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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
411

Exploring New Synthetic Routes to Frustrated Lewis Pairs

Tanur, Cheryl 25 August 2011 (has links)
Gold(I) and copper(I) imidazolium complexes were synthesized and probed for use as bulky Lewis acids in frustrated Lewis pairs (FLPs) with bulky phosphines and amines. Their reactivity with small molecules was investigated and the compounds were fully characterized by multinuclear NMR spectroscopy, elemental analysis and X-ray crystallography. Secondly, a new methylene-linked boron-sulfur Lewis acid was synthesized. Its thermodynamic properties were determined and its reactivity with terminal and internal alkynes was demonstrated. Adducts and heterocycles of this boron-sulfur system were fully characterized by multinuclear NMR spectroscopy, elemental analysis and X-ray crystallography. The application of these new systems for the activation of small molecules is described in this thesis.
412

Silicon Tetrachloride Mediated Asymmetric Aldol Addition Reaction

Tan, Duygu 01 January 2013 (has links) (PDF)
Aldol addition reaction is one of the most important and most studied carbon-carbon bond forming reactions in organic chemistry. Recent studies focused on the catalytic version of this chemistry. Different from the classical Mukaiyama-type aldol reactions, chiral lewis bases have been used as promoters. In the presence of SiCl4, these reactions proceed through a cyclic transition state leading to anti aldol product as a major product with moderate-to-good diastereo and enantioselectivities. Phosphoramide derivatives, BINAPO, BINAPO derivatives, N,N-dioxides and N-oxides have been extensively used for this purpose. Recently, our group has designed new phosphine oxy aziridinyl phosphonates (POAP) as chiral Lewis bases. These promoters were used for the asymmetric aldol addition reaction between cyclohexanone and different aldehydes in the presence of SiCl4. Moreover, our previously designed phosphine oxy ferrocenyl substituted aziridinyl methanol (POFAM) ligands were also tested as Lewis bases. Among these 6 potential promoters, POAP-A gave the best results, and the aldol product were obtained in moderate to good yields up to 80%, and with moderate enantioselectivities (the highest, 66%) after standard optimization studies. Aldehyde screening experiments provided the highest enantioselectivity (68%) with 2- naphthaldehyde.
413

Certain variables related to the change in cultural interests of Lewis and Clark College freshmen

Ennis, George William 16 April 1956 (has links)
Graduation date: 1956
414

Alice's Adventures in Wonderland : A Feminist Bildungsroman

Forss, Christoffer January 2013 (has links)
This thesis has two aims. The first one is to elucidate how Alice’s Adventures in Wonderland (1865) functions as a Bildungsroman, and the other one is to demonstrate how the novel also has a coming of age aspect based on feminism. Whilst Alice matures in the traditional sense, she also in parallel does so as a stronger female fighting for gender rights with signs of feminism. The feminist angle as well as the surreal world of Wonderland makes the novel a not very obvious Bildungsroman in a genre dominated by male protagonists. For Alice to be a young female child who ends up in a fantasy world thus makes her a very fascinating character. The central hypothesis of this thesis is that what Alice is exposed to and reacts to in Wonderland generally reflects the genre of a Bildungsroman and also specifically a feminist Bildungsroman. Theoretical framework is based on the ideas of Franco Moretti, Mikhail Bakhtin, Thomas Jeffers, Carol Lazzaro-Weis, George Eliot and Elizabeth Drew Stoddard, as well as novels by Eliot and Stoddard. This includes dynamic protagonists, unpredictable development, symbols of modernity, the quest for universality, and minor characters who make sure that the protagonist develops, as well as feminist struggle by means of disregarding the ‘cult of true womanhood’ in a genre and society dominated by men.
415

Writing Her Way Back to the Old South: History, Memory, and Mildred Lewis

DePalma, Cari A 07 August 2012 (has links)
Mildred Lewis Rutherford, as one of the most prominent members of the United Daughters of the Confederacy, has been scantly researched in the past, however her speeches and writing had a profound impact on southern historical consciousness during the New South Period. Her influence, interestingly, was not entirely based in reality. A poststructural analysis of her speeches reveals that she strategically fabricated and excluded information in order to create a specific memory of the past in the minds of southerners. Rutherford had difficulty discerning whether or not the economic benefits of industrialization outweighed the accompanying social consequences. Yet, she used the power of text in an attempt to recreate the Old South social structure based on a racial hierarchy that was bound to be defeated by the rising tide of indu-strialization.
416

What in the World are Possible Worlds?

Dondero, Mark 16 January 2010 (has links)
Ted Sider writes that "many are impressed with the utility of possible worlds in linguistics and philosophy", and this is true, in particular, of those with an interest in modal logic. However, in the midst of the marvelous milieu brought on by the development of possible world semantics, some have stopped to ask just what it is that possible worlds are. They certainly seem useful, and we seem to understand how to use them and talk about them, but what precisely is it that we're talking about when we talk of possible worlds? In this thesis, I will attempt to outline the most significant and well-recognized view in this debate: that of David Lewis. Through my discussion of him, I will find occasion to discuss some alternative views that have arisen. After finishing my presentation of Lewis, I will discuss where people have begun to take this debate and address the question of whether progress can be made towards a substantive answer. In Chapter I, I begin by presenting the motivation of the question of possible worlds found in the study of modal logic. I then present the major approaches taken to answering the questions that were raised, leading into my discussion of David Lewis's famous and robust account. I present key features of Lewis's view and then move into his criticisms of the other major responses. This much should suffice as a relatively thorough treatment of the answers that have come before. In Chapter II, I discuss the current state of the debate. I begin by mentioning several problems that can be spotted in Lewis's views in particular. I then move to Menzel's account, which tries to answer the question of possible worlds from a new angle, jettisoning the direction taken by Lewis and his contemporaries. I explain why Menzel has taken this new approach, and then move into another new approach, this time given by Stephen Yablo. I discuss how these two approaches can help serve each other in helpful ways. But, at last, I present several hurdles these two views would have to overcome in order to play together nicely.
417

Synthesis Of 2-aminopyrrole-3-carboxylates Via Zinc Perchlorate Mediated Annulation Of Alpha-cyano-gamma-ketoesters With Amines

Akca, Nazmiye Bihter 01 August 2008 (has links) (PDF)
2-Aminopyrrole-3-carboxylate derivatives are important starting materials for biologically active compounds like pyrrolotriazole, pyrrolotriazine so their synthese has great importance in the synthetic organic chemistry. There are only two methods for the synthesis of 2-aminopyrrole-3-carboxylates in the literature. Therefore, there is a great need for the design and development of a new method for the synthesis of 2-aminopyrrole-3-carboxylates. In this work, 2-aminopyrrole-3-carboxylate derivatives were synthesized starting from cyano acetic acid ethyl ester with a new method. In the first step, cyanoacetic acid ethyl ester was alkylated with bromo acetone in the presence of NaH. Then, obtained gamma-ketoester was reacted with primary amines in the presence of catalytic amount of zincpechlorate (Zn(ClO4)2). As a result, 2-aminopyrrole-3-carboxylate derivatives were obtained. Cyanoacetic acid ethyl ester was also alkylated with various bromo acetophenone derivatives in the presence of DBU (1,8-Diazabicycloundec-7-ene). As a result of these reactions, different gamma-ketoesters were obtained. The reaction of these gamma-ketoesters with primary amines in the presence of catalytic amount of Zn(ClO4)2 concluded with 2-aminopyrrole-3-carboxylate derivatives.
418

Characterization and Mapping of the Gene Conferring Resistance to Rift Valley Fever Virus Hepatic Disease in WF.LEW Rats

Callicott, Ralph J. 14 January 2010 (has links)
Rift Valley Fever Virus is a plebovirus that causes epidemics and epizootics in sub-Saharan African countries but has expanded to Egypt and the Arabian Peninsula. The laboratory rat (Rattus norvegicus) is susceptible to RVFV and has been shown to manifest the characteristic responses of humans and livestock. The rat has frequently been used as a model to study RVFV pathogenesis. Several strains have been infected and some found to be resistant to hepatic disease while others were not. This resistance was found to be associated with a dominant gene inherited in Mendelian fashion. The congenic rat strain WF.LEW and several substrains of the parental strains were used to try and locate the resistance gene. Microsatellites and single nucleotide polymorphisms were used to characterize the genomes of various rat substrains in an attempt to map the gene. Breeding and viral challenge experiments were used to further characterize the strains and assign a location to the resistance gene. The LEW/SsNHsd rats showed approximately 37% genomic difference as compared with LEW/MolTac rats, and 8% difference as compared with LEW/Crl rats. WF/NHsd rats demonstrated a difference of approximately 8% as compared with WF/CrCrl rats. Genotyping of the congenic WF.LEW revealed Lewis markers on RNO3 and RNO9. Subsequent backcross experiments and viral challenge experiments assigned the resistance gene to the distal end of RNO3.
419

Bispyridylamides as ligands in asymmetric catalysis

Belda de Lama, Oscar January 2004 (has links)
<p>This thesis deals with the preparation and use of chiralbispyridylamides as ligands in metal-catalyzed asymmetricreactions.</p><p>The compounds were prepared by amide formation usingdifferent coupling reagents. Bispyridylamides havingsubstituents in the 4- or 6- positions of the pyridine ringswere prepared by functional group interconversion of the 4- or6- halopyridine derivatives. These synthetic approaches provedto be useful for various types of chiral backbones. Pseudo C<sub>2</sub>-symmetric bispyridylamides were also synthesizedby means of stepwise amide formation.</p><p>The compounds were used as ligands in themicrowave-accelerated Mocatalyzed asymmetric allylic alkylationreaction. Ligands having ð-donating substituents in the4-positions of the pyridine rings gave rise to products withhigher branched to linear ratio. The catalytic reaction, whichproved to be rather general for allylic carbonates with anaromatic substituent, was used as the key step in thepreparation of (R)-baclofen. The Mo-bispyridylamide catalystprecursor was studied by NMR spectroscopy.</p><p>Bispyridylamide complexes of metal alkoxides were alsoevaluated in the asymmetric addition of cyanide to aldehydesand the metal complexes involved were studied by NMRspectroscopy and X-ray crystallography. Chiral diamines wereused as additives to study the ring opening of cyclohexeneoxide with azide, catalyzed by Zr(IV)-bispyridylamidecomplexes.</p><p>Various bispyridylamides were attached to solid supports oforganic or inorganic nature. The solid-supported ligands wereused in Mo-catalyzed asymmetric allylic alkylation reactionsand in the asymmetric addition of cyanide to benzaldehyde.</p><p><b>Keywords:</b>asymmetric catalysis, chiral ligand, pyridine,amide, allylic alkylation, enantioselective, cyanation,ring-opening, chiral Lewis acid.</p>
420

Aspects on wettability and surface composition of modified wood

Bryne, Lars-Elof January 2008 (has links)
<p>Wood is often combined with other materials such as thermoplastics, adhesives and coatings. In general, combinations of wood and polymers especially in outdoor exposure have poor long-term durability. This behaviour can be related to an insufficient wood-polymer adhesion due to the low intrinsic compatibility between the wood substance and the polymers used. Another source for woodpolymer de-bonding is the high hygroscopicity of wood and great difference in hygro-thermal properties between the components.</p><p> The basic conceptual idea related to this work is to reduce the hygrosensitivity of wood by applying different wood modification methods, in particular, acetylation, furfurylation and heat treatment. The effects of such chemical modifications of wood, also accompanied with ageing effects, on its adhesion properties with commonly used synthetic polymers are, however, not well understood. In this context, the over-all purpose of this thesis is to achieve a better understanding of wood-polymer adhesion and interfacial forces which also may guide us to tailor the interaction between modified wood and e.g. thermoplastics and adhesives. The main focus of this thesis is therefore to apply contact angle analysis based on the Chang-Qin-Chen (CQC) Lewis acid-base model in order to estimate the work of adhesion (<i>W</i><i>a</i>) between the wood, modified wood and certain polymers. Contact angle measurements on wood samples were performed based on the Wilhelm plate principle. Related to this, an effort was also made to characterize the studied modified wood surfaces according to morphology and chemical composition. The methods that have been used are low vacuum scanning electron microscopy (LV-SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). </p><p>Results show that so-called interaction parameters can be successfully estimated for prediction of <i>W</i><i>a</i> between wood and polymers using the applied CQC model. Furthermore, such wetting analysis was successfully related to spectroscopic findings of the chemical composition of the wood samples surface. Ageing effects, i.e. the time after preparation of the wood surface, play a central role for the surface characteristics. In most cases, ageing resulted in a significant decrease of <i>W</i><i>a</i> between wood and water and a moderate decrease between wood and thermoplastics. The surface characteristics of acetylated wood were, however, more stable over time compared to unmodified, furfurylated and heat treated wood. The predicted <i>W</i><i>a</i><sub> </sub>with the adhesives for heat treated and acetylated wood was increased due to ageing. Future work is planned to involve studies in order to relate such predicted adhesion properties with the actual performance of various wood-polymer systems.</p>

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