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  Partner: UNT Libraries
 Degree Discipline: Chemistry
 Collection: UNT Theses and Dissertations
1-(4, 4'-Dinitrodiphenylmethyl)-Piperidines; 1-(4-Nitrobenzyl)-and 1-(4-Nitrobenzoyl)-Piperdines
This study experiments with the methods of 1-(4, 4'-Dinitrodiphenylmethyl)-Piperidines; 1-(4-Nitrobenzyl)-and 1-(4-Nitrobenzoyl)-Piperdines. digital.library.unt.edu/ark:/67531/metadc107844/
2-Dialkylaminoethyl Ketals of Benzophenone; the Attempted Synthesis of some Heterocyclic Sulfones
This thesis describes two experiments: one related to antihistamines, and the other related to antitubercular compounds. digital.library.unt.edu/ark:/67531/metadc83523/
α-(4-Aminophenylsulfonyl)-Acetophenone Derivatives; N-Diphenylmethyl and N-Fluorenyl Piperidines
This thesis is a study of α-(4-aminophenylsulfonyl)-acetophenone derivatives; n-diphenylmethyl and n-fluorenyl piperidines. digital.library.unt.edu/ark:/67531/metadc83593/
Addition Reactions of Some Aromatic Aldazines
The paper explores the conclusion that the addition compound was bicyclic, and that the addition of each of the two moles of cyanic acid was dependent upon the other. digital.library.unt.edu/ark:/67531/metadc163840/
Adhesion/diffusion barrier layers for copper integration: carbon-silicon polymer films and tantalum substrates
The Semiconductor Industry Association (SIA) has identified the integration of copper (Cu) with low-dielectric-constant (low-k) materials as a critical goal for future interconnect architectures. A fundamental understanding of the chemical interaction of Cu with various substrates, including diffusion barriers and adhesion promoters, is essential to achieve this goal. The objective of this research is to develop novel organic polymers as Cu/low-k interfacial layers and to investigate popular barrier candidates, such as clean and modified tantalum (Ta) substrates. Carbon-silicon (C-Si) polymeric films have been formed by electron beam bombardment or ultraviolet (UV) radiation of molecularly adsorbed vinyl silane precursors on metal substrates under ultra-high vacuum (UHV) conditions. Temperature programmed desorption (TPD) studies show that polymerization is via the vinyl groups, while Auger electron spectroscopy (AES) results show that the polymerized films have compositions similar to the precursors. Films derived from vinyltrimethyl silane (VTMS) are adherent and stable on Ta substrates until 1100 K. Diffusion of deposited Cu overlayers is not observed below 800 K, with dewetting occurred only above 400 K. Hexafluorobenzene moieties can also be incorporated into the growing film with good thermal stability. Studies on the Ta substrates demonstrate that even sub-monolayer coverages of oxygen or carbide on polycrystalline Ta significantly degrade the strength of Cu/Ta chemical interactions, and affect the kinetics of Cu diffusion into bulk Ta. On clean Ta, monolayer coverages of Cu will de-wet only above 600 K. A partial monolayer of adsorbed oxygen (3L O2 at 300 K) results in a lowering of the de-wetting temperature to 500 K, while saturation oxygen coverage (10 L O2, 300 K) results in de-wetting at 300 K. Carbide formation also lowers the de-wetting temperature to 300 K. Diffusion of Cu into the Ta substrate at 1100 K occurs only after a 5-minute induction period. This induction period increases to 10 min for partially oxidized Ta, 15 min for carbidic Ta and 20 min for fully oxidized Ta. digital.library.unt.edu/ark:/67531/metadc2255/
The Adsorption of Radioactive Isotopes on Precipitates
This thesis concerns the investigation of radioisotopes as indicators for precipitation reactions. As a precipitate forms in the presence of a radioisotope, adsorption may take place on its surface. If this adsorption changes markedly at the stoichiometric point it will be possible to use this variation as an indicator for the reaction. digital.library.unt.edu/ark:/67531/metadc130352/
The Adsorption of Radioactive Isotopes on Specific Precipitates
The purpose of this investigation is to reveal the effects of certain factors affecting adsorption on some specific precipitates. It is hoped that the choice of precipitate types will enable extension of the information gained here to other precipitates similar to those investigated. digital.library.unt.edu/ark:/67531/metadc130408/
Aldohaloketenes and the Stereochemistry of Aldohaloketene Cycloadditions
The objective of this research problem was to synthesize aldohaloketenes and investigate the chemistry of this new class of ketenes. digital.library.unt.edu/ark:/67531/metadc164399/
Amine Derivatives of 3-chloro-5(8?)-nitro-1,4-naphthoquinone
This work deals with the preparation of amine derivatives of 3-chloro-5(8?)-nitro-1,4-naphthoquinone which are to be tested for anti-tubercular activity by Parke, Davis and Company. digital.library.unt.edu/ark:/67531/metadc130300/
Amino Acid Complexes of Rhodium(III)
This thesis will explore and study rhodium, a group VIII element that has rarely been studied. digital.library.unt.edu/ark:/67531/metadc130648/
a-Amino Alcohol Derivatives of Methyl P-Nitrophenyl Acetate
This thesis describes the synthesis of a series of dialkylaminoalkoxy derivatives of methyl p-nitrophenylacetate for testing as anti-histamine or hay fever drugs. digital.library.unt.edu/ark:/67531/metadc75629/
An analysis of the effectiveness of computer assisted instruction in general chemistry at an urban university.
The science-major General Chemistry sequence offered at the University of Houston has been investigated with respect to the effectiveness of recent incorporation of various levels of computer technology. As part of this investigation, questionnaire responses, student evaluations and grade averages and distributions from up to the last ten years have been analyzed and compared. Increased use of web-based material is both popular and effective, particularly with respect to providing extra information and supplemental questions. Instructor contact via e-mail is also well-received. Both uses of technology should be encouraged. In contrast, electronic classroom presentation is less popular. While initial use may lead to improved grades and retention, these levels decrease quickly, possibly due to a reduction in instructor spontaneity. digital.library.unt.edu/ark:/67531/metadc3129/
An Application of the Reformatsky Reaction to the Thiophene Series of Compounds
In view of the increasing importance of thiophene derivatives as chemotherapeutic agents, it was considered of interest to apply the Reformatsky reaction to the synthesis of compounds containing the thiophene nucleus with the thought that these might serve as intermediates for further syntheses. digital.library.unt.edu/ark:/67531/metadc83566/
Applications of nanomanipulation coupled to nanospray mass spectrometry in trace fiber analysis and cellular lipid analysis.
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. digital.library.unt.edu/ark:/67531/metadc9760/
An Approach Towards the Total Synthesis of Clonostachydiol
The syntheses of the unsymmetrical 14-membered bismacrolides have been reviewed. A total synthesis of clonostachydiol, the latest to join this family, has been attempted using trimethylsilyl acetylene as the builiding block and palladium catalyzed reactions for the formation of key bonds. The alkyne groups were introduced by Stille coupling of trimethylstannylethynyltrimethylsilane with an acid chloride for one fragment and by addition of lithiotrimethylsilyl acetylene to an aldehyde for the other. Lactic acid derivatives were chosen as starting materials for both fragments, thus introducing two of the chiral centers. The remaining stereocenters were introduced using stereoselective reductions of ketones. digital.library.unt.edu/ark:/67531/metadc278800/
Aromatic Amino Acid Studies
Pyridine ring analogs of the aromatic amino acids phenylalanine and tyrosine were synthesized and studied in microbiological and mammalian systems. digital.library.unt.edu/ark:/67531/metadc164455/
The Ascorbic Acid Metabolism of Fifty College Women in the North Texas State Teachers College
A study of the ascorbic acid metabolism of a group of fifty college women in the North Texas State Teachers College between the months of April and July, 1943. digital.library.unt.edu/ark:/67531/metadc75486/
Attempted Synthesis of 5,5-di(2-thienyl)barbituric acid
This study is an attempted synthesis of dithienyl barbituric acid. digital.library.unt.edu/ark:/67531/metadc75364/
Attempted Synthesis of 5-Allyl-5-(2-Thienyl)-Barbituric Acid
This thesis describes attempts to synthesize 5-allyl-5-(2-thienyl)-barbituric acid as an improved anticonvulsant. digital.library.unt.edu/ark:/67531/metadc75643/
Baeyer-Villiger Oxidation of 1,7- & 1,9-dibromopentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione
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Baeyer-Villiger oxidation of 1,9-dibromopentacyclo[5.4.0.02,6.03,10.05,9]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. digital.library.unt.edu/ark:/67531/metadc4471/
Barbituric Acids as Anticonvulsants. IV. 5-Substituted-Mercapto Derivatives of 5-Phenylbarbituric Acids.
This study involves compounds of the barbituric acid series are well known for their use as anesthetics and sedatives. digital.library.unt.edu/ark:/67531/metadc97052/
Barbituric Acids. VI. 5-substituted-mercapto Derivatives of 5-ethylbarbituric Acid
The reaction of 5-bromo-5-ethylbarbituric acid with mercaptan and pyridine in cold ether solution was studied and was found to be satisfactory for the preparation of the compounds reported in this work. digital.library.unt.edu/ark:/67531/metadc130369/
Barbituric Acids. VII. 5-alkyl-derivatives of 5-ethoxy-barbituric Acid
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. digital.library.unt.edu/ark:/67531/metadc130416/
Barbituric Acids. VIII. 5-substituted-5-(1-pyrrolidyl)barbituric Acids
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. digital.library.unt.edu/ark:/67531/metadc107955/
Barbituric Acids. V. 5-substituted-mercapto Derivatives of 5-isoamylbarbituric Acid
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. digital.library.unt.edu/ark:/67531/metadc163823/
Base Effects on the Thermal Decomposition of Sec-butyllithium Solutions
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. digital.library.unt.edu/ark:/67531/metadc130677/
Biological Inhibitors
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. digital.library.unt.edu/ark:/67531/metadc164532/
Bis Ammonium Salts of Dialkylaminoalkoxypropionitriles
This paper concerns the preparation of some bis derivatives of dialkylaminoalkoxypropionitirles from trimethylene, hexamethylene, octomethylene, and decamethylene bromides. These compounds are to be tested for curariform activity and anesthetic values by Parke, Davis and Company. digital.library.unt.edu/ark:/67531/metadc107980/
Bonding Studies in Group IV Substituted n,n-dimethylanilines
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. digital.library.unt.edu/ark:/67531/metadc164513/
Bonding Studies on Organolithium Compounds
This study is concerned with the nature of the relatively unusual bonding which occurs in organolithium compounds as a direct result of the oligomerization and possible explanations for that bonding. digital.library.unt.edu/ark:/67531/metadc131022/
Characterization of Ionic Liquid As a Charge Carrier for the Detection of Neutral Organometallic Complexes Using Electrospray Ionization Mass Spectrometry
A novel application of ionic liquid as a charge carrier for the analysis and detection of neutral organometallic complexes using a mass spectrometer has been presented. The mass spectrometer detects only charged compounds which raise a difficulty in analyzing a neutral molecule that lacks a basic site to associate with charge. Therefore, an effective way of providing charge has always been an area of keen interest in the field of mass spectrometry. Ionic liquids have a very fascinating property of forming a cation-? interaction with other molecules to give a charged complex. In order to take advantage of this, it is important to know the geometric structure of the complex. Advanced methodologies like hydrogen-deuterium exchange and computational calculations have been used assisting in better understanding of the structure of the ionic liquid complexes. digital.library.unt.edu/ark:/67531/metadc149615/
Characterization of Low Barrier Hydrogen Bonds in Enzyme Catalysis: an Ab Initio and DFT Investigation
Hartree-Fock, Moller-Plesset, and density functional theory calculations have been carried out using 6-31+G(d), 6-31+G(d,p) and 6-31++G(d,p) basis sets to study the properties of low-barrier or short-strong hydrogen bonds (SSHB) and their potential role in enzyme-catalyzed reactions that involve proton abstraction from a weak carbon-acid by a weak base. Formic acid/formate anion, enol/enolate and other complexes have been chosen to simulate a SSHB system. These complexes have been calculated to form very short, very short hydrogen bonds with a very low barrier for proton transfer from the donor to the acceptor. Two important environmental factors including small amount of solvent molecules that could possibly exist at the active site of an enzyme and the polarity around the active site were simulated to study their energetic and geometrical influences to a SSHB. It was found that microsolvation that improves the matching of pK as of the hydrogen bond donor and acceptor involved in the SSHB will always increase the interaction of the hydrogen bond; microsolvation that disrupts the matching of pKas, on the other hand, will lead to a weaker SSHB. Polarity surrounding the SSHB, simulated by SCRF-SCIPCM model, can significantly reduce the strength and stability of a SSHB. The residual strength of a SSHB is about 10--11 kcal/mol that is still significantly stable compared with a traditional weak hydrogen bond that is only about 3--5 kcal/mol in any cases. These results indicate that SSHB can exist under polar environment. Possible reaction intermediates and transition states for the reaction catalyzed by ketosteroid isomerase were simulated to study the stabilizing effect of a SSHB on intermediates and transition states. It was found that at least one SSHB is formed in each of the simulated intermediate-catalyst complexes, strongly supporting the LBHB mechanism proposed by Cleland and Kreevoy. Computational results on the activation energy for catalyzed and uncatalyzed model reactions shows that strong hydrogen bonding between catalyst and the substrate at the transition state can significantly reduce the activation energy. This implies that LBHBs are possibly playing a crucial role in enzyme catalysis by supplying significant stabilizing energy to the reaction transition state. digital.library.unt.edu/ark:/67531/metadc278586/
A Chemical Analysis of Soft Wheat
The purpose of this piece of research is to determine the chemical composition of soft winter wheat, and to make a comparative study of it. A study is also made concerning its possibilities as a balanced food. digital.library.unt.edu/ark:/67531/metadc70273/
A Chemical Analysis of the Blackeyed Pea
The purpose of this research problem is to determine the chemical composition of the blackeyed pea and to make a comparative study of the results. The value of the blackeyed pea as food, its chemical nature, and possible industrial uses are studied and recorded. digital.library.unt.edu/ark:/67531/metadc70288/
Chemical Analysis of the Bottom Deposits of Artificial Lakes with Special Emphasis on Lake Dallas
This study is for the purpose of determining the chemical content of typical artificial reservoir bottom deposits. digital.library.unt.edu/ark:/67531/metadc70267/
The Chemical Analysis of the Mebane Cottonseed Kernel
The purpose of this work is to make a fairly complete chemical analysis of the Mebane 804-50 cottonseed kernel. A brief history of cotton plant and the economic value of its products are also presented. digital.library.unt.edu/ark:/67531/metadc70290/
A Chemical Analysis of the Peanut
The object of this paper is to make an analysis of the mineral and food content of the peanut and to compare them with a balanced food. digital.library.unt.edu/ark:/67531/metadc83334/
The Chemical Analysis of the Tennessee Green Pod Pole Bean
The object of this paper is to compare the Tennessee green pod pole bean with other beans as to chemical composition and food value. digital.library.unt.edu/ark:/67531/metadc75306/
Chemical Equilibria in Binary Solvents
Dissertation research involves development of Mobile Order Theory thermodynamic models to mathematically describe and predict the solubility, spectral properties, protonation equilibrium constants and two-phase partitioning behavior of solutes dissolved in binary solvent mixtures of analytical importance. Information gained provide a better understanding of solute-solvent and solvent-solvent interactions at the molecular level, which will facilitate the development of better chemical separation methods based upon both gas-liquid and high-performance liquid chromatography, and better analysis methods based upon complexiometric and spectroscopic methods. Dissertation research emphasizes chemical equilibria in systems containing alcohol cosolvents with the understanding that knowledge gained will be transferable to more environmentally friendly aqueous-organic solvent mixtures. digital.library.unt.edu/ark:/67531/metadc278936/
A Chemical, Physical, and Biological Investigation of the Total Suspended and Dissolved Substances in Lake Dallas with Emphasis on Sanitation
The purpose of this investigation is to determine the suspended organic matter and the total phosphorus in the waters of Lake Dallas and to evaluate these findings. Since organic matter floating in lakes is largely composed of minute plants, animals, and detritus derived from animals and plants, the fertilizing effect of phosphorus must be considered as an integral part of this problem. digital.library.unt.edu/ark:/67531/metadc75354/
Chlorination of Neohexane
This thesis describes an experiment to chorinate neohexane, and the resulting compounds. digital.library.unt.edu/ark:/67531/metadc53517/
Comparison of Homework Systems (Four Web-Based) used in First-Semester General Chemistry
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. digital.library.unt.edu/ark:/67531/metadc9858/
A Comparison of the Achievements of Science and Non-Science Majors Enrolled in General Chemistry at North Texas State College
It is the specific purpose of this investigation to determine the difference, if any, in the amount of practical, everyday chemistry learned by the science majors as opposed to the non-science majors enrolled in general chemistry at the North Texas State College during the school year 1950-1951. digital.library.unt.edu/ark:/67531/metadc96990/
Computational studies of bonding and phosphorescent properties of group 12 oligomers and extended excimers.
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. digital.library.unt.edu/ark:/67531/metadc9108/
Computational studies of selected ruthenium catalysis reactions.
Computational techniques were employed to investigate pathways that would improve the properties and characteristics of transition metal (i.e., ruthenium) catalysts, and to explore their mechanisms. The studied catalytic pathways are particularly relevant to catalytic hydroarylation of olefins. These processes involved the +2 to +3 oxidation of ruthenium and its effect on ruthenium-carbon bond strengths, carbon-hydrogen bond activation by 1,2-addition/reductive elimination pathways appropriate to catalytic hydrogen/deuterium exchange, and the possible intermediacy of highly coordinatively unsaturated (e.g., 14-electron) ruthenium complexes in catalysis. The calculations indicate a significant decrease in the Ru-CH3 homolytic bond dissociation enthalpy for the oxidation of TpRu(CO)(NCMe)(Me) to its RuIII cation through both reactant destabilization and product stabilization. This oxidation can thus lead to the olefin polymerization observed by Gunnoe and coworkers, since weak RuIII-C bonds would afford quick access to alkyl radical species. Calculations support the experimental proposal of a mechanism for catalytic hydrogen/deuterium exchange by a RuII-OH catalyst. Furthermore, calculational investigations reveal a probable pathway for the activation of C-H bonds that involves phosphine loss, 1,2-addition to the Ru-OH bond and then reversal of these steps with deuterium to incorporate it into the substrate. The presented results offer the indication for the net addition of aromatic C-H bonds across a RuII-OH bond in a process that although thermodynamically unfavorable is kinetically accessible. Calculations support experimental proposals as to the possibility of binding of weakly coordinating ligands such as dinitrogen, methylene chloride and fluorobenzene to the "14-electron" complex [(PCP)Ru(CO)]+ in preference to the formation of agostic Ru-H-C interactions. Reactions of [(PCP)Ru(CO)(1-ClCH2Cl)][BAr'4] with N2CHPh or phenylacetylene yielded conversions that are exothermic to both terminal carbenes and vinylidenes, respectively, and then bridging isomers of these by C-C bond formation resulting from insertion into the Ru-Cipso bond of the phenyl ring of PCP. The QM/MM and DFT calculations on full complexes [(PCP)(CO)Ru=(C)0,1=CHPh]+ and on small models [(PCP')(CO)Ru=(C)0,1=CH2]+, respectively, offered data supportive of the thermodynamic feasibility of the suggested experimental mechanisms and their proposed intermediates. digital.library.unt.edu/ark:/67531/metadc5203/
Computational Study of Small Molecule Activation via Low-Coordinate Late First-Row Transition Metal Complexes
Methane and dinitrogen are abundant precursors to numerous valuable chemicals such as methanol and ammonia, respectively. However, given the robustness of these substrates, catalytically circumventing the high temperatures and pressures required for such transformations has been a challenging task for chemists. In this work, computational studies of various transition metal catalysts for methane C-H activation and N2 activation have been carried out. For methane C-H activation, catalysts of the form LnM=E are studied, where Ln is the supporting ligand (dihydrophosphinoethane or β-diketiminate), E the activating ligand (O, NCH3, NCF3) at which C-H activation takes place, and M the late transition metal (Fe,Co,Ni,Cu). A hydrogen atom abstraction (HAA) / radical rebound (RR) mechanism is assumed for methane functionalization (CH4 à CH3EH). Since the best energetics are found for (β-diket)Ni=O and (β-diket)Cu=O catalysts, with or without CF3 substituents around the supporting ligand periphery, complete methane-to-methanol cycles were studied for such systems, for which N2O was used as oxygen atom transfer (OAT) reagent. Both monometallic and bimetallic OAT pathways are addressed. Monometallic Fe-N2 complexes of various supporting ligands (LnFe-N2) are studied at the beginning of the N2 activation chapter, where the effect of ligand on N2 activation in end-on vs. side-on N2 isomers is discussed. For (β-diket)Fe-N2 complexes, the additional influence of diketiminate donor atom (N(H) vs. S) is briefly addressed. The remainder of the chapter expands upon the treatment of β-diketiminate complexes. First, the activation and relative stabilities of side-bound and end-bound N2 isomers in monometallic ((β-diket)M-N2) and bimetallic ((β-diket)M-N2-M(β-diket)) first row transition metal complexes are addressed. Second, the thermodynamics of H/H+/H- addition to (β-diket)Fe-bound N2, followed by subsequent H additions up to release of ammonia, is discussed, for which two mechanisms (distal and alternating) are considered. Finally, the chapter concludes with partial distal and alternating mechanisms for H addition to N2 in bimetallic (β-diket)Fe-N2-Fe(β-diket) and (β-diket)M-N2-M(β-diket) (M = Ti,V,Fe), respectively. digital.library.unt.edu/ark:/67531/metadc28462/
A Computational Study on 18+δ Organometallics
The B3LYP density functional has been used to calculate properties of organometallic complexes of Co(CO)3 and ReBr(CO)3, with the chelating ligand 2,3-bisphosphinomaleic anhydride, in 19- and 18-electron forms. The SBKJC-21G effective core potential and associated basis set was used for metals (Co/Re) and the 6-31G* basis set was used for all other elements. The differences of bond angles, bond distances, natural atomic charges and IR vibrational frequencies were compared with the available experimental parameters. The differences between the 19- and 18-electron systems have been analyzed. The results reveal that the 19th electron is mostly distributed over the ligand of 2,3-bisphosphinomaleic anhydride, although partially localized onto the metal fragment in 1 and 2*. Two different methods, IR-frequencies and natural atomic charges, were used to determine the value of δ. Present computed values of δ are compared with available experimental values, and predictions are made for unknown complexes. digital.library.unt.edu/ark:/67531/metadc3101/
Conformational Analogs of Some Phytoactive Compounds
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. digital.library.unt.edu/ark:/67531/metadc279187/
Conformationally Stable Cyclohexyllithium Compounds
Organolitnium compounds have been employed in synthetic worK for many years. However only during the last decade has much progress been made in establishing the mechanistic pathways for the reactions of these compounds. digital.library.unt.edu/ark:/67531/metadc164279/
Corrosion Inhibition with Quaternary Amines
This thesis describes experiments made to test the corrosion inhibition of quaternary amines on steel. digital.library.unt.edu/ark:/67531/metadc131169/
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