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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.
101

Fremstilling av propargylestere og anvendelse i gullkatalyserte reaksjoner / Preparation of Propargyl Esters and Applications in Gold-catalyzed Reactions

Tungen, Jørn Eivind January 2011 (has links)
Hovedmålet i masteroppgaven har vært å utforske nye gullkatalyserte reaksjoner og anvendelser av propargylestere og allenestere. Allen 14, ble syntetisert fra propargylbromid over to trinn, ved en kjent prosedyre. Kationiske gullkomplekser har en sterk alkynofil karakter som aktiverer alle typer π-systemer for nukleofilt angrep. Dette gjør allen 14 godt egnet som substrat i gullkatalyserte transformasjoner. E-Dien 22a-b, samt Z-dien 23a-b, ble syntetisert i en stereoselektiv gull(I)katalysert reaksjon. Dette er første gang diener har blitt fremstilt fra 2-substituerte allenestere, og det ble observert en høyere Z-selektivitet enn hva som tidligere har blitt observert for usubstituerte allenestere. Dien 22a og 23a ble isolert i et utbytte på henholdsvis 35% og 33% med et E/Z-forhold på 47:53. For dien 22b og 23b var E/Z-forholdet 52:48, og de ble isolert utbytter på 38% og 28%. Elektrofil addisjon til allen 14, etterfulgt av et 1,2-arylskift, ga aldehyd 25 i et utbytte på 45%. Tre nye forbindelser er blitt fremstilt ved en helt ny metode for gull(I)katalysert jodhydroksylering av allenestere. Vinyljodid 24 og 26 ble dannet i utbytter på henholdsvis 59% og 39%, mens omleiret produkt 27, ble isolert i et utbytte på 20%. Syklopropylforbindelse 28 ble syntetisert i en ny gull(I)katalysert ”tandem”-syklopropaneringsreaksjon, fra propargylester 4, i et utbytte på 34%.Fire nye syklopropylforbindelser 18a-b og 19a-b har blitt syntetisert. Disse er dannet i en sykliseringsreaksjon mellom vinylester 17 og propargylester 1b eller 4. Syklopropylforbindelse 18 og 19 er isolert i utbytter på henholdsvis 52% og 76%. Et kiralt NHC-basert gullkompleks 41 har blitt syntetisert, og testet som gull-ligand i syklopropanerings-reaksjon. Det ble funnet et enantiomert overskudd på 5% for cis-forbindelse 43a, og et enantiomert overskudd på 6% for trans-forbindelse 43b. Dette er første gang en kiral NHC-basert gullkatalysator er blitt testet i en gullkatalysert asymmetrisk syklopropaneringsreaksjon.
102

Fremstilling av et kiralt triazoliumbasert NHC-salt og anvendelse i asymmetrisk syntese / Preparation of a Chiral Triazoliumbased NHC-salt and Applications in Asymmetrical Syntheses

Solvang, Tina January 2011 (has links)
Et kiralt triazoliumbasert N-heterosykliskkarben-salt (NHC) 1 har blitt fremstilt fra L-fenylalanin 2 og fenylhydrazinhydroklorid 12 i en synteserute som går over fem trinn, og med et totalutbytte på 10%. NHC-salt 1 er blitt testet som organokatalysator i en sykliseringsreaksjon mellom aldehyd 4 og keton 5. Produktet, butyrolakton 6, ble dannet i et trans/cis-forhold på 59:41, og med et enantiomert overskudd på henholdsvis 10% og 19% for trans- og cis-forbindelse 6a og 6b.NHC-salt 1 ble testet som ligand i en gullkatalysert syklopropaneringsreaksjon. Gullkatalysator 15a og 15b ble syntetisert fra NHC-salt 1 og 16 ved hjelp av Ag2O og AuCl(Me2S) i et utbytte på henholdsvis 82% og 85%. Syklopropaneringsreaksjon mellom alkyn 18 og alken 19 ga syklopropylforbindelse 20 i et trans/cis-forhold på 41:59 for gullkatalysator 15a og 38:62 for gullkatalysator 15b. Gullkatalysator 15a ga et enantiomert overskudd på 8% og 6% for henholdsvis trans- og cis-forbindelse 20a og 20b. Gullkatalysator 15b ga et enantiomert overskudd på 10% og 9% for de samme forbindelsene. Dette er første gang en kiral triazolbasert NHC-gullkatalysator har blitt brukt i asymmetrisk syntese.
103

Screening of Inhibitors for Amine Degradation

Elnan, Jørund January 2012 (has links)
Hindering the degradation of amines in the CO2-capturing process is important both for economical purposes when it comes to loss of solvent and impacts on the process, and to prevent emissions of volatile degradation compounds such as ammonia, nitrosamines and formaldehyde. To prevent the absorbent from degrading, either a non-degrading absorbent can be developed or a degradation inhibitor can be added to minimize the degradation. The degradation inhibitors tested in this thesis are meant to inhibit the oxidative degradation that mainly occurs in the absorber. The carbamate polymerization degradation due to CO2 and temperature has to be addressed on its own. The inhibitor screening apparatus was new, and a part of the assignment was testing this setup. The first experiment conducted on the inhibitor screening apparatus used a gas blend of 6% O2/2 % CO2 (N2 balance). This did not give enough degradation, which caused the need for rebuilding the rig. In the other experiments on the screening apparatus, a gas composition of 98 % O2/2 % CO2 was used to get sufficient amount of degradation for inhibitor screening. Inhibitor screening experiments were done using 150 mL of a 30 weight% (wt%) 2-aminoethanol (MEA) solution loaded with 0,4 mol CO2/mol MEA, at 55 °C with a gas flow of 10 mL/min. To test the stability of the inhibitors at higher temperature, thermal experiments with inhibitors were conducted. 7 mL solution was filled in stainless steel cylinders and heated at 135 °C, for a period of five weeks. The solution was 30 wt% MEA loaded with 0,5 mol CO2/mol MEA. Hydrazine was screened for inhibitory effect using a circulative closed loop apparatus because of the hazards related to this compound. The experiment was run with air, using a 30 wt% MEA solution loaded with 0,4 mol CO2/mol MEA, at 55 °C. Since experiments with both 6 % and 98 % oxygen were conducted, it was natural to compare the impact of oxygen concentration on the degradation products. Results indicated that 2-oxazolidinone (OZD) was preferred at the conditions with high oxygen, while N-(2-hydroxyethyl) glycine (HeGly) concentrations increased with decreasing oxygen content. The effect of metals on product composition was also investigated. The degradation compound N-(2-hydroxyethyl) imidazole (HEI) seems to be dependent on the metal concentrations, increasing in the presence of metals. For the inhibitors screened, the inhibition ranged from 23,59-67,81 %. Two compounds gave an increase in degradation. 1-hydroxyethane 1,1-diphosphonic acid (HEDP) was the only chelating agent stable at thermal conditions. The inhibitors did not appear to have a substantial effect on the carbamate polymerization. Quantification of degradation compounds in the samples was done using liquid chromatography-mass spectrometry (LC-MS) and anion chromatography-electrochemical detector (IC-EC). Amine loss and CO2-loading were determined using titration methods. Metal concentrations were determined using inductively coupled plasma-mass spectrometry (ICP-MS). Some analyses were done gravimetrically while others were done volumetrically. For comparison purposes, simple density measurements were done, and the data converted according to the amine loss in the sample.The initial intention was to use gas chromatography - mass spectrometry (GC-MS) to analyze the samples from the thermal experiments. The system was however not operable during the time available. ICP-MS analysis was not done in time for the last experiment. Ammonia analyses were not conducted in time for this thesis.
104

Synthesis of a Precursor for a Carotenoid Cationic Lipid

Vo, Mong Truc January 2012 (has links)
The goal of this work was the synthesis of a carotenoid cationic lipid for the research of carriers of nucleic acids into defective cells via transfection therapy. In the course of this project a precursor for the carotenoid cationic lipid was successfully obtained, but because of the limited time the synthesis of the carotenoid cationic lipid itself was not performed.
105

Gold(I) Catalyzed Tandem Cyclization Reactions

Rajinder Kaur, Maya January 2012 (has links)
Through this study it has been observed that in contrast to propargyl esters which give cyclopropyl products, the high reactivity of propargyl acetals allows a new tandem cyclization to take place, resulting in bicyclic products. It has also been found that steric effects may cause propargyl acetals to react by unexpected pathways. NMR studies confirmed a particularly high reactivity of propargyl acetal compared to propargyl ester. These results show how molecular diversity can easily be achieved by varying the substrates in gold(I) catalysis.
106

Vinyl Amide Reactions in the Presence of Gold(I) Catalyst

Blakstad, Guro January 2012 (has links)
Reaksjoner med vinylderivater i nærvær av gull(I)katalysator. Sykloaddisjoner og dimeriseringsreaksjoner er studert.
107

Hur marknaden bedömer europeiska företagstillkännagivanden vid etablering i BRIC länder

Stareborn, Oscar, Jama, Sharmarke January 2012 (has links)
The aim of this study is to examine how European companies’ stock price is affected by an announcement about foreign direct investment in one of the BRIC countries. Another aim for the study is to examine if the market reacts differently to the three modes of entry methods in a given BRIC country and to examine if the market reacts differently to different European countries. The study also set out to answer if there were any effects of the three modes of entry that was visible a short time after the announcement.  To answer and examine this, the authors used the event study approach. The study was conducted with a sample of 47 companies from France, Norway, Spain, Sweden and Germany. The time period in which the study was conducted within was between the years 2001-2011. The three modes of entry that was examined were Joint Venture, Acquisition and organic expansion. The three modes of entry were submitted to conduct a hypothesis test to determine whether or not an abnormal return was created during the event window in which the announcement took place. A hypothesis test was also conducted during the post event window to determine if the announcement effect is visible a short time period after the announcement. The event window was 11 days, five days before the announcement and five days after the announcement. The post event window was 30 days after the event window. Companies with the same mode of entry in the same BRIC country were submitted to examine whether or not the announcement effect was different for the three modes of entry. Companies from the same European country were joined together after which BRIC country the announcements were about. The result of the study was that significant positive abnormal return was created during both the event and post event window. There were also modes of entry in which the announcement effect was visible a short time after the announcement.
108

Att styra utan styre? : En kvalitativ undersökning av en organisk organisation

Nilsson, Frida, Winrow, Martin January 2011 (has links)
Sammanfattning Arbetslivet förändras och i och med det även arbetets och organisationernas struktur. Större krav ställs på individen att strukturera och ansvara för sitt arbete. I dessa nya organisationer har den formella hierarkiska styrningen minskat eller försvunnit och det är därför betydelsefullt att studera vilken typ av styrning som ersätter denna. Syftet med uppsatsen är att via en kvalitativ ansats undersöka hur styrningen ser ut i ett litet företag med en organisk karaktär. För att besvara syftet har fyra kvalitativa intervjuer samt en observation genomförts på det valda företaget. För att få fram relevant information har intervjuguiden till viss del utformats med hjälp av metoden ”critical incident”. Analys av intervjuerna har sedan skett genom tematisering utifrån tidigare forskning och teori. Observationen har använts som komplement till intervjuerna. I analysen av intervjuerna framkom två teman som extra tydliga. För det första, de yttre faktorerna, där framförallt kunden framträder som en viktig styrande faktor och att denna får en betydande roll när det gäller företagets organisering. Det andra temat som framkom var den interna gruppen som även den hade en betydande styrningsfunktion. Den interna gruppen får en väsentlig roll vad gäller den interna organiseringen i avseende normer och värderingar, som beteendet i organisationen utgår ifrån.
109

Synthesis of Organic Chromophores for Dye Sensitized Solar Cells

Hagberg, Daniel January 2007 (has links)
<p>This thesis is divided into four parts with organic chromophores for dye sensitized solar cells as the common feature and an introduction with general concepts of the dye sensitized solar cells.</p><p>The first part of the thesis describes the development of an efficient organic chromophore for dye sensitized solar cells. The chromophore consists of a triphenylamine moiety as an electron donor, a conjugated linker with a thiophene moiety and cyanoacrylic acid as an electron acceptor and anchoring group. During this work a strategy to obtain an efficient sensitizer was developed. Alternating the donor, linker or acceptor moieties independently, would give us the tool to tune the HOMO and LUMO energy levels of the chromophores. The following parts of this thesis regard this development strategy.</p><p>The second part describes the contributions to the HOMO and LUMO energy levels when alternating the linker moiety. By varying the linker the HOMO and LUMO energy levels was indeed shifted. Unexpected effects of the solar cell performances when increasing the linker length were revealed, however.</p><p>The third part describes the investigation of an alternative acceptor group, rhodanine-3-acetic acid, in combination with different linker lengths. The HOMO and LUMO energy level tuning was once again successfully shifted. The poor electronic coupling of the acceptor group to the semiconductor surface proved to be a problem for the overall efficiency of the solar cell, however.</p><p>The fourth part describes the contributions from different donor groups to the HOMO and LUMO energy levels and has so far been the most successful in terms of reaching high efficiencies in the solar cell. A top overall efficiency of 7.1 % was achieved.</p>
110

Transition Metal Hydrides : Biomimetic Studies and Catalytic Applications

Ekström, Jesper January 2007 (has links)
In this thesis, studies of the nature of different transition metal-hydride complexes are described. The first part deals with the enantioswitchable behaviour of rhodium complexes derived from amino acids, applied in asymmetric transfer hydrogenation of ketones. We found that the use of amino acid thio amide ligands resulted in the formation of the R-configured product, whereas the use of the corresponding hydroxamic acid- or hydrazide ligands selectively gave the S-alcohol. Structure/activity investigations revealed that the stereochemical outcome of the catalytic reaction depends on the ligand mode of coordination. In the second part, an Fe hydrogenase active site model complex with a labile amine ligand has been synthesized and studied. The aim of this study was to find a complex that efficiently catalyzes the reduction of protons to molecular hydrogen under mild conditions. We found that the amine ligand functions as a mimic of the loosely bound ligand which is part of the active site in the hydrogenase. Further, an Fe hydrogenase active site model complex has been coupled to a photosensitizer with the aim of achieving light induced hydrogen production. The redox properties of the produced complex are such that no electron transfer from the photosensitizer part to the Fe moiety occurs. In the last part of this thesis, the development of a protocol for the transfer hydrogenation of ketones to secondary alcohols without the involvement of transition metal catalysts is described. A variety of ketones were efficiently reduced in 2-propanol using catalytic amounts of alkali alkoxide under microwave irradiation.

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