Dissertations / Theses on the topic 'Metal-free oxidation'

This thesis studies the interaction between free radical species and supported noble metal nanoparticles (silver and gold) in the context of oxidation reactions. The peroxidation of cumene is the first reaction to be discussed and the difference in peroxidation product distribution using silver nanoparticles (AgNP) versus gold nanoparticles (AuNP) is examined. Specifically, cumyl alcohol is obtained as the major product obtained when using supported AuNP, whereas cumene hydroperoxide is favoured for AgNP. Such variations in product distribution are partially explained by the differences in the nanoparticle Fenton activity, where the TiO2 support was proposed to enhance such activity due to possible electron shuttling capabilities with the nanoparticle surface. Use of hydrotalcite as a support was found to minimize this characteristic, due to its insulator properties. The stability of hydroperoxide was tested in the presence of various others supports (activated carbon, Al2O3, ZnO, SiO2 and clays) with little success, with hydroperoxide exhibiting stability in the presence of HT. Using an oxygen uptake apparatus, the interaction of the cumyl peroxyl radical with the AuNP surface was demonstrated. Furthermore, this interaction promotes decomposition leading to the corresponding alkoxyl radical and subsequent hydrogen abstraction to form the observed cumyl alcohol product. The radical interaction with supported nanoparticles, and its reversibility appear different for gold and silver and accounts for a large part of the product distribution differences observed between AuNP and AgNP, as illustrated below. The peroxidation of ethylbenzene and propylbenzene was studied and revealed the participation of a reactive surface oxygen species due to the decomposition of peroxyl radicals on the nanoparticle surface. The reactive oxygen species was found to be transient in nature in the case of AuNP . Furthermore, this surface species was found to be an important participant in hydrogen abstraction leading to peroxide product formation. Finally, supported nanoparticle catalyzed tetralin peroxidation was investigated to determine the influence of temperature on the peroxidation product distribution and how changes in the reaction temperature can effect the radical-nanoparticle surface interactions.

Les nanotubes de carbone (NTCs) dopés avec différents hétéroéléments tels que l'oxygène et l'azote connaissent un intérêt croissant dans le domaine de la catalyse hétérogène comme leur utilisation en tant que catalyseur sans métaux. L'objectif de cette thèse consiste à la synthèse et la caractérisation de matériaux catalytiques à base de NTC dopés à l'azote supportés sur du carbure de silicium SiC par voie in situ (CVD) et ex-situ méthodes. Une autre approche a été utilisée pour la fonctionnalisation de la surface des nanotubes de carbone et basées sur l'utilisation d'un agent oxydant (HNO3) en phase gazeuse. Ce procédé d'oxydation crée non seulement des défauts sur la surface des nanotubes de carbone mais également décore leur surface avec des groupes fonctionnels oxygénés. Les NTCs dopés à l'oxygène et à l'azote ainsi synthétisés ont été caractérisés par différentes techniques (XPS, MEB, MET, BET, ATG). Ces catalyseurs carbonés présentent des performances remarquables en termes d'activité et de sélectivité en soufre, et une très grande stabilité sous flux en fonction du temps dans la réaction d'oxydation partielle de l'H2S en soufre élémentaire, et ce, même à vitesse spatiale de gaz élevée (WHSV) et faible rapport O2/H2S. L'influence des différentes propriétés physico-chimiques et les défauts présents sur la surface des NTC sur les performances catalytiques ont été étudiée et discutée dans le cadre de ce travail
Carbon nanotubes (CNTs) containing different doping such as oxygen and nitrogen composites have received more and more scientific attention as metal-free catalyst in the field of heterogeneous catalysis. The aim of this thesis is related to the synthesis and characterization of nitrogen-doped CNTs decorated on SiC support using both in-situ (CVD with NH3) and ex-situ (N@C) methods. Other approach was employed for the surface functionalization of CNTs is based on the use of oxidative agent (HNO3) in gas phase. This oxidation process not only creates defects on the CNTs surface but also decorates their surface with oxygenated functional groups. The as-synthesized oxygen- and nitrogen-doped CNTs are characterized by different techniques (XPS, SEM, TEM, BET, TGA). The carbon based catalysts exhibit outstanding performances in term of activity and sulfur selectivity, and very high stability with time on stream in the partial oxidation of H2S into elemental sulfur even at high gas space velocity (WHSV) and low O2-to-H2S molar ratio. The influence of the physical-chemical properties and defects present on the CNTs surface on the catalytic performance was thoroughly investigated and discussed within the framework of this work

Grâce au développement continu de technologies d'analyse environnementale, certains produits chimiques, qui sont reconnus être nocif, ont récemment attiré l'attention, puisqu'ils constituent un menace pour l'environnement et la santé publique.Parmi ces polluants émergent, les produits pharmaceutiques et de soins personnels (PPSP)sont devenus le cibles dela recherche internationale. La chine est le plus grand producteur et le marché des médicaments dans le monde. Avec le développement de l'économie sociale et l'amélioration du niveau de vie de la population, de la production et de l'utilisation de divers PPSP présents en chine augmente rapidement. Par comparaison avec les polluants classiques, ces contaminants émergents sont généralement difficiles à analyser en raison de la limitation de technologies analytiques et de sa faible concentration dans les eaux naturelles.Les usines traditionnelles de traitement des eaux usées ne peuvent pas éliminer efficacement ces produits. La recherche sur l'évaluation des risques et le contrôle des nouveaux contaminants émergents, en chine constitue actuellement un grand défi. Il est donc essentiel de renforcer la recherche sur l'évaluation des risques pour l'environnement et les technologies de traitement efficaces pour éliminer ces polluants émergents. Les procédés d'oxydation avancée (POA) constituent une technologie de traitement efficace et ont été largement utilisés dans le traitement des polluants organiques réfractaires tels que les la destruction des contaminants émergents en milieu aqueux à cause de leur forte pouvoir d'oxydation permettant une minéralisation in situ des polluants. Le graphite, comme un nouveau type de matériau carbone adsorbant, est devenue un matériau d'électrode pour le traitement de la pollution due à son excellente conductivité et surface spécifique très élevée. Toutefois, son application dans les AOPs n'a pas été largement étudié et le mécanisme d'oxydation n'a pas été expliquée de manière systématique. Par conséquent, ce travail présent une étude détaillée sur le rôle des électrodes graphite modifiées dans les procédés électrochimiques d'oxydation avancée (PEOA) avec la préparation électrochimique des électrodes modifiées au graphène par exfoliation, et leur application dans le PEOA "électro-Fenton" (EF) pour le traitement des contaminants émergents. Ainsi le cathode en feutre de carbone modifiée au graphène a permis de d'éliminer différents contaminants émergents sans utilisation d'ions ferreux (catalyseur du procédé électro-Fenton) car les radicaux hydroxyles sont générés à travers d'un procédure catalytique grâce à la dopage du graphène à l'azote. Ensuite les cinétiques de dégradation et de minéralisation ainsi que les mécanismes d'oxydation de différents contaminants émergents ont été explorées
In recent years, with the continuous development of environmental analysis technologies, some chemicals, which have long been recognized but recently attracted attention, have been continuously entering the environment and threatening human health and ecological environment. The emergence of these new pollutants have attracted wide attention. Among them, pharmaceuticals and personal care products (PPCPs) have become international research hotspots. China is the largest medicine producer and market in the world. With the development of social economy and the improvement of people's living standards, the production and use of various PPCPs in China are increasing rapidly. Compared with the traditional pollutants, the new emerging contaminants are generally difficult to be analyzed due to the limitation of analytical technologies and its low concentration in water. The traditional sewage treatment plants can not achieve efficient degradation and removal effects. The research on risk assessment and control of new emerging contaminants in China is still a big challenge. It is necessary to strengthen the research on potential environmental risk assessment and efficient treatment technology. Advanced oxidation processes (AOPs), as an efficient pollutant treatment technology, has been widely used in the treatment of refractory organic pollutants such as new emerging contaminants in water because of its strong oxidation ability, which can effectively degrade and mineralize pollutants in water. Graphene, as a new type of carbon material, has become an efficient adsorbent and catalyst for pollution treatment due to its excellent conductivity and high specific surface area. However, its application in AOPs has not been widely reported and its mechanism has not been systematically explained. Based on this, this paper studied the role of graphene modified electrodes in electrochemical advanced oxidation processes (EAOPs) with the preparation of graphene by electrochemical exfoliation, application of graphene modified electrodes to electrochemical Fenton (EF) process for the degradation of new emerging contaminants; the construction of in-situ iron-free EAOPs with cathodes modified with nitrogen-doped graphene for abatement of new emerging contaminants and the mechanism of highly efficient catalysis with nitrogen-doped graphene have been explored

O-acyl-N-benzyllactamides are obtained in good yield by reaction of 4-benzyl-5-methyl-1,3-oxazolidine-2,4-diones with Grignards reagents and with lithium alkyls. Three alkanes and two ethers were oxidised with ozone in dichloromethane solution or in aqueous pH 3 suspension. Cyclodecane and cyclododecane were converted into the corresponding cycloalkanones. n-decane was converted into a mixture of isomeric n-decanones and carboxylic acids. An ester was formed from the ethers. Hence, one of the methylene groups of these substrates is generally converted into a carbonyl group. Some of these reactions have preparative value. The oxidation of naphthalene in dichloromethane or acetonitrile with excess ozone gives phthalic aldehyde, 2-formyl benzoic acid and phthalic anhydride. Small amounts of the (E)- and (Z)-isomer of 3-phenyl-(2-formyl)-propenal and are also observed in some cases. The reaction is faster in acetonitrile than in dichloromethane owing to the higher solubility of ozone in the former solvent. The reaction is faster on lowering the temperature because of the increase of the concentration of ozone in solution at lower temperature. With a 1:1 or a 1:2 naphthalene:ozone ratio high conversion and low selectivity for the anhydride is observed. The ozonation of cyclohexane in dichloromethane or acetonitrile gives cycloxexanone, cyclohexanol and acidic material. The influence of solvent, reactant concentration, amount of ozone, temperature, reaction time is studied. A reaction mechanism is proposed based on the results of a simulation of the reaction energetics. The ozonation of N-phenylmorpholine in dichloromethane or acetonitrile produced a lactame and a diformylderivative. These products derive from the attack of ozone at the heterocyclic ring. The reaction mechanism has been investigated by DFT calculations which show that the reaction occurs through the insertion of ozone at the carbon-hydrogen bond of a methylenic group of the morpholine ring. The regioselectivity is due to the to the significantly lower energy barrier calculated for the attack of ozone in α to nitrogen than in α to oxygen. Also, the energy barrier decreases with increasing the polarity of the solvent, accounting for the higher reaction rate observed for the reaction carried out in acetonitrile than in dichloromethane. The ozonation of trans- and cis-decalin in dichloromethane or acetonitrile gives the corresponding 9-hydroxydecalinns, 2- and 3-decalones and acidic material. The influence of solvent, reactant concentration, amount of ozone, temperature, reaction time is studied. A reaction mechanism is proposed based on the results of a simulation of the reaction energetics. The N,N bis(salicylidene)ethylenediaminocobalt(II) catalysed oxidative carbonylation of para-substituted aromatic primary amines at 100 °C in methanol gives carbamates in high yields. In presence of excess dimethylamine also N-aryl-N’,N’-dimethylureas are formed. In methylene chloride moderate yields in isocyanate are obtained. 1-methylbenzylamine gives the carbamate and the urea in high yield. i-propylamine gives only the urea. An α-aminoalcohol gives a 1,3-oxazolidin-2-one. Aliphatic secondary amines react faster and give carbamates in methanol and ureas in methylene chloride. The turnover frequency is also measured in two cases.

This research presents novel nanocarbon materials as green and metal-free carbocatalysts for advanced oxidative processes toward environmental remediation. Various nanocarbons exhibit high catalytic activity in activation of sulfate oxidants for degradation of water contaminants. The tailored surface chemistry of nanocarbons and insightful mechanistic studies for catalytic activation of superoxides were revealed via deliberate materials design, advanced characterization techniques and theoretical calculations.The findings would significantly contribute to materials chemistry, environmental science, carbocatalysis and other related fields.

The thesis entitled “Design and Development of Synthetic Methods using Metal-mediated and Metal-free Redox Reactions: Novel C-H Activations, Reductions and Oxidative Transformations” is presented in 4 chapters Chapter 1; Iodine catalyzed amination of benzoxazoles: efficient metal free route to 2-aminobenzoxazoles under mild conditions. The Chapter 1 of this thesis describes iodine catalyzed C-H activation of benzoxazole with primary and secondary amines to form oxidative aminated products. Selective C-H oxidation is a frontline area of modern chemical research as it offers the opportunities to new avenues and more direct synthetic strategies for the synthesis of complex organic molecules.1 In this context, transition metals such as palladium copper, nickel etc, are used extensively for the functional group directed C-H activation, and thus provides new, rapid, low-cost, and environmentally benign protocols for the construction of new chemical bonds.2 During the past two decades iodine and hypervalent iodine have been focus of great attention as they provide mild, chemoselective and environmentally benign strategies in contrast to toxic metal oxidants.3 In this chapter, a facile metal-free route of oxidative amination of benzoxazole with secondary or primary amines in the presence of catalytic amount of iodine (5 mol%) in aq tert-butyl hydroperoxide (1equiv) and AcOH (1.1 equiv) at ambient temperature, under the solvent-free reaction condition is presented. This user-friendly method to form C-N bonds produces tert-butanol and water as the by-products, which are environmentally benign. A wide range of benzoxazole derivatives containing electron-donating and electron-withdrawing groups were coupled with both primary and secondary amines (Scheme 1). Application of this methodology is demonstrated by synthesizing therapeutically active benzoxazoles by reacting 5-chloro-7-methylbenzoxazole with N-methylpiperazine and N-ethylhomopiperazine to obtain corresponding N-aminatedbenzaxozoles, which exhibit antidiarrhetic activity (Scheme 2).4 Scheme 2 Chapter 2: NIS catalyzed reactions. amidation of acetophenones and oxidative amination of propiophenones Chapter 2 is divided in to 2 parts. Part 1 describes the synthesis of α-ketoamides by using acetophenone and secondary amine in the presence of N-iodosuccinamide and TBHP in acetonitrile at room temperature, whereas Part 2 reveals the synthesis of 2-aminoketones by reacting aryl alkyl ketones and suitable secondary amine in the presence of NIS and TBHP. Part 1: Oxidative amidation, synthesis of α-ketoamide: Alpha α-ketoamides are important intermediates in organic synthesis that are present in a variety of natural products, and pharmaceutically active compounds. Herein, a mild and efficient conversion of acetophenones to α-ketoamide is documented by using aq.TBHP and N-iodosuccinamide (NIS) as a catalyst, at ambient temperature. This amidation reaction was found to be versatile as several aetophenone derivitives containing electron-withdrawing and electron-donating substituents underwent a facile amidation. It was also found that acetyl derivatives of heterocylic compounds could be easily converted to their corresponding ketoamides (few examples are shown in Scheme 3).5 Scheme3 Part 2 of Chapter 2 narrates a novel amination of propiophenone and its derivatives catalysed by NIS in the presence of TBHP to furnish their corresponding 2-aminoketone derivatives (Scheme 4). These derivatives are ubiquitous scaffolds that are present in a wide variety of therapeutic agents. Some of these compounds are used in the treatment of depression, smoking cessation, as monoamine uptake inhibitors, rugs for cancer. They are photoinitiators, precursors to β-aminoalcohols, such as pseudoephedrine analogues. 2-Aminoacetophenone analogues are also important intermediates for the formation of several heterocyclic compounds and are active moieties in several important drugs such as ifenprodil, Scheme 4. Chapter 3: Efficient oxidation of primary azides to nitriles This Chapter is divided in to 2 parts, which presents the oxidation of primary azides to their corresponding nitriles. Part 1: An Efficient oxidation of primary azides catalyzed by copper iodide: a convenient method for the synthesis of nitriles In Part 1, an efficient oxidation of primary azides catalyzed by copper iodide to their corresponding nitriles is reported. Herein, the oxidation of primary azide to nitrile is performed using catalytic amount of copper iodide, and aq TBHP in water at 100 ° C. This methodology is compatible with a wide range of primary benzylic azides that contain electron-donating and electron-withdrawing functional groups. The oxidation was found to be selective and a number of oxidizable functional groups were well-tolerated during the reaction conditions (few examples are shown in Scheme 5).6 Scheme 6 Furthermore, oxidation of secondary azides furnished the corresponding ketones in excellent yields (Scheme 6).6 In the Part 2 of Chapter 3, a non-metal catalysed oxidation of primary azides to nitriles at ambient temperature is reported. This part reveals the oxidation of primary azides to nitriles by employing catalytic amounts of KI (25 mol%), DABCO (25 mol%) and aq. TBHP (3 equiv., 70% solution in water). This reaction provides a good selectivity, as double and triple bonds were not oxidized under the reaction conditions. Additionally, chemoselective oxidation of benzylicazides against aliphatic azides increases the potential application of the present method (Scheme 7).7 Chapter 4: Chemoeselective reduction of olefins Part 1: Iron chloride catalysed aerobic reduction of olefins using aqueous hydrazine at ambient temperature Chapter 4 describes the reduction olefins and acetylenes, which is presented in two Parts. Part 1 documents utility of hydrazine (1.5 equiv) for the chemoselective reduction of nonpolarised carbon-carbon bond using iron catalysts. In this part, a chemoselective reduction of alkenes and alkynes in the presence of a variety of reducible functional groups is demonstrated (Scheme 8). The highlight of the present method is that the reduction proceeds well at room temperature and requires only 1.5 equiv of hydrazine hydrate. The olefin reduction by hydrazine depends upon the controlled release of diimide during the reduction. Generally, metal catalyzed reduction of olefins employ a large excess of hydrazine (10-20 equiv), which might be attributed to uncontrolled release of diimide during the reduction.8 Scheme 8 Part 2: Guanidine catalyzed aerobic reduction: a selective aerobic hydrogenation of olefins using aqueous hydrazine In Chapter 4, part 2, organocatalytic generation of diimide and its utility to reduce the double bonds is presented. Generation of diimide in situ by using organo catalysts and its use for the reduction of carbon-carbon double bond is one of the interesting topics in organic chemistry. It has been shown in this part of the thesis that the reduction of olefin at room temperature can be efficiently performed by using 10 mol% of guanidine nitrate, 2 equiv of aqueous hydrazine in oxygen atmosphere. This method tolerates a variety of reducible functional groups such as nitro, azido, and bromo and protective groups such as methyl ethers, benzyl ethers, and Cbz groups. It is also shown that terminal olefin can be selectively reduced in the presence of internal olefin (Scheme 9). Unlike other methods that employ diimide strategy, the present method is shown to be efficient in reducing substrates those contain internal double bonds such as cinnamyl alcohol and its derivatives

碩士
中原大學
化學研究所
106
By means of density functional theory (DFT) calculation, we used the carbon nanotubes with different content of doped boron as potential metal-free catalysts for the CO oxidation. In order to find the possible active sites for CO oxidation, we investigated the O2 -adsorption behavior on different position of 1 and 2 B-doped carbon nanotubes and find the most stable structures of adsorbed O2 are flat on C-B site of both nanotubes with the adsorption energies of -0.85 and -1.29 eV, respectively. Then we investigated the catalytic reaction paths of CO oxidation, divided into two parts: (1) CO + O2* → CO2 + O*, where the activation energy required for B-doped and BB-doped catalysts are 0.34 eV and 0.42 eV, respectively; (2) O* + CO → CO2: the activation energy required for BB-doped is 0.14 eV. The reaction is through the Eley-Rideal mechanism (ER) to produce carbon dioxide. After two CO oxidation processes, the carbon nanotubes can be recovered to their original structures and recycled. After calculation, we found that B-doped carbon nanotubes not only improved adsorption capacity of O2, but also reduced the activation energy of CO oxidation. According to our research, the higher stability of O2 , the more boron-doped content.

碩士
中原大學
化學研究所
104
We use density functional theory (DFT) calculation to investigate nitrogen-doped carbon nanomaterials as a potential metal-free catalyst for CO oxidation. The possible structures and reaction mechanisms, of CO oxidation are illustrated by using the same method. First, we consider the O2 adsorption and use Bader charge to analysis, the favorable adsorption sites are C-N site and C-C-1 site. The calculation results show that most stable adsorption energy are -0.82 and -1.63eV for NCNTs, and -0.84 and -0.99eV for N-C60. Then we use nudged elastic band (NEB) method to illustrate the minimum-energy paths (MEP) for the catalytic reaction of CO oxidation. The oxidation process takes place via the Eley-Rideal mechanism (ER) to generate carbon dioxide. The reaction can be divided into two part: (1) O2 + CO → CO2 + O (remaining), and (2) O (remaining) + CO → CO2. After the two CO oxidation processes, the carbon nanomaterials can be recovered their original structures and recycled. Finally, we compare those carbon materials to search and develop high catalytic activity method for CO oxidation.

Thesis (Ph. D.)--University of Notre Dame, 2007.
Thesis directed by E. E. Wolf for the Department of Chemical and Biomolecular Engineering. "December 2007." Includes bibliographical references (leaves 196-214).

碩士
國立成功大學
化學系碩博士班
98
The metal salts mediated radical reaction of quinones for constructing carbon-carbon bonds are described. Radical intermediates which created by Ag(II) or Mn(III) then underwent intermolecular and intramolecular cyclizations. The study was initiated by the methodolgy. There are two parts in this thesis: (1) Acyl and carbon radicals generated by the oxidative decarboxylation of α-ketone acid and α-amino acid respectively with silver(I) nitrate and persulfate. Besides, Acyl radicals also produced by β-ketone ester with manganese(III) and O2. Each of the radicals then underwent radical addition to 2-(1-hydroxyalkyl)-1,4-nathoquinones, 2-benzoyl-1,4-nathoquinones and 2-(1-amidoalkyl)-1,4-nathoquinones. These reactions provided effective methods for the synthesis of isofuran-1,4-nathoquinones or isopyrrole-1,4- nathoquinones. (2) Manganese (III) acetate oxidation of ethyl butyrylacetate generated radicals which then underwent radical addition to 2-benzoyl- 1,4-benzoquinones . In the present of cerium(III) nitrate as Lewis acid, benzo[c]furan-4,7-diones and anthrancene-1,4-diones could be produced with good chemoselectivity in neutral solvent .

博士
國立成功大學
化學系碩博士班
96
The use of radicals in organic synthesis has increased dramatically within the last decades. Radical carbon-carbon bond-forming reactions have grown in importance to the point where chemists are now routinely considered in strategy planning of complex targets. A typical, widely used radical cyclization involves the reduction of a halide or other functional group to a radical with R3SnH, followed by cyclization and reduction of the resulting radical to a hydrocarbon in the chain propagation steps. While this sequence often gives high yields of products, this approach is limited, leading to relatively unfunctionalized products. Oxidative free-radical reaction in which the initial radical is generated oxidatively or the cyclic radical is terminated oxidatively, has considerable synthetic potential, since more highly functionalized products can be prepared from simple precursors. In this report, we describe our results on: (1) Oxidative free radical reactions between 1,4-quinone derivatives and ketones, benzoylacetonitriles, β-enamino ketones, carboxylic acids, β- dicarbonyl compounds. Carbon radicals which can be generated effectively by metal ion oxidation of ketones,β-enamino ketones orβ-dicarbonyl compounds undergo inter- molecular free radical additions with 1,4-quinones to produce spirolactam, indole-4,7-dione or isobenzofuran-4,7-dione. (2) Oxidative free radical reactions between indole derivatives and β- dicarbonyl compounds. Radical generated by the manganese(III) oxidation ofβ-dicarbonyl compounds undergoes efficient addition to the 2-position of 3-unsubstituted indoles and 2-(3-oxo-2-indolylidene)malonates or furo[3,2-b] indoles was produced. (3) Oxidative free radical reactions of β-aminocinnamates. We describe an effective method for the synthesis of highly substituted pyrroles via oxidative free radical reaction betweenβ-aminocinnamates and enamines.

碩士
國立成功大學
化學系碩博士班
100
Free-radical reaction has been applied to formation of carbon-carbon bond for decades and it plays an important role for synthesis of heterocyclic compounds. Manganese (Ⅲ) acetate and Silver (Ⅱ) are the most common reagents for the oxidative free-radical reaction. The study was initiated by the methodology. There are two parts in this thesis: (1)The oxidative free radical reactions of 2-anilino-1,4-naphthoquinones 62 with Silver (Ⅱ) produce benzo[b]acridines 63 effectively. (2)The oxidative free radical reactions of 2-(Allylsulfonyl)-N-benzyl-N-(4’-methoxybiphenyl-2-yl)acetamide 76 with manganese (III) acetate produce spiro compound 77 and azepine compound 78 effectively.