No description available.

Hydrogenated nitrile butadiene rubber (HNBR) which is known for its excellent elastomeric properties and mechanical retention properties after long time exposure to heat, oil and air is produced by the catalytic hydrogenation of nitrile butadiene rubber (NBR). Hydrogenation of NBR is carried out preferably in solution via homogeneous catalysis. As yet, it is being commercially produced in a semi-batch process where gaseous hydrogen continuously flows into a batch of reactant polymer. Several catalysts have been exploited successfully for the hydrogenation of NBR in organic solvents, which include palladium, rhodium, ruthenium, iridium and osmium complexes. Owing to the drawbacks of batch production (such as time taken for charging and discharging the reactants/products, heating and cooling, reactor clean up), and the huge demand for HNBR, a continuous process is proposed where potential time saving is possible in addition to the high turn over of the product. Numerical investigation of the HNBR production in a plug flow reactor and a continuous stirred tank reactor showed that a reactor with plug flow behavior would be economical and efficient. A static mixer (SM) reactor with open-curve blade internal geometry is designed based on the simulation and hydrodynamic results. The SM reactor was designed with 24 mixing elements, 3.81 cm ID and 90 cm length. The reactor has a jacket in which steam is used to heat the polymer solution. The hydrodynamics in the SM reactor (open-flat blade structure) with air-water system showed that plug flow could be achieved even under laminar flow conditions (Reh < 20). For a constant mean residence time, the Peclet number was varying such that it is 4.7 times the number of mixing elements (ne) used in the SM reactor. Empirical correlations were developed for gas hold up (εG) and overall mass transfer coefficient (KLa). The mass transfer experiments showed that high KLa, 4 to 6 times compared to that of the conventional reactors could be achieved in the SM reactor at particular operating conditions. Very important information on the Peclet number, liquid hold were obtained from the hydrodynamic experiments conducted with the actual working fluids (hydrogen, polymer solutions) in the SM reactor. The superficial gas velocity had an adverse effect on both Peclet number and liquid hold up. The viscosity of the polymer solution also had a marginal negative effect on the Peclet number while a positive effect on the liquid hold up. The hydrogenation performance with the homogeneous catalyst OsHCl(CO)(O2)(PCy3)2 was performed in the continuous process with SM reactor. Complete hydrogenation of NBR was possible in a single pass. The effect of mean residence time, catalyst and polymer concentration on the final degree of hydrogenation was studied. The minimum catalyst required to achieve degree of hydrogenation over 97% was empirically found and an empirical correlation was developed for degree of hydrogenation as a function of operating conditions and parameters. Hydrogenation in the SM reactor is modeled by using plug flow with axial dispersion model that is coupled with the concentrations of carbon-carbon double bond, hydrogen and osmium catalyst. The model involves coupled, non-linear partial differential equations with different dimensionless parameters. The proposed model was verified with the experimental results obtained from the hydrogenation and hydrodynamic experiments. The model could satisfactorily predict the degree of hydrogenation obtained from experimental results at various operating conditions. In general, the designed continuous process with SM reactor performed well and was an effective method of manufacturing HNBR on a continuous basis. The designed system is amicable to the industrial operating conditions and promises to be highly efficient and economic process for production of HNBR.

Hydrogenated nitrile butadiene rubber (HNBR) which is known for its excellent elastomeric properties and mechanical retention properties after long time exposure to heat, oil and air is produced by the catalytic hydrogenation of nitrile butadiene rubber (NBR). Hydrogenation of NBR is carried out preferably in solution via homogeneous catalysis. As yet, it is being commercially produced in a semi-batch process where gaseous hydrogen continuously flows into a batch of reactant polymer. Several catalysts have been exploited successfully for the hydrogenation of NBR in organic solvents, which include palladium, rhodium, ruthenium, iridium and osmium complexes. Owing to the drawbacks of batch production (such as time taken for charging and discharging the reactants/products, heating and cooling, reactor clean up), and the huge demand for HNBR, a continuous process is proposed where potential time saving is possible in addition to the high turn over of the product. Numerical investigation of the HNBR production in a plug flow reactor and a continuous stirred tank reactor showed that a reactor with plug flow behavior would be economical and efficient. A static mixer (SM) reactor with open-curve blade internal geometry is designed based on the simulation and hydrodynamic results. The SM reactor was designed with 24 mixing elements, 3.81 cm ID and 90 cm length. The reactor has a jacket in which steam is used to heat the polymer solution. The hydrodynamics in the SM reactor (open-flat blade structure) with air-water system showed that plug flow could be achieved even under laminar flow conditions (Reh < 20). For a constant mean residence time, the Peclet number was varying such that it is 4.7 times the number of mixing elements (ne) used in the SM reactor. Empirical correlations were developed for gas hold up (εG) and overall mass transfer coefficient (KLa). The mass transfer experiments showed that high KLa, 4 to 6 times compared to that of the conventional reactors could be achieved in the SM reactor at particular operating conditions. Very important information on the Peclet number, liquid hold were obtained from the hydrodynamic experiments conducted with the actual working fluids (hydrogen, polymer solutions) in the SM reactor. The superficial gas velocity had an adverse effect on both Peclet number and liquid hold up. The viscosity of the polymer solution also had a marginal negative effect on the Peclet number while a positive effect on the liquid hold up. The hydrogenation performance with the homogeneous catalyst OsHCl(CO)(O2)(PCy3)2 was performed in the continuous process with SM reactor. Complete hydrogenation of NBR was possible in a single pass. The effect of mean residence time, catalyst and polymer concentration on the final degree of hydrogenation was studied. The minimum catalyst required to achieve degree of hydrogenation over 97% was empirically found and an empirical correlation was developed for degree of hydrogenation as a function of operating conditions and parameters. Hydrogenation in the SM reactor is modeled by using plug flow with axial dispersion model that is coupled with the concentrations of carbon-carbon double bond, hydrogen and osmium catalyst. The model involves coupled, non-linear partial differential equations with different dimensionless parameters. The proposed model was verified with the experimental results obtained from the hydrogenation and hydrodynamic experiments. The model could satisfactorily predict the degree of hydrogenation obtained from experimental results at various operating conditions. In general, the designed continuous process with SM reactor performed well and was an effective method of manufacturing HNBR on a continuous basis. The designed system is amicable to the industrial operating conditions and promises to be highly efficient and economic process for production of HNBR.

No description available.

The present work describes the design and synthesis of a series of dimers [(η5 - ring)MCl]2(μ2 -Cl)2, (where (η5 -ring)MCl = (η5 -Me4C5R)Rh(III)Cl or (η5 -Me4C5R)Ir(III)Cl). Iridium and rhodium dimeric complexes were synthesized via a microwave reaction and directly compared through single-crystal X-ray crystallography. Finally, the dimeric complexes were evaluated as potential oxidation catalysts. The modified HCp*R (R = isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, nheptyl, n-octyl, phenyl, benzyl, phenethyl, cyclohexyl, and cyclopentyl) type ligands were synthesized by reaction of 2,3,4,5-tetramethylcyclopent-2-en-1-one with the respective Grignard reagent (RMgX), followed by elimination of water under acidic conditions to produce the tetramethyl(alkyl or aryl)cyclopentadienes in moderate to excellent yields (39 - 98%). Reaction of the HCp*R ligands with [M(COD)](μ2 -Cl)2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) gave the dimeric complexes [Cp*RMCl]2(μ2 -Cl)2 in yields ranging from 16 - 96%. The dimers were characterized by nuclear magnetic resonance (NMR)spectroscopy, single-crystal X-ray diffraction (XRD) (supplemented by powder XRD), high-resolution mass spectrometry (HRMS), and elemental analysis. Complexes studied by XRD were analyzed to understand the bond lengths and bond angles throughout each complex. The dimeric complexes synthesized, will facilitate a complete study on how the R group influences catalytic activity. / Master of Science

Yes / A highly enantioselective rhodium catalysed asymmetric arylation (RCAA) of nitroolefins with arylboronic acids is presented using a newly developed, C1-symmetric, non-covalent interacted, phellandrene derived, nordehydroabietyl amide-containing chiral diene under mild conditions. Stereoelectronic effects were studied, suggesting an activation of the bound substrate through the secondary amide as a hydrogen-bond donor.

This dissertation summarizes research efforts focused on the use of boron and transition metal halides to form new carbon-carbon and carbon-halide bonds. The boron halide mediated alkyne-aldehyde coupling reaction to generate 1,3,5-triaryl-1,5-dihalo-1,4-dienes was reinvestigated in an attempt to explain the stereochemistry observed during changing of both the mode of addition and the reaction temperature. Either (Z,Z)-1,4-dienes or (Z,E)-1,4-dienes can be the predominant product depending on reaction conditions used. This mechanistic investigation also led to the discovery of several novel reactions. These include the stereoselective preparation of (Z)-3-chloroallylic ethers from the reaction of alkenylboron dichlorides with aryl aldehydes in the presence of an amine; the titanium(IV) halide coupling of alkoxides and alkynes; the haloallylation of aryl aldehydes with boron trihalide using different allylmetals; and the base induced elimination of the haloallylated products to form 1,3-dienes. The results of these studies strongly imply a cationic mechanism. The new reactions described herein can be characterized as atom-efficient, environmentally friendly, and capable of generating the desired products in good to excellent yields.

This thesis describes the syntheses of semiochemicals and their applications in the development of control methods for pest insects. The compounds synthesized are divided into three groups: 1) Lepidoptera pheromones; 2) methyl substituted chiral pheromones and 3) aphid pheromones. Different purification techniques have been explored in order to provide &gt; 99% pure semiochemicals for field tests. Examples of the techniques are uses of urea inclusion complexes, argentum chromatography, low temperature crystallization and what we call the Baeckström isolation technique. Iridoids have been produced in a synthetic strategy including an intramolecular enal-enamine [4+2] cycloaddition, a dynamic acetylation and an enantioselective transesterification mediated by a lipase from Pseudomonas cepacia. The use of chiral auxiliaries to perform the intramolecular [4+2] cycloaddition has also been investigated. A useful asymmetric route to iridoids has been developed.

<p>This thesis describes the syntheses of semiochemicals and their applications in the development of control methods for pest insects. The compounds synthesized are divided into three groups: 1) Lepidoptera pheromones; 2) methyl substituted chiral pheromones and 3) aphid pheromones. </p><p>Different purification techniques have been explored in order to provide > 99% pure semiochemicals for field tests. Examples of the techniques are uses of urea inclusion complexes, argentum chromatography, low temperature crystallization and what we call the Baeckström isolation technique.</p><p>Iridoids have been produced in a synthetic strategy including an intramolecular enal-enamine [4+2] cycloaddition, a dynamic acetylation and an enantioselective transesterification mediated by a lipase from Pseudomonas cepacia. The use of chiral auxiliaries to perform the intramolecular [4+2] cycloaddition has also been investigated. A useful asymmetric route to iridoids has been developed.</p>

Ce manuscrit présente le développement de nouvelles réactions énantiosélectives d’addition-carbocyclisation en cascade initiées par des acides boroniques pour la formation d’hétérocycles azotés chiraux. Les premiers travaux ont permis d’accéder à des pyrrolidines et des pipéridines énantioenrichies à partir d’énynes-1,6 et -1,7 possédant un alcyne en tant que point d’entrée et un ester α,β-insaturé comme seconde fonction électrophile. Une seconde réaction d’addition-carbocyclisation de céto-esters a également été mise au point pour conduire à des pipéridines chirales possédant trois centres stéréogènes contigus avec de très bonnes énantiosélectivités et diastéréosélectivités. Dans ces réactions asymétriques, les diènes chiraux ont été les ligands les plus adaptés permettant l’obtention d’énantiosélectivités élevées. Dans ce contexte, une nouvelle voie d’accès aux diènes chiraux monosubstitués de type Ar-MSBod utilisés pour la première réaction a été développée. / This manuscript presents the development of new asymmetric addition-carbocyclisation cascade reactions initiated by boronic acids for the formation of chiral N-heterocycles. Early works provided access to chiral pyrrolidines and piperidines from 1,6 and 1,7-enynes possessing an alkyne as the entry point and an α,β-unsaturated ester as a second electrophilic function. A second addition-carbocyclisation reaction of keto esters has also been developed to access polyfunctionnalised chiral piperidines with three contiguous stereogenic centers, with both high enantioselectivities and diastereoselectivities. In these enantioselective reactions, chiral dienes proved to be the most suitable class of ligands to achieve high enantioselectivities. In this context, a new route was developed to access chiral monosubstituted diene type Ar-MSBod, previously used in the first methodology.