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Grice, I. Darren, i n/a. "Some New Aspects of Radical Trapping Using an Aminoxyl Radical Trap". Griffith University. School of Science, 1993. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050915.150556.
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An investigation of the initiation mechanism in the free radical copolymerisation of acrylonitrile and vinyl acetate using the aminoxyl radical trapping technique, employing 1,1 ,3,3-tetramethyl-2,3-dihydro- 1 Hisoindol-2-yloxyl is reported. Based upon the experimental results, the mechanism of initiation is suggested as proceeding via the 'free monomer' mechanism. Additionally, the effect of Lewis acids on the initiation mechanism is reported. A study of the addition of phosphorus-centred radicals to alkenes and phenylacetylene, utilising the aminoxyl radical trapping technique is reported. The results indicate a decreased rate of addition by both diphenylphosphinyl and dimethoxyphosphinyl radicals to cyclic versus acyclic alkenes. In contrast to cyclic alkenes, both these phosphorus-centred radicals add readily to the triple bond of phenylacetylene. The stereochemistry of the addition of diphenyiphosphinyl and dimethoxyphosphinyl radicals and of the aminoxyl trap is discussed. The stereochemistry of the addition of benzoyloxyl radicals to a conformationally rigid alkene, trans-a2-octalin is reported. Attempts to examine the initiation mechanism in the free radical copolymerisation of styrene/maleic anhydride and of styrene/tetracyanoethylene utilising the aminoxyl radical trapping technique are described. Also described are attempts to synthesise some new phosphorus radical initiators.
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Grice, I. Darren. "Some New Aspects of Radical Trapping Using an Aminoxyl Radical Trap". Thesis, Griffith University, 1993. http://hdl.handle.net/10072/365216.
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An investigation of the initiation mechanism in the free radical copolymerisation of acrylonitrile and vinyl acetate using the aminoxyl radical trapping technique, employing 1,1 ,3,3-tetramethyl-2,3-dihydro- 1 Hisoindol-2-yloxyl is reported. Based upon the experimental results, the mechanism of initiation is suggested as proceeding via the 'free monomer' mechanism. Additionally, the effect of Lewis acids on the initiation mechanism is reported. A study of the addition of phosphorus-centred radicals to alkenes and phenylacetylene, utilising the aminoxyl radical trapping technique is reported. The results indicate a decreased rate of addition by both diphenylphosphinyl and dimethoxyphosphinyl radicals to cyclic versus acyclic alkenes. In contrast to cyclic alkenes, both these phosphorus-centred radicals add readily to the triple bond of phenylacetylene. The stereochemistry of the addition of diphenyiphosphinyl and dimethoxyphosphinyl radicals and of the aminoxyl trap is discussed. The stereochemistry of the addition of benzoyloxyl radicals to a conformationally rigid alkene, trans-a2-octalin is reported. Attempts to examine the initiation mechanism in the free radical copolymerisation of styrene/maleic anhydride and of styrene/tetracyanoethylene utilising the aminoxyl radical trapping technique are described. Also described are attempts to synthesise some new phosphorus radical initiators.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Science, Environment, Engineering and Technology
Full Text
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Shergill, Raminder. "Radicals and radical pairs in chemical and biological systems". Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/11008.
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Magnetic fields of different strengths can be applied to chemical and biological systems to study processes involving radicals or radical pairs. This work uses two such techniques, electron paramagnetic resonance (EPR) spectroscopy (≥ 150 mT) in addition to time resolved EPR spectroscopy and time resolved infrared (TRIR) spectroscopy (≤ 37 mT). The former are used to monitor metalloproteins, and the photochemistry of phosphorus oxides, while TRIR spectroscopy is used to record the magnetic field effects on the reaction kinetics of neutral radical pairs. The thesis begins with an introduction and an overview of the experimental techniques and developments. This is followed by an EPR study of the Fe(III) binding proteins, transferrin and lactoferrin and the effect thereon of catecholamine stress hormones. Catecholamines mediate bacterial growth by sequestering iron from the iron binding proteins. The mechanism of iron capture is unknown, however, the current work reveals Fe(III) binding by the catecholamine and supports subsequent reduction as the most likely route. Since catecholamines are also administered therapeutically, the validity of EPR as a diagnostic technique is examined and iron loss from human serum transferrin is observed. Also within this work, experiments are presented in which TRIR spectroscopy is used to investigate factors that affect the development of magnetic field effects for radical pairs in different solutions. This initially involves studies on acylphosphine oxides. In addition to the reported photoprocesses, alternative chemistry is uncovered, which occurs when bisacylphosphine oxide is in solutions where the solvent is sufficiently nucleophilic. The photochemistry is investigated using time resolved EPR and density functional theory calculations to suggest three possible structures that are responsible for the additional radicals observed. Furthermore, encapsulated organic radical pairs in reverse micelles are studied. These experiments, in combination with dynamic light scattering measurements provide insight into the magnitude of the observed magnetic field effects and the differing kinetics of the radical pair in the reverse micelles.
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Barrera, Mora Jose Felix Fernando. "On radical extensions and radical towers". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184833.
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Let K/F be a separable extension. (i) If K = F(α) with αⁿ ∈ F for some n, K/F is said to be a radical extension. (ii) If there exists a sequence of fields F = F₀ ⊆ F₁ ⊆ ... ⊆ F(s) = K so that Fᵢ₊₁ = Fᵢ(αᵢ) with αᵢⁿ⁽ⁱ⁾ ∈ Fᵢ for some nᵢ ∈ N, charF ∧nᵢ for every i, and [Fᵢ₊₁ : Fᵢ] = nᵢ, K/F is said to be a radical tower. In the first part of this work, we present two theorems which give sufficient conditions for a field extension K/F to be radical. In the second part, we present results which provide conditions under which every subfield of a radical tower is also a radical tower.
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Fabbri, Claudia. "Mechanistic aspects of lignin degradation. Role of radicals and radical ions". Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917334.
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Ishaq, Ahtsham. "The development and use of novel green radical methodology". Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158370.
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Over the last forty years the steady use of radical reactions as the key steps in syntheses has increased. The most commonly used radical reagent is tributyl tinhydride. However such tin based radical reagents are toxic and often contaminate the product as they are difficult to remove. As an alternative to these tin reagents, a novel NaBH4/U.V. system was developed. This system was successfully used to effect the radical reduction of various aromatic halides. In light of these results it was thought that other useful transformations such as C-C bond formation could be achieved. Radical cyclisation onto unsaturated bonds, halogen atom transfers radical cyclisation (HATRC) and 1-5 hydrogen atom translocations were explored. This, 1-5 hydrogen atom translocations, methodology has been successfully applied to the synthesis of the spirocyclic natural products (±) horsfiline and coerulescine. With this success the use of the NaBH4/U.V. system on pyridine substrates was explored. Unfortunately this was not achieved with our current understanding of this reaction. However the use of tributylgernamium hydride, which is considered a ‘green’ radical reagent when compared to tin based reagents, proved successful. The novel application of this reagent in the 1-5 hydrogen atom transfer reaction on pyridine substrates was successfully demonstrated. Its use was successfully employed in the synthesis of a pyridine based bioisostere derivative of horsfiline.
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McGarry, Peter F. "Radical and radical-like reactions of (1.1.1);propellane". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7811.
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(1.1.1) Propopellane, I, is the ultimate propellane in terms of its small size and the inversion of the tetrahedral geometry about its bridgehead carbons. As such I is reactive towards radicals and carbenes. We have studied the kinetics and mechanisms of reaction of various carbon and heteroatom centered free radicals with I by nanosecond flash photolysis and product studies techniques.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The addition of diphenylcarbene (DPC) and phenylchlorocarbene (PCC) to I have also been investigated. Addition of DPC proceeds via a 1,4-biradical intermediate, II, whereas with PCC it appears that the final product, III, is formed directly upon reaction. The implications of the apparent concerted addition of the singlet carbene to I are discussed.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The role of I as a quencher of electronic excited states is also reported.
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Botelho, João Francisco. "Epigênese radical". Florianópolis, SC, 2007. http://repositorio.ufsc.br/xmlui/handle/123456789/89646.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-graduação em Filosofia.Made available in DSpace on 2012-10-23T00:56:48Z (GMT). No. of bitstreams: 0
Existe na biologia contemporânea um consenso de que a genética proporcionou uma solução conciliatória para o longo debate entre preformacionistas e epigenesistas. O desenvolvimento, segundo a genética, é um processo híbrido de preformação e epigênese. A preformação persiste como informação, como um programa codificado do desenvolvimento. A epigênese persiste como a tradução do programa genético, como a revelação da informação pela expressão gênica. O presente trabalho critica esta conciliação genética a partir de duas análises epistemológicas # uma histórica e a outra conceitual # e defende uma posição alternativa # a Perspectiva dos Sistemas Desenvolvimentais (PSD). A análise histórica consiste em mostrar que o conceito de preformação é mais amplo e plástico do que a simples idéia de preexistência e pré-delineação de um organismo completo. O conceito de preformação chega ao século XX associado ao conceito de unidades hereditárias determinantes do desenvolvimento e está historicamente associado à tradição de pesquisa genética. A análise conceitual consiste em mostrar que a biologia contemporânea desautoriza o discurso preformacionista contido nas idéias de herança como transmissão genética, primazia e independência causal dos genes, herança sólida e programa genético. No lugar da conciliação genética defendo uma perspectiva estritamente epigenética dos processos celulares e desenvolvimentais como proposta pela PSD. There is a consensus in contemporary biology that genetics provided a conciliatory solution for the long-standing debate between preformationists and epigenesists. Development, according to the genetic conciliation, is a hybrid process of preformation and epigenesis. Preformation persists as information, as a codified program of development. Epigenesis persists as the translation of the genetic program, as the revelation of genetic information. The present thesis criticizes this genetic conciliation from two epistemological points of view # a historical one and a conceptual one # and supports an alternative position: the Developmental Systems Perspective (DSP). The historical analysis shows that the preformation tradition is wider than the simple idea of preexistence and pre-delineation of form. The preformation tradition arrives at the 20th century associated to the concept of units of inheritance controlling development and it is historically associated with the research tradition of genetics. The conceptual analysis consists of showing that contemporary biology discourages the preformationists assumptions enclosed in the ideas of heredity as genetic transmission, causal priority of the genes, exclusively genetic inheritance and genetic program. In the place of the genetic conciliation, we defend a strict epigenetic view of cellular and developmental processes, coherent with the DSP.
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Qureshi, Tariq. "Spin chemistry". Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365292.
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Wood, Geoffrey Paul Farra. "Theoretical Investigations of Radical-Mediated Protein Oxidation". Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1413.
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This thesis primarily details the application of high-level ab initio quantum chemistry techniques in order to understand aspects of free-radical mediated protein oxidation. Traditionally, product analysis and electron paramagnetic resonance (EPR) spectroscopy are the primary means for elucidating the chemistry of protein oxidation. However, in experiments involving relatively small proteins reacting with a controlled radical-flux, a vast array of compounds can be produced, which are often difficult to analyse. Quantum chemical techniques on the other hand, can calculate the properties of any particular species directly, without suffering from the problems associated with experiment, such as side-reactions and chain processes. The results presented in this thesis are aimed at elucidating mechanistic details of protein oxidation, which might otherwise be difficult to probe experimentally. Chapter 1 gives an overview of the free-radical hypothesis of disease and ageing. Protein-derived radicals can undergo a variety of reactions, with the particular reaction that occurs depending on numerous aspects. Many types of reactions have been identified through radiolysis experiments of amino acids, and these are detailed in this chapter. In addition, the key reactive species are characterized and their different chemistries explained. Chapter 2 details the theoretical tools used throughout this thesis. Species with unpaired electrons (radicals) present unique problems for quantum chemistry to handle, thus an appropriate choice of theoretical technique is needed. The approach taken in this thesis is to use high-level compound methods, many of which have been directly formulated to give improved results for radical species, to provide benchmark quality results by which other less demanding techniques can be assessed. During the course of this study, it became apparent there was a void in the armoury of tools that could be used for the theoretical chemistry calculations. Chapter 3 details the formulation of a new tool in an attempt to fill this gap. Historically, the formulation of this new procedure came after much of the work in this thesis had been carried out. Thus, for the study of many of the reactions of this thesis the new method has not been used. However, it is most appropriate to place its formulation after summarizing the current status of techniques in common use today. Chapters 4 and 5 detail computations carried out on models of peptides containing backbone carbon- and nitrogen-centered radicals. A number of different theoretical techniques are used in these chapters, ranging from the highly accurate and computationally intensive to the less reliable and less demanding. The highly accurate techniques are used to gauge the accuracy of the other less demanding theoretical techniques so that the latter can be used with confidence in larger systems. Not only is the choice of theoretical technique important but also the judicious choice of model is essential. With this in mind, models are incrementally built until convergence of the particular property of interest is reached. Chapters 6 and 7 detail the calculations of β-scission reactions of alkoxyl radicals, which are a particular class of reaction known to occur on peptide backbones. Alkoxyl radicals are particularly difficult for theory to describe correctly. Therefore, Chapter 6 extensively assesses and then identifies the theoretical methods needed to portray them. Chapter 7 uses the techniques identified in the previous chapter in order to predict how the preference for a particular type of β-scission reaction changes.
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Wood, Geoffrey Paul Farra. "Theoretical Investigations of Radical-Mediated Protein Oxidation". University of Sydney, 2006. http://hdl.handle.net/2123/1413.
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Doctor of Philosophy (PhD)This thesis primarily details the application of high-level ab initio quantum chemistry techniques in order to understand aspects of free-radical mediated protein oxidation. Traditionally, product analysis and electron paramagnetic resonance (EPR) spectroscopy are the primary means for elucidating the chemistry of protein oxidation. However, in experiments involving relatively small proteins reacting with a controlled radical-flux, a vast array of compounds can be produced, which are often difficult to analyse. Quantum chemical techniques on the other hand, can calculate the properties of any particular species directly, without suffering from the problems associated with experiment, such as side-reactions and chain processes. The results presented in this thesis are aimed at elucidating mechanistic details of protein oxidation, which might otherwise be difficult to probe experimentally. Chapter 1 gives an overview of the free-radical hypothesis of disease and ageing. Protein-derived radicals can undergo a variety of reactions, with the particular reaction that occurs depending on numerous aspects. Many types of reactions have been identified through radiolysis experiments of amino acids, and these are detailed in this chapter. In addition, the key reactive species are characterized and their different chemistries explained. Chapter 2 details the theoretical tools used throughout this thesis. Species with unpaired electrons (radicals) present unique problems for quantum chemistry to handle, thus an appropriate choice of theoretical technique is needed. The approach taken in this thesis is to use high-level compound methods, many of which have been directly formulated to give improved results for radical species, to provide benchmark quality results by which other less demanding techniques can be assessed. During the course of this study, it became apparent there was a void in the armoury of tools that could be used for the theoretical chemistry calculations. Chapter 3 details the formulation of a new tool in an attempt to fill this gap. Historically, the formulation of this new procedure came after much of the work in this thesis had been carried out. Thus, for the study of many of the reactions of this thesis the new method has not been used. However, it is most appropriate to place its formulation after summarizing the current status of techniques in common use today. Chapters 4 and 5 detail computations carried out on models of peptides containing backbone carbon- and nitrogen-centered radicals. A number of different theoretical techniques are used in these chapters, ranging from the highly accurate and computationally intensive to the less reliable and less demanding. The highly accurate techniques are used to gauge the accuracy of the other less demanding theoretical techniques so that the latter can be used with confidence in larger systems. Not only is the choice of theoretical technique important but also the judicious choice of model is essential. With this in mind, models are incrementally built until convergence of the particular property of interest is reached. Chapters 6 and 7 detail the calculations of β-scission reactions of alkoxyl radicals, which are a particular class of reaction known to occur on peptide backbones. Alkoxyl radicals are particularly difficult for theory to describe correctly. Therefore, Chapter 6 extensively assesses and then identifies the theoretical methods needed to portray them. Chapter 7 uses the techniques identified in the previous chapter in order to predict how the preference for a particular type of β-scission reaction changes.
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Belincanta, Juliana. "Homopolimerização e copolimerização via radical livre controlada por radicais nitroxidos". [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266269.
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Orientador: Liliane Maria Ferrareso LonaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: A polimerização viva/controlada é uma área que vem se desenvolvendo rapidamente no escopo de polímeros e engenharia. A habilidade para preparar copolímeros bem definidos do tipo bloco, estrela, redes poliméricas, bem como outros materiais pelo mecanismo da polimerização via radical livre é talvez a principal razão para o crescente interesse pela academia cientifica e meio industrial neste tipo de polimerização viva/controlada. O interesse industrial se deve a aplicabilidade desta nova técnica em áreas como colas, adesivos, surfactantes, dispersantes, lubrificantes, gel, aditivos, elastômeros termoplásticos, bem como aplicações nas áreas de eletrônica e biomedicina. Vale citar a produção industrial de dispersantes pela polimerização mediada por nitróxidos, um caso de polimerização viva/controlada. Este trabalho tem como objetivo investigar experimentalmente e por modelagem a polimerização em massa via radical livre mediada por TEMPO (2,2,6,6-tetramethyl piperidinyl-1-oxy) de estireno e estireno com divinilbenzeno, sob diversas condições experimentais. Para o caso de homopolimerização foi avaliada uma análise de sensibilidade de como as constantes cinéticas afetam o desempenho do modelo. Reações, não incluídas no modelo original, foram adicionadas ao modelo e testadas. O efeito de diferentes concentrações de TEMPO foi avaliado experimentalmente. Foi observado que esta condição afeta significativamente os resultados. Para o caso de copolimerização, resultados experimentais foram obtidos em diversas temperaturas, e concentração inicial de DVB (divinilbenzeno) e TEMPO. O gel obtido pela polimerização mediada por TEMPO apresenta diferenças marcantes daquele preparado pelo sistema convencional, com relação ao perfil de conversão de monômero. O ponto gel para este caso novo foi obtido em tempos maiores daquele obtido em sistemas convencionais. A versatilidade da polimerização mediada por nitróxidos permite a síntese de um número significativo de novas arquiteturas poliméricas. Espera-se que o modelo proposto, bem como os dados experimentais obtidos neste trabalho, seja útil para um melhor conhecimento desta nova técnica de polimerização. Palavras-chave: polimerização viva/controlada, TEMPO, polimerização em massa, experimental, modelagem
Abstract: Controlled/living radical polymerization (CLRP) is one of the most rapidly developing areas of polymer science and engineering. The ability to prepare well-defined block and graft copolymers, gradient and periodic copolymers, stars, combs, polymer networks, end-functional polymers and many other materials by free-radical mechanisms is perhaps the main reason for the increased academic and industrial interest in CLRP. The industrial interest is triggered by the potential of CLRP in areas as coatings, adhesives, surfactants, dispersants, lubricants, gels, additives, thermoplastic elastomers as well as many electronic and biomedical applications. It is pointed out the industrial production of dispersants by nitroxide-mediated radical polymerization (NMRP), one case of CLRP. This study focus on the model and experimental investigation of TEMPO (2,2,6,6-tetramethyl piperidinyl-1-oxy) mediated free radical polymerization of styrene and styrene-co-divinylbenzene carried out in bulk under different experimental conditions. For homopolymerization case, a sensitivity analyses of how kinetic constants affect the model performance was carried out. Other reactions, not included in the previous model, were included and tested. The effect of different initial concentration of TEMPO was evaluated experimentally. It was shown that this condition affects significantly the results. For copolymerization case, experimental results were obtained for different temperature, and initial concentration of DVB and TEMPO. The gel prepared by NMRP showed remarkable differences from the one prepared in the conventional system, in regard to the monomer conversion profile. The gel point was delayed for the new process compared with conventional systems. The versatility of NMRP permits the synthesis of a number of novel architectures. In conclusion, the model proposed is expected to provide useful guidelines towards a better understanding of the NMRP process. Keywords: controlled/living polymerization, TEMPO, bulk polymerization, experimental, model
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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Linares, Edlaine. "Papel do peroxinitrito na atividade leishmanicida de macrófagos em modelos murinos". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-06112008-143840/.
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Os mecanismos oxidativos pelos quais macrófagos exercem atividade microbicida permanecem em discussão, e estudos com hospedeiros animais serão essenciais para elucidar tal questão. Nesse trabalho, estudamos os mecanismos microbicidas de macrófagos in vivo comparando parâmetros de infecção nas lesões de camundongos resistentes (C57Bl/6) e suscetíveis (BALB/c) ao protozoário Leishmania amazonensis. A comparação mostrou que o controle da infecção pelos camundongos resistentes é dependente da ativação de macrófagos com expressão da enzima óxido nítrico sintase induzível, síntese de óxido nítrico e extensa nitração e hidroxilação das proteínas dos parasitas dentro dos fagolisossomos dos macrófagos. O principal agente tóxico aos parasitas parece ser derivado do peroxinitrito porque a nitração dos parasitas ocorreu na ausência virtual de células polimorfonucleares e foi acompanhada de hidroxilação. Além disso, tempol um inibidor de reações de nitração mediadas por peroxinitrito, inibiu a nitração de proteínas da lesão e aumentou o número de parasitas nelas presentes. Também, estudos com parasitas em cultura confirmaram que o peroxinitrito é citotóxico aos parasitas enquanto o óxido nítrico é citostático. O camundongo suscetível se mostrou capaz de sintetizar óxido nítrico mas o fez em estágios tardios da infecção e, provavelmente, em resposta a uma infecção secundária por bactérias. Tomados conjuntamente, os resultados indicam que o peroxinitrito e radicais dele derivados são os principais agentes leishmanicidas produzidos por macrófagos in vivo.Macrophage oxidative microbicidal mechanisms remain debatable and their elucidation is likely to depend on studies with mammalian hosts. To examine macrophage microbicidal mechanisms in vivo, we compared infection parameters in the lesions of resistant (C57Bl/6) and susceptible (BALB/c) mice to the protozoan Leishmania amazonensis. This comparison demonstrated that infection control by resistant mice relied on macrophage activation with inducible nitric oxide synthase expression, nitric oxide synthesis and extensive nitration and hydroxylation of the proteins of the parasites inside macrophage phagolysosomes. The toxic agent to the parasite is likely to be peroxynitrite-derived because parasite nitration occurred in the virtual absence of polymorphonuclear cells and was accompanied by parasite hydroxylation. In addition, tempol, an inhibitor of peroxynitrite-mediated nitrations, inhibited protein nitration of the lesions and increased the number of parasites in them. Also, studies with parasite cultures confmed that peroxynitrite is cytotoxic to the parasites whereas nitric oxide is cytostatic. The susceptible mice were also able to synthesize nitric oxide but only at late infection time and, most likely, in response to a secondary bacterial infection. Taken together, the results indicate that peroxynitrite and derived radicals are the main leishrnanicidal agents produced by macrophages in vivo.
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Clark, Jared M. "The Formation and Stability of Radical-Molecule and Radical-Radical Complexes and Their Importance in Atmospheric Processes". BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2679.
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This research explores the role that radical-molecule complexes play in the chemistry of Earth's atmosphere. The formation of such complexes can have direct and pronounced effects on the reaction and product outcome of atmospheric chemical reactions. Some attention is also given to the formation of radial-radical pre-reactive complexes in the HO + ClO system. Peroxy radicals (RO2) can form stable complexes with polar compounds such as H2O, NH3, and CH3OH. For the simplest RO2 radical, HO2, complex formation (e.g., HO2-H2O, HO2-NH3, and HO2-722;CH3OH) gives rise to a significant increase in the HO2 self-reaction rate constant. Although this phenomenon has been observed since the mid-1970s, no satisfactory explanation has been put forward to explain this effect. Herein a rationale for the enhancement of the HO2 self-reaction is given based on extensive geometric, mechanistic and natural bond orbital (NBO) analyses. The apparent lack of a rate enhancement for the methyl peroxy (CH3O2) self-reaction is also presented. The combined insights gained from these two systems are then extended to predict if a water enhancement is expected for the 2-hydroxyethyl peroxy (HOCH2CH2O2) self-reaction kinetics. The computational results of this study are then compared to experimental work and conclusions are drawn towards a general procedure to predict the presence/absence of water initiated rate enhancements in RO2 systems as a whole. Original work regarding the formation of a series of organic RO2-H2O complexes is presented. This work established the effects of different functional groups on the stability of organic peroxy radicals and makes estimates of the associated atmospheric lifetimes and equilibrium constants. This work is further extended to the family of peroxy radicals that form from the atmospheric oxidation of isoprene (the most abundant non-methane biologically emitted hydrocarbon). For the first time, complexes of isoprene peroxy radicals with water are presented along with atmospheric lifetime estimates. Conclusions are made as to the effect of water on the product branching ratio of the isoprene peroxy radical + NO2. The oxidation of hexanal to form hexanal peroxy radicals is discussed within the context of the formation of hexanal peroxy water complexes.Aerosol formation is also perturbed as a result of complexation. Aerosol formation under atmospheric conditions is hypothesized to be initiated by radical-molecule complex formation. For example, in the absence of ammonia, the nucleation of H2SO4 in water vapor to form sulfuric acid aerosols is slow. However, as the concentration of NH3 rises, a marked increase in the rate of sulfuric acid aerosol formation is observed. This work explores the effects of the photolysis products of NH3 (NH2 and NH) on the rate of aerosol formation in systems involving H2SO4, HNO3, HC(O)OH, and CH3C(O)OH. With the exception of H2SO4-NH3 and HNO3-NH3 (geometries already published in the literature), minimum energy structures are presented here for the first time for each of the acid-NHx complexes. Thermochemical data and lifetime estimates are provided for each complex. Conclusions about the relevance of acid-NH2 and acid-NH in the formation of atmospheric aerosols are set forth. Finally, mechanistic insights into the reaction of the hydroxyl radical (OH) and Cl2O are obtained via analysis of the two potential energy surfaces that both involve the formation of HO-Cl2O pre-reactive complexes.
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PIACENTINI, FRANCESCO. "AM I RADICAL, RIGHT? THE RADICAL RIGHT FAMILY IDEOLOGICAL OUTLOOK AND RADICAL RIGHT ATTITUDE AMONG THE PUBLIC". Doctoral thesis, Università degli Studi di Milano, 2022. https://hdl.handle.net/2434/945096.
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The emergence of Radical Right Parties (RRPs) has been one of the most studied European political phenomena in the last thirty years, producing a prolific flow of research on both the ideological outlook of the radical right party family and the characteristics of its voters. Nonetheless, the academic debate on these issues is far from being appeased. The following work contributes to the debate by looking at the rise of RRPs in Europe through the perspective of their ideological outlook and by investigating both the supply side and the demand side by means of a data-driven machine learning approach. The literature on RRPs ideological outlook has been prolific and discordant, yet most scholars tend to agree on two main core ideological features that appropriately characterize the radical right family and set it apart from others: nativism and authoritarianism. These core features are complemented by other ancillary elements, on which the debate is more open. The most discussed example is represented by the evolution of RRPs’ positions on economic issues. On this concern, some scholars claim that we are facing a real differentiation within the radical right that needs to be included in the ideological definition of the family, while others argue we are witnessing a series of blurrying processes that intervene on secondary issues holding limited definitory power. As far as radical right voters are concerned, their behavior has been analyzed under many different lenses, still the only condition on which all scholars agree is the centrality of individual attitudes towards immigration in shaping radical right voting. In a few words, we describe the awkward situation where ideologically complex parties, which are not considered single-issue parties, seem to mobilize voters on the basis of a single issue. The aim of the study is to put theoretical studies on the radical right ideology to an empirical test, starting from party-level data and by checking whether those who have been defined as the core features of the radical right family have a crucial role in defining the ideological borders of the radical right or not. Then, we define the potential voting base by following the ideological characterization that emerged empirically. Results confirm the centrality of both nativism and authoritarianism (and Euroscepticism, in addition) in shaping the radical right ideological outlook, while economic positions are the main division line that shapes heterogeneity within the family. The empirical clusters based on the criteria defined previously produce a classification which is coherent with the ones provided by the literature. Results also give empirical evidence of a process of radicalization that characterizes a group of center-right parties, which progressively get close to nativist and authoritarian positions, in continuity with the findings of studies on center-right radicalization. We also confirm that the emergence of a nativist, authoritarian and Eurosceptic set of attitudes among the public, which significantly shapes the probability to vote for a RRP.
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Fraser, M. A. "Radical protagonists : A study of radical periodicals in the 1790s". Thesis, University of Exeter, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377791.
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Barry, Justin. "The Solvent Cage Effect: Using Microviscosity to Predict the Recombination Efficiency of Geminate Radicals Formed by the Photolysis of the Mo-Mo Bond of Cpʹ2Mo2(CO)6". Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23713.
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Radicals are core reactive species that occur in almost every subfield of chemistry. In particular, solution phase radicals find their way into biochemistry (e.g. vitamin B12), and in polymer chemistry (e.g. radical polymerizations) just to name a few. Yet, given the proliferation of radical chemistry, there are still fundamental aspects of it that are poorly understood.
This dissertation probed factors that influence the solvent cage effect. The solvent cage effect is where two radicals are held in close proximity to one another and prevented from easily escaping (to form free radicals) by a cage of solvent molecules. A convenient metric of the solvent cage effect is the radical recombination efficiency (FcP). Typically, FcP correlates with the bulk viscosity of the solution, however, this parameter only produces qualitative assessments. This dissertation outlines a method to quantitatively predict FcP using the microviscosity. This microviscosity dependence holds for non polar, aromatic, polar, and hydrogen-bonding solvents, along with solutions that contain polymers. Microviscosity is a great metric because it addresses an underlying reason for the solvent cage effect, the strength of the cage.
Not only does the strength of the solvent cage around the radical pair affect FcP, but so does the identity of the radicals themselves. That is, the strength of the solvent cage is one piece to forming a total predictive model. FcP for the Cp'2Mo2(CO)6 dimer also varies with the wavelength of irradiation. Identifying the mechanism by which this wavelength dependence occurs may also provide another factor to include in an overall model of the solvent cage effect. Also, an attempt at synthesizing an asymmetric molybdenum dimer was performed. This asymmetric dimer would allow the study of solvent caged radical pairs that are different from each other.
Predicting the photochemical cage pair recombination efficiency (FcP) is the major topic of this dissertation. However, there is also the collisional cage recombination efficiency (Fcʹ). This is where free radicals come together in what is called a collisional solvent cage pair. A method and values of Fcʹ are detailed later in this dissertation.
This dissertation contains previously published and unpublished co-authored material.
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King-Ries, Kristin Marie. "The Heart Radical". The University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-01132009-124617/.
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A young American woman goes to China looking for quiet and respite from campus activism but finds herself drawn into a love triangle with two Chinese dissidents. Through these relationships she becomes involved in the explosive demonstrations at Tiananmen Square and her life will never be the same.
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Green, Stuart P. "Biomimetic radical reactions". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357914.
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Walkington, Andrew J. "Biomimetic radical cyclisations". Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280293.
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Kilgour, Christopher Edward. "Radical convolution algebras". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319998.
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Downey, Adrian. "Radical sensorimotor enactivism". Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/67116/.
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In this thesis I develop a novel approach to conscious perception, which I label “radical sensorimotor enactivism” (RSE). In chapter one, I explain how the development of RSE is guided by the tenets of activity and knowledge-how. In chapter two, I outline and explain RSE. Throughout the thesis, I will pit RSE against cognitivist accounts of conscious perception and argue that RSE is to be preferred. In chapters three and four, I highlight two problems facing cognitivist accounts of conscious perception which RSE avoids. I argue that cognitivist accounts of conscious perception face the ‘hard problem of perceptual consciousness', whilst RSE can provide a phenomenologically plausible deflation of this problem. I next explain why cognitivist accounts are incapable of providing a satisfactory explanation of split-brain syndrome. Then, I argue that RSE can provide a parsimonious explanation of this syndrome. Theories predicated on activity and knowledge-how are often rejected for being incapable of accounting for the brain's role in conscious perception. In chapter five, I argue that RSE can account for the brain's role by adopting a non-representational version of predictive processing (PP). Moreover, I argue that the resultant account improves upon cognitivist alternatives. Then, in chapter six, I argue that even representational explanations of PP can be subsumed within RSE by accepting fictionalism about their representational posits. Consequently, I conclude that RSE cannot be objected to for failing to account for the brain's role in conscious perception. Finally, in chapter seven, I discuss ‘non-veridical' experiences. Accounts like RSE are often rejected because it is thought they are incapable of explaining the existence of these phenomena. I explain how the existence of such phenomena is wholly compatible with the truth of RSE. Thus, I conclude that RSE should not be rejected solely on the basis that non-veridical experiences exist.
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Gonçalves, Maria Cecilia. "Estudo experimental da polimerização via radical livre controlada em presença de radicais nitroxido (NMRP)". [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266346.
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Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-07T10:01:06Z (GMT). No. of bitstreams: 1 Goncalves_MariaCecilia_M.pdf: 1216282 bytes, checksum: 2482b360196051d5ed291cc3d7fa0ccc (MD5) Previous issue date: 2006
Resumo: A polimerização via radical livre controlada mediante radicais nitróxido (NMRP) tem recebido cada vez mais atenção como uma técnica para produção de polímeros com estrutura altamente controlada. Distribuições de pesos moleculares estreitas são obtidas, com polidispersidades baixas. Neste trabalho, será estudado o processo NMRP, no qual ocorre a adição de um radical nitróxido estável, como o 2,2,6,6-tetrametil-l-piperidinoxil (TEMPO) para capturar o radical em crescimento. Embora o processo NMRP de ao polímero características controladas (polidipersidades baixas e pesos moleculares que aumentam linearmente com a conversão), ainda existe um desafio nos processos controlados, por apresentarem baixas velocidades de reação. O objetivo principal deste trabalho está focado num estudo experimental do processo NMRP visando aumentar a velocidade de reação sem perder as características principais do processo. O efeito de dois iniciadores BPO (peróxido de benzoíla) e TBEC (tert-butilperóxido-2-etilhexil carbonato) foi analisado. Observou-se que o TBEC (iniciador com constante de decomposição baixa) foi capaz de aumentar significativamente a taxa de polimerização do processo NMRP, quando comparado ao BPO, pois conversões mais altas foram obtidas, num mesmo tempo de reação, mantendo a característica controlada do sistema. O uso do TBEC apresenta uma vantagem frente ao BPO em processos controlados, não somente porque reduz o tempo de reação, mas também porque concentrações menores de iniciador e controlador foram usadas, obtendo uma taxa de reação ainda maior, o que reduz o custo operacional. Para as condições estudadas, comprovou-se experimentalmente que a taxa de reação é inversamente proporcional à concentração inicial de TEMPO, para uma mesma concentração de iniciador. A análise dos resultados através da aplicação da técnica de planejamento de experimento auxiliou numa melhor compreensão do sistema e na obtenção de condições ótimas de operação para se obter baixas polidispersidades e baixos tempos de polimerização
Abstract: NMRP process (Nitroxide Mediated Radical Polymerization) has received increasing attention as a technique for production polymers with highly controlled structures, narrow molecular weight distribution (MWD) and polydispersity index dose to 1.0. In this work 2,2,6,6-tetramethyl-l-piperidinoxyl (TEMPO) is used as the stable radical to reversibly terminate the growing polymer chain. Polymerizations were performed in ampoules, using TBEC (tert-butylperoxy-2-ethylhexyl carbonate) and BPO (benzoyl peroxide) as initiators. With the purpose of enhancing the reaction rate for NMRP process maintaining the controlled and living characteristics of the polymer synthesized (low polidispersity and molecular weights increasing linearly with conversion) an experimental study was done to evaluate the effect of two different initiators (BPO and TBEC). It was observed that TBEC (initiator with low decomposition rate) was able to enhance significant1y the polymerization rate compared to BPO, keeping the living and controlled characteristics of the system. The results show that TBEC seems to be a promising initiator that make the NMRP process more efficient, not only because it reduces the polymerization time, but also because it allows smaller amounts of controller and initiator to be used. For the operational conditions studied, experimental results with TBEC exposed that the polymerization rate in inversely proportional to the initial concentration of TEMPO, for the same amount of initiator. Using a statistical planning, it was possible to obtain a better understanding of the system and to search for operating conditions that bring low polydispersity and low reaction rates. Finally, the results are expected to have significant benefits for controlled polymerization on an industrial setting
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Capdevila, i. Cortada Marçal. "Long, Multicenter Bonding Present in Radical-Radical Interactions: A Computational Study". Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/277254.
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It is well established that organic radical-anions, such as reduced tetracyanoethylene (i.e., [TCNE]•(-)), may form dianionic dimers exhibiting long, multicenter bonding. This bond arises from the overlap of the b(2g) SOMOs of [TCNE]•- to form a doubly-occupied bonding and an empty antibonding combination of orbitals of b2u and b1g symmetry, respectively, leading to a diamagnetic pi-[TCNE](2(2-)) dimer. Long, multicenter bonds were first experimentally and theoretically characterized in crystals of [TCNE]•- salts, whose dimers exhibit an intermonomer distance of ~2.9 Å, and they were found to present the same electronic properties as conventional covalent bonds. Further studies in dichloromethane solution at low temperature determined its equilibrium constant KD and enthalpy and entropy of dimerization (delta-HD and delta-SD) by UV-vis and EPR measurements. Since their first characterization several other organic radicals have been shown to exhibit long, multicenter bonding; among them, other radicalanions such as tetracyanobenzene (TCNB) or tetracyanopyrazine (TCNP), radical-cations such as tetrathiafulvalene (TTF), or neutral radicals such as phenalenyl derivatives.
Salts of the aforementioned organic radical-ions are well known to exhibit technologically important properties such as magnetic ordering, metal-like electrical conductivity, and even superconductivity. TCNE, TCNQ, and TCNP, to list a few examples, are building blocks in molecule-based bulk ferromagnets having magnetic ordering temperatures above room temperature. However, the electron pairing resulting from the formation of long, multicenter dimers would impede these physical properties. Moreover, recent experimental and theoretical work showed the presence of long, multicenter bonded pi-[TTF](2(2+)) dimers in supramolecular aggregates at room temperature. These supramolecular aggregates were recently proposed as an emerging class of materials with potential ability on molecular switching applications. It is thus of high importance to achieve a complete understanding on the formation and nature of such interactions.
The present thesis focuses in the computational study of long, multicenter bonding. The work is divided into two parts: a first part where the fundamentals of long, multicenter bonding are evaluated, and a second part where room-temperature long, multicenter bonding is studied. In the first part, an extensive characterization with a wide variety of density functionals and active spaces is performed in the gas phase, for the pi-[TCNE](2(2-)), pi-[TTF](2(2+)), pi-[TCNB](2(2-)), and pi-[TCNP](2(2-)) dimers. Moreover, a comprehensive study of the pi-[TCNE](2(2-)) dimer in explicit dichloromethane solution is performed by means of molecular dynamics. Finally, the last two articles focus in solid state long, multicenter bonded dimers. The relative orientation of the pi-[TCNB] (2(2-)) and pi-[TCNP]2(2(2-)) dimers is challenged in the former, while a thorough characterization of the four polymorphs of the [TTF][TCNE] charge-transfer crystal is done in the latter. In the latter, the two established kinds of pi-[TCNE](2(2-)) dimers, actually only found in the pi and pi- polymorphs of [TTF][TCNE], are revised.
The second part of the thesis focuses in room-temperature long, multicenter bonding. There are two categories where long, multicenter bonding is still preserved at room temperature: oligomeric donors or acceptors and supramolecular aggregations. In this thesis, some examples of both categories of room-temperature long, multicenter bonding are analyzed. The dimerization of oxidized alpha, beta-substituted heptathienoacene, [D4T7]•+ is investigated, as well as the effect of adding bulky substituents. Furthermore, the room-temperature formation of pi- [TTF] (2(2+)) involving its inclusion in the cavity of a CB[8], and as a building block of a molecular clip and a [3]catenane is also carefully studied. It is quantitatively shown in the thesis that the extra stability, which permits the room-temperature observation of long, multicenter bonding, is due to an increase of dispersion interactions while a decrease of the internal repulsion between the radical-ions.La següent tesi s’emmarca dins l’estudi dels enllaços multicentre a llarga distància entre radicals orgànics. Aquests enllaços varen ser observats per primer cop a finals dels anys 60, però no fou fins al 2001 quan, a través d’un estudi teòric-experimental, es caracteritzaren. Els enllaços multicentre a llarga distància s’originen entre radicals orgànics a distàncies força majors que els enllaços covalents, però inferiors a distàncies de van der Waals (típicament, el dímer pi[TCNE](2)(2-) té una distància d’equilibri de 2.89 Å). En la seva distància d’equilibri, els orbitals SOMO dels radicals se solapen i combinen formant una combinació enllaçant doblement ocupada (l’HOMO) i una combinació antienllaçant desocupada (el LUMO), resultant-ne un dímer diamagnètic. El treball realitzat en aquesta tesi es divideix en dues parts, l’estudi fonamental dels enllaços multicentre a llarga distància i l’estudi d’aquest fenomen a temperatura ambient. En la primera part, es realitza un extens estudi metodològic de quatre dímers que presenten aquest tipus d’enllaç, pi-[TCNE] (2)(2)-, pi-[TCNB] (2)(2-), pi-TCNP] (2)(2-) i pi-[TTF] (2)(2+), pels quals es calibren diversos espais actius i fins a 23 funcionals de la densitat. A més a més, es realitza un estudi del dímer de pi-[TCNE] (2)(2-) en fase condensada, on s’obtenen dades de la seva solvatació i del seu comportament a diferents temperatures. També es fa un estudi en estat sòlid dels dímers pi-[TCNB] (2)(2-) i pi-[TCNP] (2)(2-), on es compara la naturalesa de la seva interacció en fase gas i estat sòlid i s’estudia la seva orientació relativa. Finalment s’han estudiat les quatre formes polimòrfiques del cristall de [TTF][TCNE], on s’ha caracteritzat l’enllaç a llarga distància entre pi-[TTF•••TCNE]. En la segona part, certs exemples de les dues famílies de compostos que exhibeixen enllaços multicentre a llarga distància a temperatura ambient han estat estudiades. Aquestes dues famílies són els oligòmers de donadors o acceptors i els agregats supramoleculars. Un oligòmer de tiofè, l’oligotienoacè (anells de tiofè fusionats) de set membres, ha estat estudiat. S’ha avaluat l’impacte de substituents laterals, així com l’efecte de la solvatació i de tenir un excés de contraions en la dissolució. De la segona família de compostos s’ha estudiat la inclusió d’un dímer pi-[TTF] (2)(2+) dins la cavitat d’un macrocicle cucurbit[8]uril, així com la dimerització de clips moleculars que contenen TTF i un compost mecànicament entrellaçat [3]catenan el qual conté TTF en els macrocicles exteriors.
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Zhu, Hai. "Construction of carbo- and oxacycles using radical relay cyclizations initiated by alkoxy radicals". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44759.
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An investigation of a versatile radical relay cyclization methodology for the rapid construction of carbo- and heterocycles from simple linear precursors has been presented in this thesis. This thesis mainly focuses on 1,5-hydrogen atom translocation and subsequent cyclization reactions (radical relay cyclization reactions). In Chapter 1, an up-to-date literature review of this concept (radical relay cyclization) is presented including 1,5-hydrogen translocation reactions initiated by carbon radicals as well as oxygen and nitrogen radicals. In Chapter 2, the formation of cyclopentane and cyclohexane derivatives utilizing radical relay cyclization reactions initiated by alkoxy radicals has been described. The diastereoselectivity of final carbocycles is discussed. In Chapter 3, the formation of 1,2-disubstituted tetrahydrofuran and tetrahydropyran derivatives utilizing radical relay cyclization reactions has been described. With the incorporation of an oxygen atom into the precursors, the diastereoselectivity has been increased dramatically compared to carbon analogs. In Chapter 4, the formation of 2,3,5-trisubstituted tetrahydrofuran derivatives utilizing radical relay cyclization reactions has been described. With the strategic incorporation of an oxygen atom into cyclization precursors, 1,5-hydrogen atom translocation and subsequent cyclization reactions are able to compete over direct cyclization reactions and β-fragmentation reactions through the dative control. Furthermore, the incorporation of an oxygen atom into precursors enables 1,6-hydrogen atom translocation reactions to outcompete 1,5-hydrogen atom translocation reactions. In Chapter 5, the application of this radical relay cyclization methodology for the synthesis of the tetrahydrofuran fragment within (–)-amphidinolide K has been demonstrated. The final fragment in (–)-amphidinolide K can be achieved in 60% yield with a >95:5 ratio of cis to trans isomers.
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Friedline, Robert Alan. "The Reaction Kinetics of Neutral Free Radicals and Radical Ions Studied by Laser Flash Photolysis". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11157.
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t-Butoxyl radical has been used as a chemical model for hydrogen abstractions in many enzymatic and biological systems. However, the question has arisen as to how well this reactive intermediate mimics these systems. In addressing this concern, absolute rate constants and Arrhenius parameters for hydrogen abstraction by t-butoxyl radical were measured for a broad class of substrates including amines, hydrocarbons, and alcohols using laser flash photolysis. Initially, no obvious reactivity relationship between rate constant and substrate structure was observed for these homolytic reactions. However, by closely examining the Arrhenius parameters for hydrogen abstraction, a pattern was revealed. For substrates with C-H bond dissociation energy (BDE) > 92 kcal/mole, activation energy increases with increasing BDE (as expected). However, for substrates with a lower BDE, the activation energy levels out at approximately 2 kcal/mole, essentially independent of structure. Viscosity studies with various solvents were conducted, ruling out the possibility of diffusion-controlled reactions. Entropy rather than enthalpy appears to be the dominating factor at 25°C, contributing to the free energy barrier for these reactions.
Laser flash photolysis was also used to study radical anions. Using an indirect photoexcitation method, the properties of radical anions, generated from aryl ketones, were investigated. These radical anions, such as t-butyl phenyl ketone and cyclopropyl phenyl ketone, measured to have decay rate constants of 1.0 x 106 s-1, although they are known to be persistent when studied electrochemically. They also had measured activation energies around 6.0 kcal/mole and log A values close to 9.5. By extending the molecules's conjugation, the decay rate constants increased to greater than 107 s-1, decreased their activation energy by half, and lowered the log A values to 8.0. This trend was observed in aryl ketones such as trans-1-benzoyl-3-phenyl cyclopropane. It is believed that the generation of a benzyl radical during the decay that facilitates the enhancement of the unimolecular decays. These unimolecular decays were also observed with the previously studied hypersensitive SET probes, 5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one and 1,1,-dimethyl-5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one. The decay rate constants for these radical anions were measured to be greater than 108 s-1, driven by the formation of an aromatic ring.Ph. D.
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Mathews, M. R. "The personal and professional development of a radical non-radical : an overview". Thesis, University of South Wales, 2006. https://pure.southwales.ac.uk/en/studentthesis/the-personal-and-professional-development-of-a-radical-nonradical(790ffc11-4aca-4540-9dfd-4060911e1720).html.
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This overview explains the perceived origins of the candidates research record beginning with the study and work experiences which led the candidate to the research work that has taken up the majority of his professional career. The overview then considers a number of important publications in three groups which, it is argued, have influenced others interested in social and environmental accounting. In addition some investigation of the extent of citation of the candidates work has been reported herein, together with details of a number of publications that have reproduced the candidates work as examples of important contributions to the study of this sub-branch of accounting. The overview concludes with statements justifying the overall contribution as being worthy of consideration for the award of the degree of Doctor of Philosophy by publication.
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Mitroka, Susan M. "Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77137.
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Oxidative processes are linked to a number of major disease states as well as the breakdown of many materials. Of particular importance are reactive oxygen species (ROS), as they are known to be endogenously produced in biological systems as well as exogenously produced through a variety of different means. In hopes of better understanding what controls the behavior of ROS, researchers have studied radical chemistry on a fundamental level. Fundamental knowledge of what contributes to oxidative processes can be extrapolated to more complex biological or macromolecular systems.
Fundamental concepts and applied data (i.e. interaction of ROS with polymers, biomolecules, etc.) are critical to understanding the reactivity of ROS. A detailed review of the literature, focusing primarily on the hydroxyl radical (HO•) and hydrogen atom (H•) abstraction reactions, is presented in Chapter 1. Also reviewed herein is the literature concerning high density polyethylene (HDPE) degradation. Exposure to treated water systems is known to greatly reduce the lifetime of HDPE pipe. While there is no consensus on what leads to HDPE breakdown, evidence suggests oxidative processes are at play.
The research which follows in Chapter 2 focuses on the reactivity of the hydroxyl radical and how it is controlled by its environment. The HO• has been thought to react instantaneously, approaching the diffusion controlled rate and showing little to no selectivity. Both experimental and calculational evidence suggest that some of the previous assumptions regarding hydroxyl radical reactivity are wrong and that it is decidedly less reactive in an aprotic polar solvent than in aqueous solution. These findings are explained on the basis of a polarized transition state that can be stabilized via the hydrogen bonding afforded by water. Experimental and calculational evidence also suggest that the degree of polarization in the transition state will determine the magnitude of this solvent effect.
Chapter 3 discusses the results of HDPE degradation studies. While HDPE is an extremely stable polymer, exposure to chlorinated aqueous conditions severely reduces the lifetime of HDPE pipes. While much research exists detailing the mechanical breakdown and failure of these pipes under said conditions, a gap still exists in defining the species responsible or mechanism for this degradation. Experimental evidence put forth in this dissertation suggests that this is due to an auto-oxidative process initiated by free radicals in the chlorinated aqueous solution and propagated through singlet oxygen from the environment. A mechanism for HDPE degradation is proposed and discussed. Additionally two small molecules, 2,3-dichloro-2-methylbutane and 3-chloro-1,1-di-methylpropanol, have been suggested as HDPE byproducts. While the mechanism of formation for these products is still elusive, evidence concerning their identification and production in HDPE and PE oligomers is discussed.
Finally, Chapter 4 deals with concluding remarks of the aforementioned work. Future work needed to enhance and further the results published herein is also addressed.Ph. D.
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Grau, Etienne. "Polymerization of ethylene : from free radical homopolymerization to hybrid radical / catalytic copolymerization". Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10242/document.
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Ce travail concerne l'étude de la polymérisation de l'éthylène allant de l'homopolymérisation purement radicalaire jusqu'à la copolymérisation utilisant un mécanisme hybride radicalaire/catalytique. Ce travail montre que le polyéthylène peut être synthétisé par voie radicalaire dans des conditions expérimentales beaucoup plus douces que celles utilisées industriellement (P>1000 bar et T>100°C). L'éthylène a été polymérisé à partir de 10°C et 5 bar de pression d'éthylène. Un important effet activateur du solvant a été mis en évidence. De plus la polymérisation en milieu dispersé aqueux de l'éthylène a aussi été étudiée. Des latex stables de PE avec des taux de solide de 40% ont pu être obtenus. Deux morphologies de nanoparticules, cylindre ou sphère, ont été observées. La copolymérisation radicalaire avec des monomères vinyliques polaires a été également étudiée en solution ou en émulsion. Des insertions d'éthylène jusqu'à 50% ont été obtenues. De plus l'influence du comonomère et du solvant organique utilisé sur la polymérisation radicalaire de l'éthylène a été quantifiée. Une nouvelle technique de polymérisation hybride radicalaire/catalytique a été développée pour pouvoir obtenir toute la gamme de compositions possibles de copolymères éthylène/monomère polaire à partir d'un complexe de nickel qui amorce la polymérisation radicalaire et catalyse également la polymérisation de l'éthylène. Ce complexe subit une rupture homolytique réversible de la liaison nickel carbone et permet la synthèse de copolymères multiblocs. Des insertions d'éthylène de 1% à 99% ont été obtenues en faisant varier la pression d'éthylène et la concentration en comonomères polairesThis work aims to study ethylene polymerization from the free radical polymerization process to the copolymerization by a hybrid radical/catalytic mechanism. PE is synthesized by free radical polymerization under milder experimental conditions than industrial ones (P>1000 bar and T>100°C). Indeed free radical polymerization of ethylene is efficient even down to pressure of 5 bar and temperature of 10°C. Several unexpected behaviors are observed such as a high solvent activation effect. Beside the slurry process in organic solvent, polymerization in aqueous dispersed media is also performed. Stable PE latexes are obtained with solid contents up to 40%. Two different PE particles morphologies are observed cylinder-like and sphere-like. Then free radical copolymerization is studied using a broad range of polar vinyl monomers in organic solvent and emulsion. Insertions up to 50% of ethylene are obtained under mild conditions. The ambivalent role of comonomer as monomer and activator of the polymerization is highlighted. In order to obtain a wide range of composition of polar/non-polar copolymers a new technique of polymerization has been developed. A nickel complex is used to initiate the free radical polymerization and to catalyse the coordination/insertion ethylene polymerization. This nickel complex is capable of a reversible homolytic cleavage of its nickel-carbon bond. Finally, this hybrid process is used to copolymerize efficiently ethylene with various polar vinyl monomers. Multiblock copolymers with ethylene content from 1% to 99% are obtained by simply varying the monomer feeds
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Rosero, Mesa Paola Viviana. "Modelagem da homopolimerização via radical livre controlada em presença de radicais nitroxido". [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267475.
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Orientador: Liliane M. Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Neste trabalho foi desenvolvido um modelo matemático para a polimerização via radical livre controlada em presença de radicais nitróxidos (NMRP), que inclui a obtenção dos pesos moleculares médios e o índice de polidispersidade para polímeros de estrutura linear. Por ser a polimerização via radical livre (FRP) uma das polimerizações mais estudadas, este trabalho contemplou o estudo do processo FRP em sistemas homogêneos como base para a modelagem da polimerização via radical livre controlada (LFRP). A LFRP se destaca por ser capaz de obter polímeros com polidispersidade perto de 1,0 e distribuições de peso molecular estreitas. Existem diferentes mecanismos LFRP, dos quais se destaca o mecanismo NMRP, o qual consegue obter polímero com peso molecular controlado mediante a adição de um radical nitróxido à polimerização via radical livre, gerando uma reação reversível capaz de bloquear as cadeias em crescimento. Para obtenção dos pesos moleculares médios e a distribuição do peso molecular (MWD) no processo FRP, foram utilizados o método instantâneo e o método dos momentos; já no novo processo (NMRP) foi usado o método dos momentos para a obtenção dos pesos moleculares médios e o índice de polidispersidade. O modelo matemático foi baseado nas constantes cinéticas de taxa e na teoria do volume livre para o processo FRP e nas constantes cinéticas no processo NMRP. Os resultados foram comparados com dados experimentais para avaliar o modelo. Como casos estudo foram analisadas as polimerizações de estireno e de metilmetacrilato para o processo FRP e as polimerizações de estireno no processo NMRP. Os resultados de validação obtidos mostraram que o modelo sugerido é capaz de modelar o processo monomolecular e bimolecular NMRP a diferentes condições de temperatura e concentração de espécies. Os resultados do modelo também mostraram como no processo NMRP, a espécie polimérica morta surge de radicais poliméricos que não conseguem ser capturados no processo. Foi mostrado como radicais nitróxidos menos estáveis geram resultados mais favoráveis em termos de produtividade e qualidade de produto
Abstract: A practical methodology for the computer modeling of number-and weight-averages molecular weight and molecular weight distribution of polymer with linear structure obtained from nitroxide mediated radical polymerization (NMRP) has been developed. Since free-radical polymerization (FRP) is one of the most important chain-growth polymerization, this work embraces a free-radical polymerization in homogeneous systems as reference point to model the "Iiving" free-radical polymerization. The "living" free-radical polymerization (LFRP) emphasizes the production of polymers with highly controlled structures, narrows MWD and polydispersity index closed to 1.0. Different mechanisms have been proposed to carry out LFRP, among them, Nitroxide-mediated radical po/ymerization (NMRP), which attains polymers with controlled molecular weight by mediated nitroxide radicais acting as trapping agent, in which the polymer chain that is growing are reversibly trapped. To obtain number- and weight-averages molecular weight and molecular weight distributions (MWD) for FRP process the instantaneous and moments methods were used. On the other hand, for the process NMRP the method of moments was used to obtain the number- and weight-averages molecular weight and polydispersity index. The mathematical model was based on kinetics constant rates and free-volume theory for FRP and kinetics constant rates for NMRP. Simulations were compared with experimental data to validate the model. Styrene and methylmethacrilate was analyzed as cases studies for FRP process and styrene polymerization for NMRP process. The model was able to modeling monomolecular and bimolecular NMRP process to different conditions of temperature and species concentrations. It showed the dead polymer chain appear by live polymeric chain not captured by nitroxide radicais in the NMRP processo. Then, NMRP can obtain "Iiving" characteristic if exists enough quantity of nitroxide radical. This permits the radicais created to be captured. Nitroxide radicais more unstable generate best results in relation to productivity and product quality
Mestrado
Mestre em Engenharia Química
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Thunholm, Mattias, i Marcus Boström. "Radical Hotel : En affärsplan". Thesis, University of Kalmar, Baltic Business School, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hik:diva-257.
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Vi åsyftar att undersöka möjligheterna att starta upp och driva det mindre hotellet. Vi vill med denna affärsplan undersöka marknaden och upptäcka eventuella brister i idén före den blir verklighet.
Frågeställning: Hur etableras och drivs det mindre hotellet på ett framgångsrikt sätt?
Vi har gjort en kvalitativ fallstudie på tre hotellföretag och använts oss av semi-strukturerade intervjuer med berörda personer på de tre olika hotellen. Teorin har insamlats genom relevant litteratur inom ekonomi och marknadsföring samt via elektroniska källor.
Vi har visat på att det finns goda möjligheter att skapa en hotellverksamhet i en stad som Göteborg. Dock under vissa förutsättningar; att vi får tag i en lokal som passar våra behov samt att vi får en omsättningsbaserad hyra så vi slipper tunga investeringskostnader.
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Gravelle, Kristian G. "Radical cyclizations of hydrazones". Thesis, University of Ottawa (Canada), 1997. http://hdl.handle.net/10393/9806.
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The preparation of various hydrazones for use in radical cyclizations is described. The radical cyclization of (A) and (B) under various radical conditions led to the tandem cyclization of octahydroindoles (C) and (D) under neutral conditions. The reaction of (E) under various radical conditions led to the first synthesis of a seven membered ring by attack of a carbon radical onto a carbon-nitrogen multiple bond, forming (F).* ftn*Please refer to the dissertation for diagrams.
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Lopes, Carlos Eduardo. "Behaviorismo radical e subjetividade". Universidade Federal de São Carlos, 2006. https://repositorio.ufscar.br/handle/ufscar/4813.
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Previous issue date: 2006-02-10Universidade Federal de Minas Gerais
In radical behaviorism, subjectivity is studied, generally speaking, in terms of the theory of private events. The theory of private events has its roots in the problem of accessibility in the thesis, that is, that a person has privileged access to certain events that occur under his skin (privacy). If we examine the origins of this thesis, we will find that it reaches radical behaviorism via the paths of dualism and logical positivism (through methodological behaviorism). However, if we interpret radical behaviorism on the basis of a relational metaphysics, the influence of dualism and logical positivism can be overlooked. This opens the possibility that radical behaviorism can do without the theory of private events. Nevertheless, if we abandon the theory of private events, what will be the consequence for of the study of subjectivity? The main objective of this work is to answer this question. Here, we uphold the thesis that the study of subjectivity in radical behaviorism, without reference to the theory of private events, can be fruitfully pursued. This can be achieved through the concepts of body and world , and through the construction of a theory of the self compatible with radical behaviorism. Thus, this work seeks to offer an interpretation of radical behaviorism, based on a relational metaphysics, which separates subjectivity from privacy. This interpretation also considers the possibility of productive dialogues between radical behaviorism and other psychological and philosophical theories (such as James psychology, Gestalttheorie , and analytic philosophy). According to this interpretation, subjectivity is related to the products of discriminative verbal behavior (identified as the I). As this product depends on a verbal community (which arranges discriminative contingencies), subjectivity comes to be considered social. Moreover, the person-verbal community interface renders the defense of a pure subjectivity not viable, as well as that of an unmitigated objectivism. Because of this, radical behaviorism may be capable of deconstructing the objective-subjective debate: these terms are subordinated to the relation of behavior. It is concluded that the radical character of radical behaviorism is not due to its dealing with private events, but to the study of behavior without resorting to non-behavioral instances.
No behaviorismo radical a subjetividade é estudada, geralmente, recorrendo-se à teoria de eventos privados. A teoria de eventos privados tem em sua raiz a problemática da acessibilidade , ou seja, a tese de que a pessoa tem acesso privilegiado a determinados eventos que ocorrem sob sua pele (privacidade). Analisando a origem dessa tese encontraremos que ela chega ao behaviorismo radical pela via do dualismo e do positivismo lógico (através do behaviorismo metodológico). No entanto, quando se interpreta o behaviorismo radical a partir de uma metafísica relacional, elimina-se a influência tanto do dualismo, quanto do positivismo lógico. Com isso, o behaviorismo radical pode abandonar a teoria de eventos privados. Mas diante dessa possibilidade como ficaria o estudo da subjetividade? Responder a essa questão é o principal objetivo deste trabalho. Defende-se, aqui, a tese de que é viável empreender um estudo da subjetividade no behaviorismo radical desvinculado da teoria de eventos privados. Isso pode ser feito através dos conceitos de corpo e mundo, e da construção de uma teoria do self compatível com o behaviorismo radical. Dessa forma, o presente trabalho busca apresentar uma interpretação do behaviorismo radical, pautada em uma metafísica relacional, que desvincula subjetividade de privacidade. Essa interpretação considera também a possibilidade de diálogos produtivos entre o behaviorismo radical e outras teorias psicológicas e filosóficas (tais como psicologia jamesiana, Gestalttheorie e filosofia analítica). De acordo com essa interpretação, subjetividade está relacionada com os produtos do comportamento verbal discriminativo (que se identifica com o eu). Como esse produto depende de uma comunidade verbal (que arranja contingências discriminativas) a subjetividade passa a ser considerada social. Além disso, a interface pessoa-comunidade verbal torna inviável a defesa de uma subjetividade pura, bem como de um objetivismo pleno. Com isso, o behaviorismo radical parece ser capaz de desconstruir o debate subjetivo-objetivo: esses termos estão subordinados à relação comportamental. Por fim, conclui-se que a radicalidade do behaviorismo radical não está em considerar os eventos privados em sua explicação do comportamento, mas em estudar o comportamento sem recorrer a instâncias não-comportamentais.
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Gravelle, Kristian. "Radical cyclizations of hydrazones". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20975.pdf.
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Smil, David V. "Boron tethered radical cyclizations". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0006/MQ40735.pdf.
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Ding, Shijie. "Atom transfer radical polymerization". Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1225138911&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Coll, Mármol Jesús. "Interpretación radical y escepticismo". Doctoral thesis, Universidad de Murcia, 2006. http://hdl.handle.net/10803/10822.
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En este trabajo se examina si de las consideraciones que Donald Davidson ha hecho del caso de la interpretación radical se sigue algo así como una refutación del escepticismo. Se argumenta que tal conclusión no se sigue de las posiciones acerca de la naturaleza del pensamiento y del lenguaje mantenidas por este filósofo americano, ni siquiera con la ayuda del así llamado argumento del intérprete omnisciente. También se rechaza la idea de que concebir su argumentación como un argumento trascendental modesto proporcione mejores resultados antiescépticos. Finalmente se defiende que el mejor modo de articular su posición es como un diagnóstico teórico del escepticismo al estilo del defendido por Michael Williams en su libro Unnatural Doubts. Desde este punto de vista lo que la filosofía davidsoniana haría sería reprochar al escéptico su adhesión al representacionismo y mostrar una alternativa al mismo que explique la posibilidad del pensamiento y del lenguaje. Concebida así la filosofía davidsoniana no constituiría una victoria definitiva ante el escepticismo, sino que más bien mostraría que su posición no es obligatoria y, al menos, garantizaría una presunción de inocencia para nuestras creencias ante el reto del escéptico global.This work examines whether it follows a refutation of scepticism from Donald Davidson's work on radical interpretation. It is argued that such a conclusion does not follow from Donald Davidson's views on thought and language, not even with the help of the so called omniscient interpreter argument. This work also rejects that such views on language and thought lead to a better result against scepticism when interpreted as a modest transcendental argument. Finally it is claimed that the best way of articulating Davidson's antisceptical strategy is as a theoretical diagnosis of scepticism in a similar vein as Michael Williams has developed in his book Unnatural Doubts. From this point of view what Davidson's philosophy would do is, on the one hand, to reproach the sceptic his adherence to representationism and, on the other hand, to defend an alternative to this philosophical view that explains how thought and language are possible. Conceived of in this way, Davidson's philosophy would not constitute a definitive victory against scepticism. However it would show that scepticism is not compulsory and, at the very least, it would guarantee a presumption of innocence for our beliefs when they face the sceptical threat.
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Carter, A. "Marx : A radical critique". Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375882.
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Barreto, Joao Pedro Cabaco Moniz. "Dioxygen free radical reactions". Thesis, Oxford Brookes University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389105.
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Winning, Leonard H. "New Radical Cascade Chemistry". Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494312.
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Gladwin, Amanda R. "Radical cascades in synthesis". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336947.
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Nature utilises several modes of construction to synthesise a plethora of important polycyclic natural products. This is illustrated in a brief summary in the Introduction which describes the electrophilic processes involved in terpene biosynthesis. The attempts made by synthetic organic chemists to mimic these electrophilic reactions are then described, and the concept of exploiting tandem, free radical reactions in such processes is then introduced. Chapter Two examines the uses of tandem, free radical processes with the ultimate goal of an efficient and flexible synthesis of the CD-ring portion found in vitamin D3. A review of investigations into the use of tandem radical macrocyclisation-transannulations and also sequential radical cyclisations is presented as the background to our work in this area. Application of these strategies towards the synthesis of the CD-portion of vitamin D3 has culminated in the synthesis of a range of interesting substituted 5,6- and 6,6- ring fused carbobicycles. A related study of radical-mediated transannulation reactions in medium and large ring, naturally occurring terpenes is described in Chapter Three. Successful transannulation of the II-membered ring sesquiterpene humulene, via a radical addition-transannulation process, is presented along with a discussion of product manipulation to provide a crystal suitable for X-ray analysis. Finally, our attempts to cyclise the diterpenes (+)-cembrene, (+)-isocembrene and (+)-cembrenene under a variety of similar radical conditions are then detailed.
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Patterson, Christopher William. "Radical fragmentation of oxiranes". Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329877.
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Euapermkiati, Anucha. "Free radical telomerisation reactions". Thesis, University of Bradford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278895.
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Shooter, Andrew James. "Living free radical polymerisation". Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263817.
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Brown, David William. "Radical additions to butenolides". Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360719.
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Wilmshurst, Martin Philip. "Fluoroalkyl radical cyclisation reactions". Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286192.
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Aldabbagh, Fawaz. "Radical cyclisations onto imidazoles". Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/32471.
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This thesis describes the development of new pathways towards the synthesis of novel antimicrobial (and anticancer) agents. Two synthetic protocols based on free radical chemistry are studied, which are used to access polycyclic heterocyclic compounds of potential biological importance. Both these procedures involve the generation of radicals using Bu3SnH and AIBN initiators, and the subsequent intramolecular radical cyclisation onto the imidazole ring. Radical cyclisations onto benzimidazoles and pyrroles are also described.
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McCallum, Terry. "Radical Adventures in Photochemistry". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37825.
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A field in bloom: photoredox catalysis has allowed chemists access to highly reactive intermediates via the photo-mediated excitation of transition metal complexes and organic dyes for the mild generation of free radicals. These complexes and dyes are designed based on Nature’s blueprints of light-harvesting biomolecules that transform solar energy (photons) into chemical energy during photosynthesis. Light-mediated chemical activation is regarded as one of the most sustainable forms of chemical activation being that the energy provided by the sun is considered renewable and largely underutilized and presents an attractive avenue for research and development of new transformations that are mild, efficient, and waste-limiting in organic synthesis. Radical chemistry and photochemistry are united in their inherent ability to undergo single (or photoinduced) electron transfers by one-electron reaction modes. Combining these unique fields, photoredox catalysis has emerged as a mild and efficient alternative to classic alkyl radical generation using hazardous initiators and organostannanes. Photoredox catalysis has been dominated by ruthenium- and iridium-based polypyridyl complexes. These complexes are limited by their inherent redox potentials, restricting their reactivity towards relatively activated bonds. Nonactivated bromoalkanes and arenes are considered challenging substrates to engage using redox chemistry and typically only accessible in the realm of organostannane chemistry. Described herein are the efforts towards the discovery of free radical based organic transformations derived from nonactivated bromoalkanes and arenes mediated by photochemical excitation of polynuclear gold(I) complexes as photoredox catalysts. This work represents some of the first uses of a photoredox catalyst in the reduction of substrates having such high reduction potentials and offers a practical and useful alternative to classic radical reactions mediated by initiators (peroxides, persulfates, and azo compounds) and toxic organostannanes (Bu3SnH). Using gold based photoredox catalysts, the research conducted has provided many methodological advancements for the mild and efficient formation of carbon-carbon bonds using nonactivated bromoalkanes and a large collection of radical acceptors.
Establishing the use of these photoexcited polynuclear gold(I) complexes in the context of classic radical reactions in organic synthesis was important for their validation as useful photocatalysts. First, the Ueno-Stork cyclization of nonactivated bromoalkanes was used to demonstrate the powerful reducing capabilities of the excited-state gold(I) complexes. Next, a photo-mediated variant of the Appel reaction was described, where the transformation of an alcohol to a bromoalkane was achieved using carbontetrabromide and N,N-dimethylformamide through the intermediacy of a Vilsmeier-Haack reagent. In combination with the hydrodebromination chemistry developed with photoexcited polynuclear gold(I) complexes, a photo-mediated one-pot formal deoxygenation reaction of alcohols was described; a useful alternative to the organostannane mediated Barton-McCombie deoxygenation reaction. Finally, in the field of medicinal chemistry, the functionalization of heteroarenes is of high interest for the discovery of drug candidates and bioactive molecules. In this respect, one of the most useful reactions for the functionalization of heteroarenes by alkyl radicals is the Minisci reaction using silver salts, carboxylic acids, and persulfates. Detailed are the efforts for the development of a photo-mediated redox-neutral improvement of the Minisci reaction, needing only gold(I) photocatalyst and nonactivated bromoalkane in the presence of heteroarenes.
Overall, the work described in this thesis represents the push for mild and efficient alternatives to the relatively harsh conditions and/or toxic reagents and byproducts associated with classic radical chemistry. These studies demonstrate the ability to control highly reactive alkyl radical intermediates with the goal of their broader application in synthetic organic chemistry. The use of photoexcited polynuclear gold(I) complexes as potent reductants compared to ruthenium- and iridium-based polypyridyl complexes is illustrated through the genesis of highly reactive alkyl radicals from nonactivated bromoalkanes.
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Vega, Hernández Karen de la. "Radical Germylzincation of Alkynes". Thesis, Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=http://theses-intra.upmc.fr/modules/resources/download/theses/2019SORUS072.pdf.
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Le développement d'une approche radicalaire pour la germylzincation des alcynes en tant que voie simple et générale pour la préparation de vinylgermanes polysubstitués était l'axe central de ce travail. Dans le cadre de ce projet, nous avons démontré que l'addition régio- et stéréosélective de germanium et de zinc sur la triple liaison C‒C d’ynamides terminaux et internes peut être réalisée par réaction avec un mélange d'hydrogermane et de diéthylzinc dans un processus radicalaire. La principale caractéristique de cette nouvelle approche est la possibilité de fonctionnaliser la liaison C(sp2)‒Zn créée par substitution électrophile in situ cupro- ou pallado-catalysée avec rétention de la géométrie de la double liaison. Notamment, la fonctionnalisation de la liaison C(sp2)‒Ge a également été réalisée, augmentant la valeur synthétique des germylénamides. L’approche de germylzincation radicalaire a été étendue à d’autres alcynes substitués avec un hétéroatome en α, ainsi qu’aux alcynes classiques, avec d’excellents niveaux de stéréocontrôle. Ce travail représenté une avancée importante par rapport à l’état de l’art en offrant un accès modulaire à des vinylgermanes di-, tri- et tétrasubstitués élaborés, inaccessibles jusqu’à présent par d’autres méthodes. Dans une perspective plus large, la généralisation de l’approche d’élémentozincation radicalaire a également été abordée de manière préliminaireThe development of a general radical approach for the germylzincation of alkynes as a straightforward route for the preparation of polysubstituted vinylgermanes was the central axis of this work. Within this project, we disclosed that the regio- and stereoselective addition of germanium and zinc across the C‒C triple bond of terminal and internal ynamides was achieved by reaction with a combination of a hydrogermane and diethylzinc in a radical chain process. The key feature of this new approach was the possibility of using the C(sp2)‒Zn bond created as linchpin for subsequent in situ Cu(I)- or Pd(0)-mediated electrophilic substitution with retention of the double bond geometry. Notably, functionalization of the C(sp2)‒Ge bond was also achieved, enhancing germylenamides’ synthetic value. The radical germylzincation approach was further extended to other α-heteroatom-substituted alkynes, as well as more challenging conventional alkynes with excellent levels of stereocontrol. This work marked an important advance over prior art by offering modular access to elaborated di-, tri- and tetrasubstituted vinylgermanes that were not accessible by other methods thus far. From a wider perspective, the generality of the radical elementozincation approach was also preliminarily considered
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Qi, Genggeng. "Unconventional radical miniemulsion polymerization". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26547.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jones, Christopher W.; Committee Chair: Schork, F. Joseph; Committee Member: Koros, William J.; Committee Member: Lyon, Andrew; Committee Member: Nenes, Athanasios. Part of the SMARTech Electronic Thesis and Dissertation Collection.