La substitution des métaux nobles par des métaux de transition abondants et bon marché est un challenge majeur de ce siècle en chimie de synthèse. Récemment, les métaux abondants tels que le fer et le manganèse (1er et 3ème en abondance dans l'écorce terrestre) ont connu un essor remarquable en catalyse homogène, notamment en réduction. Les travaux de thèse ont portés sur le développement de nouveaux catalyseurs bien-définis efficaces du fer et du manganèse pour effectuer des réactions d'hydrogénation de dérivés carboxyliques, de réduction par prêt d'hydrogène et de déshydratation d'amides. / The substitution of noble metals by abundant and cheap transition metals is a major challenge of this century in synthetic chemistry. Recently, abundant metals such as iron and manganese (1st and 3rd in abundance in the Earth's crust) have seen remarkable growth in homogeneous catalysis, especially in reduction. The thesis work focused on the development of new well-defined efficient catalysts of iron and manganese to carry out reactions of hydrogenation of carboxylic derivatives, reduction by hydrogen and dehydration of amides.

Master of Science / Department of Chemical Engineering / Larry E. Erickson / As our society continues to better prepare itself to address biological, radiological, chemical, and environmental emergencies, there is a need for better and more readily available emergency planning information for program managers and military/business personnel. An online hazardous materials and emergency planning tool for the Environmental Knowledge and Assessment Tool (EKAT: www.ekat-tool.com) would adequately fill that need. The proposed online Emergency Preparation and Green Engineering (EPGE) tool would provide the user with information regarding links to local emergency response teams and resources, guides for developing emergency plans and reports, Hazardous Materials (HAZMAT) training information, case studies to illustrate HAZMAT situations, and the ability to judge the environmental friendliness of chemicals. In this way it will serve as a means of facilitating and educating individuals for best responses in an organized fashion. In order to address their environmental responsibilities, public and private organizations are adopting Environmental Management Systems (EMS). The EPGE tool can be used in conjunction with Environmental Management Systems (EMS) to begin to address sustainability in a more practical setting. Currently the development of a comprehensive tool that identifies environmental, health, and safety concerns along with supplying relevant emergency data would be applicable to any business or organization. This tool will be available as an initial building block for the sustainability of the company. It can be used as a guide to better characterize and solve the environmental issues that could affect any business.

Les années 1990 ont été marquées par le développement de la Chimie Verte avec les premiers travaux sur le sujet et l’introduction des Douze Principes. Depuis, le nombre de recherches sur la Chimie Verte n’a cessé de croître. Ces travaux de thèse portent sur le développement de méthodes de déshydratation dans le but de former des molécules à haute valeur ajoutée en utilisant les Douze Principes de la Chimie Verte en tant que ligne directrice. Deux molécules cibles ont été sélectionnées : (i) le phénylacétaldéhyde, obtenu par déshydratation du 1-phényléthane-1,2-diol, qui est utilisé dans la composition de parfums, de médicaments, d’insecticides, etc., ou en tant qu’intermédiaire réactionnel ; et (ii) le furfural, formé par la triple déshydratation du D-xylose (monomère principal des hémicelluloses), qui peut être utilisé comme solvant sélectif ou comme molécule plateforme pour produire une large gamme de composés d’intérêt. Plusieurs points-clés ont été identifiés pour concevoir des procédés de déshydratation verts: le solvant (l’eau ou le solvant éco-compatible CPME), la méthode d’activation (utilisation d’irradiation micro-ondes ou d’un réacteur en flux continu) et le catalyseur (chlorures de métaux ou résine échangeuse d’ions). / The 1990s have witnessed the development of Green Chemistry with the first researches on the subject and the introduction of the Twelve Principles. Since then, the number of scientific works on Green Chemistry has continuously grown. This PhD work focus on the development of dehydration methods to form high added value molecules by using the Twelve Principles of Green Chemistry as a guiding framework. Two target molecules were selected: (i) phenylacetaldehyde, obtained by the dehydration 1-phenylethane-1,2-diol, which is used in perfume compositions, for the preparation of pharmaceuticals, insecticides, etc., or as a chemical intermediate; and (ii) furfural, formed thanks to the triple dehydration of D-xylose (the main sugar unit of hemicellulose), which can be used as a selective solvent or as a platform molecule to produce a wide range of high-value chemicals. The optimisation of green production processes was focused on several key points: solvents (water and the eco-friendly CPME), activation method (microwave irradiation and continuous flow) and catalysis (metal chlorides and ion-exchange resin).

The synthesis and characterization of a series of chiral indium complexes bearing a tridentate NNO ligand are reported. The ligand 2-[[[(dimethylamino)cyclohexyl]amino]methyl]- 4,6-bis(tert-butyl) phenol (H₂NNO) was synthesized via a previously published procedure and bound to indium by both a protonolysis and salt metathesis route. A dimethylated indium complex (NNO)InMe₂ (1) was isolated by reaction of InMe₃ with H₂NNO. A one-pot saltmetathesis route was used to produce a unique mixed-bridge dinuclear indium complex [(NNO)InCl] ₂(μ-OEt)(μ-Cl) (3) from a mixture of indium trichloride, potassium ethoxide and the monopotassiated salt of the ligand, KH(NNO). Direct reaction of KH(NNO) and indium trichloride resulted in the formation of (NNO)InCl₂ (4) which was carried forward to 3 by reaction with sodium ethoxide. The complex 3 is active for the ROP of β-butyrolactone ε-caprolactone and lactide and is the first reported indium-based catalyst for lactide or β-butyrolactone ROP. Kinetic studies of 3 for ROP of LA revealed that catalyst was well-behaved, and that the rate was first order with regard to lactide and catalyst. The enthalpy and entropy of activation for the ROP were experimentally determined. Polymer produced by ROP by 3 has narrow molecular weight distribution and a good correlation is seen between the observed moleular weight and monomer loading. A mechanism was proposed for 3 acting as a catalyst for the ROP of lactide; however further experiments are required to confirm this mechanism. Polymer samples isolated from the ROP of rac-lactide by rac-3 show isotactic enrichment. It is postulated that the chiral catalyst 3 is exerting stereocontrol via an enantiomorphic site control mechanism. / Science, Faculty of / Chemistry, Department of / Graduate

Amine transaminases are enzymes that catalyze the mild and selective formation of primary amines, which are useful building blocks for biologically active compounds and natural products. In order to make the production of these kinds of compounds more efficient from both a practical and an environmental point of view, amine transaminases were incorporated into multi-step one-pot reactions. With this kind of methodology there is no need for isolation of intermediates, and thus unnecessary work-up steps can be omitted and formation of waste is prevented. Amine transaminases were successfully combined with other enzymes for multi-step synthesis of valuable products: With ketoreductases all four diastereomers of a 1,3-amino alcohol could be obtained, and the use of a lipase allowed for the synthesis of natural products in the form of capsaicinoids. Amine transaminases were also successfully combined with metal catalysts based on palladium or copper. This methodology allowed for the amination of alcohols and the synthesis of chiral amines such as the pharmaceutical compound Rivastigmine. These examples show that the use of amine transaminases in multi-step one-pot reactions is possible, and hopefully this concept can be further developed and applied to make industrial processes more sustainable and efficient in the future. / <p>QC 20170113</p>

Orientador: Claudio Airoldi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T05:25:35Z (GMT). No. of bitstreams: 1 Melo_JulioCesarPerinde_D.pdf: 28431838 bytes, checksum: 0460daaa92bb9d6b56903affddf613c8 (MD5) Previous issue date: 2012 / Resumo: O trabalho foi realizado com biopolímeros orgânicos naturais: celulose e lignocelulósicos, modificados quimicamente aumentando a capacidade de sorção de contaminantes em líquidos. Foram caracterizados por IV, RMN de C, DRX, MEV and TG. Assim, as inércias química e física foram superadas através dos seguintes procedimentos sintéticos: esterificação com anidridos de celulose (maleato: 2,82, succinato: 3,07, ftalato: 2,99 mmol g) e de mesocarpo de babaçu (maleato: 141,79, succinato:176,99, ftalato:149,27 mg g); cloração da celulose com cloreto de tionila (4,95 mmol g); aminação de celulose com etileno-1,2-diamina (3,03 mmol g); reação de etilenossulfeto com mesocarpo (86,7 mg g) e epicarpo de babaçu (20,2 mg g). Com as modificações químicas dos biopolímeros as propriedades de sorção se tornaram superiores as dos biopolímeros de partida e as novas capacidades máximas de remoção de contaminantes foram: anidridos de celulose [maleato (Ni = 1,75 e Co = 2,40 mmol g), succinato: (Ni = 2,46 e Co = 2,46 mmol g) e ftalato: (Ni = 2,26 e Co = 2,43 mmol g)]; anidridos com mesocarpo de babaçu (maleato: (Cu = 19,88 mg g), succinato: (Cu = 38,58 mg g) e ftalato: (Cu = 30,63 mg g) soluções hidroalcoólicas); aminação de celulose com etileno-1,2-diamina (Cu = 2,32, Co = 1,35, Ni= 1,70 e Zn = 1,65 mmol g); reação de etilenossulfeto com mesocarpo (Cu = 39,6 mg g) e epicarpo (Cu = 39,2 mg g) de babaçu. A celulose também foi oxidada com metaperiodato aquoso para dar origem à celulose em sua forma oxidada, o 2,3-dialdeídocelulose, material de partida para outras reações, as quais foram: redução dos grupos aldeído do 2,3-dialdeídocelulose, seguido da reação deste material com os anidridos malêico, succínico e ftálico; em seguida cada um dos materiais na forma ácida foi reagido separadamente com etileno-1,2-diamina, dietil-1,2,4-triamina, trietil-1,2,4,6-tetramina. A outra rota foi a reação do 2,3-dialdeído-celulose com as poliaminas etileno-1,2-diamina, dietil-1,2,4-triamina, trietil-1,2,4,6-tetramina e em seguida, com cada um dos materiais aminados obtidos, reagí-los separadamente com os anidridos malêico, succínico e ftálico. / Abstract: The natural organic biopolymers, cellulose and lignocellulosics, were chemically modified in order to increase their sorption capacities for contaminants from liquids. The technics employed for characterization were IR, C NMR, XDR, SEM and TGA. Chemical modification and the degree of substitution were: esterification of cellulose with anhydrides [maleate: 2,82 mmol g, succinate: 3,07 mmol g, phthalate: 2,99 mmol g) and esterification of babassu mesocarp coconut with anhydrides (maleate: 141,79 mg g, succinate: 176,99 mg g, phthalato: 149,27 mg g); chlorination of cellulose with thionyl chloride (4,95 mmol g); amination of cellulose with ethylene-1,2-diamine (3,03 mmol g); reaction of ethylenesulfide with babaçu coconut mesocarp (86,7 mg g) and epicarp (20,2 mg g) The sorption capacities of these chemically modified biopolymers were outlighted as confirmed by the maxima sorption results and were: cellulose with anhydrides (maleate: (Ni = 1,75 e Co = 2,40 mmol g), succinate: (Ni = 2,46 e Co= 2,46 mmol g) e ftalate: (Ni = 2,26 e Co = 2,43 mmol g)); babassu mesocarp coconut with anhydrides [maleate: (Cu = 19,88 mg g), succinate: (Cu = 38,58 mg g) e ftalate: (Cu = 30,63 mg g) hydroalcoholic solution]; aminated cellulose (Cu = 2,32, Co = 1,35, Ni = 1,70 e Zn = 1,65 mmol g); babaçu coconut thyol-mesocarp (Cu = 39,6 mg g) e epicarp (Cu = 39,2 mg g). Cellulose was also oxidized with aqueous methaperiodate to produce cellulose-2,3-dialdehyde, which was used in other reactions: reduction of aldehyde groups, followed by reacting it with maleic, succinic and phthalic anhydrides; each of these materials in their acid form was reacted with ethylene-1,2-diamine, diethyl-1,2,4-triamine, triethyl-1,2,4,6-tetramine. The 2,3-dialdehyde-cellulose was also reacted with ethylene-1,2-diamine, diethyl-1,2,4-triamine, triethyl-1,2,4,6-tetramine and the aminated cellulose was separately reacted with maleic, succinic and phthalic anhydrides. / Doutorado / Quimica Inorganica / Doutor em Ciências

No description available.

<p>Cryogenic transmission electron microscopy (cryoEM) has become an increasingly common tool for determining structures of proteins and protein complex at near atomic resolution. We seek to determine the structure of p97 by cryoEM using an affinity capture approach that employs a family of novel synthetic lipids bearing water soluble PEG units and known high affinity inhibitor molecules at the distal end of the polymer. A library of inhibitor modified affinity lipopolymers of 5000 KD PEG molecular weights were synthesized. The inhibitor modified lipid coated grids were used to capture p97. The reconstruction of p97 revealed the structure at dimeric state at 3.64 Å and monomeric state at 4.33 Å. A PEG unit composed of 20000 KD molecular weight based polyrotaxane containing NTA ligand as affinity tag has been synthesized, used to concentrate 6x-his tagged p97 on TEM which also enabled to see all 3D orientation of the target particles and an initial model of 10.64 Å resolution of p97 structure was resolved. </p>

Layered double hydroxides (LDHs) are clay-like minerals commonly referred to as anionic clays" with a wide range of physical and chemical properties. LDHs often find application in pharmaceuticals, as polymer additives, as additives in cosmetics, as nanomaterial's and in catalysis. This is due to having variable layer charge density, reactive interlayer space, ion exchange capabilities, a wide range of chemical compositions and rheological properties (Forano et al., 2006). Various techniques exist for the synthesis of layered double hydroxides. These include co-precipitation, the urea method, induced hydrolysis, sol-gel and hydrothermal methods. Many of these produce environmentally unfriendly effluents or by-products, are energy intensive, make use of metallic salts or require inert synthesis environments (Rives, 2001). Limitations associated with these existing processes make LDH synthesis at an industrial level expensive or difficult to achieve. The need for 'green', affordable and repeatable synthesis methods are therefore often sought after. Recently the use of mechanochemistry as an alternative synthesis technique has gained wide-spread attention. Mechanochemistry involves the breaking and forming of chemical bonds due to an induced mechanical force. Various mechanochemical techniques for the synthesis of LDH materials exist or have been explored. These include methods such as single-step, two-step and mechano-hydrothermal grinding techniques. Grinding methods can be conducted dry, wet or collectively (Qu, Zhang, et al., 2015a). Mechanochemistry has further been used in conjunction with micro-wave energy and ultrasonic irradiation. The use of mechanochemistry as a synthesis method has proven to be promising with successful and unique LDHs produced. Intercalation of unique or complex anions within the interlayer has further been proven possible. The versatility and robust nature of this synthesis method makes it ideal for industrial application. Although many studies exist it was noted that limited research has been conducted on single-step wet grinding for LDH synthesis and warrants further investigation (Qu, Zhang, et al., 2015a) (Iwasaki,Yoshii, et al., 2012). This was due to factors such as incomplete conversion, difficulties associated with grinding and morphological imperfections. Single step wet milling could be benifi cial as a synthesis procedure as it eliminates hazards associated with dry powder, contains less process steps and is therefore possibly more cost effective and can be conducted batch, semi-batch or continuously due to fluid flow. Throughout the literature research conducted it was further noted that not many different milling devices have been explored. Ball mills, mixer mills and manual grinding were the most common methods used to supply mechanical energy to a system. The study therefore aims to expand on single-step wet synthesis of LDH materials by making use of a different milling device, namely a Netzsch LME 1 horizontal bead mill. The selected mill is designed for wet grinding application and can easily be up-scaled to a commercial batch, semi-batch or continuous process. Raw materials selected were a combination of oxides, hydroxides and basic carbonates. This would eliminate hazardous salt by-products and effluent, promoting 'green' synthesis of LDH materials. It was noted that the synthesis of LDH with the use of these materials have previously proven to be challenging (Qu, Zhang, et al., 2015a). The study was divided up into two sections namely a 'parameter study' and a 'versatility study'. The 'parameter study' involved exploring the in influence of milling and experimental parameters, such as rotational speed, retention time, solids loading, bead size and jacket water temperature, on the synthesis of Mg-Al LDH. The raw materials selected were MgO and Al(OH)3 combined at a divalent to trivalent cationic ratio of 2:1. The parameters were individually investigated, with the exception of jacket water temperature as it was varied with a change in retention time and a change in rotational speed. Unless stated otherwise or under investigation, parameters were investigated at a set speed of 2000 rpm, jacket water temperature of 30 °C, solids loading of 10 %, retention time of 1 h and with 2 mm yttrium stabilised zirconia beads. Therefore when investigating a specific c parameter, the others remained as stated above. Comparatively the 'versatility' study further explores the synthesis of Mg-Al, Ca-Al, Cu-Al and Zn-Al LDH by adapting optimal synthesis conditions, derived from existing mechanochemical techniques and methods, to the selected process. These were related to the divalent to trivalent cationic ratio and selected starting materials. Ageing of the samples obtained through the 'versatility study' were further explored to determine if the potential for a two-step commercial process exists. The study was investigated at a set speed of 2000 rpm, jacket water temperature of 30 °C, solids loading of 10 %, retention time of 1 h and with 2 mm yttrium stabilised zirconia beads. Half of the sample collected was subjected to ageing at 80 °C for 24 h under atmospheric conditions. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2020. / This research was funded by Techsparks (Pty) Ltd and the Technology and Human Resources for Industry Programme (THRIP) administered by the Department of Trade and Industry, South Africa, (grant number THRIP/133/31/03/2016) / Chemical Engineering / MEng (Chemical Engineering) / Unrestricted

In this work, a comparative electrochemical study has been performed to evaluate corrosion inhibition property of several film-forming corrosion inhibitors provide by Akzo Nobel on carbon steel in a chloride solution. For carbon steel exposed to 1 M NaCl solution with and without added inhibitor, electrochemical measurements including electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) at different exposure time intervals, and potentiodynamic polarization at the termination of the exposure, have been performed to investigate the film forming process and to evaluate corrosion inhibition efficiency of the inhibitors, as well as its evolution with time. The corrosion resistance data obtained from the EIS and LPR measurements are in good agreement. The results indicate different inhibition properties of the inhibitors tested. The inhibition effect of SSF CI-1 is negligible in the first hour of exposure, but it increases steadily with time for 1 day, and then remains the same level during the exposure up to one week. SSF CI-2 exhibits a good inhibition effect in the first hour, but the effect decreases with time to a low level after 8 hours, and then increases again with prolonged exposure. SSF CI-4 shows a low inhibition effect during the first day, and then increases to a maximum level after three days’ exposure. For SSF CI-5 and SSF CI-6, the inhibition effect within 8 hours is relative low but higher than that of SSF CI-4, and the effect increases with time during prolonged exposure. The SSF CI-5 seems to be better than SSF CI-6 because of a more stable inhibition effect. The EIS results indicate that most of the inhibitors form a resistive surface film on carbon steel, which becomes more resistive and protective after several days’ of exposure. However, in the initial stage of exposure, the SSF CI-6 does not show an effect of formation of a resistive film on the surface. The potentiodynamic polarization measurements suggest that, SSF CI-1 and SSF CI-2 are anodic type inhibitor, SSF CI-4 is cathodic type inhibitor, and SSF CI-5 and SSF CI-6 are mix type inhibitor. Moreover, the inhibitors tested show a similar corrosion inhibition effect as mussel adhesive protein (MAP) at the low dosage level.