Thesis (M.A.)--University of Puerto Rico, Mayagüez Campus, 2004. / Printout. Includes bibliographical references (leaves 192-202).

This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions. The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained employing hydroxy- and methoxy-containing ligands in the catalytic reaction. This type of hydrogen bond was further studied in phenanthroline metal complexes. As expected for a hydrogen bond, the strength of the bond was found to increase with increased electron density at the metal and with increased acidity of the hydroxy protons. The second part deals with the use of hydroxy- and methoxy-containing phosphinooxazoline ligands in the rhodium- and iridium-catalyzed asymmetric hydrosilylation reaction. The enantioselectivities obtained were profoundly enhanced upon the addition of silver salts. This phenomenon was explained by an oxygen–metal coordination in the catalytic complexes, which was confirmed by NMR studies of an iridium complex. Interestingly, the rhodium and iridium catalysts nearly serve as pseudo-enantiomers giving products with different absolute configurations. The final part deals with ditopic pyridinobisoxazoline ligands and the application of their metal complexes in asymmetric cyanation reactions. Upon complexation, these ligands provide catalysts with both Lewis acidic and Lewis basic sites, capable of activating both the substrate and the cyanation reagent. Lanthanide and aluminum complexes of these ligands were found to catalyze the addition of the fairly unreactive cyanation reagents ethyl cyanoformate and acetyl cyanide to benzaldehyde, whereas complexes of ligands lacking the Lewis basic coordination sites failed to do so. / QC 20100709

This thesis deals with method development in asymmetric catalysis and specifically syntheses of enantioenriched O-functionalized cyanohydrins. The first part describes the development of a method for the synthesis of O‑alkoxycarbonylated and O-acylated cyanohydrins. Ethyl cyanoformate and acyl cyanides were added to aldehydes in a reaction catalyzed by a chiral dimeric Ti-salen complex together with a tertiary amine. High yields and enantioselectivities were in most cases obtained. Mechanistic studies were performed and a reaction mechanism was proposed. ­ The second part describes a method in which the undesired minor enantiomer in a Lewis acid–Lewis base-catalyzed acylcyanation is continuously recycled into prochiral starting material. Close to enantiopure O‑acylated cyanohydrins were obtained in high yields. The third part deals with asymmetric acylcyanations of ketones. Acetyl cyanide was found to add to α‑ketoesters in a reaction catalyzed by a chiral Lewis base. Yields up to 77% and 82% ee were obtained. The final part describes an enzymatic method for high-throughput analysis of O‑acylated cyanohydrins. The enantiomeric excess and conversion were determined for products obtained from a number of aromatic and aliphatic aldehydes. / QC 20100818

Introduction: Alice in Wonderland is perhaps the most renowned fantasy book for children. Over and above this though, it has relevance for adults. People too often dismiss it as purely escapist reading, a means to escape from the monotony of everyday realism by delving into the realms of fantasy. Many critics propose that it operates on more than one level and I would have to agree - it is a pioneer of children's literature as well as a product and critique of the Victorian age. It is a story that has captured the world's imagination, with vivid characters and exciting adventures. The sequel, Through the Looking-Glass, although not as well known, equally offers an insight into the late nineteenth-century. I intend to explore the many layers found in these stories, and hope to expose them as being more than mere narratives, but as pieces of literature that thrive because they are so cleverly constructed Perhaps also their success lies in that they deal with the universal theme (for children and adults alike) of making sense of the seemingly nonsensical aspects of life and society. The stories, as well as the strange characters and happenings, are reminiscent of the Absurdist genre in drama, in which the objective is to turn the world upside down, so to speak, in order to understand people and society. My dissertation will begin by exploring the literary trends of children's books prior to 1865, in other words, before Alice in Wonderland was published. I intend to present an overview of Victorian and pre-Victorian children's fiction, tracing the development of the story for teaching and religious instruction, up until the time when the story was liberated to be simply the vehicle for pleasurable recreational purposes. Thus my opening chapter is an exploration of the didactic children's literature that dominated the early nineteenth century, examining the educationalists that helped expand the genre of children's literature. Next, I will include a brief biography of Lewis Carroll. It is important to my overall theme in that a biography sums up, in one human centre, the forces at play in Victorian sensibility. As a modern audience, we seem to seize upon the idea of his 'character', desperately attempting to understand what motivated him to write such tour de force stories. The interest for me at this point is to examine how academics have portrayed Carroll's 'character'. The motive behind this section is to beg the question of whether his complex personality affects our reading of the texts, or whether they can be seen as entirely separate from a life to which some scandal has been attributed. In the remainder of my dissertation, I shall focus on how the texts are a reflection of a typical Victorian child's experiences, and discuss how Alice 'grows' as a character, and what she reveals about her society in the process of discovering how she should define herself. Alice is the vehicle for Carroll's subversive commentary about his society, and her experiences in Wonderland and Looking-Glass land are often rooted in the undermining of conventional behaviour and traditions. Lastly, I will examine Carroll's stylistic organization of the narratives, paying particular attention to his treatment of time, dreams and language in the texts. I will discuss what his intentions are in creating 'nonsense that makes sense', as well as what this 'nonsense' discloses about the society he lived in and the values he seems to object to. / Thesis (M.A.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Biomass is increasingly used as a feedstock in global energy production. This may present operational challenges in energy conversion processes which are related to the inorganic content of these biomasses. As a larger variety of biomass is used the need for a basic understanding of ash transformation reactions becomes increasingly important. This is not only to reduce operational problems but also to facilitate the use of ash as a nutrient source for new biomass production. Ash transformation reactions were examined in the present work using the Lewis acid-base concept. The model presented in Paper I was further extended and discussed, including the definition of tertiary ash transformation reactions as reaction steps where negatively charged molecular ions, Lewis bases, other than hydroxides are present in the reactants. The effect of such reactions for bonding of various metal ions, Lewis acids, were discussed. It was found that the formation of various phosphates through secondary and tertiary ash transformation reactions is important for the behaviour of biomass ash in combustion. The suggested model was supported by findings in Papers II-VIII. The experimental findings in Papers II-VIII were discussed in terms of ash transformation reactions. The fuel design choices made to investigate the effect of phosphorus in particular on ash transformation reactions were high-lighted. Addition of phosphoric acid to woody-type and agricultural biomasses showed that phosphate formation has a large influence on the speciation of Si, S, and Cl. Co-combustion of a problematic agricultural residue with other biomasses showed that the relation between phosphorus, alkali and alkaline earth metal content is important. Co-combustion of biosolids with wheat straw was shown to greatly improve the combustion properties of wheat straw. It was suggested that fuel analyses should be presented using molar concentration (mole/kg) in diagrams based on ash transformation reactions and elements forming Lewis acids or bases. This may facilitate the assessment of the combustion behaviour of a fuel. Some comments were made on fuel design and additives, specifically pointing out that phosphorus content should always be carefully considered in relation to alkali and alkaline earth metals in fuels and fuel blends.

Submitted by Noeme Timbo (noeme.timbo@metodista.br) on 2017-01-25T13:38:43Z No. of bitstreams: 1 Paulo Cruz.pdf: 1065817 bytes, checksum: c89d4c886e6d9f4f04095b666ec92c44 (MD5) / Made available in DSpace on 2017-01-25T13:38:43Z (GMT). No. of bitstreams: 1 Paulo Cruz.pdf: 1065817 bytes, checksum: c89d4c886e6d9f4f04095b666ec92c44 (MD5) Previous issue date: 2016-03-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This paper presents a study on C. S. Lewis’ Space Trilogy — that embraces Out of the Silent Planet, Perelandra, and That Hideous Strength. We analize the theological concepts used by the author, specially the Original Sin doctrine and its relations with the concept of moral imagination, developed by the american thinker Russell Kirk. / O presente trabalho apresenta um estudo da obra Triologia Cósmica de C. S. Lewis — composta pelas obras Além do Planeta Silencioso, Perelandra e Essa força medonha —, analisando os conceitos teológicos utilizados pelo autor, sobretudo a doutrina do Pecado Original, e suas relações com o conceito de Imaginação Moral, desenvolvido pelo filósofo americano Russell Kirk.

Ce travail a essentiellement porté sur la description et la rationalisation de certaines propriétés des complexes du Zinc contenant des ligands de base de Schiff par le biais d’approches mixtes théorique et expérimentale. La première partie de ce travail concerne la synthèse et la caractérisation d’un nouveau complexe dinucléaire de Zn(II) à ligand base de Schiff tétra-azoté N4. Ce complexe s’auto-assemble en hélice à double brin avec un environnement tétraédrique rarement observé pour l’ion Zn2+ avec ce type de ligand. Ce complexe s’est avéré être thermodynamiquement instable en présence de traces d’eau, subissant ainsi une démétallation rapide. De ce fait, sa réactivité vis-à-vis de l’eau a été étudiée par des mesures spectroscopiques et des calculs DFT. Puis, le mécanisme réactionnel de démétallation a été élucidé pour la première fois et pourrait facilement être généralisé à l’hydrolyse des complexes Zn-sal(ph)en apparentés. Dans la seconde partie, le caractère acide de Lewis, principal facteur de la réactivité/coordination des complexes Zn-sal(ph)en a été étudié au moyen des descripteurs de la DFT-conceptuelle. Une analyse préliminaire a été réalisée sur un prototype modèle à savoir [ZnCl4]2-, et les résultats ont été généralisés aux complexes de Zn-sal(ph)en comportant différents types d’espaceurs diamine (flexible, semi-rigide, et rigide) afin de rationaliser l’acidité de Lewis de ces complexes avec la nature du pont diamine. L’inclusion des densités des états excités par le biais du descripteur dual dit « state specific dual descriptor» a permis de décrire avec succès la réactivité appropriée du complexe choisi. Enfin, la troisième partie de ce travail, est consacré à l’effet dit de « self-interaction » survenue dans la modélisation de la réaction de cyclo-addition du CO2 sur les époxydes catalysée par un complexe Zn-N4 base de Schiff en présence de NBu4X (X=I). Cette erreur menant à des profils énergétiques irréalistes au niveau DFT, a été identifiée et une nouvelle approche théorique a été proposée et développée afin de contourner cette erreur / In this work, we focus our interest on the description and rationalization of some properties of Zinc complexes of Schiff bases schemes through theoretical and experimental approaches. The first study deals with the syntheses and characterization of a novel Zn-N4-Schiff base L= ((±) -trans-N, N’-Bis(2-aminobenzylidene)-1,2-diaminocyclohexane) showing an unexpected self-assembled double-stranded helicate structure , in which zinc atoms are in distorted tetrahedral environments, revealing an M- (R, R) left-handed helicity in its asymmetric unit. This dimer is thermodynamically unstable in presence of water traces and undergoes a rapid demetallation process that is studied by both experimental and theoretical approaches. The reaction is monitored through DOSY NMR analysis, and the theoretical mechanism of the demetallation process is elucidated for the first time using DFT method and which should be easily generalized to the demetallation of N2O2 sal(ph)en Zn complexes. In the second part of this study, the Lewis acidic behavior, the main factor of the reactivity/coordination of Zn-sal(ph)en complexes, is studied using conceptual density functional theory descriptors. This Lewis acidic character is addressed in a first stage to a prototype complex, namely [ZnCl4]2- and the results have been generalized to Zn-sal(ph)en complexes with different diamine bridges through flexible to semi-rigid then to rigid ranges, in order to characterize and rationalize this Lewis acid effect in relation with the nature of the diamine bridge. The inclusion of the electronic excited state densities by the so-called state specific dual descriptor allows us to recover successfully the appropriate reactivity of these chosen complexes. Finally, in the third part, we consider the effect of the « self-interaction » occurring when modeling the cycloaddition of CO2 to epoxide reactions catalyzed via the binary system Zn-N4 Schiff base /NBu4X (X=I). This error leading to unrealistic energy profiles at the DFT level has been identified and a new theoretical approach is proposed and developed to correct this error

Une nouvelle tentative pour faire face au défi sceptique est menée depuis une quarantaine d’années. Cette tentative repose sur une théorie de la connaissance centrée sur la notion d’alternatives pertinentes. La thèse se propose de montrer les faiblesses de cette théorie, même lorsqu’elle s’appuie sur l’appareillage des mondes possibles, et suggère que le scepticisme demeure la meilleure position épistémologique. Dans le premier chapitre on passe en revue une série de difficultés liées au sujet des alternatives pertinentes et l'on essaye d'argumenter en faveur de l'idée qu'il n'y a peut-être pas, finalement, de moyens en quelque sorte objectifs pour établir quelles sont les alternatives pertinentes relativement à une situation quelconque. À partir du deuxième chapitre, il est procédé à une analyse critique des tentatives de certains auteurs qui se sont servis, pour élaborer leurs propres conceptions bien précises, du langage des mondes possibles. Dans le deuxième chapitre, l'on se concentre surtout sur la question du degré de proximité qu'un monde possible donné doit exhiber pour être considéré comme suffisamment proche du monde actuel et l'on essaye de montrer qu'il n’est probablement pas possible de tracer d'une manière non arbitraire une ligne de démarcation entre ces mondes possibles qu’on peut ignorer et ceux qu’on ne peut ignorer dans nos attributions de connaissance. Dans le troisième chapitre, l'on se concentre surtout sur la question des critères qui devraient guider nos évaluations de proximité et l'on essaye de montrer le caractère discutable de n'importe quelle règle visant à établir quels seraient ces critères-là. / Over the last forty years, a new attempt to answer to the skeptic challenge has been proposed. This attempt is based on a theory of knowledge, which is grounded on the notion of relevant alternative. My dissertation aims to show the problems of such a theory, even when formulated in terms of possible worlds, and suggests that in the end skepticism remains the best epistemological option. In the first chapter, I will offer a discussion of the issue of relevant alternatives, and I will argue in favor of the idea that perhaps there are no objective criteria to establish which are the relevant alternatives with respect to a certain given situation. In the second chapter, I will propose a critical analysis of the attempts of some philosophers to formulate their own proposals in the language of possible worlds. In particular, I will focus on the issue of the proximity degree that a certain possible world must have in order to be considered as sufficiently closed to the real world, and I will try to show that perhaps it is not possible to draw a sharp line of demarcation between those possible worlds that we can ignore and those that we must take into account in our attribution of knowledge. In the third chapter, I will critically discuss the criteria that should guide our evaluations about proximity, and I will show the problematic aspects of any rule aimed to establish which these criteria in effect should be.

Le concept de “paires frustrées de Lewis” (plus communément désignés par l’acronyme anglais FLPs) a suscité un vif intérêt depuis sa formulation en 2006. Initialement décrit à partir d’une phosphine encombrée comme base de Lewis et d’un borane comme acide de Lewis pour l’activation coopérative d’hydrogène sans métal, ce concept a été ensuite très largement développé en utilisant divers éléments du groupe principal (N/B, P/Al, N/Al …). Le concept a ensuite été étendu aux métaux de transitions pour pallier cette faiblesse: sont ainsi apparues les premières paires frustrées de Lewis organométalliques (OmFLPs). Dans le but de développer de telles OmFLPs, nous nous sommes intéressés à la synthèse de complexes cationiques titanocèniques et zirconocèniques en présence d’une amine. La première partie de cette thèse présente les travaux précédemment décrits sur les ligands azotés, en vue de synthétiser des complexes du groupe 4 N-fonctionnalisés. Une description plus détaillée du concept de FLP est ensuite réalisée, et un parallèle est fait avec des concepts connexes (coopérativité métal-ligand, systèmes ambiphiles). La seconde partie de ce manuscrit développe la synthèse de nouveaux ligands (aminomethyl)cyclopentadiènylure de potassium ainsi qu’une étude de leur coordination aux métaux du groupe 4. Cette étude a permis d’accéder à toute une série de nouveaux complexes dichlorotitanocènes et zirconocènes porteurs d’une fonction amine tertiaire encombrée (diisopropylaminyl et 2,2,6,6-tétraméthylpipéridine) à proximité du centre métallique. Ces travaux ont montré que l’amine ne se coordine pas audit centre métallique. Les métallocènes ainsi formés ont ensuite été transformés en cation afin de renforcer le caractère acidité de Lewis du centre métallique. Ces espèces ont montré une réactivité inattendue donnant lieu à des réarrangements par activation CH au voisinage de l’atome d’azote. Ces réarrangements ainsi que des études mécanistiques font l’objet du troisième chapitre. La quatrième partie de ce mémoire porte sur la synthèse de complexes phosphido- et amidotitanocènes cationiques. Ces complexes montrent une très bonne activité en catalyse d’hydrogénation de petites molécules dans des conditions relativement douces, vraisemblablement pour des raisons d’effets coopératifs entre le métal et le ligand. Dans une dernière partie, la synthèse de complexes titanocéniques cationiques portant une fonction iminophosphorane est développée, suivie d’une étude de réactivité de ces complexes en tant que paires frustrées de Lewis organométalliques. / In 2006, the concept of “frustrated Lewis pairs” (called FLPs) was introduced. The main characteristic of these compounds is their ability to activate cooperatively small molecules without the use of a metal (H2, CO2, alkene alkyne…). Initially based on P/B combination, the concept has been extended to several other main group elements (N/B, P/Al, N/Al …). Recently, FLPs have been extended to the transition metal realm. These organometallic FLPs (OmFLPs) are obviously non-metal free systems but they extend significantly the scope of FLP applications. Seeking to develop such systems, a research toward new omFLP combinations (N/Ti+, N/Zr+) has been initiated in our group, based on the synthesis of N-based titanocene and zirconocene complexes. The first part of this manuscript deals with a survey of the literature of such compounds, and a more detailed presentation of FLPs and related concepts (metal-ligand cooperativity, ambiphilic ligands) are also developed. In a second chapter, the synthesis of new N-based cyclopentadienyl ligands and their coordination to group 4 metals is presented. The formation of a cationic complex is then developed in a third part on selected titanocenes. In these complexes, the amine function undergoes CH activation by the cationic metal centre, leading to unexpected rearrangements. Investigations on their plausible mechanism are also presented. In a fourth part, the synthesis of new cationic phosphido- and amidotitanocenes, discovered in the course of our study on OmFLPs, is developed. The cationic amidotitanocenes are shown to be catalytically active towards hydrogenation of small molecules. Lastly, the potential of cationic titanocenyl iminophosphoranes as OmFLPs, was developed.

Dans un contexte de diminution des émissions polluantes émises par les moteurs à combustion interne, le secteur des transports assiste à une amélioration des motorisations mais également à une diversification des carburants pour l’automobile. L’utilisation de ces différents carburants entraîne souvent un impact sur les performances de la combustion. Dans le cas du moteur à allumage commandé, la performance dépend du dégagement d’énergie, image de la vitesse de la combustion, soit du front de flamme consommant le mélange air-carburant. Or toute flamme en expansion est théoriquement soumise à des effets de courbure et de cisaillement, toutes deux contributions de l’étirement. La réponse à l’étirement étant propre à chaque type de mélange air-carburant (lié au carburant proprement dit, à la richesse du mélange, à la dilution …), ce travail de thèse est centré sur la compréhension de l’impact de l’étirement sur les performances des carburants dans les moteurs à allumage commandé. Pour cela, différents mélanges air-carburant similaires du point de vue des propriétés thermodynamiques et des vitesses fondamentales de combustion laminaire mais avec des sensibilités à l’étirement différentes ont été sélectionnés. Ces mélanges ont ensuite été étudiés dans différentes configurations expérimentales et à l’aide de différentes techniques de mesure: moteur monocylindre opaque et à accès optiques, chambre sphérique de combustion turbulente. Les résultats montrent que les propriétés de sensibilités à l’étirement déterminées en régime laminaire comme la longueur de Markstein et le nombre de Lewis sont indicatrices du comportement des mélanges en combustion turbulente, comme dans la chambre de combustion caractéristique des moteurs à allumage commandé, et sont des paramètres à prendre en considération afin de prédire les performances plus globales de ces carburants que ce soit expérimentalement qu’en simulation. / In a context of decreasing pollutant emissions, the transport sector is facing an improvement of engine concept as well as a fuel diversification. The use of these different fuels often involves an impact on the combustion performance itself. In the case of Spark ignition engine, the efficiency is a function of the released heat, image of the combustion speed, i.e. the flame front speed consuming the air-fuel mixture. It is well known that every expanding flame is submitted to flame curvature and strain rate which are both contributors to flame stretch. As the answer of each air-fuel mixture (i.e. the fuel itself, the equivalence ratio, the dilution …) is different to flame stretch, the objective of this work is to understand flame stretch impact on fuel performance in Spark-Ignition engines. To achieve this goal, different fuel-air mixtures with similar unstretched laminar burning speed and thermodynamic properties but different responses to stretch were selected. Those mixtures were then studied with different experimental devices with different measurement techniques: single-cylinder metallic and optical engines, turbulent combustion spherical vessel. Results show that flame stretch sensitivity properties such as Markstein length and Lewis number, determined in laminar combustion regime, are relevant parameters to describe the flame propagation in turbulent combustion as in the combustion chamber of the Spark-Ignition engine and need to be taken into consideration to evaluate global performance of these fuels, experimentally and also in modeling simulation.