies, IPCE of 8% was reported for enriched SWCNT(7,6)-ZnP donor-acceptor systems. In summary, the present investigation on the various nanocarbon sensitized donor-acceptor hybrids substantiates tremendous prospect, that could very well become the next generation of materials in building efficient solar energy harvesting devices andphotocatalyst.
Date: December 2013
Creator: Das, Sushanta Kumar

Catalytic Calcination of Calcium Carbonate

Description: The calcination of calcium carbonate in a cement or a lime kiln uses approximately two to four times the theoretical quantity of energy predicted from thermodynamic calculation depending upon the type of the kiln used (1.4 x 10^6 Btu/ton theoretical to 6 x 10^6 Btu/ton actual). The objective of this research was to attempt to reduce the energy required for the calcination by 1. decreasing the calcination temperature of calcium carbonate, and/or 2. increasing the rate of calcination at a specific temperature. Assuming a catalytic enhancement of 20 percent in the industrial applications, an energy savings of 300 million dollars annually in the United States could be reached in the cement and lime industries. Three classes of compounds to date have shown a positive catalytic effect on the calcination of calcium carbonate. These include alkali halides, phospho- and silico-molybdate complexes, and the fused carbonates system.
Date: August 1985
Creator: Safa, Ali Ibrahim, 1953-

Characterization of Aprotic Solutes and Solvents using Abraham Model Correlations

Description: Experimental data were obtained for the computation of mole fraction solubilities of three dichloronitrobenzenes in organic solvents at 25oC, and solubility ratios were obtained from this data. Abraham model equations were developed for solutes in tributyl phosphate that describe experimental values to within 0.15 log units, and correlations were made to describe solute partitioning in systems that contain either "wet" or "dry" tributyl phosphate. Abraham model correlations have also been developed for solute transfer into anhydrous diisopropyl ether, and these correlations fit in well with those for other ethers. Abraham correlations for the solvation of enthalpy have been derived from experimental and literature data for mesitylene, p-xylene, chlorobenzene, and 1,2-dichlorobenzene at 298.15 K. In addition, the enthalpy contribution of hydrogen bonding between these solutes and acidic solvents were predicted by these correlations and were in agreement with an established method. Residual plots corresponding to Abraham models developed in all of these studies were analyzed for trends in error between experimental and calculated values.
Date: December 2016
Creator: Brumfield, Michela Lynne

Characterization of Ionic Liquid Solvents Using a Temperature Independent, Ion-Specific Abraham Parameter Model

Description: Experimental data for the logarithm of the gas-to-ionic liquid partition coefficient (log K) have been compiled from the published literature for over 40 ionic liquids over a wide temperature range. Temperature independent correlations based on the Gibbs free energy equation utilizing known Abraham solvation model parameters have been derived for the prediction of log K for 12 ionic liquids to within a standard deviation of 0.114 log units over a temperature range of over 60 K. Temperature independent log K correlations have also been derived from correlations of molar enthalpies of solvation and molar entropies of solvation, each within standard deviations of 4.044 kJ mol-1 and 5.338 J mol-1 K-1, respectively. In addition, molar enthalpies of solvation and molar entropies of solvation can be predicted from the Abraham coefficients in the temperature independent log K correlations to within similar standard deviations. Temperature independent, ion specific coefficients have been determined for 26 cations and 15 anions for the prediction of log K over a temperature range of at least 60 K to within a standard deviation of 0.159 log units.
Date: December 2014
Creator: Stephens, Timothy W.