Browsing by Subject "Chromium"
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Item A study of the thermal decomposition of some chromium (III) and cobalt (III) ammine complexes(Texas Tech University, 1960-08) Bear, John LaRueNot availableItem Chromium-Catalyzed Homoaldol Equivalent Reaction, Indium-Mediated Cycloisomerization, and Palladium-Catalyzed Cross-Coupling Reaction(2011-10-21) Kang, JunThe homoaldol reaction is one of the most powerful methods for the construction of C?C bonds as well as 1,4-oxygenated compounds yet this reaction remains in challenging tasks due to the instability of homoenolates which spontaneously cyclize to the cyclopropanolate. A regioselective catalytic homoaldol equivalent reaction of 3-bromo vinyl acetate with aldehydes under Cr(III)-Mn(0) redox condition was developed. This homoaldol equivalent reaction allows access to the 1,4-oxygenated compounds that are not possible by a conventional aldol process. Mild hydrolysis of the vinyl acetate and reduction of the homoaldol adducts generated diols and lactols in high yield (99%). Further manipulation including stereoselective epoxidation and cyclopropanation was achieved in an efficient manner. Furans, found in many natural products and utilized in drug discovery, have been well studied but current synthetic methods toward furans have some limitations in functional group tolerance, substrate scope, and low product yield in many cases. A highly efficient and catalytic cycloisomerization reaction that transforms acetylenic ?,?-epoxides to 2,3,5-tri-substituted furans under InCl3 catalysis was developed. This reaction sequence allows access to rapid construction of highly valuable, tri-substituted furan derivatives. Cross-coupling reactions utilizing transition metals and Lewis acids are important synthetic tools for the formation of C?C and C?N bonds and a number of cross-coupling reactions between ?-bromo carbonyl compounds and metal reagents such as aryl metals, alkenyl metals, and alkyl metals have been reported. Transition metal-catalyzed cross-coupling reaction for the construction of ?-alkynyl carbonyl compounds has reported in a limited case. The first approach to secondary ?-alkynyl carbonyl compounds from secondary ?-bromo esters and amides with tributyl(phenylethynyl)stannane under palladium-catalyzed cross-coupling reaction conditions was developed. This synthetic method allows access to secondary ?-alkynyl carbonyl compounds which are valuable precursors in pharmaceuticals and agricultural applications.Item Multidimensional instrumental analysis of wet-blue leather hydrolysate(Texas Tech University, 2002-12) Martinelango, ParamakalyaniThe U.S. leather industry generates more than 60,000 metric tons of chromium containing solid wastes every year, of which roughly half is attributed to chrome shavings. Much of these have been disposed in landfills. Owing to increasing environmental concern and a decrease in the number of disposal sites, extensive research has been done on the recovery of protein (collagen) and chromium from the shavings. The main objective of this work is to obtain a deeper insight into magnesium oxide (MgO) hydrolysis of chrome shavings and to look at newer ways of exploiting the products. Collagen hydrolysates are studied by various analytical techniques such as electrophoresis, chromatography and mass spectrometry. MgO hydrolysis produced fractions with molecular weight and charge heterogeneity as seen from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focusing (lEF), capillary zone electrophoresis (CZE) and reverse phase-high performance chromatography (RP-HPLC). Consistent and complementary results are obtained from electrophoresis and chromatography. We created a multidimensional analytical mediodology to acquire a thorough, molecular-level characterization of these hydrolysates. The enhanced resolution space provided by these different techniques yields definitive and the most complete results, to date. The results obtained in this work provide useful information on the characteristics of the hydrolysates. This information will be helpful to develop better value-added applications for the chrome shavings. Such value-added products create a demand for the chrome shavings that will keep them out of the landfill.Item Observation of fine structures in the k-alpha x-ray lines of chromium and cobalt(Texas Tech University, 1970-08) Shah, Saiyid Masroor,Not availableItem Observation of Fine Structures of X-Ray Lines in Some Transition Elements(Texas Tech University, 1971-08) Priest, John FinleyNot Available.Item Perturbations of the homo level of oxo-bridged chromium(III) dimers(Texas Tech University, 1992-12) Tekut, Thomas FrancisNot availableItem The chemistry of oxo- and hydroxo-bridged chromium (III) dimers with aromatic amine ligands(Texas Tech University, 1989-08) Gafford, Boyd GlennThe chemistry of Cr(III) dimers with a linear oxygen bridge has seen a considerable amount of interest since the discovery of the (|l-oxo)bis pentaainminechromium(in)} (basic rhodo) dimer by Jorgensen (1882).i This interest is due to markedly different substitutional and spectral properties over those of simple Cr(in) monomers, a manifestation of the very different bonding that occurs as a result of the linear Cr-O-Cr unit. For example, the loss of NH3 in aqueous base from the basic rhodo cation occurs in just nainutes,^ whUe the loss of NH3 from Cr(NH3)53+ occurs over several days.^ In addition, the intense transitions in the UV-visible spectrum of the basic rhodo cation are in sharp contrast to the well known, very broad, weak d-d transitions seen in Cr(III) monomeric species.Item The thermal and photochemical dissociation of the tris (ethylenediamine) chromium (III) complexes(Texas Tech University, 1964-05) Stembridge, Charles HenryNot availableItem The thermal matrix reaction of some tris (diamine) chromium (III) complexes(Texas Tech University, 1966-05) Sveum, Larry KNot available