京都大学 / 新制・課程博士 / 博士(工学) / 甲第23213号 / 工博第4857号 / 新制||工||1758(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 松原 誠二郎, 教授 杉野目 道紀, 教授 中尾 佳亮 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The selectivity mechanism of the UV-light activated metal oxide semiconductor (MOS) gas sensors was studied. A reaction model based on two competing redox processes was presented to solve the selectivity problem. A concept named dynamic equilibrium of adsorbed oxygen concentration was brought about in this model and two reaction responses were discussed: (1) when most of the MOS surface is adsorbed with oxygen, the resistance of the MOS gas sensor will decrease upon the injection of reducing agents (RAs); (2) when most of the MOS surface is not adsorbed with oxygen, the resistance of the MOS gas sensor will increase upon the injection of RAs. Finally, experiments were conducted on ZnO MOS gas sensors to prove the proposed hypothesis of the reaction mechanism. / Thesis / Master of Applied Science (MASc)

Thesis advisor: Jia Niu / This dissertation discusses two main projects focusing on synthesizing degradable vinyl copolymers. The first project describes the development of a general approach to synthesizing degradable vinyl random copolymers through photocontrolled radical ring-opening cascade copolymerization (rROCCP). The rROCCP of a macrocyclic allylic sulfone with acrylates or acrylamides mediated by visible light at ambient temperature achieved near-unity comonomer reactivity ratios over the entire range of feed compositions. Such a powerful approach provides degradable vinyl random copolymers with comparable material properties to their non-degradable counterparts. Experimental and computational evidence also revealed an unusual reversible inhibition of chain propagation by in situ generated sulfur dioxide (SO2), which was successfully overcome by reducing the solubility of SO2 during polymerization. The second project depicts a general method for organocatalyzed photocontrolled radical copolymerization of a macrocyclic allylic sulfone and various types of vinyl monomers, including acrylates, acrylamides, styrene, and methacrylate. Catalyzed by Eosin Y under visible light irradiation, copolymerization of the macrocyclic allylic sulfone and acrylic monomers displayed near unity comonomer reactivity ratios by fitting the copolymer composition to the Beckingham-Sanoya-Lynd integrated model. The macrocyclic allylic sulfone was also successfully copolymerized with styrene or methyl methacrylate to generate degradable polystyrene and poly(methyl methacrylate). These degradable vinyl copolymers exhibited tunable thermal properties correlated with the incorporation of degradable main-chain diester motif. / Thesis (PhD) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

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Three simultaneous isotope effects have been determined for the Tschugaeff reaction, i.e., the thermal decomposition of an xanthate ester. The ratio of the rate constants, k32/k34, was found to be 1.009 for the thion sulphur atom and 1.002 for the thio-ether sulphur atom. The rate ratio k12/k13, for the xanthate carbon atom was found to have a value of 1.000. The findings of previous investigators of the Tschugaeff reaction had been consistent with either of two mechanisms. However, with the determination of the isotope effects referred to above, it has been possible to distinguish between the two possible mechanisms and to gain considerable information about the transition state of the Tschugaeff reaction. The measured isotope effects have been discussed in terms of Bigeleisen's isotopic rate equation. In addition, it has been possible to carry out theoretical calculations for each reaction mechanism by assuming an appropriate potential function and in this manner make the interpretation of the measured isotope effects more quantitative. / Thesis / Master of Science (MS)

Orientador: Nelson Henrique Morgon / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T17:33:08Z (GMT). No. of bitstreams: 1 Lima_JoseCarlosBarretode_M.pdf: 1046152 bytes, checksum: 5cac61f65804d91e30491970eb62e5a9 (MD5) Previous issue date: 2008 / Resumo: O principal objetivo deste trabalho foi analisar quatro mecanismos teóricos para a redução (em fase gasosa) do ácido acético a etanol. Foi empregado NaBH4 na presença de um eletrófilo (H2SO4). Todos os cálculos foram realizados com a teoria CBS-QB3 usando o programa Gaussian 98. Foi observado que esta metodologia teve sucesso em predizer afinidades por próton e por elétron em um custo computacional mais baixo. A comparação entre seis teorias (CBS-4M, CBS-QB3, G2(MP2), G3(MP2), G2 e G3) usando uma análise estatística através do valor médio, do desvio padrão e da raíz média quadrática, mostrou um desempenho melhor da teoria CBS-QB3 para obter as propriedades. Uma metodologia geral foi proposta baseada nos resultados teóricos para as propriedades estruturais (comprimento do ângulo e da ligação) e termodinâmicas (variação da energia livre e da entalpia). As estruturas obtidas para mínimo local e para estados de transição na superfície da energia livre foram analisadas, bem como a consideração de efeitos solventes com um modelo contínuo (PCM) / Abstract: The main objective of this work was to analyze four theoretical mechanisms to the reduction (in gas-phase) of acetic acid to ethanol. It was employed NaBH4 in presence of an electrophile (H2SO4). All the calculations were carried out at CBSQB3 method using the Gaussian 98 program. It was found that this methodology suceeds in predicting proton and electron anities at a lower computational cost. The comparison among six theories (CBS-4M, CBS-QB3, G2(MP2), G3(MP2), G2 and G3) using statistical analysis, evaluating average value, standard deviation and root-mean-square, showed a better performance of CBS-QB3 to obtain the properties. A general methodology was proposed based on the theoretical results of structural (angle and bond length) and thermodynamics (enthalpy and free energy variation) properties. Structures of minimum and transistion states on the free energy surface were analyzed, and the inclusion of solvent effects with a continuum model (PCM) / Mestrado / Físico-Química / Mestre em Química

The 2,2'-disubstituated 1,1'-binaphthyls (BINOLs) are important ligands in enantioselective synthesis . The major approach for their preparation is based on transition-metal-mediated oxidative C-C coupling of 2-substituted naphtalenes. This diploma thesis examined the mechanism of the coupling reaction in the gas phase using mass spectrometry with electrospray ionization. The aim of this thesis was to compare the selectivity of the copper(II)- catalyzed coupling reaction of 2-naphthol and its derivative with an electron-withdrawing group, to detect possible reaction intermediates, and to determine the origin of the preference of the cross-coupling. The electron-withdrawing group of naphthol slows down the coupling reaction which enabled us to detect the reaction intermediates. The intermediates in the reaction of 2-naphthol were not observed, because the coupling reaction proceeds too quickly. Hence, we have observed only complexes of the coupling products. The preferential cross coupling was explaned on the basis of an interplay between the probability of the formation of binuclear copper complexes and the reactivity of such complexes.

Doctor of Philosophy / Department of Chemical Engineering / Peter H. Pfromm / Approximately 45% of the global hydrogen production (from fossil fuels such as natural gas or coal totaling 2% of the global energy generation) is absorbed as feedstock in the synthesis of over 130 million metric tons ammonia (NH[subscript]3) annually. To achieve food security for a growing world population and to allow for additional uses of the nitrogen-fertilizer for production of bio-energy feedstock or as combustion fuel or H[subscript]2 carrier - demand for NH[subscript]3 is projected to increase. This work pursues the synthesis of ammonia at atmospheric pressure and without fossil fuel. Conceptually, concentrated solar radiation is utilized to transfer electrons from the lattice oxygen of a transition metal oxide to the metal ion. This yields a metallic reactant that provides the reducing power for the subsequent six-electron reductive cleavage of N[subscript]2 forming a transition metal nitride. In a second reaction, the generated lattice nitrogen is hydrogenated with hydrogen from H[subscript]2O to NH[subscript]3. This furnishes the transition metal oxide for perpetuated NH[subscript]3 synthesis. Theory and experimentation identified manganese nitride as a promising reactant with fast diffusion characteristics (8 ± 4 x 10[superscript]-9 cm[superscript]2 s [superscript]-1 apparent nitrogen diffusion constant at 750 degree C) and efficient liberation of 89 ± 1 mol% nitrogen via hydrolysis at 500 degree C. Opposed to only 2.9 ± 0.2 mol% NH[subscript]3 from manganese nitride, 60 ± 8 mol% of the nitrogen liberated from molybdenum nitride could be recovered as NH[subscript]3. Process simulation of a Mo-based NH[subscript]3 synthesis at 500-1200 degree C estimates economically attractive production under fairly conservative process and market conditions. To aid the prospective design of a Mn or Mo-based reactant, correlating the diffusion constants for the hydrolysis of seven nitrides with the average lattice nitrogen charge (9.96-68.83%, relative to an ideal ionic solid) indicates the utility of first-principle calculations for developing an atomic-scale understanding of the reaction mechanism in the future.

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

This thesis uses dynamic electrochemical impedance spectroscopy (dEIS) to study how nickel undergoes electrooxidation. An electropolishing step is used to make a clean surface, and then the transformation of nickel to α-Ni(OH)2 is studied, including how a holding potential affects the double layer capacitance, surface structure and charge transfer resistance. Also, NiOOH is grown on the surface by sweeping to more positive potentials, and the activity of NiOOH toward glycerol electrooxidation is studied. It is shown that the free water content decreases on the surface (all or some portions of the surface, or possibly one or two monolayers close to the nickel surface) during the potential hold as determined by the decrease in measured capacitance. Oxidation of glycerol to glyceraldehyde is found to be the main reaction and the reaction mechanism is discussed. / Graduate / 2019-10-23