Um die anderen Arten von Veröffentlichungen zu diesem Thema anzuzeigen, folgen Sie diesem Link: Greener synthesis.
Dissertationen zum Thema „Greener synthesis“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-50 Dissertationen für die Forschung zum Thema "Greener synthesis" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
1
Howie, Rowena Anne. „Metal-organic frameworks : towards greener synthesis“. Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41707/.
Der volle Inhalt der QuelleAnnotation:
Metal Organic Frameworks (MOFs) are an interesting class of porous materials, for potential commercial applications such as storage and separation of gases. However, the industrial use of MOFs would require their synthesis on a much larger scale, necessitating the development of scalable synthesis techniques that are both greener and faster than those currently employed. This Thesis describes the recent progress towards the clean and scalable synthesis of MOF materials via the use of high temperature water (HTW) and related solvents. Supercritical ethanol extraction is also presented as a greener alternative for the removal of impurities, such as unreacted ligand, from within the pores of MOFs. Chapter 1 introduces the concepts explored during this work, such as green chemistry, and includes a brief overview of MOF materials, covering their properties, applications and synthesis, as well as the challenges facing their industrial implementation. The properties of HTW and supercritical ethanol, in relation to their use as cleaner solvents for MOF processing, are summarised and the aims of this project stated. The high pressure equipment and analysis techniques used during this work are then described in Chapter 2. Detailed descriptions and standard operating procedures for the following equipment are included: high pressure mini autoclaves; a continuous flow HTW reactor for the synthesis of MOF materials; and a supercritical ethanol extraction set up, for the removal of impurities from within MOF samples. (Information regarding a new continuous flow rig developed during this project can be found in Chapter 6). The use of supercritical ethanol as a cleaner alternative method for the removal of uncoordinated ligand from within the pores of MOF materials is explored in Chapter 3, where MIL 53(Al), an archetypal aluminium MOF, was used as an example throughout. The impact of this technique on the properties of the resulting MOF samples are also considered within this chapter. Chapter 4 illustrates the broad applicability of HTW to MOF materials, demonstrating the synthesis of a wide range of MOFs, primarily as fast batch reactions. Unlike typical MOF syntheses which require several days, reaction times of just 10 minutes were used during this investigation. This highlights the fact that the synthesis of MOFs in HTW is both faster and cleaner than many previous methods. The variety of MOFs synthesised in this chapter contain different metal centres and ligands, confirming that HTW synthesis is not limited to a small sub set of MOF materials. MOFs successfully synthesised in this manner include: MIL 96(Al); NOTT 300(Al); NOTT-300(In); scandium terephthalate, plus amine and nitro group containing analogues; and MOF 74(Ni). The synthesis of a larger (10 g) sample of one of these MOFs, NOTT 300(Al), is the subject of Chapter 5, which can be viewed as a case study into the challenges facing the scalable synthesis of MOF materials in both batch and continuous flow. Building on experience gained during this investigation, a new continuous flow HTW MOF synthesis reactor was designed and constructed, the development and testing of which forms the basis of Chapter 6. This new reactor was then implemented in Chapter 7, which describes the HTW synthesis of a range of functionalised aluminium MOFs, based on the MIL 53(Al) structure, containing additional amine or nitro groups, in both batch and flow. These MOFs were the first examples of the synthesis of functionalised MOF materials in HTW, demonstrating the flexibility of this technique and suggesting that it may be successfully applied to a much wider range of MOFs in the future. Finally, Chapter 8 revisits the aims set out in Chapter 1, providing a summary of the progress made towards meeting each aim and highlighting possible future directions.
2
Nada, Majid Hameed. „Greener synthesis of nanocrystalline ZSM-5“. Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/3149.
Der volle Inhalt der QuelleAnnotation:
Nanocrystalline ZSM-5 zeolite, which is a well-known catalyst used in a variety of applications in industry, environment, and medicine, can be synthesized using different methods. However, a big challenge in synthesizing nanocrsytalline ZSM-5 is the use of an organic template such as TPAOH, which is very expensive. The template is required to facilitate the growth of the nanocrsytalline ZSM-5 during the synthesis. However, to use the nanocrsytalline ZSM-5, the template has to be removed by a calcination process to open the pores and reveal the active surface of the nanocrystalline ZSM-5. The calcination process requires a high temperature for a long time to remove the organic template. Consequently, synthesizing nanocrystalline ZSM-5 by using a templated method is considered to be time, energy, and materials inefficient. In addition, the production of CO2 from the calcination process is a negative impact on the environment. Therefore, finding another method to synthesize nanocrystalline ZSM-5 without using an organic template would be beneficial. Here, nanocrystalline ZSM-5 was synthesized successfully in high yield and quality by using a seed-assisted method and without using the organic template. In addition, the effect of synthesis temperature, synthesis time, basic environment, amount of seeds, size of seeds, aging time, and use of calcined and uncalcined seeds are investigated in this study. The synthesized nanocrystalline ZSM-5 materials were characterized by using X-ray diffraction (XRD), gas adsorption isotherm (BET/BJH), and transmission electron microscopy (TEM).
3
Harsanyi, Antal. „Elemental fluorine for the greener synthesis of life-science building blocks“. Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11705/.
Der volle Inhalt der QuelleAnnotation:
Fluorinated organic compounds are increasingly important in many areas of our modern lives, especially in pharmaceutical and agrochemical applications where the incorporation of this element can have a major influence on biochemical properties. The introduction of the carbon-fluorine bond into such systems is typically carried out using well established multistep, nucleophilic fluorination processes that usually lead to large waste streams. Despite the availability of alternative electrophilic fluorination methods which have found several applications on discovery scale, the direct transformation of C-H to C-F bonds on large scale is scarce. Elemental fluorine is the only electrophilic fluorinating reagent that is viable for manufacturing scale applications, but, in spite of the advances in this field in the past 25 years, there are only a handful of processes where it is used, most notably in the manufacturing of 5-fluorouracil. In this thesis the direct fluorination of several industrially relevant organic systems was investigated with an aim to provide optimised, high yielding and scalable processes that could be compared with existing manufacturing methods using a green chemistry metrics package developed by the EU IMI Chem21 consortium.
4
Luitel, Govinda Prasad. „Greener synthesis of some new isoxazolidine and isoxazoline derivatives via 1,3-dipolar cycloaddition reactions and studies of biological activities of the cycloadducts“. Thesis, University of North Bengal, 2017. http://ir.nbu.ac.in/handle/123456789/2576.
Der volle Inhalt der Quelle
5
Nasr, Kifah. „Enzyme-catalyzed synthesis of polyesters by step-growth polymerization : a promising approach towards a greener synthetic pathway“. Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR030.
Der volle Inhalt der QuelleAnnotation:
La polymérisation catalysée par des enzymes a fait l'objet d'une attention croissante ces dernières années en tant qu’alternative écologique à la catalyse à base de métal. L'objectif de notre travail est de synthétiser une série de polyesters par catalyse enzymatique basée sur différents diols et diesters aliphatiques et aromatiques, où nous nous sommes concentrés sur l'influence des paramètres de réaction, des structures de monomères et avons décrit les avantages et les limites de la catalyse enzymatique dans la synthèse de polymères. L'enzyme utilisée tout au long de nos travaux était Novozym 435, une lipase de Candida antarctica, immobilisée sur une résine acrylique. Dans le Chapitre 1, nous avons passé en revue les différentes méthodes et approches utilisées dans la littérature pour synthétiser des polymères par catalyse enzymatique. Dans le Chapitre 2, nous avons effectué la réaction entre l’hexane-1,6-diol et l'adipate de diéthyle via une approche de polycondensation en deux étapes où nous avons évalué l'effet de certains paramètres sur la masse molaire moyenne en nombre (Mn). L'effet de la température, du vide et de la charge enzymatique a été déterminé à l'aide d'un plan d’expérience de type plan composite centré. D'autres facteurs tels que le milieu réactionnel, le temps d'oligomérisation et la recyclabilité de l’enzyme ont également été évalués. Dans le Chapitre 3, des copolyesters à base de furane ont été synthétisés, où nous avons montré que nous pouvons incorporer des quantités plus élevées de dérivés furaniques lors de l'utilisation de diols aliphatiques avec des chaînes plus longues tels que le dodécane-1,12-diol. Dans le Chapitre 4, le lévoglucosan, une structure cyclique anhydre à 6 carbones et un produit de pyrolyse d'hydrates de carbone tels que l'amidon et la cellulose, a réagi avec des diesters de différentes longueurs de chaîne en présence de diols aliphatiques et de Novozym 435 comme catalyseur. Les polyesters produits étaient limités en terme de masse molaire moyenne en nombre (Mn) et de quantité de lévoglucosan incorporée. En augmentant la longueur du diester, nous avons augmenté la quantité de lévoglucosan incorporée ainsi que la masse molaire moyenne en nombreEnzyme-catalyzed polymerization have been witnessing a growing attention in recent years as an eco-friendly substitute to metal-based catalysis. The objective of our work is to synthesize a series of polyesters via enzymatic catalysis based on different aliphatic and aromatic diols and diesters, where we focused on the influence of reaction parameters, monomer structures, and depicted the advantages and limitation of enzymatic catalysis in polymer synthesis. The enzyme used throughout our work was Novozym 435, a lipase from Candida antarctica, immobilized on an acrylic resin. In Chapter 1, we reviewed the different methods and approaches used in the literature to synthesize polymers via enzymatic catalysis. In Chapter 2, we performed the reaction between hexane-1,6-diol and diethyl adipate via a two-step polycondensation approach where we monitored the effect of certain parameters on the number average molecular weight (Mn). The influence of temperature, vacuum, and the amount of enzyme loading were determined using a central composite design. Other factors such as the reaction media, oligomerization time, and catalyst recyclability were also assessed. In Chapter 3 furan-based copolyesters were synthesized, where we showed that we can incorporate higher amounts of furan when using aliphatic diols with longer chains such as dodecane-1,12-diol. In Chapter 4, levoglucosan, an anhydrous 6-carbon ring structure and a pyrolysis product of carbohydrates such as starch and cellulose, was reacted against different chain length diesters in the presence of aliphatic diols and Novozym 435 as a catalyst. The polyesters produced were limited in their number average molecular weight (Mn) and the amount of levoglucosan that was successfully incorporated into the polymeric structure. Nevertheless, by increasing the chain length of the diester, we were able to produce a copolymer containing higher amounts of levoglucosan and a higher molecular weight
6
Rai, Neelam. „Greener synthesis and 1, 3-dipolar cycloaddition reactions of a amino nitrones and studies of biological activities of the cycloadducts“. Thesis, University of North Bengal, 2017. http://ir.nbu.ac.in/handle/123456789/2663.
Der volle Inhalt der Quelle
7
Mestres, Ricard Sola. „Greener approaches for chemical synthesis : ball mill and microwave assisted synthesis of fluoxetine and duloxetine and enantioselective catalysed addition of organometallic reagents to aldehydes“. Thesis, Manchester Metropolitan University, 2017. http://e-space.mmu.ac.uk/618791/.
Der volle Inhalt der QuelleAnnotation:
This PhD thesis focuses on the development of “greener” synthetic methodologies in organic synthesis. Turning chemical production into a more sustainable industry - by reducing the waste generated and the electricity consumption - is highly desired in a world with limited resources and increasing population. This thesis, in particular, focuses on three of the ‘12 Principles of Green Chemistry’, reducing the amount of solvent and energy consumption in a chemical process, and the use of catalytic reagents instead of stoichiometric. In the first chapter of this thesis, a greener synthetic route for the preparation of the antidepressant fluoxetine (Prozac) was developed. The use of ball milling allowed a decrease of the solvent used in the process, furthermore, microwave assisted heating provided a more efficient method compared to the traditional heating using an oil bath. Fluoxetine was synthesised with 47% yield through two different synthetic routes (3 and 4 steps respectively). In addition, the scope of the developed methodologies was tested by the attempted synthesis of the antidepressant duloxetine. The second chapter of this thesis focuses on the catalytic enantioselective synthesis of chiral alcohols. More specifically, two different methodologies for the catalytic enantioselective addition of organolithium reagents to aldehydes were successfully developed, achieving excellent yields and enantioselectivities. Furthermore, a new methodology for the use of organozirconium reagents as nucleophiles in the catalytic enantioselective 1,2-addition of alkenes to aldehydes was also developed. Last, the implementation of a catalytic enantioselective step to the previous syntheses of fluoxetine was attempted.
8
Saba, Sumbal. „Synthesis of unsymmetrical diorganyl chalcogenides by using arylboronic acids or C (sp2)-H bond functionalization of arenes under greener conditions“. reponame:Repositório Institucional da UFSC, 2016. https://repositorio.ufsc.br/xmlui/handle/123456789/168202.
Der volle Inhalt der QuelleAnnotation:
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, 2016.Made available in DSpace on 2016-09-20T05:02:32Z (GMT). No. of bitstreams: 1 341356.pdf: 20337282 bytes, checksum: 2c692523891aae34c8c39befe4a17c29 (MD5) Previous issue date: 2016
No presente trabalho desenvolveram-se procedimentos robustos, econômicos e sustentável para a síntese de dicalcogentos de organoíla não simétricos usando uma variedade de ácidos borônicos arílicos substituídos e arenos [O- ou N-] subtituídos. Na primeira parte, desenvolvemos um sistema catalítico oxidativo que combina iodo/DMSO para a síntese de uma grande variedade de dicalcogenetos de diorganoíla não simétricos (S, Se, Te), utilizando vários ácidos borônicos arílicos sob irradiação de micro-ondas. As reações foram realizadas pela mistura de ácidos boronicos com os dicalgenetos desejados, na presença de 10 mol% de iodo, um equiv. ácidos borônicos arílicos II, 0,5 equiv. de vários dicalcogenetos de diorganoíla I e 2 equiv. de DMSO (como oxidante). Os produtos calcogenados desejados III foram obtidos em rendimentos de bons a excelentes. Todas as reações foram realizadas sem a exclusão de ar e umidade a 100 °C durante 10 minutos sob irradiação de microondas. Vários substituintes com diferentes efeitos eletrônicos e estéricos foram tolerados nas condições ótimas de reação. A metodologia desenvolvida demonstrou ser robusta e pode ser facilmente efetuada na escala de 10 mmol, sem qualquer perda significativa de rendimento. A química aqui descrita representa um protocolo livre de solvente e de metal de transição para a preparação de calcogenetos de diorganoíla não simétricos. O escopo da presente metodologia de acoplamento foi estendido usando trifluoroboratos de potássio vinilícos IV como uma alternativa para os ácidos borônicos, utilizando os parâmetros da condição otimizada. A reação de ditelureto e disseleneto de dirganoíla I ocorreu sem problemas e proporcionou a formação dos produtos acoplados correspondentes em rendimentos isolados de 87% e 89%. Considerando a importância dos compostos organocalcogênio, na segunda etapa deste trabalho, desenvolveu-se um método regiosseletivo, rápido e ambientalmente seguro, catalisado por iodo para a síntese de calcogentos de organoíla. Essa metodologia ocorre pela formação de ligações C-Se / C-S via clivagem oxidativa de ligação C (sp2) -H utilizando arenos [O- ou N-] substituídos. Esse processo é realizado pela calcogenação direta de dicalcogenetos de organoíla I com vários arenos VI, catalisados por 20 mol% de iodo na presença de 3 equivalentes de DMSO (como oxidante). Essa metodologia regiosseletiva, sob irradiação de micro-ondas, permitiu obter os produtos desejados funcionalizados com um substituinte organocalcogenoíla, em 10 min, em bons rendimentos. Outras vantagens desse método são: condições livres de solvente e metal de transição; procedimento experimental sem a exclusão de ar e umidade. A reação também foi efetuada em escala de 10 mmol sem perda significativa de rendimento. Além disso, por este protocolo, foi possível funcionalizar heteroarenos biologicamente importantes contendo S/Se, tais como: pirimidinas, piridinas e tiazóis. A versatilidade da metodologia desenvolvida permitiu ainda a utilização de tiofenol VIII e hidrazidas de sulfonila VIII como agentes sulfenilação e N,N-dimetilanilina IX alternativos, levando-se o produto tiolado X desejados em bom rendimentos, em um tempo de reação curto usando irradiação de micro-ondas.
Abstract : In the present work we developed robust, economical and greener procedures for the synthesis of unsymmetrical diorganyl chalcogenides by using various substituted arylboronic acids and [O or N]- containing arenes. In the first part, we developed Iodine/DMSO catalyzed oxidative system for the synthesis of a variety of unsymmetrical diorganyl chalcogenides (S, Se, Te) using various arylboronic acids under microwave irradiations. The desired chalcogenated products III were obtained in good to excellent yields in the presence of 10 mol% of iodine, one equiv. of arylboronic acids II, half equiv. of various diorganyl dichalcogenides I and 2 equiv. of DMSO (as an oxidant). All the reactions were performed without the exclusion of air and moisture at 100 0C for 10 min under microwave irradiation. Various substituents with different electronic and steric effects tolerated in the optimized reaction conditions. The developed methodology was shown to be robust and could easily be scaled-up without any significant loss of yield. The chemistry described herein represents a transition metal and solvent free method for the preparation of unsymmetrical diorganyl chalcogenides. We were also successful in scaling up the reaction in up to 10 mmol. The scope of this coupling methodology was extended by using potassium vinyltrifluoroborate IV as an alternative to boronic acid in these tellurylation and selenylation reactions by applying the optimal reaction parameters. The reaction of ditelluride and diselenide I proceeded smoothly and afforded the corresponding coupled products V in 87% and 89% isolated yield. Considering the importance of diorganyl chalcogenides, we developed a regioselective, rapid and greener iodine-catalyzed method for the synthesis of diorganyl chalcogenides through oxidative C Se/C S formation via direct C(sp2)-H bond cleavage using [O or N]-containing arenes. In this work, we reported the synthesis of unsymmetrical diorganyl chalcogenides VII via direct chalcogenation reactions between dichalcogenides I and various arenes VI catalyzed by 20 mol% of iodine in the presence of 3 equiv. of DMSO (as an oxidant). This regioselective methodology allowed us to obtain desired chalcogenated product in good to excellent yields under transition metal and solvent-free conditions, without the exclusion of air and moisture, applying microwave irradiations for 10 min. The reaction was also scaled-up to 10 mmol. Additionally, by this protocol, we were able to access biologically important Se/S containing heteroarenes, such as, pyrimidines, pyridines, thiazole. The versatility of the developed methodology was observed by using thiophenol VIII and sulfonyl hydrazides VIII as another sulfenylating agents and N,N-dimethylaniline IX, affording the desired sulfonated product X in very good yield, in a short reaction time using MW irradiation.
9
Dhakal, Ram Chandra. „New Approaches To Heterocycle Synthesis: A Greener Route To Structurally Complex Protonated Azomethine Imines, And Their Use In 1,3-Dipolar Cycloadditions“. ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/777.
Der volle Inhalt der QuelleAnnotation:
1-Aza-2-azoniaallene salts are reactive intermediates that undergo [3+2] cycloaddition with many different types of multiple bonds. For the past several years, the Brewer group has studied the reactivity of these intermediates in intramolecular reactions, and have discovered that these cationic heteroallenes can react through a variety of other, mechanistically distinct, pathways to give different classes of nitrogen heterocycles. For example, prior work in the Brewer group revealed that 1-aza-2-azoniaallene salts could react in an intramolecular [4+2] cycloaddition reaction to give protonated azomethine imine salts containing a 1,2,3,4-tetrahydrocinnoline scaffold. Further study of the scope and limitations of this Diels-Alder-like reaction are described herein. These studies primarily focused on how varying the N-aryl ring and alkene substituents affected the reaction. We discovered that in several instances, the metal mediated reaction did not facilitate the cycloaddition very well, so we searched for alternative ways to facilitate the reaction. We discovered that a non-metallic Lewis acid (TMSOTf) provided very clean products with α-chloroazo compounds. I hypothesized that changing the leaving group adjacent to the azo might further improve the reaction. With this in mind, I developed a technique to prepare α-trifluoroacetoxyazo compounds by treating aryl hydrazones with trifluoroacetoxy dimethylsulfonium trifluoroacetate. This technique is compatible with all types of functional groups including nitro aryl compounds, which gave low yields of the corresponding chloroazo derivatives. Importantly, these α-trifluoroacetoxyazo compounds gave even better cycloaddition results when treated with TMSOTf, and this method is more practical, more environmentally friendly, and greener than the metal mediated technique. This process even returned sterically hindered products in high yield, and provide a dearomatized non-protonated azomethine imine salt, which further verified the proposed mechanism of the [4+2] cycloaddition. Azomethine imines are well known to undergo 1,3-dipolar cycloadditions with alkenes. We wondered if the protonated azomethine imine salts generated by the [4+2] cycloaddition could be used in a subsequent base-mediated [3+2] cycloaddition to generate structurally complex tetra- or pentacyclic products. We were pleased to find that the protonated azomethine imines indeed reacted smoothly with a variety of π-system in the presence of triethylamine to give the corresponding cycloadducts in high yields with moderate to high diastereoselectivities. In an attempt to understand the diastereoselectivity of these [3+2] cycloadditions better, I modeled them computationally.
10
Sharma, Prawin Kumar. „Greener approach to the synthesis of some novel class of isoxazolidine and isoxazoline derivatives using N-methyl and N-phenyl-a-chloro nitrones“. Thesis, University of North Bengal, 2016. http://ir.nbu.ac.in/handle/123456789/1884.
Der volle Inhalt der Quelle
11
Matarín, Morales Joan Antoni. „Syntheses of (S)-Bicalutamide and Somatostatin analogs, and development of Green procedures for Peptide synthesis“. Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673027.
Der volle Inhalt der QuelleAnnotation:
Peptides are defined as compounds that contain between two and fifty amino acids connected together by amide bonds. Inside our body, peptides are natural biological messengers that play critical roles in human physiology as hormones, neurotransmitters, growth factors or antibacterial agents. Since the first efforts on peptide synthesis circa 1900 and the introduction of cleavable protecting groups (PGs), the real breakthrough in the field was the concept of solid-phase peptide synthesis (SPPS) reported by B. Merrifield in 1963. This strategy conceived the use of a polymeric insoluble resin to make the peptide chain grow without having to isolate synthetic intermediates as in previous solution-phase methods. To date, Fmoc/tBu SPPS has gained almost optimal efficiency in terms of coupling efficiency and duration in detriment of solvent consumption, which has been recognized as environmental issue under a Green Chemistry point of view. The first objective (Chapter 2) of this doctoral thesis was to chemically explore new green SPPS methodologies that permit: i) the reduction of hazardous organic solvents using water as the main one; and ii) the minimization of PGs using N-α-unprotected amino acids.
The use of orthogonal PGs such as Fmoc (base labile) for the α-amino group or the acid-labile PGs for the sidechains (e.g. Boc, tBu, Trt, Pbf) permitted to use trifluoroacetic acid (TFA) only once, specifically, in the last cleavage/deprotection step of the synthesis. Once the acidic peptide solution is separated from the polymeric resin, the peptide must be precipitated with great volumes of cold diethyl ether (DEE). Under the perspective of Green Chemistry, both TFA and DEE are considered as high concern substances. Therefore, the reduction of these substances is very desirable in industrial acidolysis processes. The second objective (Chapter 3) of this doctoral thesis was to study the possible use of green solvents in peptide cleavage and deprotection procedures.
Somatostatin (SST14) is a 14-amino acid cyclopeptide hormone discovered in 1973 that in our body acts as a neuromodulator, a neurotransmitter and a potent inhibitor of various secretory processes and cell proliferation. Because of its broad modulatory activity, SST14 was conceived as an interesting peptide for clinical applications. However, its full therapeutic potential could not be exploited because of its short plasma half-life (t1/2 < 3 min). Therefore, since the 1980s great efforts on finding shorter somatostatin analogs (SSAs) have been performed. The strategy of BCN Peptides and Riera Lab consisted in modifying the original SST14 sequence with unnatural aromatic amino acids maintaining the 14-amino acid structure. By doing this, both the conformation of the synthesized analogs and
1
their biological activity could be effectively modulated. The third objective (Chapter 4) of this doctoral thesis was to design and develop new stable analogs maintaining the 14-amino acid structure of the parent peptide. Unnatural aromatic and D-amino acids were used for the design of these new analogs.
Bicalutamide is an oral non-steroidal anti-androgenic drug that has been used in the treatment of prostate cancer since 1995. Bicalutamide is clinically administered in its racemic form, though the anti- androgenic activity is exclusively found in the (R)-enantiomer, being (S)-bicalutamide inactive and non-toxic. Recently, Farrera and co-workers at BCN Peptides demonstrated in vitro the potential use of (S)-bicalutamide as an exocytosis activating compound that could be used as a universal treatment for Lysosomal Storage Diseases (LSDs), which involve the accumulation of macromolecules inside the lysosomes. This abnormal accumulation might initiate a cascade of secondary effects, ultimately leading to irreversible cellular damage or cell death. Despite the in vitro results, the effectiveness of (S)-bicaluamide must be confirmed in vivo in preclinical and clinical studies. The fourth objective (Chapter 5) of this doctoral thesis was to design and develop a synthetic route to obtain (S)-bicalutamide, as well as its precursors using large-scale procedures and methodologies. In addition, this synthetic route was adapted to follow Good Manufacturing Practices (GMP) to produce (S)-bicalutamide according to the required quality standards to use it in preclinical studies.Los péptidos son compuestos que contienen entre 2 y 50 aminoácidos conectados por enlaces amida. Dentro de nuestro cuerpo, los péptidos son mensajeros biológicos naturales que tienen un papel importante en la fisiología humana como hormonas, neurotransmisores o factores de crecimiento. Actualmente, la estrategia Fmoc/tBu de síntesis de péptidos en fase sólida (SPPS) es la que ha llegado a un nivel óptimo de eficiencia y duración en detrimento del consumo de reactivos y disolventes, lo cual es reconocido como un problema para el medio ambiente. El primer objetivo de la tesis consiste en explorar nuevas metodologías sintéticas que permitan reducir el uso de disolventes y grupos protectores en la síntesis de péptidos. En relación con esto, el segundo objetivo de la tesis consiste en desarrollar una metodología verde de acidólisis que permita reducir el uso de ácidos y disolventes peligrosos usados en este tipo de procesos. La Somatostatina (SST14) es una hormona de estructura cíclica formada por 14 aminoácidos que actúa en nuestro cuerpo como neurotransmisor o como un potente inhibidor de procesos secretorios o de proliferación celular. Pese a estas actividades terapéuticas, su potencialidad está limitada por su corto tiempo de semivida en plasma sanguíneo (t1/2 < 3 min). A diferencia de otros análogos comerciales más cortos, la estrategia de BCN Peptides y Riera Lab consiste en modificar la estructura original de SST14 con aminoácidos aromáticos no naturales y D-aminoácidos, consiguiendo modular la conformación de los análogos y su actividad biológica. El tercer objetivo de la tesis consiste en el desarrollo de nuevos análogos de Somatostatina usando la estrategia anterior. La bicalutamida es un fármaco anti-andrógeno que se ha utilizado para el tratamiento del cáncer de próstata desde 1995. Aunque se administra vía oral como racémico, la actividad anti-andrógena es exclusiva del enantiómero (R), siendo la (S)-bicalutamida inactiva e inocua. Recientemente, J. Farrera y otros colaboradores han demostrado la potencialidad in vitro de la (S)-bicalutamida como un compuesto que activa la exocitosis celular, lo que permitiría a este compuesto ser una terapia universal en Enfermedades de Almacenaje Lisosomal (LSDs). Dicha efectividad in vitro se tiene que verificar en estudios in vivo de tipo preclínico y clínico. Debido a esto, el cuarto objetivo de la tesis doctoral consiste en el desarrollo de un método de síntesis GMP de (S)-bicalutamida.
12
Carkner, Andrew. „Green metal nanoparticle synthesis“. Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22037.
Der volle Inhalt der QuelleAnnotation:
Title: Green Metal Nanoparticle Synthesis Silver and nickel nanoparticles have diverse applications in catalysis, composite materials, and electronics. Current production methods rely on high-energy processes or harsh chemicals; thus it is preferable to use environmentally benign compounds for their synthesis. This project studied the aqueous synthesis of nickel nanoparticles from nickel acetate using glucose, formate, and hydrazine as reducing agents. It was found that although the reactions are thermodynamically favourable, nickel nanoparticles could not be produced using glucose or formate at pH 4-12 and T ≤ 100oC. The conversion was negligible even after 8 hours. With hydrazine, high temperature and pH are necessary for a rapid reaction. At pH 12, 100oC, and 20 mM nickel acetate, a conversion of 70% can be achieved in 30 minutes. For pH below 10 or temperature below 80oC, conversion is negligible even after 3 hours.Titre: Production vert de nanoparticules métalliques Les nanoparticules d'argent et de nickel ont de diverses applications en catalyse, matériaux composites et électronique. Cependant la production actuelle utilise soit beaucoup d'énergie soit de composés dangereux ; il sera mieux pour la santé et l'environnement de trouver d'alternatives. Ce projet a examiné le glucose et le formate comme alternatifs au hydrazine pour la synthèse aqueuse des nanoparticules. Quoique les conditions thermodynamiques sont favorables, je n'ai pas pu produire de nanoparticules de nickel sauf avec le hydrazine dans la région pH 4-12 et T ≤ 100oC. Avec le glucose ou le formate, la conversion demeure insignifiant après 8h. Avec le hydrazine, une haute température et pH sont nécessaires pour une réaction rapide. Avec pH 12, 100oC et 20 mM d'acetate de nickel, la conversion est 70% après 30 minutes. Sous pH 10 et 80oC, la conversion est négligeable même après 3 heures.
13
Noe', Marco <1981>. „Greeneer syntheses & solvents for fine and pharmaceutical chemicals“. Doctoral thesis, Università Ca' Foscari Venezia, 2012. http://hdl.handle.net/10579/1143.
Der volle Inhalt der QuelleAnnotation:
In this PhD thesis new eco-friendly methodologies for the preparation of fine and pharmaceutical chemicals are presented.
A set of carbonate ionic liquids were prepared using a new green procedure. The obtained CILs have been used as base catalysts for the condensation of aldehydes and ketones with nitroalkanes without the addition of solvent. CILs were further reacted with both water and protic acids to produce anion exchanged ionic liquids. Nitrate phosphonium ionic liquids were able to promote electrophilic aromatic oxychlorination without the addition of solvent.
The preparation of Tadalafil using more enviromental compatible solvents and reactants was studied. The use of ionic liquids and dimethylcarbonate as solvents was considered in order to improve the overall mass index of the preparation.
In partnership with Galentis S.r.l. we sought new synthetic methodologies for the preparations of the following compounds: i) chlorinated [2.2]-p-cyclophanes (polymer intermediates) ii) trimethylorthoesters (used for steroids derivatisation) and iii) furaniminium bromide (intermediate in the Loperamide preparation).In questa tesi di dottorato vengono presentate nuove metodologie ecosostenibili per la preparazione di prodotti della chimica fine e farmaceutica. Una serie di liquidi ionici carbonato (CILs) sono stati preparati utilizzando una nuova procedura "green". I CILs sono stati utilizzati come catalizzatori basici per la condensazione di aldeidi e chetoni. I CILs sono stati fatti reagire con acqua e acidi protici ottenendo nuovi liquidi ionici. Liquidi ionici nitrato sono stati in grado di promuovere ossiclorurazione elettrofila aromatica in assenza di co-solvente. Viene riportato lo studio sulla preparazione di Tadalafil mediante l'uso di solventi e reagenti più eco-compatibili. L'utilizzo di liquidi ionici e dimetilcarbonato come solventi è stato proposto col fine di ridurre l'impatto ambientale della preparazione. In collaborazione con Galentis S.r.l. sono state indagate nuove metodologie di sintesi per la preparazione dei seguenti composti: i) [2.2]paraciclofani clorurati (intermedi per polimeri) ii) trimetilortoesteri (utilizzati per derivatizzazione di steroidi) e iii) furaniminio bromuro (intermedio nella preparazione della Loperamide).
14
Baheti, Payal. „Clean synthesis of novel green surfactants“. Thesis, Montpellier, Ecole nationale supérieure de chimie, 2018. http://www.theses.fr/2018ENCM0012.
Der volle Inhalt der QuelleAnnotation:
Les polymères en étoile connaissent un intérêt accru en raison de leurs propriétés thermiques et mécaniques inimitables. Partant du constat qu’en parallèle la chimie durable se développe à un rythme sans précédent, nous proposons dans cette thèse de développer une stratégie plus « verte » pour la synthèse de polymères en étoile de type D-sorbitol-poly(ε-caprolactone) (star PCL-OHx). Ces derniers seront synthétisés sans solvant (en masse) ou dans des solvants « propres » (CO2 supercritique) et en présence du catalyseur métallique Sn(Oct)2 (qui a été approuvé par la FDA) ou d’un catalyseur enzymatique (Novozym® 435). L’influence de ces paramètres sur l’architecture des étoiles (nombre de bras, masse molaire des bras…) a été rigoureusement analysée et confirmée par différentes techniques d’analyse (RMN 1H, SEC-MALS, SEC-UC, analyse RMN 31P quantitative via la méthode de phosphitylation). Des polymères linéaires monohydroxy (PCL-OH) et téléchéliques dihydroxy (OH-PCL-OH) ont également été synthétisés en parallèle. Ces différentes PCL ont été utilisées comme macroamorceurs hydrophobes pour la polymérisation du monomère cyclique hydrophile éthyl phosphonate d’éthylène. Une large gamme de copolymères amphiphiles a ainsi pu être développée (i.e. des copolymères diblocs en étoile ou des copolymères diblocs et triblocs linéaires). Le comportement d’auto-assemblage en solution de ces copolymères a été étudié par DLS ainsi que par TEM et cryo-TEM. Nous avons également montré que les copolymères amphiphiles triblocs et en étoile sont capables de diminuer la tension de surface (γ) de l’eau en dessous de 45 mN m-1. Enfin, les étoiles PCL-OHx synthétisées en présence d’enzyme ont été fonctionnalisées par réaction avec l’anhydride maléique. Des polymères en étoile, ioniques, tensio-actifs et directement dispersables dans l’eau ont ainsi pu être obtenus. Dans un second temps, ces mêmes polymères ont été photopolymérisés en présence d’une faible quantité de tri(éthylène glycol) divinyl éther (~ 9% par rapport à la masse totale). Les films afférents à ces copolymères en étoile réticulés sous UV ont été analysés par IRTF, DSC et ATGStar polymers have attracted considerable attention because of their unique thermal and mechanical properties. At the same time, as sustainable chemistry field is growing in impact at an unprecedented rate, we propose in this work to implement a greener pathway for the synthesis of star D-sorbitol-poly(ε-caprolactone) (star PCL-OHx) using clean solvents (polymerisation in the bulk or in supercritical CO2) and either FDA-approved Sn(Oct)2 catalyst or enzyme catalyst (Novozym® 435). The influence of these parameters on the star architecture (number of arms, MW of arms etc.) was rigorously analysed and corroborated with various analytical techniques (1H NMR, SEC-MALS, SEC-UC, phosphitylation quantitative 31P NMR approach). Linear monohydroxy PCL-OH and dihydroxy telechelic OH-PCL-OH samples were also prepared. The PCL materials obtained were used as hydrophobic macroinitiators for the polymerisation of cyclic hydrophilic ethylene ethyl phosphonate monomer for the synthesis of a range of different amphiphilic materials (i.e. star diblock, linear diblock and triblock copolymers). Self-assembly behaviour in aqueous solution of these copolymers was investigated by DLS, TEM and cryo-TEM. Triblock and star amphiphilic copolymers were revealed to be able to reduce the surface tension (γ) of water down to 45 mN m-1. Finally, enzyme catalysed star PCL-OHx polymers were functionalised with carboxylic end-groups using maleic anhydride. Water-dispersible surface-active ionic star polymers were then obtained. These maleate-functionalised star polymers were then photopolymerised with a small amount of tri(ethylene glycol) divinyl ether (~9wt% of total composition). The UV-cured crosslinked star PCL films produced were then analysed by FTIR, DSC and TGA
15
Kythreoti, Georgia. „Green Routes to the Synthesis of Cephalosporins“. Thesis, University of Manchester, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492767.
Der volle Inhalt der QuelleAnnotation:
This thesis is concerned with studies on the enzyme carbamoyl transferase (CT) of the C cephalosporin intermediate (7-adipoyl-3-carbamoyloxymethyl cephalosporin) is an important step towards the demonstration of a novel and efficient bioprocess to make this intermediate.
16
Disci-Zayed, Duygu [Verfasser]. „Green synthesis of nanoparticles / Duygu Disci-Zayed“. Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1197055215/34.
Der volle Inhalt der Quelle
17
Li, Tao. „Characterization of lutein biosynthesis in green alga chlorella pyrenoidosa under heterotrophic condition“. HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1399.
Der volle Inhalt der Quelle
18
Bunn, Brittney Michalle. „Unraveling Genetically Encoded Pathways Leading to Bioactive Metabolites in Group V Cyanobacteria“. Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1448271831.
Der volle Inhalt der Quelle
19
Bayat, M., und M. Khatibzadeh. „A Review On Green Methods for Synthesis of Silver Nano Particles“. Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35238.
Der volle Inhalt der QuelleAnnotation:
Metal nano particles are one of the most attractive aspects of nano materials in recent years. The reason
for this growing attraction is because of their special physical and chemical properties, which are more enhanced
from bulk material. Hence they find wide application in various fields like catalysis, photonics, optoelectronics,
information storage, antibacterial applications, etc. While considering metal nano particles,
electrical conductivity is one of the most important properties that can be used for humans’ benefit and
should be enhanced. Silver nano particles can be used in the electronics industry as conductive fillers because
of their unique properties such as high electrical and thermal conductivity, high resistance to oxidation.
It is impressive that eco friendly methods are being developed for synthesizing these nano particles,
using different kinds of plant extracts and water soluble component as capping agents, which results in different
forms of particle morphologies.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35238
20
CHUGH, MOHITA. „GREEN SYNTHESIS OF SILVER NANOPARTICLES FROM CHLORELLA MINUTISSIMA“. Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18838.
Der volle Inhalt der QuelleAnnotation:
The development of a remediation technique that is environment friendly, efficient and
economical for the abatement of heavy metals and dyes will be an important step towards
the treatment of water pollutants. For this, silver nanoparticles were synthesized from
green algae Chlorella minutissima extract. For the enhancement of silver nanoparticles
synthesis, various optimization studies were carried out where different cell disruption
techniques (sonication, heating and autoclave), various range of pH (4 to 12) of reaction
mixture, various salt and biomass concentration along with contact time were studied.
Later, characterization techniques like visual detection and UV-Visible spectroscopy are
used for the characterization of silver nanoparticles. In the end, the application of these
silver phyconanoparticles were assessed in the remediation of six different heavy metals
and 5 different dyes. It is observed that it can remediate more than 96% of EY, MO and
EB and more than 87% CV and MB within 5 minutes and 65.18% nickel, 45.83% copper,
42% mercury, 33.84% cadmium within 1 hour and are less efficient in the case of cobalt
(4.5%) and chromium (0.5%). These results have shown the potential of silver
nanoparticles in the field of remediation of heavy metals and dyes. This project aims to
develop a more economical, sustainable and promising tool for the remediation of heavy
metals and dyes.
21
Hollingshead, Kyle Brady. „SYNTHESIS OF A NEW GREEN REFRIGERANT: HFE-143“. Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192490.
Der volle Inhalt der Quelle
22
CABRAS, VALENTINA. „Green Synthesis Approach to Coordination Polymers by Mechanochemistry“. Doctoral thesis, Università degli Studi di Cagliari, 2017. http://hdl.handle.net/11584/249603.
Der volle Inhalt der QuelleAnnotation:
The field of Metal-Organic Frameworks, also known with the abbreviation MOFs, has been subjected to an accelerated growth in the last 15 years. The process of mixing quickly available metal precursors with organic ligands—many of which are commercially available—to produce a wide range of frameworks, is capturing the interest of chemists and materials scientists worldwide.
There is an important link between MOF chemistry and fields of inorganic and coordination chemistry, there is also a conceptual link into the field of materials chemistry that has evolved applications ranging from catalysis to energy storage. Organic chemistry is also able to contribute to the MOFs design by the synthesis of new ligands with the aim of giving different properties to the MOF wall. X-ray crystallography and solid-state chemistry provide information about the structures of MOFs so that the process of designing and synthesizing MOFs can be refined to control a targeted property of those frameworks.
My PhD thesis aims to explore, especially from the point of view of synthetic and structural, morphological, thermal and textural characterizations, the chemistry of Coordination Polymers (CPs) and Metal-Organic Frameworks (MOFs). Mechanochemical synthesis has been adopted as a powerful method for environmentally-friendly CPs and MOFs synthesis. The experimental section, have been divided in four parts: the first part concerns the efficient mechanosynthesis of an iron(III) trimesate MOF and its usage for the adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from a simulated low-sulfur diesel fuel. In the second, the structural, thermal and morphological properties of CPs based on unsatured Ni(II) dithiophostato/ dithiophospnonato complexes and 4,4’-bipyridine as linker are outlined. The third part dials with an array study of reactivity under mechanochemical conditions of a set of CPs based on the same unsatured Ni(II) complexes with different topologies of polydentate ligands. The final part is dedicated to the attempt to obtain thio-functionalized ligands for design, synthesis and future application in CP/ MOF architecture.
23
Bhattarai, Badri Bhattarai. „Green Synthesis and Gold Alloying of Silver Molecular Nanoparticles“. University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533312041161417.
Der volle Inhalt der Quelle
24
Ahmed, Ejaz. „Room-Temperature Synthesis of Transition Metal Clusters and Main Group Polycations from Ionic Liquids“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-80124.
Der volle Inhalt der QuelleAnnotation:
Main group polycations and transition metal clusters had traditionally been synthesized via high-temperature routes by performing reactions in melts or by CTR, at room-temperature or lower temperature by using so-called superacid solvents, and at room-temperature in benzene–GaX3 media. Considering the major problems associated with higher temperature routes (e.g. long annealing time, risk of product decomposition, and low yield) and taking into account the toxicity of benzene and liquid SO2 in room-temperature or lower temperature synthesis, a soft and sustainable chemical approach has been developed, employing a Lewis-acidic IL [bmim]Cl/AlCl3. This new alternative reaction medium has proven to be an excellent solvent system for the single–step synthesis of main group polycations and transition metal clusters. X-ray diffraction and Raman spectroscopy have been used for the structural characterization of the isolated compounds. Physical properties and quantum chemical calculations of some of the compounds have also been carried out.
25
Ballard, Leslie Roy. „Synthesis and Selfhood: A Comparative Study of Kierkegaard and Kant“. Thesis, Boston College, 2010. http://hdl.handle.net/2345/3745.
Der volle Inhalt der QuelleAnnotation:
Thesis advisor: Vanessa P. RumbleSynthesis and Selfhood: A Comparative Study of Kierkegaard and Kant By Leslie Roy Ballard Advisor: Vanessa Rumble Many commentators on Kierkegaard's philosophy acknowledge that his writings draw from Kant's philosophy; but few essays trace the origin of specific categories in Kierkegaard's thought to their Kantian roots. While young scholars are especially prone to see in the philosophy of the previous century numerous links to Kierkegaard's writings, few question their ultimate source. The question of Kierkegaard's indebtedness to Kant recommends itself, then, to serious explorers of the sources of Kierkegaard's notion of selfhood, the role of Kant's ontology and moral philosophy in the latter, and the differences in their understandings of the relation between religious faith and moral obligation. Ronald M. Green and Ulrich Knappe examine Kierkegaard's familiarity with Immanuel Kant's philosophy. Green consults lecture notes, journal entries, and university documents to determine the nature and extent of Kierkegaard's engagement with Kant; he reviews public auction records to discover the books by Kant that Kierkegaard owned at the time of his death. Knappe bypasses such investigations to analyze the Kantian ideas apparent in Kierkegaard's texts — often a more substantive reflection than Green's, albeit sometimes speculative. This dissertation identifies and addresses interpretive problems like the ultimate unity of Kant's critical and ethical philosophies, and the autonomy of Kierkegaard's pseudonyms. Conclusions concerning Kierkegaard's use of Kant are drawn within these parameters. The early Climacus alludes to Kant's pure intuitions of space and time and the origin of consciousness in reflection. In spite of similarities in their depictions of the synthesis implied in human consciousness and knowledge, Climacus later criticizes Kant's presumed neglect of ethics for theory. Climacus' criticism, I argue, is based on a conflation of non-religious and religious ethics. The dissertation takes as its point of departure Kant's and Kierkegaard's non-religious formulations of identity in order to learn how each thinker understands human being and to allow each to present a conception of Christian selfhood. Three different, sometimes overlapping, stages emerge in the pseudonymous writings: the esthetic, the ethical, and the religious. In Either/Or, the first two are analogous to Kant's hypothetical and categorical motivation in terms of the universality and necessity of the law. A cogent analogy between their ethics requires the pseudonyms, however, to describe the law as a priori. William twice refers to a priority and mentions his familiarity with Kantian ethics. It is argued that William's ethical stage is a Kantian a priori ethics that other pseudonyms--namely, Silentio--overcome in the religious. The corpora understand sin differently, but agree that it hinders moral progress and causes the breakdown of the non-religious person. Anti-Climacus writes that revelation imparts knowledge of sin, and Haufniensis asserts that the convert needs dogmatics to guide the new self-understanding. Religious passion rather than reason primarily motivates the theological self. Kant thinks theology and its self-conception are good only insofar as they help pure practical reason to attain perfection; passion remains mostly suspect, and pure practical reason maintains its authority in moral deliberation. Silentio and Kant disagree whether the faith of religious life can be justified in violating universal ethical principles. Silentio claims that Abraham's sacrifice of Isaac presupposes the teleological suspension of universal ethics. Kant asserts that the laws of pure practical reason admit no exception. Abraham must comprehend the apparition's command as a temptation to commit murder, and not heed it. Silentio envisions extraordinary acts of faith apart from moral justification, but Kant argues the ethical is inviolate. Silentio welcomes the passionate and the miraculous; Kant leaves open the question whether his ethical rigorism is compatible with true biblical faith
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Philosophy
26
Portolés, Gil Núria. „Green synthesis of coordination polymers using supercritical carbon dioxide“. Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669382.
Der volle Inhalt der QuelleAnnotation:
Recentment l’interès per la investigació en polímers de coordinació (CPs) i en xarxes metal·lorgàniques (MOFs) ha crescut degut al potencial d’aquests materials per nombroses aplicacions com per exemple, l’alliberació controlada de fàrmacs, la catàlisi i l’emmagatzematge i la separació de gasos. Generalment aquests materials són sintetitzats utilitzant dissolvents orgànics tòxics i altes temperatures. Per aquest motiu, és necessari desenvolupar rutes sintètiques més sostenibles per accelerar l'expansió industrial d'aquests productes. L’objectiu principal del treball és sintetitzar CPs utilitzant tecnologies sostenibles basades en l’ús del diòxid de carboni supercrític (scCO2) com a dissolvent. Fins avui, la utilització d’aquest dissolvent en l’àrea dels CPs i MOfs ha estat restringida a etàpes d’activació o neteja post-sintètica. No obstant l’ús de scCO2 pot anar més enllà i pot ser utilitzat també com a solvent en la síntesi d’aquest materials. Per tant, l’objectiu principal d’aquesta tesi és demostrar aquesta possibilitat, establir un protocol sintètic.
Per tal d’aconseguir aquest objectiu, s’ha desenvolupat una nova metodologia per explorar la síntesis de nous polímers de coordinació homometàl·lics o heterometal·lics de diferents dimensionalitats. Els CPs s’han obtingut mitjançant la reacció de complexos metàl·lics insaturat i els lligands orgànics en scCO2. S’han seleccionat diferents complexes organometàl·lics fluorats i lligands orgànics N-donadors tenint en compte la seva solubilitat en scCO2. Pels sistemes on s’utilitzen complexos metàl·lics amb baixa solubilitat, s’ha desenvolupat una alternativa basada en la utilització de lligands auxiliars pel metall. També s’han utilitzat connectors tipus bipiridina lineals o polipiridina trigonals. L’interès en la utilització d’aquests N-donadors per la síntesi de CPs està relacionat amb la geometria plana del nucli, que és ideal per generar estructures molt simètriques. Degut al caràcter sostenible de la síntesi s’ha considerat també el seu ús per la síntesi de materials biocompatibles. Per aquest motiu, com a prova de concepte, s’han utilitzat els productes naturals curcumina i àcid ferúlic com a lligands biocompatibles per la síntesi de bioMOFs de dos i de tres dimensions.
En resum, al llarg dels diferents capítols de la tesis es demostra la viabilitat de la utilització del scCO2 per la síntesis de CPs i MOFs. S’ha aconseguit cristal·litzar 17 nous CPs i la majoria s’han pogut resoldre cristal·logràficament. A través dels diversos capítols es descriu la manera de superar els obstacles sintètics trobats al emprar scCO2 com a solvent, tals com la baixa solubilitat dels reactius o la ràpida precipitació de les fases cinètiques. També són presentades aplicacions en adsorció de gasos, magnetisme i alliberació controlada de fàrmacs.Recently, the research in coordination polymers (CPs) and porous metal-organic frameworks (MOFs) has raised a large interest, since these materials are considered potential candidates for numerous applications, including drug delivery, catalysis, gas separation and storage. Generally, these materials are synthetized using toxic organic solvents and high temperatures. Therefore, the development of sustainable synthetic approaches becomes necessary to speed up the industrial expansion of these products. The main aim of this work is to synthetize CPs using a green technology based on supercritical carbon dioxide (scCO2) solvent. To date, the use of scCO2 in the field of CPs and MOFs has been mainly limited to the post-synthetic activation or cleaning steps. The use of scCO2 can go further, including the synthesis of these materials. Hence, the main objective of this work is to demonstrate this possibility, stablishing a synthetic protocol. In order to achieve the main aim, a new methodology has been developed to explore the synthesis of new single and mixed-metal CPs with different dimensionalities. CPs have been obtained by reacting a metallic complex and an organic linker in scCO2. Fluorinated organometallic complexes (i.e., hexafluoroacetylacetonate) and N-donor organic linkers have been selected taking into account their significant solubility in scCO2. Alternatives for systems involving metal complexes with low solubility have been also developed, based on the use of ancillary ligands for the metal. Linear bipyridyl and trigonal polypyridyl connectors have also been used. The growing interest in the synthesis of these CPs based on N-donor organic linkers is related to their core’s planar geometry, ideally suited to generate highly symmetrical structures. Most importantly, the green character of the synthesis allows to consider its use for the synthesis of biocompatible materials. Therefore, as a proof of concept the use of bio-linkers, e.g., curcumin and ferulic acid, for 2D and 3D bioMOFs synthesis has been explored. In short, along the different Chapters the viability of the easy, fast and eco-friendly synthesis of CPs and MOFs using scCO2 has been demonstrated. Using diverse metal nodes and linkers, 17 new CPs have been crystallized in this solvent, most of them elucidated crystallographically. The way in which synthetic obstacles in scCO2, such as low solubility of reagents or fast precipitation of kinetic phases are overcome, has been described along the different Chapters. Applications in gas adsorption, magnetism and drug delivery have also been presented.
27
Kopetzki, Daniel. „Exploring hydrothermal reactions : from prebiotic synthesis to green chemistry“. Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5258/.
Der volle Inhalt der QuelleAnnotation:
In this thesis chemical reactions under hydrothermal conditions were explored, whereby emphasis was put on green chemistry. Water at high temperature and pressure acts as a benign solvent. Motivation to work under hydrothermal conditions was well-founded in the tunability of physicochemical properties with temperature, e.g. of dielectric constant, density or ion product, which often resulted in surprising reactivity. Another cornerstone was the implementation of the principles of green chemistry. Besides the use of water as solvent, this included the employment of a sustainable feedstock and the sensible use of resources by minimizing waste and harmful intermediates and additives.
To evaluate the feasibility of hydrothermal conditions for chemical synthesis, exemplary reactions were performed. These were carried out in a continuous flow reactor, allowing for precise control of reaction conditions and kinetics measurements. In most experiments a temperature of 200 °C in combination with a pressure of 100 bar was chosen. In some cases the temperature was even raised to 300 °C.
Water in this subcritical range can also be found in nature at hydrothermal vents on the ocean floor. On the primitive earth, environments with such conditions were however present in larger numbers. Therefore we tested whether biologically important carbohydrates could be formed at high temperature from the simple, probably prebiotic precursor formaldehyde. Indeed, this formose reaction could be carried out successfully, although the yield was lower compared to the counterpart reaction under ambient conditions. However, striking differences regarding selectivity and necessary catalysts were observed. At moderate temperatures bases and catalytically active cations like Ca2+ are necessary and the main products are hexoses and pentoses, which accumulate due to their higher stability. In contrast, in high-temperature water no catalyst was necessary but a slightly alkaline solution was sufficient. Hexoses were only formed in negligible amounts, whereas pentoses and the shorter carbohydrates accounted for the major fraction. Amongst the pentoses there was some preference for the formation of ribose. Even deoxy sugars could be detected in traces.
The observation that catalysts can be avoided was successfully transferred to another reaction. In a green chemistry approach platform chemicals must be produced from sustainable resources. Carbohydrates can for instance be employed as a basis. They can be transformed to levulinic acid and formic acid, which can both react via a transfer hydrogenation to the green solvent and biofuel gamma-valerolactone. This second reaction usually requires catalysis by Ru or Pd, which are neither sustainable nor low-priced. Under hydrothermal conditions these heavy metals could be avoided and replaced by cheap salts, taking advantage of the temperature dependence of the acid dissociation constant. Simple sulfate was recognized as a temperature switchable base. With this additive high yield could be achieved by simultaneous prevention of waste. In contrast to conventional bases, which create salt upon neutralization, a temperature switchable base becomes neutral again when cooled down and thus can be reused. This adds another sustainable feature to the high atom economy of the presented hydrothermal synthesis.
In a last study complex decomposition pathways of biomass were investigated. Gas chromatography in conjunction with mass spectroscopy has proven to be a powerful tool for the identification of unknowns. It was observed that several acids were formed when carbohydrates were treated with bases at high temperature. This procedure was also applied to digest wood. Afterwards it was possible to fermentate the solution and a good yield of methane was obtained. This has to be regarded in the light of the fact that wood practically cannot be used as a feedstock in a biogas factory. Thus the hydrothermal pretreatment is an efficient means to employ such materials as well. Also the reaction network of the hydrothermal decomposition of glycine was investigated using isotope-labeled compounds as comparison for the unambiguous identification of unknowns. This refined analysis allowed the identification of several new molecules and pathways, not yet described in literature.
In summary several advantages could be taken from synthesis in high-temperature water. Many catalysts, absolutely necessary under ambient conditions, could either be completely avoided or replaced by cheap, sustainable alternatives. In this respect water is not only a green solvent, but helps to prevent waste and preserves resources.In dieser Arbeit wurden chemische Reaktionen unter Hydrothermalbedingungen untersucht. Darunter versteht man Wasser als Reaktionsmedium, welches eine Temperatur über 100 °C aufweist. Der flüssige Zustand wird dabei durch erhöhten Druck aufrecht erhalten. Typischerweise wurden die Reaktionen bei 200 °C und einem Druck von 100 bar durchgeführt, also dem 100-fachen des Normaldrucks. Dieses System kann man auch mit einem Dampfdrucktopf vergleichen, wobei durch die erhöhten Temperaturen chemische Reaktionen sehr schnell ablaufen und überraschende Reaktivität auftritt. Die Motivation, Wasser als Lösemittel zu benutzen, ist auch in seiner Umweltfreundlichkeit gegenüber klassischen organischen Lösemitteln begründet. Da solche Hydrothermalbedingungen auf der frühen Erde häufiger anzutreffen waren, wurde untersucht, ob wichtige Biomoleküle bei solch hoher Temperatur gebildet werden können. In der Tat konnten Zucker aus der sehr einfachen Verbindung Formaldehyd synthetisiert werden. Hierzu war lediglich eine leicht basische Lösung nötig und keine der bei moderaten Temperaturen essentiellen Katalysatoren. Zucker stellen zudem den größten Teil der pflanzlichen Biomasse dar und können daher als Grundlage für eine nachhaltige Chemie dienen. Sie können relativ einfach zu Lävulin- und Ameisensäure umgesetzt werden. Aus diesen wiederum kann die wichtige Basischemikalie gamma-Valerolacton hergestellt werden. Der Schlüsselschritt, die Reduktion von Lävulinsäure, erforderte bisher die Zuhilfenahme seltener Edelmetalle wie Ruthenium. Es konnte nun gezeigt werden, dass unter Hydrothermalbedingungen diese Rolle von einfachen Salzen, z. B. Natriumsulfat, übernommen werden kann. Hierbei macht man sich zunutze, dass sie nur bei hoher Temperatur basisch wirken, nicht aber wenn die Lösung wieder abgekühlt ist. Neben Kohlenhydraten besteht Biomasse auch aus Aminosäuren, von denen Glycin die einfachste darstellt. Unter Abspaltung von CO2 können aus ihnen synthetisch wichtige Amine hergestellt werden. Diese Reaktion findet unter Hydrothermalbedingungen statt, daneben treten jedoch noch andere Produkte auf. Unbekannte Verbindungen wurden mittels Massenspektroskopie identifiziert, wobei die Masse des Moleküls und bestimmter Molekülfragmente bestimmt wurde. Dies erlaubte es, bisher noch unbekannte Reaktionswege aufzuklären. Zusammenfassend lässt sich sagen, dass Wasser unter Hydrothermalbedingungen eine interessante Alternative zu organischen Lösemitteln darstellt. Desweiteren können bestimmte Katalysatoren, die bei moderaten Temperaturen nötig sind, entweder vollständig eingespart oder ersetzt werden. In dieser Hinsicht ist Wasser nicht nur ein umweltfreundliches Lösemittel, sondern trägt dazu bei, Abfall zu vermeiden und Ressourcen zu schonen.
28
Shahid, Robina. „Green Chemical Synthesis of II-VI Semiconductor Quantum Dots“. Doctoral thesis, KTH, Funktionella material, FNM, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104980.
Der volle Inhalt der QuelleAnnotation:
Nanotechnology is the science and technology of manipulating materials at atomic and molecular scale with properties different from bulk. Semiconductor QDs are important class of nanomaterials with unique physical and chemical properties owing to the quantum confinement effect. Size dependent optical properties make research on semiconductor QDs more attractive in the field of nanotechnology. Semiconductor QDs are usually composed of combination of elements from groups II–VI, III–V, or IV–VI of the periodic table. Group II-VI semiconductor QDs (ZnS, ZnSe, ZnO, CdSe, CdS) are most extensively studied systems, having bandgap which can be engineered through the variation of the material composition and size. Most common QDs are made of CdE (E=S, Se, Te) which are toxic. Recent environmental regulations restrict the use of toxic metals and therefore QDs containing nontoxic metals such as Zn are of great importance. The chemical synthesis of QDs involves different methods. Usually high temperature thermal decomposition of organometallic compounds in high boiling point organic solvents is used which needs long reaction time and involves complex synthesis procedures. New simpler and efficient synthetic routes with alternative solvents are required. Recently the synthesis of non-toxic QDs using green chemical routes is a promising approach receiving increasing attention. The aim of this Thesis is to develop novel routes for synthesis of semiconductor QDs employing green nanomaterial synthesis techniques. Therefore, in this work, we developed different green chemical routes mainly for the synthesis Zn-based QDs. Low temperature synthesis routes were developed for the synthesis of ZnS and ZnO QDs. Microwave irradiation was also used as efficient heating source which creates numerous nucleation sites in the solution, leading to the formation of homogeneous nanoparticles with small size and narrow size distribution. Different polar solvents with high MW absorption were used for synthesis of ZnS QDs. We also introduced ionic liquids as solvents in the synthesis of ZnS QDs using microwave heating. ILs are excellent reaction media for absorbing microwaves and are recognized as ‘green’ alternative to volatile and toxic organic solvents. For ZnS systems, the QDs produced by different methods were less than 5 nm in size as characterized by high-resolution transmission electron microscopy (HR-TEM). Selected area electron diffraction (SAED) patterns revealed that ZnS QDs synthesized by low temperature synthesis technique using conventional heating are of cubic crystalline phase while the QDs synthesized by using MW heating are of wurtzite phase. The optical properties were investigated by UV-Vis absorption spectrum and show a blue shift in absorption as compared to bulk due to quantum confinement effect. The photoluminescence (PL) spectra of ZnS QDs show different defect states related emission peaks and depend on different synthesis methods, high bandedge related emission is observed for ZnS QDs synthesized by using ionic liquids. ZnO QDs synthesized by low temperature route were found to be less than 4 nm in size and also show a blue shift in their absorption. The PL spectrum show bandedge related emission which is blue shifted compared with bulk with no emission originating from surface defect levels. The results show that QDs are of high crystalline quality with narrow size distribution. A comparative study of using conventional and MW heating in the synthesis of CdSe QDs was performed. The reactions involving microwave heating showed enhanced rates and higher yields. The developed methods involve all principles for green nanomaterials synthesis i.e. design of safer nanomaterials, reduced environmental impact, waste reduction, process safety, materials and energy efficiency.QC 20121115
29
McGregor, Stuart Thomas. „Clean green chemistry : enzyme-catalysed and chemical asymetric synthesis“. Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485058.
Der volle Inhalt der QuelleAnnotation:
Chapter 1 provides an introduction to the metabolism of aromatic compounds by enzymes, and the use of bioproducts in synthesis. A brief introduction into the synthesis and potential applications of amino alcohols is also discussed. Finally, a summary of a number of methods for the-determination of enantiomeric excess concludes the chapter. Chapter 2 investigates the synthesis oftrans-dihydrodiols from their cis-dihydrodiol precursors. The desymmetrisation ofmeso-l,2-dihydroxycyclohexane is also discussed. The chemoenzymatic synthesis oftrans-I,2-aminocyclohexanols, including the biologically important compound vesamicol is examined. Chapter 3 explores the synthesis of a number ofcis- and trans-azido alcohols from bromo- and chIoro- benzene, and the conversion ofthe azido alcohols to cis- and trans-amino alcohols. A brief investigation into the substitution ofthe halide atom in bromobenzene-cis-diol is discussed as a potential route to a library ofcis- and (rmlS- amino alcohols. Chapter 4 is divided into three parts. The first section discusses a number of synthetic routes to vicinal cis- and trmls- amino alcohol derivatives of naphthalene. The second section outlines the bacterial metabolism ofselected polycyclic aromatic hydrocarbons and the formation of bis-cis-diols. The final section introduces a new class of bacterial metabolites from acetonide-protected diol substrates.
30
Dahl, Jennifer Ann. „Synthesis of functional nanomaterials within a green chemistry context /“. Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2007. http://hdl.handle.net/1794/6131.
Der volle Inhalt der QuelleAnnotation:
Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 158-183). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
31
Olsen, Sarah. „Synthesis of Copper Sulphides: A Green Chemistry Microwave Approach“. Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279452.
Der volle Inhalt der Quelle
32
Dahl, Jennifer Ann 1976. „Synthesis of functional nanomaterials within a green chemistry context“. Thesis, University of Oregon, 2007. http://hdl.handle.net/1794/6131.
Der volle Inhalt der QuelleAnnotation:
xvii, 183 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.In recent years, nanoscience has evolved from a multidisciplinary research concept to a primary scientific frontier. Rapid technological advancements have led to the development of nanoscale device components, advanced sensors, and novel biomimetic materials. However, potential negative impacts of nanomaterials are sometimes overlooked during the discovery phase of research. The implementation of green chemistry principles can enhance nanoscience by maximizing safety and efficiency while minimizing the environmental and societal impacts of nanomaterials. This dissertation introduces the concept of green nanosynthesis, demonstrating the application of green chemistry to the synthesis of nanornaterials. A comprehensive review of the synthesis of metal nanomaterials is presented, demonstrating how individual green chemistry principles can improve traditional synthetic routes as well as guide the design of new materials. Detailed examples of greener syntheses of functionalized gold nanoparticles with core diameters of 2-10 nm are described in subsequent chapters, beginning with a method for functionalizing citrate-stabilized gold nanoparticles that are desirable for advanced applications. Although citrate-stabilized gold nanoparticles can be easily produced from a classic procedure using mild reagents and benign methods, functionalization via ligand exchange is often unsuccessful. It was discovered that an ill-defined layer comprised of citrate and other ligands interferes with functionalization processes. By removing excess citrate in a manner where overall structure and stability is maintained, gold cores produced by this route are readily functionalized by incoming thiols, affording unprecedented control over surface composition and functionality. A direct route to functional nanomaterials using Bunte salt precursors is discussed next, describing the use of easily synthesized shelf-stable alternatives to thiols in the preparation of water-soluble gold nanoparticles. Control of core size and surface chemistry is demonstrated through simple manipulation of reagent ratios, yielding products similar to those produced by traditional direct syntheses which rely on the use of thiols. The use of functionalized nanoparticles as "building blocks" for more complex structures was demonstrated in self-assembly processes. Cationic gold particles were deposited upon DNA scaffolds to create linear arrays. A discussion of the future outlook of green nanosynthesis concludes this work, identifying immediate challenges and long-term goals. This dissertation contains previously published and co-authored materials.
Adviser: James E. Hutchison
33
Choudhury, Prasun. „Carbonaceous nanomaterials and composites green techniques for organic synthesis“. Thesis, University of North Bengal, 2020. http://ir.nbu.ac.in/handle/123456789/4336.
Der volle Inhalt der Quelle
34
Wong, Ka-ho, und 王家豪. „Transgenic chlamydomonas reinhardtii as an experimental system to study the regulation of carotenoid biosynthesis in green microalgae“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37728337.
Der volle Inhalt der Quelle
35
Nixon, Emily Cummings. „Silanes in sustainable synthesis: applications in polymer grafting, carbon dioxide capture, and gold nanoparticle synthesis“. Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45847.
Der volle Inhalt der QuelleAnnotation:
Vinyltrialkoxysilanes are grafted onto polyolefins via a radical mechanism; in a subsequent step, the pendant alkoxysilanes hydrolyze and condense upon exposure to water, resulting formation of crosslinks. Straight chain hydrocarbons were used as model compounds to investigate the regioselectivity of vinyltrimethoxysilane grafting. To stabilize the water-sensitive grafted products, the methoxy groups were substituted using phenyllithium. It was found that this reaction must be carried out for a minimum of three days to ensure full substitution. The grafted products were then separated on a weight basis using semi-preparative HPLC. Analysis of the di-grafted fraction using edited HSQC and HSQC-TOCSY NMR showed that radical propagation occurs via 1,4- and 1,5-intramolecular hydrogen shifts along the hydrocarbon backbone, resulting in multiple grafts per backbone. Post-combustion carbon capture targets CO₂ emissions from large point sources for capture and sequestration. A new class of potential carbon capture agents known as reversible ionic liquids (RevILs) has been synthesized and evaluated in terms of potential performance parameters (e.g. CO₂ capacity, viscosity, enthalpy of regeneration). These RevILs are silylated amines, which react with CO₂ to form a salt comprising an ammonium cation and a carbamate anion that is liquid at room temperature. Structural modifications of the basic silylamine skeleton result in drastic differences in the performance of the resulting RevIL. Systematic variation of the silylated amines allowed determination of a structure-property relationship, and continued iterations will allow development of an ideal candidate for scale-up. The properties and potential applications of gold nanoparticles (AuNP) are highly dependent on their size and shape. These properties are commonly controlled during liquid-phase synthesis through the use of capping agents, which must be removed following synthesis. Reverse micelles can also be used to control the morphology of AuNP during their synthesis. When RevILs are used in the formation of these reverse micelles, either as the disperse phase or as the surfactant, the built-in switch can be used to release the nanoparticles following their synthesis. This release on command could decrease the post-synthetic steps required to clean and purify AuNP prior to use. We have successfully synthesized AuNP using a number of different RevILs.
36
Armstrong, Lyle. „Synthesis, spectra and photochemistry of trifluoroethyl substituted triphenylmethane dyes“. Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303385.
Der volle Inhalt der Quelle
37
Mokone, Mmola. „The assessment of the bactericidal effect of green synthesized silver nanoparticles against a panel of infectious microorganisms“. University of the Western Cape, 2016. http://hdl.handle.net/11394/5450.
Der volle Inhalt der QuelleAnnotation:
>Magister Scientiae - MScThe emergence of multiple drug resistant microorganisms poses a major threat to human life. These microorganisms have made the currently used antibiotics ineffective and therefore continue to thrive. Therefore, there is a need for development of new, broad-secptrum antibiotics which is effective against almost every infectious microorganism. These antibiotics should ensure high effectiveness against the infectious pathogens while it is less detrimental to human health. Thus the search is channelled in nanoscience and nanotechnology in order to develop antibiotics that can kill infectious microorganisms effectively and hindering the development of drug resistance by these microorganisms. Nanoscience is the study of properties of a material when reduced to it smallest size (below 100 nm). It is a newly developing field of science which includes chemistry, physics and biology and has made it easy to synthesise nanomaterials for applications in many sectors of life including in medicine. The synthesis of nanoparticles can be achieved by physical and chemical methods. However, these methods are energy and capital intensive. Additionally, chemical method of synthesis uses chemicals that may be toxic which restrict the use of resultant nanoparticles in medicine. Therefore, there is a need for the use of eco-friendly methods of nanoparticle synthesis. The synthesis of silver and gold nanoparticles in this study was carried out by a green synthesis method, at room temperature, using an aqueous extract from the endemic brown alga Sargassum incisifolium. For comparison, commercially available brown algal fucoidans were also used to synthesise these nanoparticle, in addition to conventional methods of synthesis. The formation of nanoparticles was followed by the use of UV-Vis spectrophotometry. The characterization of the nanoparticles was done by TEM, XRD, DLZ and FT-IR. The rate of nanoparticle formation varied with specific reducing agent used. The faster reaction rate was recorded with S. incisifolium aqueous extracts pretreated with organic solvents while extracts obtained without this pretreatment produced slightly slower reaction rates. However, the commercially available fucoidans were less effective and required elevated temperatures for nanoparticle formation. Sodium borohydride reduction of silver nitrate was faster than the biological methods while the reduction of auric chloride by the S. incisifolium extracts and sodium citrate proceeded at similar rates. The nanoparticles synthesised with the help of the untreated aqueous extract were bigger than those synthesised from pre-treated extracts with both giving irregular shaped of nanoparticles. Also the nanoparticles formed from commercially available fucoidans were not of the same size, with bigger sizes recorded with Macrocystis fucoidan and smaller sizes with Fucus fucoidan. The shapes of nanoparticles from these fucoidans were spherical. From the conventional method, the nanoparticle sizes were smaller compared to the green synthesised nanoparticles and were predominantly spherical. The silver nanoparticles synthesised from the Sargassum aqueous extracts showed excellent antimicrobial activity against five pathogenic microorganisms including A. baumannii, K. pneumoniae, E. faecalis, S. aureus, and C. albicans. The gold nanoparticles were much less effective. To adequately assess the antimicrobial activities of the nanoparticles, it is or paramount importance to also asses their cytotoxicity activity. Three cell lines were used in this study namely, MCF-7, HT-29 and MCF-12a. The silver nanoparticles were found to be toxic to HT-29 and MCF-7 cell lines, exhibiting sligtly less toxicity against MCF-12a cells. The gold nanoparticles showed lower toxicity but a similar trend was observed.
38
Hassan, Noor. „New green technologies for organocatalytic asymmetric epoxidation applications in synthesis“. Thesis, University of East Anglia, 2014. https://ueaeprints.uea.ac.uk/49466/.
Der volle Inhalt der QuelleAnnotation:
This thesis describes the application of asymmetric epoxidation reactions on chromene substrates mediated by Page’s iminium salt catalysts. Organocatalytic asymmetric epoxidation is an efficient tool to access enantiomerically rich epoxides. This study is divided into three main parts which are discussed in each chapter. The first part of this research is the preparation of iminium salt catalysts followed by synthesis of several chromene substrates. The final part is the application of the asymmetric epoxidation of the readily prepared iminium salts on chromene substrates. The first chapter reviews brief introduction and historical background of organocatalysis, chromene substrates and asymmetric epoxidation reactions. Towards the end of the chapter, several examples are described of past and current development of asymmetric epoxidation by organocatalysts. In the last part of Chapter 1, the discussion focuses on asymmetric epoxidation on chromene substrates. Chapter 2 discusses the preparation of Page’s iminium salts and improvement of previous methods followed by several approaches to synthesis of chromene substrates. The final part is discussing application of asymmetric epoxidation using synthesized iminium salts on the chromene substrates. Excellent enantioselectivities were observed in nonaqueous condition using TPPP as oxidant for 6-cyano-2,2’-dimethylchromene giving ee >99% while reactions under aqueous conditions afforded the corresponding diol giving ees as high as 71%. In Chapter 3, experimental procedures and data for all the compounds synthesized are included. Appendices contain HPLC trace data, NMR and IR data of several compounds.
39
Kalabegishvili, T., A. Faanhof, E. Kirkesali, M. V. Frontasyeva, S. S. Pavlov und I. Zinicovscaia. „Synthesis of Gold Nanoparticles by Blue-Green Algae Spirulina Platensis“. Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34969.
Der volle Inhalt der QuelleAnnotation:
The synthesis of gold nanoparticles by one of the many popular microorganisms – blue-green algae
Spirulina platensis was studied. The complex of optical and analytical methods was applied for investigation
of experimental samples after exposure to chloroaurate (HAuCl4) solution at different doses and for
different time intervals. To characterize formed gold nanoparticles UV-vis Spectrometry, Transmission
Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy-dispersive analysis of X-rays
(EDAX) were used. It was shown that after 1.5 – 2 days of exposure the extracellular formation of nanoparticles
of spherical form and the distribution peak within the interval of 20-30 nm took place. To determine
gold concentrations in the Spirulina platensis biomass neutron activation analysis (NAA) was applied.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34969
40
Rosenthal-Kim, Emily Quinn. „Green Polymer Chemistry: Synthesis of Poly(disulfide) Polymers and Networks“. University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386525065.
Der volle Inhalt der Quelle
41
Kortusová, Dominika. „Příprava nanočástic green syntézou“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232068.
Der volle Inhalt der QuelleAnnotation:
This thesis deals with green synthesis of noble metals nanoparticles. The first part contains secondary literature research which maps both the traditional and newly developed techniques of nanoparticles preparation. Most attention is given to the various types of green synthesis, which constitute an environmentally friendly alternative to industrially applied methods. The second part deals with the preparation of noble metal nanoparticles using tea broths. The section describes the entire synthesis process and includes photographic documentation. A total of eight colloidal solutions were prepared, four of each metal. The nanoparticles were subsequently analyzed using UV-vis spectroscopy. A time-lapse spectroscopic description of each synthesis was also undertaken. Furthermore, the size distribution of the particles by volume was measured and compared with the pictures obtained by scanning electron microscopy. The results have showed that tea broths, especially those from black tea and rooibos, are suitable for the biosynthesis of stable noble metal nanoparticles.
42
CATERINA, RISI. „Studies on organic synthesis through sustainable catalysis“. Doctoral thesis, Università di Siena, 2020. http://hdl.handle.net/11365/1094721.
Der volle Inhalt der QuelleAnnotation:
Today the development of sustainable processes in the chemical industry is critical, and Green Chemistry represents an evolution from the conventional concepts of process efficiency. Twenty years ago, Paul Anastas and John Warner introduced this concept within the twelve principles. In this work, many aspects the twelve principles are applied, developing sustainable methods involving the use of metal catalysis and biocatalysis through one pot and cascade reactions.In the first part of the PhD period, the use of the micellar catalysis was investigated, to perform reactions in water avoiding (or limiting) the use of the traditional organic solvents. The possibility to apply the micellar conditions for the hydrogen borrowing (HB) reaction to prepare amines was explored. Different Ru catalysts were screened using water as medium, under Microwave (MW) dielectric heating. Once optimized, the scope of the reaction was investigated using differently substituted amines and alcohols. Besides, the use of a biomass-derived solvent (GVL) was explored in Pd/C catalysed transformations to avoid the arching phenomena frequently observed using conventional solvents (e.g. toluene). A sustainable protocol for the synthesis of benzimidazoles employed different aliphatic and aromatic amines through a hydrogen transfer Pd/C. A heating profile and various studies of stability have been reported. A biocatalytic approach to pyridine and furans is also reported. These heterocycles are fundamental building blocks for the synthesis of pharmaceuticals, agrochemicals and organic material. Furthermore, these compounds are also employed in flavour and fragrance industry owing to their peculiar olfactory properties. Classical methodologies for their synthesis are based on low-yielding multistep methods, which involve the use of harsh conditions. Therefore, novel mild and greener methodologies for the preparation of heterocycles compounds are highly desirable. Aromatization of substituted 1,2,3,6-tetrahydropyridines (THPs) was performed using whole-cell monoamine oxidase MAO-N (variants from Aspergillus niger) catalyst. The aromatization of the tetrahydropyridine starting materials into the pyridine products was monitored through 1H NMR spectroscopy. During the optimization, different pyridine compounds are prepared to screen the best co-solvents and MAO-N variants. The kinetic profile of the biocatalytic transformation by MAO-N was also monitored via in situ 19F NMR experiments. Aromatization of different 2,5-dihydrofurans into corresponding furans was also performed using the Laccase/TEMPO catalytic system using mild conditions. A chemo- enzymatic cascade reaction starting directly from acyclic aliphatic precursor has been developed showing that metathesis Grubb's catalyst and the Laccase/TEMPO system can be used in combination for an efficient protocol.
43
Rolihlahla, Bangile Noel. „Electrochemistry and photophysics of carbon nanodots-decorated nigs(Ni(In, Ga)Se2) quantum dots“. university of western cape, 2020. http://hdl.handle.net/11394/7309.
Der volle Inhalt der QuelleAnnotation:
>Magister Scientiae - MScCurrently, non-renewable sources are mostly used to meet the ever-growing demand for energy. However, these sources are not sustainable. In addition to these energy sources being not sustainable, they are bad for the environment although the energy supply sectors highly depend on them. To address such issues the use of renewable energy sources has been proven to be beneficial for the supply of energy for the global population and its energy needs. Advantageous over non-renewable sources, renewable energy plays a crucial role in minimizing the use of fossil fuel and reduces greenhouse gases. Minimizing use of fossil fuels and greenhouse gases is important, because it helps in the fight against climate change. The use of renewable energy sources can also lead to less air pollution and improved air quality. Although solar energy is the most abundant source of renewable energy that can be converted into electrical energy using various techniques, there are some limitations. Among these techniques are photovoltaic cells which are challenged by low efficiencies and high costs of material fabrication. Hence, current research and innovations are sought towards the reduction of costs and increasing the efficiency of the renewable energy conversion devices.
44
Bertolucci, Elisa. „Green Synthesis of magnetic nanostructures suitable as recoverable nanocatalysts and conductive nanomaterials“. Doctoral thesis, Scuola Normale Superiore, 2016. http://hdl.handle.net/11384/86197.
Der volle Inhalt der Quelle
45
Rahm, Martin. „Green Propellants“. Doctoral thesis, KTH, Fysikalisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25835.
Der volle Inhalt der QuelleAnnotation:
To enable future environmentally friendly access to space by means of solid rocket propulsion a viable replacement to the hazardous ammonium perchlorate oxidizer is needed. Ammonium dinitramide (ADN) is one of few such compounds currently known. Unfortunately compatibility issues with many polymer binder systems and unexplained solid-state behavior have thus far hampered the development of ADN-based propellants. Chapters one, two and three offer a general introduction to the thesis, and into relevant aspects of quantum chemistry and polymer chemistry. Chapter four of this thesis presents extensive quantum chemical and spectroscopic studies that explain much of ADN’s anomalous reactivity, solid-state behavior and thermal stability. Polarization of surface dinitramide anions has been identified as the main reason for the decreased stability of solid ADN, and theoretical models have been developed to explain and predict the solid-state stability of general dinitramide salts. Experimental decomposition characteristics for ADN, such as activation energy and decomposition products, have been explained for different physical conditions. The reactivity of ADN towards many chemical groups is explained by ammonium-mediated conjugate addition reactions. It is predicted that ADN can be stabilized by changing the surface chemistry with additives, for example by using hydrogen bond donors, and by trapping radical intermediates using suitable amine-functionalities. Chapter five presents several conceptual green energetic materials (GEMs), including different pentazolate derivatives, which have been subjected to thorough theoretical studies. One of these, trinitramide (TNA), has been synthesized and characterized by vibrational and nuclear magnetic resonance spectroscopy. Finally, chapter six covers the synthesis of several polymeric materials based on polyoxetanes, which have been tested for compatibility with ADN. Successful formation of polymer matrices based on the ADN-compatible polyglycidyl azide polymer (GAP) has been demonstrated using a novel type of macromolecular curing agent. In light of these results further work towards ADN-propellants is strongly encouraged.QC 20101103
46
Waddell, Daniel C. „Environmentally friendly synthesis using high speed ball milling“. University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1330024874.
Der volle Inhalt der Quelle
47
Nivangune, N. „Catalytic synthesis of dimethyl carbonate and its application as a green reagent for the synthesis of aromatic carbamates“. Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4491.
Der volle Inhalt der QuelleAnnotation:
Dimethyl carbonate (DMC), is an important intermediate and is widely used in industry due to its non-toxicity, good biodegradability, and excellent solubility.1 DMC is used as an alternative, to harmful phosgene for the synthesis of aromatic polycarbonates and isocyanates and also as a carbonylation agent; DMC is about 1000 times less toxic than phosgene. It is also use in methylation reaction as a safe substitute for dimethyl sulfate, methyl halides; which are toxic and corrosive.2 Moreover, because of its versatile chemical properties, DMC is used as an electrolytic solution in secondary lithium battery, foodstuff flavoring agent and as a solvent in the field of paints. Owing to all these properties DMC is considered as an environmentally benign chemical and a safe reagent for many important transformations.3 Future demand for DMC is expected to grow in view of the stringent environmental regulations.Hence research work is being carried out on the development of safer routes for DMC synthesis and it’s utilization to value added products i.e. aromatic carbamates by methoxycarbonylation of aromatic amines.4
Methyl N-phenyl carbamate (MPC) is the simplest aromatic carbamate, are widely used as intermediates in the synthesis of pesticides, insecticides, herbicides, plastics and often used as protecting groups for amine functionality.5 MPC is an important precursor for preparing methylene diphenyl diisocyanate (MDI) by condensation of MPC with formaldehyde, which is an important intermediate for the synthesis of polyurethanes(PUs).6 PUs are among the most valuable polymers produced by the chemical industry. In 2007 the global consumption of PUs as raw material was about 12 million metric tons/year and the average annual growth rate is about 5%.CSIR - National Chemical Laboratory, Pune
AcSIR
48
Nivangune, N. T. „Catalytic synthesis of dimethyl carbonate and its application as a green reagent for the synthesis of aromatic carbamates“. Thesis(Ph.D.), CSIR-National Chemical Laboratory Pune, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4501.
Der volle Inhalt der Quelle
49
Borghese, Sophie. „Toward green processes organic synthesis by catalysis with metal-doped solids“. Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01017796.
Der volle Inhalt der QuelleAnnotation:
Nowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future.
50
Pickard, Olubukunola. „Synthesis and cardioprotective activities of green tea polyphenols and their analogues“. Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/362977/.
Der volle Inhalt der QuelleAnnotation:
Cardiovascular disease is a major killer worldwide and it is becoming clear the significance of our diet in curbing the disease. Green tea is one of the most widely consumed beverages in the world and has recently attracted significant attention in the scientific community for its health benefits. Its consumption has been associated with lower incidences of coronary artery diseases in the Japanese population. This is mainly attributed to its polyphenolic constituents that include epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate. The aim of this research was to synthesise the four major polyphenols present in green as well as analogues. These compounds would then be tested on H9C2 cardiac myoblast cells and neonatal rat cardiomyocytes in order to further understand the structure-activity relationship as well as potentially improve the cardioprotective function of these polyphenols following oxidative stress and ischaemia/reperfusion injury focusing on the expression of STAT-1 and ERK-1/2 proteins. In H9C2 cardiac myoblast cells following the induction of oxidative stress using H2O2, EGCG, EGC and to a minor extent ECG inhibited STAT-1 activation but not ERK- 1/2 phosphorylation suggesting that although the ERK-1/2 pathway gets activated, its downstream activation of STAT-1 is inhibited by the above polyphenols. EC, on the other hand, inhibited ERK-1/2 activation which in turn cannot activate STAT-1. Quantitative assessment of viable cells showed that pretreatment with EGCG resulted in the lowest amount of non-viable cells reducing cell death by 30%. With neonatal rat cardiomyocytes following ischaemia/reperfusion injury, pretreatment with EGCG reduced the amount of non viable cells by 5% but pretreatment with acetylated EGCG at half the concentration of EGCG reduced non-viable cells by 8%. Structure-activity relationships of the green tea polyphenol analogues identified some key aspects in the structures of the polyphenols important in their cardioprotective function. Results indicated that ABD ring system is required for cardioprotective function but the presence of a third OH group in the ring may not be necessary. Substitution of ring C with benzoic and naphthoic rings improved the potency by more than 13-fold compared to EGCG with EC50 values of 1.60 and 0.77 μM respectively. Further research into these analogues could realise their potential and contribute to the understanding of the cardioprotective activities of green tea. A review on the previous synthesis approaches, isolation and biosynthesis of the green tea polyphenols is presented in Chapter 1 and also the different signalling pathways of interest in this work. An evaluation of the biological activities of the four major polyphenols is provided in Chapter 3. Experimental procedure and characterisation data are in Chapter 5.