Global ETD Search

1	Homogenous transition metal Zeevaart, Jacob 26 October 2006 (has links) Faculty of Science School of Chemistry 0100505x jzeevaart@csir.co.za / The application of homogenous transition metal catalysis to the arylation of enolates to develop new synthetic procedures which are more environmentally benign, atomefficient and economically viable than current methods was the motivation behind the current work. The specific choice of molecules with an aromatic group in the a- position of a ketone, carboxylic acid, amide or other electron-withdrawing group arose from the fact that many natural products, pharmaceutical actives and synthetic intermediates contain such a substructure while the syntheses of these substructures are often cumbersome. The application of homogenous catalysis to various types of enolates was explored and in the process several developments were achieved and discoveries made. These included the use of inorganic bases under phase transfer conditions for the Heck reaction of acrylic acid as well as the synthesis and application of phosphine and phosphite ligands in the Heck reaction of acrylic acid esters. The successful use of low palladium loadings (as low as 0.01mol%) in the arylation of diethyl malonate using aryl chlorides and the application to the synthesis of ketoprofen and phenobarbital was demonstrated. The novel application of palladium catalysis to the arylation of methanesulfonamides and the first example of a bromoindole derivative as the aryl halide partner in an enolate arylation reaction was demonstrated. Ligand-free palladium catalysed phenylation of pinacolone followed by Baeyer Villiger oxidation led to a proposed novel synthetic route to tert-butyl esters of 2-arylacetic acids. The palladium and copper catalysed arylation of acetoacetate esters, with in situ decarbonylation, provided a different route to 2-arylacetic acid esters which are useful in the preparation of non-steroidal anti-inflammatory compounds. Arylation Aryl Halide Bromobenzene Acetoacetate Enolate
2	The reactivity and selectivity of the reaction of sulfur trioxide and bromobenzene Blau, Sullivan E. 01 June 1970 (has links) The sulfonation of bromobenzene with sulfur trioxide in liquid sulfur dioxide at -12 to -13° C. was studied to determine its relative reactivity. The relative rate constant ratio, kbenzene/kbromobenzene, was found to be 28.6 in a competitive reaction between benzene and bromobenzene. The isomer distribution was found to be 0.15 ± 0.02% for the meta, 0.91 ± 0.04% for the ortho and 98.93 ± 0.14% for the para isomers. The partial rate factors were calculated to be pf= 0.208, of= 0.0096 and mf = 0.00018. The relative rate data exhibited a distinctive behaviour previously noted in related systems, possibly due to secondary reactions. Data, generated artiticially, which showed similar behaviour, indicate that possibly the primary and secondary reactions both produce the final products in competition with each other at significantly different selectivities. Sulphur trioside Bromobenzene Chemistry Physical Sciences and Mathematics
3	Attenuation of bromobenzene-induced hepatotoxicity by poly(adp-ribose) polymerase inhibitors Hall, Kelly Waggoner 01 June 2005 (has links) Previous studies have shown extensive cellular damage can activate poly(ADP-ribose) polymerase-1 (PARP-1) and cause a rapid decrease in the levels of NAD+ and ATP, thereby preventing apoptosis and promoting necrosis and inflammation. The purpose of this study was to extend previous observations that inhibitors of PARP-1 could alter acetaminophen and carbon tetrachloride-induced hepatotoxicity. Bromobenzene (BB) a glutathione dependent hepatotoxicant was tested. Groups of male mice were treated with a single dosage of 112mg/kg (0.075 ml/kg) BB by the intraperitoneal (ip) route. All animals were maintained in a controlled environment and provided food and water ad libitum. This dosage of BB resulted in hepatotoxicity as measured by an increase in serum alanine transferase (ALT). BB treatment resulted in a 5-fold increase in ALT. Moderate hepatotoxicity was detected with this treatment regime. Subsequently, another group of mice were treated with three treatments of nicotinamide at 0.5, 1 and 2 hours following BB treatment. Serum ALT elevations were reduced by 90% at 24 hours following BB and nicotinamide treatments. BB-induced liver pathology was also blocked by nicotinamide. Mortality among BB treated animals was also significantly reduced by nicotinamide treatment. Mortality among mice treated with BB and nicotinamide was near control. The model was verified with a more potent and specific inhibitor, Phen. BB treatment was keep at the same level as in the previous study, and Phen was administered concomitantly. Serum ALT elevations were reduced by 75%. Phen also blocked BB-induced liver pathology. Mortality among mice treated with BB and Phen was reduced 75%. PARP-1 inhibitors appear to alter chemical-induced hepatotoxicity that has either a glutathione dependent or independent mechanism. Poly(adp-ribose)polymerase Nicotinamide 6(5h)-phenanthridone Bromobenzene Hepatotoxicity American Studies Arts and Humanities
4	The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers Etchison, Kerry C. 08 1900 (has links) Two aluminum spherical mirrors with radii of 203.2 mm and radii of curvature also of 203.2 mm have been used to construct a tunable Fabry-Perót type resonator operational at frequencies as low as 500 MHz. The resonator has been incorporated into a pulsed nozzle, Fourier transform, Balle-Flygare spectrometer. The spectrometer is of use in recording low J transitions of large asymmetric molecules where the spectra are often greatly simplified compared to higher frequency regions. The resonators use is illustrated by recording the rotational spectra of bromobenzene and iodobenzene. In related experiments, using similar equipment, the pure rotational spectra of four isotopomers of SrS and all three naturally occurring isotopomers of the actinide-containing compound thorium monoxide have been recorded between 6 and 26 GHz. The data have been thoroughly analyzed to produce information pertaining to bond lengths and electronic structures. Microwave spectroscopy low frequency iodobenzene bromobenzene thorium Oxide Strontium Sulfide Diatomic molecules -- Spectra. Benzene -- Spectra.
5	Free Molecular and Metal Clusters Studied by Synchrotron Radiation Based Electron Spectroscopy Rosso, Aldana January 2008 (has links) The main purpose of this Thesis is the experimental characterization of the electronic and geometric structures of objects called clusters. A cluster consists of a finite group of bound atoms or molecules. Due to its finite size, it may present completely different properties than those of the isolated atom and the bulk. The clusters studied in this work are constituted by rare-gas atoms, organic molecules, and metal atoms. Intense cluster beams were created using either an adiabatic expansion source or a gas-aggregation source, and investigated by means of synchrotron radiation based photoelectron spectroscopy. The reports presented in this Thesis may be divided into three parts. The first one deals with results concerning homogeneous molecular clusters (benzene- and methyl-related clusters) highlighting how molecular properties, such as dipole moment and polarizability, influence the cluster structure. The second part focuses on studies of solvation processes in clusters. In particular, the adsorption of polar molecules on rare-gas clusters is studied. It is shown that the doping method, i.e. the technique used to expose clusters to molecules, and the fraction of polar molecules are important factors in determining the location of the molecules in the clusters. Finally, a summary of investigations performed on metal clusters is presented. The applicability of solid state models to analyse the cluster spectra is considered, and the differences between the atomic, cluster and solid electronic structures are discussed. nanoparticles free clusters molecular clusters metal clusters photoelectron spectroscopy synchrotron radiation local structure core level spectroscopy auger spectroscopy heterogeneous clusters nucleation bromomethane chloromethane benzene bromobenzene chlorobenzene potassium sodium simple metals Physics Fysik
6	Impact of Halogenated Aliphatic and Aromatic Additives on Soot and Polycyclic Aromatic Hydrocarbons -- An Ethylene-air Laminar Co-flow Diffusion Flame Study Kondaveeti, Rajiv 21 August 2012 (has links) No description available. Aerospace Engineering Analytical Chemistry Automotive Engineering Chemical Engineering Chemistry Engineering Environmental Engineering Mechanical Engineering Organic Chemistry Petroleum Engineering Co-Flow Ethylene-Air Diffusion Flame Flame retardants Halogenated additives Brominated Chlorinated Benzene Chlorobenzene Bromobenzene Chlorobutane Bromobutane Bromochloro mixtures Emissions Soot PAHs Polycyclic Aromatic Hydrocarbons Enols

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