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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.
261

Thermodynamique des équilibres entre phases appliquée à la définition des conditions d'extraction et de purification de la N-aminopyrrolidine

Frangieh, Marie-Rose 21 January 2011 (has links) (PDF)
Ce travail est consacré à l'étude du procédé de synthèse, d'extraction et de purification d'une hydrazine exocyclique à applications cosmétiques, la N-aminopyrrolidine (NAPY). Dans un premier temps, l'optimisation des conditions de synthèse par la voie Raschig e été conduite en étudiant l'influence de deux paramètres, rapport molaire des réactifs (NH2Cl, pyrrolidine) et la température, sur le rendement de la réaction. Les solutions brutes de synthèse étant très diluées (≈5%g en NAPY), l'extraction et la purification du produit utile sont souvent liées à des opérations successives de démixtion et de distillation. La détermination de ces conditions de séparation requière alors la connaissance des propriétés thermodynamiques des équilibres entre phases impliqués dans ces opérations unitaires. L'optimisation de la démixtion nécessite alors l'étude du système ternaire solide-liquide-liquide NaOH/Pyrrolidine/Eau. Trois coupes isothermes isobares ont été complètement déterminées, par ATI (Analyse Thermique Isopléthique) combinée à des dosages chimiques. La méthode du diamètre et des modules a été mise au point pour la détermination du point critique de la courbe de démixtion. Les opérations de distillation mettent en jeu le système ternaire NAPY/Pyrrolidine/Eau. Le binaire limite liquide-vapeur Eau/Pyrrolidine a été déterminé par ébulliométrie à la pression atmosphérique. Pour essayer de mieux comprendre les interactions hétéromoléculaires ayant lieu en phase liquide, deux autres binaire liquide-vapeur eau/amine ont été obtenus. L'étude su système ternaire liquide-vapeur nous a permis de déduire deux schémas de distillation possibles. Une fois les conditions de synthèse et d'extraction définies et un schéma de procédé a été proposé, la NAPY est obtenue conforme aux spécifications cosmétiques
262

Homogeneous and heterogeneous Cp*Ir(III) catalytic systems : Mechanistic studies of redox processes catalyzed by bifunctional iridium complexes, and synthesis of iridium-functionalized MOFs

González Miera, Greco January 2017 (has links)
The purpose of this doctoral thesis is to investigate and develop catalytic processes mediated by iridium(III) complexes. By understanding the mechanisms, the weaknesses of the designed catalysts can be identified and be overcome in the following generation. The thesis is composed of two general sections dedicated to the synthesis and applications of homogeneous catalysts and to the preparation of heterogeneous catalysts based on metal-organic frameworks (MOFs). After a general introduction (Chapter 1), the first part of the thesis (Chapters 2-4, and Appendix 1) covers the use of several homogeneous bifunctional [Cp*Ir(III)] catalysts in a variety of chemical transformations, as well as mechanistic studies. Chapter 2 summarizes the studies on the N-alkylation of anilines with benzyl alcohols catalyzed by bifunctional Ir(III) complexes. Mechanistic investigations when the reactions were catalyzed by Ir(III) complexes with a hydroxy-functionalized N-heterocyclic carbene (NHC) ligand are discussed, followed by the design of a new generation of catalysts. The chapter finishes presenting the improved catalytic performance of these new complexes.    A family of these NHC-iridium complexes was evaluated in the acceptorless dehydrogenation of alcohols, as shown in Chapter 3. The beneficial effect of a co-solvent was investigated too. Under these base-free conditions, a wide scope of alcohols was efficiently dehydrogenated in excellent yields. The unexpected higher activity of the hydroxy-containing bifunctional NHC-Ir(III) catalysts, in comparison to that of the amino-functionalized one, was investigated experimentally. In the fourth chapter, the catalytic process presented in Chapter 3 was further explored on 1,4- and 1,5-diols, which were transformed into their corresponding tetrahydrofurans and dihydropyrans, respectively. Mechanistic investigations are also discussed. In the second part of the thesis (Chapter 5), a Cp*Ir(III) complex was immobilized into a MOF. The heterogenization of the metal complex was achieved efficiently, reaching high ratios of functionalization. However, a change in the topology of the MOF was observed. In this chapter, the use of advanced characterization techniques such as X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analyses enabled to study a phase transformation in these materials. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.</p>
263

Ethylbromo Acetate as an Olfactory Probe

McClure, Fred Leland 08 1900 (has links)
Olfactory transduction mechanisms are best studied when specific blocking agents are available with which to modify cellular responses to odorant stimulation. This study is an electrophysiological investigation of functional group-specific olfactory acceptor mechanisms using ethylbromo acetate (EtBrAc), a World War I war gas which inhibits olfactory responses to odorant stimulation. The major findings of this investigation show that (1) vaporous EtBrAc is found to be a quick and effective inhibitor of electroolfactogram (EOG) responses to odorant stimulation, (2) isoamyl acetate is shown to protect EOG responses to a wide variety of odorants, inclusive of itself, from the inhibition effect of EtBrAc treatment, and (3) amine acceptor sites exist which are resistant to the inhibitory effects fo EtBrAc treatment.
264

Valorisation en synthèse organique des phytoconstituants (dérivés du gossypol) extraits de Cienfuegosia Digitata. Cav / Valorization in organic synthesis of phytoconstituents (Gossypol derivatives) extracted from Cienfuegosia Digita. Cav

Sidi Boune, Mohamed Vall 15 January 2019 (has links)
Cette thèse décrit une méthodologie innovante d’extraction et d’hémisynthèse simultanée, dénommée SECheM (Simultaneous Extraction and Chemical Modification) sur une plante mauritanienne le Cienfuegosia digitata Cav. Cette méthodologie présente plusieurs avantages : (a) elle permet d’éviter les étapes critiques au niveau de la séparation et de la purification du gossypol, un polyphénol instable isolé de la plante ciblée (b) elle permet de stabiliser le gossypol thermiquement en le transformant en base de Schiff beaucoup plus stable. (c) elle présente un avantage en termes de réduction du nombre d’étapes et de temps. La même méthodologie a été utilisée pour accéder à des analogues bases de Schiff énantiomériquement pures du gossypol seulement en 2 étapes. Ces dernières transformées efficacement en complexes métalliques énantiomériquement purs se sont montrés être intéressants d’un point de vue catalytique. / This PhD work describes an innovative methodology for simultaneous extraction and semisynthesis, named SECheM (Simultaneous Extraction and Chemical Modification) on a Mauritanian plant: Cienfuegosia digitata Cav. This methodology offers many advantages: (a) It is a perfect solution to circumvent critical steps in the extraction, separation and purification processes of gossypol that is unstable polyphenol isolated from the targeted plant (b) It allows an in-situ preparation of more stable gossypol Schiff base derivatives (c) It shows an important reduction of step number and also the time needed for the process. The same SECheM methodology was used to access enantiomerically pure Schiff base derivatives of gossypol in only two steps. The latters were efficiently transformed into enantiomerically pure metallic complexes that appear to be very interesting in a catalytic reaction.
265

Estudos de incorporação de solutos não-iônicos em micelas de detergentes zwitteriônicos / Studies on incorporation of non-ionic solutes in zwitterionic surfactant micelles

Freitas, Adilson Alves de 18 April 2001 (has links)
Entre as mais importantes propriedades de soluções aquosas micelares está a capacidade de incorporar substâncias orgânicas com diferentes polaridades e graus de hidrofobicidade. Como demonstrado por Quina et aI. (J Phys. Chem., 1995, 99, 11708-11714), um dos métodos mais promissores para a obtenção de correlações entre e a eficiência de solubilização em micelas e as estruturas do soluto e do detergente é através do uso de relações lineares de energia livre (LSERs). No presente trabalho, investigou-se a incorporação de uma série de solutos neutros em micelas dos detergentes zwitteriônicos dimetil-hexadecilamônio-propano sulfonato (CDAPS; 31 solutos) e o N-óxido de dimetil-dodecilamina (DDAO; 33 solutos), bem como em micelas catiônicas da forma protonada de DDAO (DDAOH+; 33 solutos). As constantes de incorporação dos solutos foram determinadas experimentalmente por meio de técnicas fotofísicas, métodos de solubilização e cromatografia líquida e gasosa. A análise dos resultados foi efetuada através de técnicas de regressão múltipla, obtendo-se as seguintes LSERs: CDAPS: Log Ks = - 0,55 + 0,99 R2 - 0,82 &#960;2 + 0,36 &#931;&#945;2 - 0,99 &#931;&#946;2 + 2,73 Vx DDAOH+: Log Ks = - 0,68 + 1,30 R2 - 0,78 &#960;2 + 0,67 &#931;&#945;2 - 1,45 &#931;&#946;2 + 2,29 Vx DDAO: Log Ks = - 0,46 + 0,89 R2 - 0,61 &#960;2 + 0,82 &#931;&#945;2 - 1,66 &#931;&#946;2 + 2,59 Vx onde &#931;&#945;2 e &#931;&#946;2 representam a \"acidez\" e a \"basicidade\" do soluto, com relação à formação de pontes de hidrogênio, R2 corresponde à refração molar em excesso, &#960;2 representa a dipolaridade e Vx é o volume molar do soluto. As LSERs obtidas indicam que os detergentes zwitteriônicos formam sistemas distintos dos demais estudados até o momento. No entanto, os sistemas DDAO e DDAOH+ apresentam LSERs muito semelhantes entre sí, sugerindo que a incorporação dos solutos não é afetada por uma mudança da estrutura (carga) da cabeça do detergente. / One of the most important properties of aqueous micellar solutions is their capacity to incorporate organic solutes with different degrees of polarity and hydrophobicity. As demonstrated by Quina et aI. (J. Phys. Chem., 1995, 99, 1170811714), one of the most promissing methods for obtaining correlations between solubilization eficiency and the solute and surfactant structure is via the use of linear solvation energy relationships (LSERs). The present work investigates the incorporation of a series of neutral solutes in micelles of the zwitterionic detergents hexadecyldimethylammonium propanesulfonate (CDAPS; 31 solutes) and the N-oxide of dodecyldimethylamine (DDAO; 33 solutes), as well as in the cationic micelles of the protonated form of DDAO (DDAOH+; 33 solutes). The incorporation constants were determined experimentally by photophysical techniques, from solubility measurements and by liquid and gas chromatographic methods. Analysis of the results by multiple regression techniques led to the following LSERs: CDAPS: Log Ks = - 0,55 + 0,99 R2 - 0,82 &#960;2 + 0,36 &#931;&#945;2 - 0,99 &#931;&#946;2 + 2,73 Vx DDAOH+: Log Ks = - 0,68 + 1,30 R2 - 0,78 &#960;2 + 0,67 &#931;&#945;2 - 1,45 &#931;&#946;2 + 2,29 Vx DDAO: Log Ks = - 0,46 + 0,89 R2 - 0,61 &#960;2 + 0,82 &#931;&#945;2 - 1,66 &#931;&#946;2 + 2,59 Vx where &#931;&#945;2 and &#931;&#946;2 are the hydrogen bond acidity and basicity of the solute, R2 is the excess molar refraction, &#960;2 is the dipolarity and Vx corresponds to the molar volume of the solute. The LSERs obtained demonstrate that zwitterionic surfactants are distinct from the other systems investigated previously. However, the similarity of the LSERs of DDAO and DDAOH+ suggests that incorporation of solutes is not affected by changes in the structure (charge) ofthe polar headgroup.
266

S?ntese, caracteriza??o e aplica??o de MCM-41 funcionalizado com diisopropilamina no processo de adsor??o do di?xido de carbono

Barbosa, Marcela Nascimento 12 August 2009 (has links)
Made available in DSpace on 2014-12-17T15:41:45Z (GMT). No. of bitstreams: 1 MarcelaNBpdf.pdf: 2700913 bytes, checksum: 95100e939e95f8047d0ef3d50eb366ab (MD5) Previous issue date: 2009-08-12 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Emissions of CO2 in the atmosphere have increased successively by various mechanisms caused by human action, especially as fossil fuel combustion and industrial chemical processes. This leads to the increase in average temperature in the atmosphere, which we call global warming. The search for new technologies to minimize environmental impacts arising from this phenomenon has been investigated. The capture of CO2 is one of the alternatives that can help reduce emis ions of greenhouse gases. The CO2 can be captured through the process of selective adsorption using adsorbents for this purpose. Were synthesized by hydrothermal method, materials of the type MCM-41 and Al-MCM-41 in the molar ratio Si / Al equal to 50. The synthesis of gels were prepared from a source of silicon, sodium, water and aluminum in the case of Al-MCM-41. The period of synthesis of the materials was 5 days in autoclave at 100?C. After that time materials were filtered, washed and dried in greenhouse at 100 ? C for 4 hours and then calcined at 450 ? C. Then the calcined material was functionalized with the Di-isopropylamine (DIPA) by the method of wet impregnation. We used 0.5 g of material mesopores to 3.5 mL of DIPA. The materials were functionalized in a closed container for 24 hours, and after this period were dried at brackground temperature for 2 hours. Were subsequently subjected to heat treatment at 250?C for 1 hour. These materials were used for the adsorption of CO2 and were characterized by XRD, FT-IR, BET / BJH, SEM, EDX and TG / DTG. Tests of adsorption of CO2 was carried out under the following conditions: 100 mg of adsorbent, temperature of 75?C under flow of 100 mL/min of CO2 for 2 hours. The desorption of CO2 was carried out by thermogravimetry from ambient temperature to 900?C under flow of 25 mL min of He and a ratio of 10?C/min. The difratogramas X-ray for the synthesized samples showed the characteristic peaks of MCM-41, showing that the structure of it was obtained. For samples functionalized there was a decrease of the intensities of these peaks, with a consequent reduction in the structural ordering of the material. However, the structure was preserved mesopores. The adsorption tests showed that the functionalized MCM-41 is presented as a material promising adsorbent, for CO2 capture, with a loss of mass on the desorption CO2 of 7,52%, while that in Al-MCM- 41 functionalized showed no such loss / As emiss?es de CO2 na atmosfera v?m aumentando sucessivamente devido a v?rios mecanismos provocados pela a??o humana, principalmente como a queima de combust?veis f?sseis e processos qu?micos industriais. Isso leva ao aumento da temperatura m?dia na atmosfera, a qual chamamos de aquecimento global. A busca por novas tecnologias para minimizar os impactos ambientais decorrentes deste fen?meno tem sido investigadas. A captura de CO2 ? uma das alternativas que podem ajudar a diminuir as emiss?es desses gases. O CO2 pode ser capturado atrav?s do processo de adsor??o utilizando adsorventes seletivos para este fim. Foram sintetizados pelo m?todo hidrot?rmico, materiais do tipo MCM-41 e Al- MCM-41 na raz?o molar Si/Al igual a 50. Os g?is de s?nteses foram preparados partindo deuma fonte de sil?cio, s?dio, ?gua destilada e alum?nio no caso do Al-MCM-41. O per?odo de s?ntese dos materiais foi de 5 dias em autoclave a 100?C. Ap?s esse tempo os materiais foram filtrados, lavados e secos em estufa a 100?C durante 4 horas, e posteriormente calcinados a 450?C. Em seguida os materiais calcinados foram funcionalizados com a Di-iso-propilamina (DIPA) atrav?s do m?todo de impregna??o por via ?mida. Foi utilizado 0,5 g de material mesoporoso para 3 mL de DIPA. Os materiais funcionalizados ficaram em um recipiente fechado durante 24 horas, e ap?s esse per?odo foram secos em temperatura ambiente durante 2 horas. Posteriormente foram submetidos a um tratamento t?rmico a 250?C durante 1 hora. Estes materiais foram utilizados para o processo de adsor??o de CO2 e foram caracterizados por DRX, FT-IR, BET/BJH, MEV, EDX e TG/DTG. Os ensaios de adsor??o de CO2 foram realizados nas seguintes condi??es: 100 mg de adsorvente, temperatura de 75?C sob fluxo de 100 mL/min de CO2 durante 2 horas. A dessor??o do CO2 foi realizada atrav?s da termogravimetria, da temperatura ambiente at? 900?C, sob fluxo de 25 mL/min de He e uma raz?o de 10?C/min. Os difratogramas de raios-X para as amostras sintetizadas apresentaram os picos caracter?sticos do MCM-41, evidenciando que a estrutura do mesmo foi obtida. Para as amostras funcionalizadas observou-se uma diminui??o das intensidades desses picos, consequentemente, uma diminui??o do ordenamento estrutural do material. No entanto, a estrutura mesoporosa foi preservada. Os testes de adsor??o mostraram que o MCM-41 funcionalizado se apresentou como um material adsorvente promissor, para captura de CO2, com uma perda de massa referente ? dessor??o do CO2 de 7,52 %, enquanto que no Al-MCM- 41 funcionalizado n?o apresentou essa perda
267

Relations structure-propriétés de surfaces carbonées électroactives : impact de la couche organique et du substrat / Structure-properties relationships of electroactive carbon surfaces : impact of organic layer and substrate

Touzé, Ewen 16 November 2018 (has links)
Les nouveaux matériaux carbonés modifiés par des films organiques constituent un domaine de recherche très actif depuis plusieurs décennies. Ces matériaux suscitent un intérêt grandissant dans les secteurs de l’énergie, de la santé et de l’environnement. Afin d’améliorer les performances de ces matériaux, les innovations reposent notamment sur la maîtrise de la fonctionnalisation des surfaces, le contrôle de la stabilité de la couche immobilisée ou encore sur les nouvelles propriétés liées à la modification. Selon les fonctions chimiques greffées, les applications sont multiples : détection et/ou la capture d’éléments chimiques, hydrophobicité, stockage d’énergie électrique ou de gaz ou encore biocompatibilité. Dans ce contexte, les travaux de cette thèse portent sur la modification de surfaces carbonées par différents composés organiques, dans le but d’une part de déterminer les relations structurepropriétés du film déposé et d’autre part d’améliorer les performances de supercondensateurs carbonés. Nos investigations reposent sur la synthèse d’un ensemble de composés conjugués ou non, suivi d’un greffage indirect passant par une construction sur surface ou par greffage direct via l’oxydation d’amine. Ces greffages ont été explorés méthodologiquement afin de déterminer l’impact de la conjugaison au sein du film organique déposé et l’influence de la structure du matériau carboné. Nous montrons également qu’une fonctionnalisation contrôlée sur carbone activé permet d’avoir une meilleure intégration des molécules dans des supercondensateurs carbonés. L’enjeu consiste à mieux comprendre les interactions molécules-substrat au cours de la modification de matériaux. / The new carbon materials modified with organic films has been a very active field of research for several decades. These materials are attracting increasing interest in the fields of energy, health and environmental. In order to improve the performance of these materials, the innovations are based in particular on the control of the functionalization of the surfaces, the control of the stability of the immobilized layer or on the new properties related to the modification. According to the chemical units grafted, the applications are numerous: detection and/or capture of chemical elements, hydrophobicity, storage of electrical energy or gas or also biocompatibility. In this context, the work of this thesis deals with the modification of carbon surfaces by various organic compounds firstly to determine the structureproperties relationships of the deposited film and secondly to improve the performance of carbon supercapacitors. Our investigations are based on the synthesis of conjugated or unconjugated compounds, followed by indirect grafting by build steps or direct grafting via amine oxidation. These grafts were explored methodologically to determine the impact of the conjugation within the deposited organic film and the influence of the structure of carbon material. We also show that controlled activated carbon functionalization allows for better integration of molecules into carbon supercapacitors. The challenge is to understand molecule-substrate interactions during the modification of materials.
268

Mesoporous organosilica materials with amine functions : surface characteristics and chirality / Mesoporous organosilica materials with amine functions : surface characteristics and chirality

Voß, Rebecca January 2005 (has links)
In this work mesoporous organisilica materials are synthesized through the silica sol-gel process. For this a new class of precursors which are also surfactant are synthesized and self-assembled. This leads to a high surface area functionality which is analysized with copper (II) and water adsorption. / Im Rahmen dieser Arbeit werden mesoporöse Amin-funktionalisierte Organo-Silikate durch den Silika Sol-Gel Prozess hergestellt. Dabei werden neue Alkoxysilyl-Precursoren synthetisiert und condensiert die die gewünschte Funktion auf die Oberfläche dirigieren. Herstellt werden primäre, secundäre und chirale Amine. Die Oberflächenfunktionalität wird mit Kupfer (II) und Wasser Adsorption analysiert.
269

Des germylenes aux germynes : Synthèse et réactivité de ces analogues lourds des carbenes et des alcynes

Bonnefille, E. 26 September 2007 (has links) (PDF)
Les métalla-alcynes du groupe 14-M=C-(M=Si, Ge, Sn) constituent une nouvelle fonction de la chimie organométallique ; cette fonction apparaît extrêment prometteuse tant du point de vue fondamental qu'appliqué. En effet si l'étude d'une nouvelle liaison du carbone présente un évident intérêt fondamental, ces dérivés apparaissent surtout prometteurs par leurs nombreuses applications potentielles : précurseurs de polymères organométalliques, nouveaux ligands en chimie des métaux de transition, catalyse...<br />Aucun germa-alcyne n'a été isolé à ce jour et un seul exemple, de courte durée de vie, a été caractérisé au sein de notre équipe par réaction de piégeage. Notre stratégie pour préparer de telles molécules met en jeu la décomposition photochimique d'un diazogermylène. Dans ce travail notre effort a plus particulièrement porté sur la recherche de substituants susceptibles de stabiliser ces espèces par des effets électroniques et stériques.<br />Nous avons utilisé un nouveau ligand (Ar=2-diisopropylaminoéthyl-4,6-diterbutylphényl) qui présente l'intérêt d'ajouter à l'effet stérique l'effet électronique d'une coordination intramoléculaire N->Ge. Sa décomposition photochimique conduit bien ensuite, après départ d'azote au germa-alcyne Ar-Ge=C-SiMe3. Ce dernier constitue le 2ème germa-alcyne connu ; il a été caractérisé par sa réaction avec l'eau et le tertiobutanol. Le diazogermylène offre par ailleurs une chimie riche et originale ; il permet d'obtenir en particulier des germathione, germa-sélénone et germa-tellurone >Ge=Y (Y=S, Se, Te) étonnamment stables à l'état monomère et dont il existe peu d'exemples.
270

New approaches to preparation of macroporous monoliths for use in liquid chromatography

Nguyen, Anh Mai January 2009 (has links)
High performance liquid chromatography (HPLC) is one of the major techniques in separat-ion sciences. Faster separation and higher efficiency are required to meet ever-growing demands. Despite numerous studies and achievements on improving mass transfer in particulate packings discontinuity seems to be the cornerstone drawback in their development. Macroporous continuous beds or monoliths are therefore a promising alternative to the particle medium. This thesis deals with preparation of new monoliths used as carrier for HPLC. Two different approaches were developed for two polymer systems. One was based on polycondensation of epoxy resins and polyamines which were components of an oil-in-water emulsion. An epoxy resin mixture was dispersed in aqueous polyamine phase with the aid of a surfactant. The other involved a traverse of a ready-made polymer solution around its upper critical solution temperature (UCST). In other words, linear polyamides, non-covalently crosslinked polymers, dissolved in a solvent at temperature higher than their UCST followed by slow cooling to below the critical temperature to precipitate the polymers. Partly re-established hydrogen bonds resulted in the formation of crystallites that interconnected into a network structure. Factors controlling morphology and porosity of final products were investigated. The study also deals with surface modifying for chromatographic applications. Functionalization pathways attempted in the thesis were quaterization of inherent amine of the epoxy-based monoliths and grafting tentacle ion groups via glycidyl methacrylate by atom transfer radical polymerization (ATRP) for ion exchange chromatography (IEC).

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