In the last ten years, N-heterocyclic carbenes(NHCs) have gained tremendouspopularity, notably as highly versatile ligands for transition metals. Their strong -donatingproperties, associated with high steric hindrance, often impart enhanced stability and activity to a given metallic center. Two main successes of the NHCs in homogeneous catalysis are arguably the ruthenium-mediated olefin metathesis and the palladium-promoted crosscoupling reactions.In this work, we have studied the effect of N-heterocyclic carbenes as supporting ligands in well-defined complexes of palladium(II), gallium(III), and gold(I) that we used in homogeneous catalysis.Notably, we have synthesized, in very straightforward manners, two families of palladium compounds of formulae [(NHC)Pd(L)Cl], where L, which is a R-allyl or R-acac moiety, acts as a protecting shell for the catalytically active [(NHC)Pd0] species. Hence,upon activation under the reaction conditions, these new Pd complexes were found extremely active in the Suzuki-Miyaura, the Buchwald-Hartwig, and the -ketone arylation cross-coupling reactions. More precisely, the more active "R-allyl family" allowed for reactions to be performed with as low as 10 ppm of palladium.A series of [(NHC)GaCl3] complexes wa synthesized via a simple one-step procedure. The resulting unprecedented NHC-GaIII compounds were found extremely stable but showed only moderate activity in isomerization reactions.Demonstrating further the versatile application of NHCs in metal-based catalysis, wedeveloped several new catalytic transformations using [(NHC)AuCl] complexes. Hence,these pre-catalysts, activated in situ with a silver salt, proved to be excellent activators ofalkynes, allenes, and alkenes. This led to the development of efficient synthetically usefulprotocols, encompassing enyne cycloisomerization, indene cyclization,formation of conjugated enone, and allylic rearrangement.KEYWORDS gallium - gold - homogeneous catalysis - N-heterocyclic carbene - palladium 8 / En los últimos diez años, los carbenos N-heterocíclicos (NHCs) han ganado una granpopularidad, especialmente como ligandos versátiles de metales de transición. Su fuertecarácter −donor, asociado con su gran impedimento estérico, confieren a menudo unamayor estabilidad y actividad al centro metálico en cuestión. Los dos mayores éxitos de losNHCs en catálisis homogénea se encuentran, sin duda, en la metátesis de olefinas catalizadapor rutenio y en las reacciones de acoplamiento cruzado promovidas por paladio.En este trabajo, hemos estudiado el efecto de los carbenos N-heterocíclicos comoligandos en complejos bien definidos de paladio(II), galio(III) y oro(I), que hemos empleadoen catálisis homogénea.En particular, hemos sintetizado, de forma directa, dos familias de compuestos de paladio de fórmula general [(NHC)Pd(L)Cl] donde L, grupo R-alilo o R-acac, actúa como protector para las especies catalíticamente activas [(NHC)Pd0]. De hecho, tras la activaciónen las condiciones de reacción, estos nuevos complejos de paladio se mostraron extremadamente activos en las reacciones de Suzuki-Miyaura, de Buchwald-Hartwig y en la -arilación de cetonas. Más concretamente, la 'familia R-arilo', más activa, permitió llevar a cabo estas reacciones con tan sólo 10 ppm de paladio.Una serie de complejos [(NHC)GaCl3] fue preparada en una simple etapa. Los compuestos resultantes NHC-GaIII, sin precedentes en la literatura, se mostraron extremadamente estables pero sólo moderadamente activos en reacciones de isomerización.Con el fin seguir ampliando la gran aplicabilidad de los NHCs en catálisis conmetales, estudiamos varias nueva transformaciones utilizando los complejos [(NHC)AuCl].De hecho, estos pre-catalizadores, activados in situ con una sal de plata, demostraron ser excelente activadores de alquinos, alenos y alquenos. Esto llevó al desarrollo de protocolos eficientes, y sintéticamente útiles, tales como la cicloisomerización de eninos, la ciclación deindenos, la formación de enonas conjugadas, y reordenamientos arílicos.

Los compuestos organoborados son considerados de gran interés en síntesis orgánica debido a que el enlace C-B puede ser transformado en una amplia variedad de grupos funcionales. La adicción catalítica de H-B o B-B a enlaces C-C insaturados se considera uno de los procesos catalíticos con mayor control selectivo en la formación de dichos intermedios organoborados. En el capítulo primero de la presente tesis se muestra la evolución a través de la bibliografía de las tres principales reacciones de adición catalítica de boro a alquenos, como son hidroboración, diboración y -boración. El segundo capítulo describe por primera vez la hidroboración catalítica asimétrica tanto en version homogénea como heterogeneizada de sistemas alilícos heterofuncionalizados. También describe el primer ejemplo de diboración de fenil alil sulfonas con sistemas catalíticos de Pt modificados con ligandos N-heterocíclicos. El tercer capítulo muestra la diboración catalítica de alquenos con sistemas catalíticos formados por Cu, Pd e Ir modificados con ligandos NHC. La presencia de una base y la adicción de un exceso de diborano son esenciales para obtener un alto grado de actividad y selectividad. El cuarto capítulo muestra una efectiva síntesis de boro enolatos quirales usando metales de bajo coste como son Cu y Ni modificados con ligandos NHC quirales y ligandos difosfina quirales respectivamente. El quinto capítulo describe las reacciones tándem "in situ" tales como adición de boro-acoplamiento cruzado catalizadas por complejos de Pt modificado con ligandos carbenos y Pd modificados con ligandos difosfina. / Organoboron compounds are some of the most useful reagents in organic synthesis. The carbon-boron bond, once formed, can be cleaved in a variety of ways, with or without homologation, leading to a wide range of useful functional groups. The catalytic addition of H-B or B-B across to unsaturated C-C bond is one of the catalytic processes with higher selective control in the C-B bond formation. In the first Chapter of this thesis shows the evolution through the literature of the three main catalytic reactions of boron addition to alkenes, such as hydroboration, diboration and -boration.Chapter 2 describes the first attempt at the catalytic asymmetric hydroboration in both homogeneous and heterogenised version of functionalised allylic system. In addition, the first example of the diboration reaction of these mentioned substrates with complexes based on Pt modified with NHC ligands is described.Chapter 3 discusses catalytic diboration of alkenes based on Cu, Pd and Ir- catalytic system modified with NHC ligands. The presence of a base and the use of an excess of diboron reagent are essential to obtain high degree of activity and selectivity.Chapter 4 shows the successful synthesis of chiral boron enolates by using inexpensive metals such as copper and nickel modified with chiral NHC ligands and modulated chiral commercially available diphosphines respectively. In Chapter 5 describes complexes containing transition metals such as platinum and palladium modified with NHC ligands and P,P respectively capable to perform the in situ tandem catalytic boron-addition-Suzuki-Miyaura cross-coupling.

<p>The production of biodiesel (methyl esters) from vegetable oils represents analternative means of producing liquid fuels from biomass, and one which is growing rapidly in commercial importance and relevance due to increase in petroleum prices and the environmental advantages the process offers. Commercially, biodiesel is produced from vegetable oils, as well as from waste cooking oils and animal fats. These oils are typically composed of C14-C20 fatty acid triglycerides. In order to produce a fuel that is suitable for use in diesel engines, these triglycerides are usually converted into the respective mono alkyl esters by base-catalyzed transesterification with short chain alcohol, usually methanol. In the first part of this study, the transesterification reactions of three different vegetable oils / sunflower (SFO), soybean (SBO) and waste cooking oil (WCO) with methanol was studied using potassium hydroxide as catalyst in a conventional batch process. The production of biodiesel from waste cooking oil was also studied via continuous operation systems (employing the use of low frequency ultrasonic technology and the jet loop reactor). The characterisation of the feedstock used and the methyl ester products were determined by different analytical techniques such as gas chromatography (GC), high performance liquid chromatography (HPLC) and thin layer chromatography (TLC). The effects of different reaction parameters (catalyst amount, methanol to oil ratio, reaction temperature, reaction time) on methyl ester/FAME yield were studied and the optimum reaction conditions of the different process systems were determined. The optimum reaction conditions for production of methyl esters via the batch process with the fresh oil samples (SFO and SBO) were established as follows: a reaction time of 60 min at 60 &ordm / C with a methanol: oil ratio of 6:1 and 1.0 KOH % wt/wt of oil / while the optimum reaction conditions for the used oil (WCO) was observed at a reaction time of 90 min at 60 &ordm / C, methanol: oil ratio of 6:1 and 1.5% KOH wt/wt of oil. The optimum reaction conditions for the transesterification of the WCO via ultrasound technology applied in a continuous system in this study were: a reaction time of 30 min, 30 &ordm / C, 6:1 methanol/oil ratio and a 0.75 wt% (KOH) catalyst concentration. The ultrasound assisted transesterification reactions performed at optimum conditions on the different oil samples led to higher yields of methyl esters (96.8, 98.32 and 97.65 % for WCO, SFO and SBO respectively) compared to methyl esters yields (90, 95 and 96 % for WCO, SFO and SBO respectively) obtained when using conventional batch procedures. A considerable increase in yields of the methyl esters in the ultrasound assisted reaction process were obtained at room temperature, in a remarkably short time span (completed in 30 min) and with a lower amount of catalyst (0.75 wt % KOH) while the results from the continuous jet loop process system showed even better results, at an optimum reaction condition of 25 min of reaction, a methanol: oil ratio of 4:1 and a catalyst amount of 0.5 wt%. This new jet loop process allowed an added advantage of intense agitation for an efficient separation and adequate purification of the methyl esters phase at a reduced time of 30 min. The use of homogeneous catalysts in conventional processes poses many disadvantages / heterogeneous catalysts on the other hand are attractive on the basis that their use could enable the biodiesel production to be more readily performed as a continuous process resulting in low production costs. Consequently, a solid base catalyst (KNO3/FA) prepared from fly ash (obtained from Arnot coal power station, South Africa) and a new zeolite, FA/Na-X synthesized from the same fly ash were used as solid base catalysts in the transesterification reactions in the conversion of a variety of oil feedstock with methanol to methyl esters. Since fly ash is a waste product generated from the combustion of coal for power generation, its utilization in this manner would allow for its beneficiation (as a catalytic support material and raw material for zeolite synthesis) in an environmentally friendly way aimed at making the transesterification process reasonably viable. Arnot fly ash (AFA) was loaded with potassium (using potassium nitrate as precursor) via a wet impregnation method while the synthesized zeolite FA/Na-X was ion exchanged with potassium (using potassium acetate as precursor) to obtain the KNO3/FA and FA/K-X catalysts respectively. Several analytical techniques were applied for characterization purposes. The results of the XRD and XRF showed that the AFA predominantly contained some mineral phases such as quartz, mullite, calcite and lime. The high concentration of CaO in AFA was apparent to be beneficial for the use of fresh fly ash as a support material in the heterogeneous catalysed transesterification reactions. XRD characterisation of KNO3/FA results indicated that the structure of KNO3/FA gradually changed with the increase in KNO3 loading. The catalyst function was retained until the loading of KNO3 was over 10 %. IR spectra showed that the KNO3 was decomposed to K2O on the fly ash support during preparation at a calcination temperature of 500 &ordm / C. The CO2-TPD of the KNO3/FA catalysts showed that two basic catalytic sites were generated which were responsible for high catalytic abilities observed in the transesterification reactions of sunflower oil to methyl esters. On the other hand, XRD results for the as- received zeolite synthesized from AFA showed typical diffraction peaks of zeolite NaX. SEM images of the FA /NaX showed nano platelets unique morphology different from well known pyramidal octahedral shaped crystal formation of faujasite zeolites and the morphology of the FA /KX zeolite did not show any significant difference after ion exchange. The fly ash derived zeolite NaX (FA /NaX) exhibited a high surface area of 320 m2/g. The application of the KNO3/FA catalysts in the conversion reactions to produce methyl esters (biodiesel) via transesterification reactions revealed methyl ester yield of 87.5 % with 10 wt% KNO3 at optimum reaction conditions of methanol: oil ratio of 15:1, 5 h reaction time, catalyst amount of 15 g and reaction temperature 160 &deg / C, while with the use of the zeolite FA/K-X catalyst, a FAME yield of 83.53 % was obtained for 8 h using the ion exchanged Arnot fly ash zeolite NaX catalyst (FA/KX) at reaction conditions of methanol: oil ratio of 6:1, catalyst amount of 3 % wt/wt of oil and reaction temperature of 65 &ordm / C. Several studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to uniquely demonstrate the utilization of South African Class F AFA both as a catalyst support and as a raw material for zeolite synthesis / these catalyst materials subsequently applied sucessfully as solid base catalysts in the production of biodiesel.</p>

In this thesis, we present a new viewpoint of the universal minimal flow in the language of near ultrafilters. We apply this viewpoint to generalize results of Kechris, Pestov and Todorcevic about a connection between groups of automorphisms of structures and structural Ramsey theory from countable to uncountable structures. This allows us to provide new examples of explicit descriptions of universal minimal flows as well as of extremely amenable groups. We identify new classes of finite structures satisfying the Ramsey property and apply the result to the computation of the universal minimal flow of the group of automorphisms of $\P(\omega_1)/\fin$ as well as of certain closed subgroups of groups of homeomorphisms of Cantor cubes. We furthermore apply our theory to groups of isometries of metric spaces and the problem of unique amenability of topological groups. The theory combines tools from set theory, model theory, Ramsey theory, topological dynamics and ergodic theory, and homogeneous structures.

Detached Eddy Simulation (DES) is a hybrid turbulence model, a modification to the one-equation model proposed by Spalart and Allmaras (1997) [26]. It combines the advantages of both the RANS and LES models to predict any fluid flow. Presently, the focus is on using Homogeneous Turbulence to test the DES model. In an attempt to scrutinize this model, many cases are considered involving the variance of DES grid spacing parameter, CDES, the grid density, Reynolds number and cases with different initial conditions. Choosing Homogeneous Turbulence for our study alienates complications related to the geometry, boundary conditions and other flow characteristics helping us in studying the behavior of the model thoroughly. Also, the interdependencies of the model grid spacing parameter, grid density and the numerical scheme used are also investigated. Many previous implementations of the DES model have taken the value of CDES=0.65. Through this work, many issues including the sensitivity of CDES will be made clear. The code used in running the test cases is called LESTool, developed at University of Kentucky, Lexington. The two main test cases considered are based on the benchmark experimental study by Comte Bellot and Corrsin (1971) [12] and the Direct Numerical Scheme (DNS) simulation by Blaisdell et al. (1991) [10].

The complex phenomenon of indentation deformation is studied using finite element analysis for both homogeneous and layered materials. For the homogeneous materials, the elastic-plastic deformation at large indentation depth is studied. The variation of the load-displacement curves as well as the variation of the energy ratio with the applied indentation depth for different strain hardening indices is presented. The power law relation between the indentation load and depth for shallow indentation becomes invalid for deep indentation. The ratio of plastic energy to total mechanical work is a linear function of the ratio of residual indentation depth and maximum indentation depth. For the layered materials (film-substrate systems), the elastic deformation under an indenter is studied. Various material parameters are investigated, including film thickness and modulus. A generalized power law equation is presented for characterizing the indentation load-displacement responses of film-substrate structures.

For the study of homogeneous catalytic reaction mechanisms, the ideal technique would be capable of identifying and measuring in real time the abundances of all components of the reaction mixture, including reactants, products, byproducts, intermediates, and catalyst resting states. This thesis details the development of methodologies designed to transform electrospray ionization mass spectrometry into just such a tool. Species of interests must be charged otherwise invisible in ESI-MS. Therefore, charge-tagged aryl iodide ([4-I-C6H4CH2PPh3]+[Br]-) and a terminal alkyne ([para-(HCC)C6H4CH2PPh3]+[Br]-) were synthesized as the ESI-active substrates for the homogeneous catalysis study. A method named PSI (pressurized sample infusion) was developed to introduce the air and moisture sensitive reaction mixtures to the ESI-MS. The analytical aspects of the method were investigated and optimized. Applicability of the technique was demonstrated through several organic and organometallic mechanism investigations. The above developments were employed to the detailed study of the copper-free Sonogashira (Heck alkynylation) reaction and the hydrodehalogenation of the charged-tag aryl iodide. Simultaneous monitoring of the charged substrate, products and intermediates in the copper-free Sonogashira reaction by PSI-ESI-MS provided rich information about the kinetic and mechanism of this reaction. Kinetic isotope effect study shows a remarkable inverse kinetic isotope effect which is completely unexpected. Numerical models were constructed to simulate the mechanistic observation and to extract the rate constant of each step in the proposed mechanism cycle. The same methodology (PSI technique) was used to the study of the hydrodehalogenation reaction. Key intermediates were detected under the typical reaction conditions. Kinetic isotope effect study was performed in CH3OD and CD3OD. A primary KIE was observed in both deuterated solvents. A revised mechanism cycle was suggested for this reaction based on KIE results, numerical modelling and other experiments. In the proposed cycle deprotonation of methanol occurs on the palladium metal centre instead of the conventional in solution deprotonation (off metal deprotonation). The mechanism of the ligand substitution of charged-tag of a palladium aryl iodide [Pd(TMEDA)(Ar)(I)]+ (Ar = [C6H4CH2PPh3]+[PF6]-) complex against PPh3 was studied in methanol by PSI-ESI-MS. Results revealed that the pathway proceeds quite differently to what had been assumed by others; there was a very fast displacement of [I]– by PPh3 to form [Pd(TMEDA)(Ar)(PPh3)]2+ , followed by a much slower displacement of TMEDA and recoordination of [I]– to form the product [Pd(PPh3)2ArI]+. We successfully integrated UV/Vis spectroscopy, as a complementary method with ESI-MS to shed light into the systems where ESI-MS only is unable to provide a full assignment to homogenous catalysis. The combination of the two fast and sensitive techniques provides a unique opportunity to study the composition of the organometallic reaction mixtures over time. / Graduate / 0486 / zohrabahmadi@gmail.com

It is important, for companies operating on a homogeneous product market, to understand and adapt to customer needs. Since coffee is a homogeneous product in food retail it is vital for coffee companies to work extensively with differentiation and the fierce competition. The prevailing homogenity makes it difficult for companies to develop the product itself and must therefore work to create added value to the product. The purpose of this thesis is to carry out a study on consumer decision-making when purchasing homogeneous products, and to examine how companies work to strengthen their brand and gain market share in a homogeneous product market. The market that this thesis highlights is the coffee market. To answer the purpose of this thesis the writers have conducted a questionnaire survey regarding consumers’ decision-making process and interviewed two marketing managers for two major actors on the coffee market. The results of the survey show that the availability and the price are key factors for consumers when choosing coffee, and the generated responses from the interviews emphasize the importance of working with strengthening a brand and finding an identity for the product.

In this thesis, we present a new viewpoint of the universal minimal flow in the language of near ultrafilters. We apply this viewpoint to generalize results of Kechris, Pestov and Todorcevic about a connection between groups of automorphisms of structures and structural Ramsey theory from countable to uncountable structures. This allows us to provide new examples of explicit descriptions of universal minimal flows as well as of extremely amenable groups. We identify new classes of finite structures satisfying the Ramsey property and apply the result to the computation of the universal minimal flow of the group of automorphisms of $\P(\omega_1)/\fin$ as well as of certain closed subgroups of groups of homeomorphisms of Cantor cubes. We furthermore apply our theory to groups of isometries of metric spaces and the problem of unique amenability of topological groups. The theory combines tools from set theory, model theory, Ramsey theory, topological dynamics and ergodic theory, and homogeneous structures.

For the last two decades, the possibility of using synthetic membranes for industrial gas separations has attracted considerable interest since membrane separation technologies have the advantages of energy efficiency, simplicity and low cost. However, for wider commercial utilization there is still a need to develop membranes with higher permeant fluxes and higher transport selectivities. Conductive polymers, due to their high gas transport selectivities, give rise to a new class of polymeric materials for membrane based gas separation though poor mechanical properties obstruct the applications for this purpose of use. This problem led researches to a new idea of combining the conducting polymers with insulating polymers forming mixed matrix composite membranes. In the previous studies in our group, polypyrrole was chosen as the conductive polymer, and different preparation techniques were tried and optimized for membrane application. As the insulating polymer, previously poly(bisphenol-Acarbonate) was used to support the conductive polymer filler in order to constitute a conductive composite membrane. For this study, as the polymer matrix, hexafluorobisphenol A based poly(arylene ether ketone) was targeted due to its physical properties and temperature resistance which can be important for industrial applications. First of all, permeabilities of N2, CH4, Ar, H2, CO2, and H2 were measured at varying temperatures ranging from 25&deg / C to 85&deg / C through a homogenous dense membrane of chosen polymeric material to characterize its intrinsic properties. Measurements were done using laboratory scale gas separation apparatus which makes use of a constant volume variable pressure technique. The permeability results were used for the calculations of permeation activation energies for each gas. These permeation activation energies were found to be differing slightly for each gas independently from the kinetic diameters of gases. In this study, mixed matrix membranes of conducting polymer, polypyrrole (PPy) and insulating polymer, hexafluorobisphenol A based poly(arylene ether ketone) (PAEK) were also prepared. It was observed that PAEK and PPy form a composite mixed matrix structure, which can function as permselective membrane. The effect of conducting polymer filler content was investigated with two different filler ratios. When comparing with the pure PAEK membranes, meaningful increases for both permeability and selectivity were obtained for some of the gases.