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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Reakční intermediáty v homogenní zlatné katalýze / Reaction intermediates in homogeneous gold catalysis

Shcherbachenko, Elena January 2016 (has links)
The presented master thesis is devoted to the investigation of reaction intermediates in homogeneous gold catalysis. Electrospray ionization mass spectrometry (ESI-MS) was used as the primary research technique in this study. Delayed reactant labeling was used as the main method. I have focused mainly on the hydration of 1-phenyl-1-propyne catalyzed by the gold complex [Au(IPr)(MeCN)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2- ylidene). I have detected two main intermediates containing one or two gold atoms, respectively (monoaurated and diaurated intermediate). I have obtained rate constants for the degradation of the reaction intermediates and their half-lives. I have derived kinetic isotope effects for the formation and the decomposition of the detected intermediates. I have shown that the kinetics of the degradation of both intermediates is identical, therefore I conclude that hydration of alkynes catalyzed by gold complex [Au(IPr)(MeCN)]BF4 proceeds most probably via neutral monoaurated intermediates. These neutral intermediates are detected by ESI-MS as protonated (monoaurated intermediate) or tagged by a second gold cation (diaurated intermediate). Key words: gold catalysis, reaction intermediates, electrospray ionization, mass spectrometry.
12

Katalytická příprava polyanilinů / Catalytic synthesis of polyanilines

Bláha, Michal January 2012 (has links)
This Ph.D. thesis is dealing with catalytic polymerization of aniline (ANI) and partially also of substituted anilines with FeCl3/H2O2 catalyst system, in which according to obtained results both active species, Fe3+ and HO , participate in the overall polymerization mechanism, creating a synergic system. The Fe3+ /H2O2 catalyst system, also called Fenton's system can considerably lower contamination of forming neat polyanilines (PANIs) by side-products characteristic of stoichiometric polymerization. However, catalytically prepared PANIs exhibit reduced conductivity related most probably to side reactions involving radicals generated as integral components of the FeCl3/H2O2 system. Catalytic polymerization of ANI with FeCl3/H2O2 system was found to be the reaction of approx. 2nd order with respect to ANI and gives PANIs of a good quality only when [H2O2] in the reaction mixture was kept low, i.e., at under- stoichiometric ratios [H2O2]/[ANI]. At over-stoichiometric ratio [H2O2]/[ANI], PANIs of lowered conductivity, worse spectroscopic characteristics and increased size of PANI nanostructures were obtained; nevertheless, these PANIs were not over-oxidized to pernigraniline state. The reaction-time profiles of the open-circuit potential of reaction mixtures exhibited an inflection related to the...
13

Syntéza polycyklických sloučenin obsahujících kvarterní uhlíková centra / Synthesis of polycyclic compounds containing quaternary carbon centers

Vašíček, Tomáš January 2018 (has links)
In this diploma Thesis, a method for the preparation of polycarbocyclic compounds containing all-carbon quaternary centers embedded in triquinane skeleton was prepared. The key reaction sequence leading towards the preparation of these carbocycles was Pd-catalyzed tandem cyclization/Suzuki cross-coupling reaction followed by halocarbocyclization. In the first part of synthetic project, a model oxygen-containing polycyclic derivative was prepared. In the second part, 3 novel polycarbocyclic compounds containing all-carbon quaternary centers were successfully prepared. Synthetic procedure for the starting material required for the key reaction sequence was developed. This approach represents another pathway for the synthesis of polycarbocyclic natural products. Keywords: synthesis, polycyclic compounds, quaternary centers, catalysis
14

Fosfinoferrocenové ligandy s polárními amidovými substituenty / Phosphinoferrocene ligands with polar amide substituents

Charvátová, Hana January 2016 (has links)
Title: Phosphinoferrocene ligands with polar amide substituents Author: Hana Charvátová Department: Department of Inorganic Chemistry Supervisor: prof. RNDr. Petr Štěpnička, Ph.D. Abstract: This thesis is focused on phosphino-urea ferrocene ligands that are still rather neglected in the literature. It describes the synthesis of novel polar amides and hydrazides of 1'-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) with or without ethylene linker bearing various urea and guanidine terminal functional groups. Urea and guanidine derivatives with ethylene bridge can be prepared from Hdpf and appropriate amine with amidation agents. Phosphine ureas without the linker are accessible from reactions of primary amide of Hdpf with suitable acylation agents while analogical guanidine is obtained from guanylation of amide-amine generated from Hdpf acylbenzotriazole and ethylenediamine. Reaction of the acylbenzotriazole with free guanidine leads to [1-(diphenylphosphino)ferrocenecarbonyl]guanidine hydrochloride. These ferrocene ligands were used to prepare four types of palladium(II) complexes, viz. where L denotes the newly synthesized ligands and LNC is 2- [(dimethylamino)methyl]phenyl-C,N auxiliary chelating ligand. Catalytic efficiency of complexes with ethylene bridge was tested on reactions of aromatic...
15

Výzkum reakcí katalyzovaných zlatem / Research of gold catalyzed reactions

Jašíková, Lucie January 2016 (has links)
The main focus of the current dissertation thesis is research of gold catalyzed reactions. I was using mass spectrometry as the primary research technique. I complemented the results with infrared multiphoton dissociation spectroscopy, nuclear magnetic resonance spectroscopy and quantum chemical calculations. I have investigated the interaction of the gold(I) cation with unsaturated hydrocarbons in the first part of my thesis. Secondly, I have studied gold(I) or silver(I) affinity to gold acetylides. In the last part, I have investigated the reaction mechanism of a gold mediated addition of methanol to alkynes. I found out that the gold(I) cation interacts stronger with gold acetylides than with nonactivated triple CC bonds. I showed that the complexes containing two gold atoms represent the key intermediates in the mechanism of addition of methanol to alkynes and that the ligand on the gold catalyst plays a fundamental role in the determination of the mechanism. Powered by TCPDF (www.tcpdf.org)
16

Měďné komplexy s fosfinonitrilovými donory / Copper(I) complexes with phosphinonitrile donors

Horký, Filip January 2017 (has links)
Title: Copper(I) complexes with phosphinonitrile donors Author: Bc. Filip Horký Department: Department of Inorganic chemistry Supervisor: prof. RNDr. Petr Štěpnička, Ph.D. Abstract: Although coordination compounds with phosphinonitrile ligands are already well known, in the vast majority of these complexes these ligands coordinate as simple P-donors with their cyano groups acting as auxiliary substituents. This led us to synthesize and study a series of Cu(I) complexes with two isomeric phosphinonitrile donors, namely 2-(diphenylphosphino)benzonitrile (Lo ) and 2-(diphenylphosphino)benzonitrile (Lp ), with different ligand-to-metal ratios and possibly characterize further coordination modes offered by these hybrid donors. This work describes the preparation of phosphinonitrile complexes from the aforementioned ligands and simple copper(I) halides (CuX, X = Cl, Br, I), pseudohalides (X = CN) and from [Cu(MeCN)4][BF4]. The products were characterized by nuclear magnetic resonance, infrared spectroscopy and elemental analysis, mass spectrometry, and their solid-state structures were determined by single-crystal X-ray crystallography. In addition, luminescent properties of the Cu(I) complexes were studied and catalytic activity of selected complexes was tested in copper-catalyzed alkyne-azide cycloaddition...
17

Mikrofluidní reaktory pro chemickou syntézu / Microfluidic reactors for chemical synthesis

Jaklová, Natalie January 2021 (has links)
The main topic of the Diploma Thesis is the conversion of the batch N-alkylation reaction into a continuous regime. It is the reaction of 10α-methoxydihydrolysergic acid methyl ester to 1-methyl-10α-methoxydihydrolysergic acid methyl ester. It represents one step in the industrial synthesis of Nicergoline, a pharmaceutical used for senile dementia treatment. This methylation reaction is performed in two immiscible liquid phases. Phase-transfer catalysis is used to increase the efficiency of the reaction, which allows the reaction to proceed in the entire volume of the organic solvent, not only at the phase interface. The reaction is rapid, with an exothermic character. The advantages of continuous arrangement are better control of the reaction, increased operational safety due to handling smaller volumes of reaction components, and more intensive removal of heat of the reaction. The Thesis deals with the influence of reaction conditions on the course of the reaction in a microfluidic reactor. The glass microchip reactor was chosen to perform the reaction in a flow arrangement. This reactor could produce up to grams of the product per hour. Several series of experiments were performed on this apparatus. The conversion of the starting material, and selectivities to the product and the side products...
18

Studium perovskitových oxidových katalyzátorů pro parciální oxidace metanu / Study of Perovskite Type Oxide Catalysts for Partial Oxidation of Methane

Cihlář, Jaroslav January 2011 (has links)
Research was curried out on the perovskite systems with general formula A1-xA‘xB1-yB‘yO3± (where A=La, Sm, A´=Ca, B´=Al, B=Co,Fe,Mn and Cr). Perovskite oxides were sythesized by polymerisation methods and characterised by RTG analysis, BET method, SEM and EDX. TPD spectra and catalyst testing were measured in high temperature plug flow reactor and products were analysed by mass spectrometry. It was found, that metane oxidation at ratio O2/CH40,5 depended on the temperature. Total oxidation proceeded at the temperature betwen 300-700oC to the carbon dioxide and water, while the partial oxidation of metane (POM) occured at above 700oC to the hydrogen and carbon oxid (syngas). This was ascribed by equilibrium of O2 betwen gas phase and solid perovskite. There was used 12 perovskite systems, which catalysed methane oxidation by the same way. Dry reforming of methane run above temperature 700oC. Cobaltite and ferite type perovskites were found as the most active catalytic systems. On the base of obtained results the Mars van Krevelen mechanism was established for explanation of oxidation and reformation of methane by perovskite systems. It was showed, that POM was running by two steps mechanism. Products of total oxidation was occured in the first step, which were passed over to the syngas (H2+CO) in the second step.
19

Interakce jednoduchých molekul s redukovatelnými oxidy: modelové studie H2O/CeOx and CO/CuOx / Interaction of simple molecules with reducible oxides: model studies of H2O/CeOx and CO/CuOx

Dvořák, Filip January 2014 (has links)
The thesis is focused on the investigation of fundamental catalytic properties of two model catalysts-CeOx/Cu(111) and CuOx/Cu(111)-by means of advanced surface science techniques. The investigations performed on CeOx are devoted to the study of the relationship between the surface structure and the surface activity of ceria. We develop the preparation method leading to growth of epitaxial CeOx(111) thin films with the adjustable morphological parameters-the step density and the ordering of surface oxygen vacancies. By using the CeOx(111) films with precisely controlled structure we identify the role of the step edges and of the oxygen vacancies in the interaction of water with ceria. The investigation performed on CuOx is focused on the microscopic characterization of the reduction process of Cu2O(111) on the molecular level directly under a near ambient pressure of CO. In direct microscopic study we identify the active initiation centers, the intermediate oxide phases, and the kinetics of the reduction reaction of Cu2O(111).
20

Elektronické a strukturní vlastnosti modelových katalyzátorů na bázi oxidu ceru / Electronic and structural properties of model catalysts based on cerium oxide

Duchoň, Tomáš January 2017 (has links)
Catalysts based on cerium oxide are ubiquitous in industrial-scale chemical conversion. Here, a thorough study of their fundamental properties is undertaken via a model system ap- proach with the goal of furthering rational design in heterogeneous catalysis. A focus is put on understanding the behavior of oxygen vacancies in cerium oxide with respect to atomic co-ordination and electronic structure perturbations. Utilizing state-of-the-art probing tech- niques, a scalable model system framework is developed that allows for control over both the oxygen vacancy concentration and local co-ordination. High precision of the innova- tive approach facilitated observation of new phases of substoichiometric cerium oxide and lead to a first-of-a-kind investigation of the electronic structure of cerium oxide throughout isostructural transition from CeO2 to Ce2O3. The acquired results advance fundamental understanding of essential properties of cerium oxide that are relevant to its utilization in heterogeneous catalysis and open new pathways for functionalization of cerium oxide-based materials. Furthermore, the methodology developed in the thesis is transferable to other important reducible oxides. 1

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