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The Vacuum Ultraviolet Spectra of Cyclohexane, Cyclohexene, 1,4-Cyclohexadiene, Isotetralin, and Several Methyl Substituted Analogs

Description: A paucity of literature exists on the Independent System analysis of adjacent, parallel transition dipoles. Applying this theory and certain spectral information semiemperical calculations were made to predict absorption profiles and band intensities. To aid in the assignment of the 7*+7 absorption bands it was necessary to obtain the vacuum ultraviolet spectra of cyclohexane and cyclohexene. Because the spectra of these molecules contained sharp, atomic-like absorption bands a Rydberg series could be fitted to certain absorptions, thus the determination of their ionization potentials. Using Independent System analysis profiles and intensities of 7*+q-- absorption bands ins 'several methyl substituted 1,4- cyclohexadienes and isotetralin were predicted where general agreement was found with observed experimental spectra.
Date: December 1974
Creator: Tidwell, Edgar Rhea
Partner: UNT Libraries

Synthesis and Study of Glutaryl-S-(ω-aminoalkyl)-L-cysteinylglycines as Inhibitors of Glyoxalase I

Description: This thesis describes the synthesis and preliminary enzymatic study of glutaryl-S-(8-aminooctyl)-L-cysteinylglycine and glutaryl-S-(10-aminodecyl)-L-cysteinylglycine as inhibitors of glyoxalase I. These analogs of glutathione were prepared as potential ligands for affinity chromatography purification of glyoxalase I. The compounds were synthesized by a seven-step procedure in overall yields of 24% for the octyl analog and 33% for the decyl analog. Both compounds exhibited mixed type inhibition of the enzyme, with the decyl derivative being more inhibitory than the octyl derivative. The inhibition was nonlinear (parabolic) for both compounds. Although less inhibitory than the corresponding S-substituted glutathione derivatives, these analogs are promising candidates for affinity chromatography ligands. Such compounds may also be useful in studying the mechanism of glyoxalase I.
Date: May 1975
Creator: Phillips, Gerald Wayne
Partner: UNT Libraries

Isozymes and In Vivo Activity of Triosephosphate Isomerase

Description: The distribution of isozymes of triosephosphate isomerase was normal in all human tissues examined. This finding argues against the existence of tissue-specific isozymes. Normal distributions of isozymes were also found in patients with cri-du-chat syndrome. Thus it is unlikely that a gene for triosephosphate isomerase is located on the short arm of chromosome five in man. When triosephosphate isomerases from a wide range of species were examined by starch gel electrophoresis, definite evolutionary patterns were found. Kinetic studies were conducted on human triosephosphate isomerase under conditions simulating the intracellular environment of the erythrocyte. Calculations using the kinetic parameters obtained indicate that even in triosephosphate isomerase deficiency disease, enough enzyme activity remains that the rate of glycolysis should not become inhibited.
Date: May 1974
Creator: Snapka, Robert Morris
Partner: UNT Libraries

Isolation and Characterization of Proteus vulgaris Methylglyoxal Synthetase

Description: Methylglyoxal synthetase, which catalyzes the formation of methylglyoxal and inorganic phosphate from dihydroxyacetone phosphate, was found in extracts of Proteus vulgaris. An efficient purification procedure utilizing ion exchange column chromatography and isoelectric focusing has been developed. Homogeneity of the enzyme preparation was confirmed by polyacrylamide gel electrophoresis and rechromatography.Two components of methylglyoxal synthetase were obtained upon isoelectric focusing. A comparison of the chemical and physical properties of the two components was carried out. The enzyme is a dimer. In the presence of inorganic phosphate, the hyperbolic saturation kinetics with dihydroxyacetone phosphate are shifted to sigmoidal.
Date: May 1975
Creator: Tsai, Pei-Kuo
Partner: UNT Libraries

Preparation of Pyridinium Derivatives of 2,3-Dichloro-5(8?)-Nitro-1,4-Naphthoquinone

Description: This paper describes the preparation of pyridine derivatives of 2,3-dichloro-5(8?)-nitro-1,4-naphthoquinone. A method for the nitration of 2,3-dichloro-1,4-naphthoquinone is also described. Certain 4-n-alkyl, 3,4-dialkyl, and 4-cycloalkyl pyridine derivatives are caused to undergo condensation reactions with the nitrated naphthoquinone, giving rise to a series of compounds of the preceding type (X). All of the compounds prepared will be tested for anti-tubercular activity by Parke-Davis and Company.
Date: 1955
Creator: Mahon, Frank
Partner: UNT Libraries

Metallization and Modification of Low-k Dielectric Materials

Description: Aluminum was deposited onto both Teflon AF and Parylene AF surfaces by chemical vapor deposition of trimethylaluminum. This work shows that similar thin film (100 Angstroms) aluminum oxide adlayers form on both polymers at the low temperature dosing conditions used in the studies. Upon anneal to room temperature and above, defluorination of the polymer surfaces increased and resulted in fluorinated aluminum oxide adlayers; the adlayers were thermally stable to the highest temperatures tested (600 K). Angle-resolved spectra showed higher levels of fluorination toward the polymer/adlayer interface region. Copper films were also deposited at low temperature onto Teflon AF using a copper hexafluoroacetylacetonate-cyclooctadiene precursor. Annealing up to 600 K resulted in the loss of precursor ligands and a shift to metallic copper. As with aluminum adlayers, some polymer defluorination and resulting metal (copper) fluoride was detected. Parylene AF and polystyrene films surfaces were modified by directly dosing with water vapor passed across a hot tungsten filament. Oxygen incorporation into polystyrene occurred exclusively at aromatic carbon sites, whereas oxygen incorporation into parylene occurred in both aromatic and aliphatic sites. Oxygen x-ray photoelectron spectra of the modified polymers were comparable, indicating that similar reactions occurred. The surface oxygenation of parylene allowed enhanced reactivity toward aluminum chemical vapor deposition. Silicon-carbon (Si-Cx) films were formed by electron beam bombardment of trimethylvinylsilane films which were adsorbed onto metal substrates at low temperatures in ultra-high vacuum. Oxygen was also added to the films by coadsorbing water before electron beam bombardment; the films were stable to more than 700 K, with increasing silicon-oxygen bond formation at elevated temperatures. Copper metal was sputter deposited in small increments onto non-oxygenated films. X-ray photoelectric spectra show three-dimensional copper growth (rather than layer-by-layer growth), indicating only weak interaction between the copper and underlying films. Annealing at elevated temperatures caused coalescence or growth ...
Date: December 2008
Creator: Martini, David M.
Partner: UNT Libraries

Applications of Nanomanipulation Coupled to Nanospray Mass Spectrometry in Trace Fiber Analysis and Cellular Lipid Analysis.

Description: The novel instrumentation of nanomanipulation coupled to nanospray mass spectrometry and its applications are presented. The nanomanipulator has the resolution of 10nm step sizes allowing for specific fine movement used to probe and characterize objects of interest. Nanospray mass spectrometry only needs a minimum sample volume of 300nl and a minimum sample size of 300attograms to analyze an analyte making it the ideal instrument to couple to nanomanipulation. The nanomanipulator is mounted to an inverted microscope and consists of 4 nano-positioners; these nano-positioners hold end-effectors and other tools used for manipulation. This original coupling has been used to enhance the current abilities of cellular probing and trace fiber analysis. Experiments have been performed to demonstrate the functionality of this instrument and its capabilities. Histidine and caffeine have been sampled directly from single fibers and analyzed. Lipid bodies from cotton seeds have been sampled indirectly and analyzed. The few applications demonstrated are only the beginning of nanomanipulation coupled to nanospray mass spectrometry and the possible applications are numerous especially with the ability to design and fabricate new end-effectors with unique abilities. Future study will be done to further the applications in direct cellular probing including toxicology studies and organelle analysis of single cells. Further studies will be directed in forensic applications of this instrument including gunshot residue sampled from fibers.
Date: December 2008
Creator: Ledbetter, Nicole
Partner: UNT Libraries

Preparation of flat dendrimers and polycyclic aromatic hydrocarbons connected via 1,3,5-triethynylbenzene core.

Description: Flat dendrimers, consisting of a hexavalent aromatic core and rigid ethynyl units locked in place by ether connections were developed based upon the divergent synthetic method. Alternating functional groups were adopted on each site of the hexa-substituted benzene, in order to avoid undesired cyclization pathways. The flat structures of conjugated dendrimers would allow investigation on the discotic liquid crystal properties. In addition, these ethylnyl dendrimers are expected to show directed energy and electron transfer with a highly conjugated system, and thus are effective in the preparation of photoreactive materials such as electronic sensors or light harvesting materials. Conjugated polycyclic aromatic hydrocarbons, consisting of naphthalene, anthracene, pyrene, and phenanthrene groups connected via 1,3,5-triethynylbenzene cores, were synthesized. These molecules exhibited luminescence properties and the π-complexation with a mercury trifunctional lewis acid are expected to enhance the phosphorescence in the presence of the heavy metal due to the spin-orbit coupling. Besides, owing to the presence of heavy metal atom in the Au (I) complexes linked by s-bonded triethynyltriphenylene luminophore, the phosphorescence occurs from a metal-centered emission. The conjugated organic luminophores have been developed to produce excellent quantum efficiencies, brightness, and long lifetimes.
Date: December 2008
Creator: Jung, Jiyoung
Partner: UNT Libraries

Reducing the Computational Cost of Ab Initio Methods

Description: In recent years, advances in computer technology combined with new ab initio computational methods have allowed for dramatic improvement in the prediction of energetic properties. Unfortunately, even with these advances, the extensive computational cost, in terms of computer time, memory, and disk space of the sophisticated methods required to achieve chemical accuracy - defined as 1 kcal/mol from reliable experimental data effectively - limits the size of molecules [i.e. less than 10-15 non-hydrogen atoms] that can be studied. Several schemes were explored to help reduce the computational cost while still maintaining chemical accuracy. Specifically, a study was performed to assess the accuracy of ccCA to compute atomization energies, ionization potentials, electron affinities, proton affinities, and enthalpies of formation for third-row (Ga-Kr) containing molecules. Next, truncation of the correlation consistent basis sets for the hydrogen atom was examined as a possible means to reduce the computational cost of ab initio methods. It was determined that energetic properties could be extrapolated to the complete basis set (CBS) limit utilizing a series of truncated hydrogen basis sets that was within 1 kcal/mol of the extrapolation of the full correlation consistent basis sets. Basis set truncation for the hydrogen atom was then applied to ccCA in the development of two reduced basis set composite methods, ccCA(aug) and ccCA(TB). The effects that the ccCA(aug) and ccCA(TB) methods had upon enthalpies of formation and the overall percent disk space saved as compared to ccCA was examined for the hydrogen containing molecules of the G2/97 test suite. Additionally, the Weizmann-n (Wn) methods were utilized to compute the several properties for the alkali metal hydroxides as well as the ground and excited states of the alkali monoxides anion and radicals. Finally, a multi-reference variation to the correlation consistent Composite Approach [MR-ccCA] was presented and utilized in the computation ...
Date: August 2008
Creator: Mintz, Benjamin
Partner: UNT Libraries

Comparison of Homework Systems (Four Web-Based) used in First-Semester General Chemistry

Description: Web-based homework systems are becoming more common in general chemistry as instructors face ever-increasing enrollment. Yet providing meaningful feedback on assignments remains of the utmost importance. Chemistry instructors consider completion of homework integral to students' success in chemistry, yet only a few studies have compared the use of Web-based systems to the traditional paper-and-pencil homework within general chemistry. This study compares the traditional homework system to four different Web-based systems. Data from eight, semester classes consisting of a diagnostic pre-test, final semester grades, and the number of successful and unsuccessful students are analyzed. Statistically significant results suggest a chemistry instructor should carefully consider options when selecting a homework system.
Date: May 2009
Creator: Belland, Joshua
Partner: UNT Libraries

Molecular Dynamics and Interactions in Liquids

Description: 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.
Date: May 1985
Creator: Chen, Jen Hui
Partner: UNT Libraries

Computational Studies of Bonding and Phosphorescent Properties of Group 12 Oligomers and Extended Excimers.

Description: Density functional (ca, BLYP, BPW91, B3LYP and B3PW91), MP2 and CCSD(T) methods in combination with LANL2DZ or cc-pVxZ-PP (where x=D(double), T(triple) Q(quadruple), and 5(quintuple)) basis sets have been employed in computing electronic transition energies of zinc and cadmium monomers. CCSD(T)/aug-cc-pV5Z-PP combination finds values that are 150 cm-1 from the experimental value for the zinc monomer and 240 cm-1 remove from the cadmium monomer excitation experimental value. These method/basis set combinations are also used to find spectroscopic values (re, De, we, wexe, Be , and Te) that rival experimental values for dimers and excimers. Examples of this can be seen with the CCSD(T)/aug-cc-pV5Z-PP combination phosphorescent emission results. The values found are within 120 cm-1 of the zinc emission energy and 290 cm-1 of the cadmium emission energy. While this combination rigorously models spectroscopic constants for monomers, dimers, and excimers, it does not efficiently model these constants for larger clusters with available modern computational resources. It is important to show spectroscopic trends (bonding, phosphorescent excitation and emissions) as clusters increase as the monomer and dimer emission energies do not model solid state metallophilic interactions and phosphorescence. The MP2/LANL2DZ combinations show qualitative cooperative bonding trends in group oligomers and extended excimers as size increases and shape change. Changes in excitation and emission energies are also shown as a function of size and shape of the clusters.
Date: August 2008
Creator: Determan, John J.
Partner: UNT Libraries

Synthesis, characterization, and kinetics of isomerization, C-H and P-C bond activation for unsaturated diphosphine-coordinated triosmium carbonyl clusters.

Description: Substitution of MeCN ligands in the activated cluster Os3(CO)10(MeCN)2 by the unsaturated diphosphine ligands (Z)-Ph2PCH=CHPPh2 (cDPPEn) or 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) proceeds rapidly at room temperature to furnish the ligand-bridged cluster 1,2-Os3(CO)10(P-P) (P-P represents cDPPEn or bpcd). Heating 1,2-Os3(CO)10(P-P) leads to the formation of the thermodynamically more stable chelating isomer 1,1-Os3(CO)10(P-P). Each compound of Os3(CO)10(P-P) has been characterized by x-ray diffraction, IR, 31P NMR and 1H NMR. Ligand isomerization kinetics have been investigated by UV-VIS and 31P NMR (for cDPPEn) or 1H NMR (for bpcd) spectroscopies. The isomerization mechanism is discussed based on the activation parameters and CO inhibition (for cDPPEn) or ligand trapping experiments (for bpcd). Thermolysis of 1,1-Os3(CO)10(bpcd) in refluxing toluene gives the hydrido cluster HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] and the benzyne cluster HOs3(CO)8(μ3-C6H4)[μ2,η1-PPhC=C(PPh2)C(O)CH2C(O)]. Photolysis of 1,1-Os3(CO)10(bpcd) using near UV light affords HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] as the sole product. HOs3(CO)8(μ3-C6H4)[μ2,η1-PPhC=C(PPh2)C(O)CH2C(O)] has been characterized in solution by IR and NMR spectroscopies. Furthermore its molecular structure has been determined by X-ray crystallography. Reversible C-H bond formation in HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] is demonstrated by ligand trapping studies to give 1,1-Os3(CO)9L(bpcd) (where L = CO, phosphine) via the unsaturated intermediate 1,1-Os3(CO)9(bpcd). The kinetics for reductive coupling in HOs3(CO)9[γ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] and DOs3(CO)9[μ-(PPh2-d10)C=C{P(Ph-d5)(C6D4)}C(O)CH2C(O)] in the presence of PPh3 give rise to a kH/kD value of 0.88, whose magnitude supports the existence of a preequilibrium involving the hydride(deuteride) cluster and a transient arene-bound Os3 species that precedes the rate-limiting formation of 1,1-Os3(CO)9(bpcd). Strong proof for the proposed hydride(deuteride)/arene preequilibrium has been obtained from photochemical studies employing the isotopically labeled cluster 1,1-Os3(CO)10(bpcd-d4ortho), whose bpcd phenyl groups each contain one ortho hydrogen and deuterium atom. Equilibrium and kinetic isotope effects in the orthometallation step has been determined by 1H NMR in photochemical studies. Kinetics for the transformation from HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] to HOs3(CO)8(μ3-C6H4)[μ2,η1-PPhC=C(PPh2)C(O)CH2C(O)] has been studied by UV-VIS spectroscopy for which the mechanism is discussed.
Date: May 2008
Creator: Wu, Guanmin
Partner: UNT Libraries

Applications of Single Reference Methods to Multi-Reference Problems

Description: Density functional theory is an efficient and useful method of solving single-reference computational chemistry problems, however it struggles with multi-reference systems. Modifications have been developed in order to improve the capabilities of density functional theory. In this work, density functional theory has been successfully applied to solve multi-reference systems with large amounts of non-dynamical correlation by use of modifications. It has also been successfully applied for geometry optimizations for lanthanide trifluorides.
Date: May 2015
Creator: Jeffrey, Chris C.
Partner: UNT Libraries

Computational Studies of C–H/C–C Manipulation Utilizing Transition Metal Complexes

Description: Density Functional Theory (DFT) is an effective tool for studying diverse metal systems. Presented herein are studies of a variety of metal systems, which can be applied to accomplish transformations that are currently difficult/impossible to achieve. The specific topics studied utilizing DFT include: 1) C–H bond activation via an Earth-abundant transition metal complex, 2) C–H bond deprotonation via an alkali metal superbase, 3) and amination/aziridination reactions utilizing a CuI reagent. Using DFT, the transformation to methanol (CH3OH) from methane (CH4) was examined. The transition metal systems studied for this transformation included a model FeII complex. This first-row transition metal is an economical, Earth-abundant metal. The ligand set for this transformation includes a carbonyl ligand in one set of complexes as well as a phosphite ligand in another. The 3d Fe metal shows the ability to convert alkyls/aryls to their oxidized counterpart in an energetically favorable manner. Also, “superbasic” alkali metal amides were investigated to perform C—H bond cleavage. Toluene was the substrate of interest with Cs chosen to be the metal of interest because of the highly electropositive nature of this alkali metal. These highly electrophilic Cs metal systems allow for very favorable C—H bond scission with a toluene substrate. Finally, the amination and aziridination of C–H and C=C bonds, respectively, by a CuI reagent was studied. The mechanism was investigated using DFT calculations. Presently, these mechanisms involving the use of coinage metals are debated. Our DFT simulations shed some insight into how these transformations occur and ultimately how they can be manipulated.
Date: May 2015
Creator: Pardue, Daniel B.
Partner: UNT Libraries

Hydantoin Derivatives as Anticonvulsants. I. 5-Cyclohexylalkyl-5-(2-Thienyl)Hydantoins

Description: The study herein described represents a continuation of the work on 5-(2-thienyl)-5-substituted hydantoins which has been in progress in the laboratories of the North Texas State College for the past several years. It has for its purpose the study of the effect of lengthening the carbon chain connecting a cyclohexyl radical to 5-(2-thienyl)hydantoin in the 5- position.
Date: 1949
Creator: Baker, Andy Albert
Partner: UNT Libraries