Дисертації з теми "Radical‐ Molecule Reactions"

This dissertation is a collection of works that investigates issues related to environmental chemistry. The first portion of this research explores the role of water vapor on the kinetics of important atmospheric reactions. Work is presented on the self-reaction of β-hydroxyethyl peroxy radical (β-HEP) and the catalytic increase in reaction rate by water vapor. β-HEP serves as a model system for investigating the possible role of water vapor in perturbing the kinetics and product branching ratio of atmospheric reactions of other alkyl peroxy radicals. The self-reaction rate coefficient of β-HEP was investigated between 276-296 K with 1.0 × 10^15 to 2.5 × 10^17 molecules cm^-3 of water vapor at 200 Torr total pressure by slow-flow laser flash photolysis coupled with UV time-resolved spectroscopy and long-path, wavelength-modulated, diode-laser spectroscopy. The overall disproportionation rate constant is expressed as the product of temperature-dependent and water vapor-dependent terms giving k(T,H2O) = 7.8 × 10^-14 (e^8.2 ^(±2.5) ^kJ/RT)(1 + 1.4 × 10^-34 × e^92 ^(±11) ^kJ/RT[H2O]). The results suggest that formation of a β--HEP-H2O complex is responsible for the observed water vapor enhancement of the self-reaction rate coefficient. Complex formation is supported with computational results identifying three local energy minima for the β--HEP-H2O complex. Both the temperature range and water vapor concentrations used were chosen because of their significance to conditions in the troposphere. As the troposphere continues to get warmer and wetter, more complexes with water will form, which in turn may perturb the kinetics and product branching ratios of atmospheric reactions. Future studies are proposed for the reaction of β-HEP + NO leading to NO2 formation. A laser-induced fluorescence cell was designed, built, and tested in preparation for studies of NO2 formation. Additionally Harriott-cell optics were manufactured and tested to detect HO2 using two-tone frequency-modulated diode-laser spectroscopy. In a related work, the breakdown of the environmental contaminants polychlorinated biphenyls (PCB's) was investigated using a new method. A new method for analyzing anaerobic digestion is also presented. The degradation rate and efficiency of digestion processes are typically measured by introducing a substrate or pollutant into a digester and then monitoring the effluents for the pollutant or substrate, a costly and slow process. A new method for rapid measurement of the rates and efficiencies of anaerobic degradation of pollutants and lignocellulose substrates from various pretreatments is described. The method uses micro-reactors (10-30 mL) containing a mixed culture of anaerobic bacteria obtained from a working anaerobic digester. The rates of degradation and metabolism of pollutants are measured in parallel sets of micro-reactors. Measurements of metabolic rate and pollutant degradation simultaneously is an effective means of rapidly examining pollutant degradation on a micro-scale. Calorimetric measurements alone allow rapid, relative evaluation of various substrate pretreatment methods. Finally calorimetric and electrophoretic methods were used to further knowledge in analytical techniques applied to important problems. In the last section of this dissertation the thermal and photolytic breakdown of promethazine hydrochloride is reported. Promethazine hydrochloride is a mediation that is commonly used as an antihistamine, a sedative, and an antiemetic, and to treat motion sickness. Perivascular extravasation, unintentional intra-arterial injection and intraneuronal or perineuronal infiltration may lead to irreversible tissue damage if the drug is not properly diluted or is administered too quickly. Data on the stability of promethazine hydrochloride diluted in sodium chloride 0.9% are lacking. This study evaluates the thermal and photolytic degradation of promethazine hydrochloride concentrations of 250 µg/mL and 125 µg/mL diluted in sodium chloride 0.9% over a period of 9 days. Degradation rates of promethazine hydrochloride were determined under UV-light, fluorescent light, and no light at various temperatures and concentrations to determine medication stability. The shelf-life (<10% degradation) at 25°C under normal fluorescent lights is 4.9 days, at 25°C protected from light, 6.6 days, and at 7°C in the dark, 8.1 days. These results may increase patient safety by improving current protocols for intravenous promethazine administration

L’allergie de contact est une pathologie touchant de 15 à 20 % de la population occidentale. A l’heure actuelle il n’existe aucun traitement, la seule façon efficace de prévention étant l’éviction totale des allergènes. Les tests de sensibilisation de nouvelles molécules avant leur mise sur le marché ont été réalisés sur l’animal jusqu’à l’interdiction dans le 7ème amendement à la directive Européenne concernant l’industrie cosmétique. Dans ce contexte il est primordial de développer des méthodes alternatives. Ce travail de thèse propose d’analyser la problématique de l’allergie de contact en allant de la molécule au tissu pour les allergènes réagissant par voie radicalaire :In chemico : étude de la réactivité des hydroperoxydes allyliques vis-à-vis des acides aminés par la RMNIn situ : études de radicaux issus de ces composés sur des épidermes humains reconstitués par RPEIn cellulo : étude du stress oxydant sur les cellules dendritiques et la voie de signalisation Keap1/Nrf2/ARE
Allergic contact dermatitis is a pathology affecting 15 to 20% of the Western population. Until now no treatment exists, the prevention is the eviction of allergens. In the past, tests concerning new molecules for the market were tested on animals until the prohibition in the 7th amendment of the European directive concerning the cosmetics industry. In this context it is essential to develop alternative methods to assess the allergenic potential of chemicals.This manuscript proposes to analyze the problem of the allergic contact dermatitis from the molecule to the tissue for allergens reacting through radical mechanisms:In chemico: study of the reactivity profile of allylic hydroperoxides toward amino acids by NMRIn situ: radical intermediates formation on reconstructed human epidermis from allylic hydroperoxides by EPR In cellulo: study of the oxidative stress from allylic hydroperoxides on dendritic cells trough the Keap1/Nrf2/ARE sensor pathway

Ce memoire presente l'etude experimentale de reactions neutre-neutre (molecule-radical et radical-radical) sur un grand intervalle de temperature allant de la temperature ambiante jusqu'a des temperatures extremement basses de l'ordre de 10 k. Ce type de reaction est tres important d'un point de vue astrochimique, dans l'etude d'atmospheres planetaires et dans la confrontation avec la theorie. La technique c. R. E. S. U. (cinetique de reaction en ecoulement supersonique uniforme) permettant d'avoir un ecoulement uniforme de temperature tres basse et la technique plp-lif (pulse de photolyse laser-fluorescence induite par laser) ont permis les premieres etudes de reactions avec les radicaux cn, oh et ch a des temperatures aussi basses que 13 k. Les coefficients de vitesse des reactions de cn avec o#2 et de cn avec nh#3 croissent de facon monotone quand la temperature diminue. Ces mesures confrontees a la theorie montrent que l'on doit inclure, en plus des interactions a longue portee, celles a courte portee. Les premieres etudes de la reaction du radical oh avec trois butenes sont utiles pour une meilleure comprehension des pollutions de l'atmosphere terrestre. La forte dependance negative en temperature du coefficient de vitesse de la reaction du radical oh avec hbr a fait apparaitre une sous estimation du coefficient de vitesse aux temperatures regnant dans la stratosphere terrestre. Ceci a une incidence dans le cycle de l'ozone. Les premieres mesures du coefficient de vitesse de la reaction de oh avec no en fonction de la temperature et de la pression sont utiles dans l'etude d'atmospheres planetaires, notamment celle de la terre. Les premieres etudes de reactions entre le radical ch et plusieurs molecules et radicaux neutres indiquent que ch reagit rapidement a tres basse temperature. L'etude spectroscopique des radicaux cn et oh a montre que l'ecoulement supersonique presente un reel equilibre thermodynamique

Ce memoire reporte l'etude experimentale de la cinetique de divers processus reactionnels entre especes neutres en phase gazeuse a tres basses temperatures (jusqu'a 23 k). La connaissance de la vitesse de ces processus dans ces conditions extremes est utile a la comprehension de la synthese des molecules dans le milieu interstellaire et dans les atmospheres planetaires froides. La dependance en temperature de la vitesse de reactions permet egalement de faire progresser nos connaissances des mecanismes reactionnels. Le dispositif experimental utilise combine la technique aerodynamique cresu (cinetique de reaction en ecoulement supersonique uniforme), qui permet de generer un jet de gaz de tres basse temperature a l'equilibre thermodynamique, et la technique plp-lif (photolyse laser pulsee - fluorescence induite par laser), qui permet de mesurer la vitesse des reactions impliquant des atomes ou des radicaux et des molecules neutres. Les reactions d'association entre le radical ch et les molecules n#2 et co ont ainsi ete etudiees a 53 k afin d'etendre la connaissance de la cinetique de ces reactions a des temperatures pertinentes pour differentes atmospheres extra-terrestres. Les coefficients de vitesse de deux reactions impliquant des atomes (al + o#2 alo + o et si + o#2 sio + o) ont ete mesures pour la premiere fois en dessous de la temperature ambiante (entre 23 et 295 k). La vitesse de ces deux reactions augmente lorsque la temperature diminue et la dependance en temperature de la premiere reaction a ete reproduite de maniere satisfaisante par une theorie de capture tenant compte des interactions a longue portee entre les reactants. Enfin, l'etude de la relaxation dans la structure fine de l'atome al (#2p#j) par collisions avec l'argon a ete effectuee entre 44 et 137 k. Completee par une etude theorique, elle a permis de caracteriser le potentiel d'interaction entre al et ar. Les eventuelles implications astrophysiques de l'ensemble de ces mesures ont egalement fait l'objet de discussions tout au long de ce memoire.

The temperature dependence of the rate coefficient of radical-molecule reactions is studied using novel flow techniques. The methodology makes use of the cooling extant in uniform and free supersonic expansions to produce low temperature (90-250 K in the uniform expansion and near 1 K in the free jet) environments which are not at chemical equilibrium. The design of the axisymmetric Laval nozzles, which are integral in producing the uniform supersonic expansion, is reviewed in depth. The experimental details pertinent to the characterization and operation of the pulsed uniform supersonic expansion flow reactor are considered. The application of free jet flows for the study of radical-molecule reactions at temperatures near I K is also discussed. The rate coefficient of the atmospherically important termolecular reactions OH + NO and OH + NO₂ were investigated at several temperatures between approximately 100 and 250 K and pressures between 0.1 and 10. The results are found to be well fit by a simple k = CT⁻ⁿ dependence suggested by statistical unimolecular theory within the collision complex model. The suggested variation of the reaction, OH + NO, is k = 7.0(±2.0) X 10⁻³¹ (T/300 K)^(2.6±0.3) over the range 90 to 550 K. The reaction, OH + N02, displayed falloff behavior in the pressure range studied here, so recommendation of the absolute low pressure rate coefficient awaits further pressure dependent study. The purely bimolecular reaction, OH + HBr, has been studied at temperatures between 76 and 242 K using the pulsed uniform supersonic expansion flow reactor and near 1 K using the free jet flow reactor. This reaction displays a complex temperature dependence not well predicted by current dynamical theory. The results are evaluated in the light of previously obtained rate coefficients, generally at higher temperatures, and of theoretical predictions of the absolute value and temperature dependence of the rate coefficient. Impact on the modeling of low temperature environments is discussed.

L'eau joue un rôle fondamental dans la photochimie du milieu interstellaire (MIS), à travers la formation d'espèces très réactives comme OH. Les radicaux OH peuvent par la suite interagir avec d'autres molécules hydrogénées pour reformer H2O par abstraction d'hydrogène: R-H + OH → R* + H2O. Dans le cadre de ce travail de thèse, nous avons étudié l'influence des photons VUV sur des analogues de glace interstellaire. Nous montrons que l'incorporation d'une petite quantité d'eau dans NH3 et CH4 glaces augmente considérablement la formation de radicaux réactifs comme NH2 et CH3 pendant le processus de photolyse et que le chauffage des glaces binaires irradiées telles que NH3-H2O et CH4-H2O conduit à la formation de NH2OH et d'espèces alcooliques plus complexes comme le propanol et le métoxyméthanol. Nous avons également entamé d'autres études en parallèle sur le l'évolution thermique des glaces de NH2OH d'une part et la formation de propanol par voies énergétiques (irradiation VUV) et non énergétique (réaction d'addition H) d'autre part afin de tenter d'expliquer la non-détection des ces espèces organiques dans le milieu interstellaire. L'étude des glaces mixtes irradiées NH3-CH4-H2O a montré la formation à basse température d'espèces plus exotiques en combinant les spectrométries IR et de masse. Nous avons réussi à identifier des composés organiques très complexes déjà détectés ou activement recherchés dans le MIS
Water plays a fundamental role in the photochemistry of the interstellar medium (ISM), through OH radical formation. OH radicals can interact with other H-containing species to form H2O through a hydrogen abstraction reaction: R-H + OH → R* + H2O. In this work, we have investigated the VUV processing on different interstellar ice analogs. We show that the incorporation of small amount of water in NH3 and CH4 ices greatly increases the formation of reactive NH2 and CH3 radicals during the photolysis processing. Thermal treatments of irradiated NH3-H2O and CH4-H2O ices lead to the formation of NH2OH and larger alcoholic species such as propanol and metoxymethanol. Further studies of thermal processing of NH2OH ice and formation of propanol through energetic (VUV irradiation) and non-energetic (surface H-addition reaction) processing were carried out in the context of this thesis in order to try explaining their non-detection in the interstellar medium. The study of the irradiated mixed NH3-CH4-H2O ices showed the formation of more exotic species by combining the IR and mass spectrometries. We managed to identify very large complex organic compounds already detected or tensively sought in the ISM

Operationally friendly protocols to produce libraries of novel small molecules with high molecular complexity are in huge demand for the interrogation of biological systems. As such, development of new MCRs and post-condensation modification of the MCR products have proven fruitful in the quest for new molecular probes and their expedited progression along the drug discovery value chain. The products thereof have found their way into numerous corporate compound collections. Crixivan (Indinavir), an antiretroviral, and Xylocaine (Lidocaine), a local anesthetic, are two examples of drugs derived from an MCR that have been marketed. The research topic of this dissertation encompasses the design and development of fifteen novel drug-like chemotypes in an operationally friendly, green, and expedited (≤ 3 synthetic operations) manner involving the Ugi MCR coupled with MAOS and high-throughput purification platforms. Over 500 drug-like small molecules (purity > 90% based on UV 214 nm and ELSD) have been synthesized, purified, and submitted to the NIH MLSMR for further biological evaluation against protein targets of interest. Furthermore, non-electrochemical carbamate oxidations enabling formation of N-acyliminium ion precursors, which are reactive intermediates that form the basis of a multitude of synthetic routes to natural products, have also been developed.

Two key routes of the oxidation of ammonia is the reaction between the aminyl radical with molecular oxygen and superoxide. Fundamental insights in its oxidation is of great importance to both our understanding of atmospheric chemistry, biological effects as well as the safety assessments in nuclear industry. The gas phase reactions differ largely in rate compared to the aqueous reactions. In this work, the mechanism for the aqueous reactions have been studied computationally using ab initio quantum chemical calcultions. Reaction barriers have been quantified and compared with experimental data in the litterature. Also, the absorbtion spectrum of one of the postulated intermediates is verified using TDDFT. Furthermore, ã-radiolysis experiments have been conducted to test a model for aqueous radical oxidation of ammonia by investigating the yield of one of the final products, peroxynitrite. The model consists of a large part of reported reactions relevant to the aqueous radiolysis of nitrogen containing solutions (with an emphasis on ammonia). The dependence of the yield on the chosen experimental conditions is compared to that calculated using the model. The results of the quantum chemical computations for the reaction with oxygen is in agreement with earlier experimentally reported absorption spectrum and rate of decomposition of a key intermediate, the aminyl peroxide radical. Both properties, however, only agree when a large enough number of explicit water molecules are included in the computations. The dependence of the results on the chosen number of water molecules as well as the level of theory is discussed. The evaluation of the model for radiolysis of aqueous ammonia shows that the current understanding of oxygenated systems where superoxide is in excess with respect to hydroxyl radical is good. For systems deficient in superoxide, the model fails to accurately predict the yield of the final product under investigation, peroxynitrite, and it raises the question whether some unknown process has been overlooked in earlier studies.

A pulsed supersonic Laval nozzle flow reactor has been employed to investigate a variety of neutral-radical reaction processes at temperatures between 53 and 188 Kelvin. These supersonic flows simulate the conditions found in the Earth's upper atmosphere as well as certain environments in the interstellar medium and outer planetary atmospheres and thus provide direct information on the chemistry and physical processes occurring in those environments. Studies of this type, in the limit of 0 Kelvin, coupled with modern astronomical observations of planetary atmospheres and dense molecular clouds provide for a global understanding of chemistry in cold environments. With this in mind, the flow reactor was used to conduct fundamental studies involving the reactivity of hydroxyl (OH) and imidogen (NH) radical species with a variety of partners. More specifically, the reactions of OH+HBr and all of the H/D isotopic variants were explored between 53 and 135 K, with the goal of elucidating the kinetic isotope effects, both primary and secondary, for a reaction system occurring over a potential energy surface without an appreciable barrier, that demonstrates inverse temperature dependence. While not of direct astronomical importance, the reaction of OH+HBr does affect the partitioning of Br in the Earth's atmosphere, and knowledge of kinetic isotope effects helps one understand the chemistry leading to H/D fractionation observed in a variety of interstellar environments. The reactions of NH radical with NO, saturated, and unsaturated hydrocarbons were also studied between 53 and 188 Kelvin in the Laval nozzle flow reactor. These species were chosen as most are important constituents in the atmosphere of Titan, which is known to possess a rich organic chemistry. The reactions of NH with the unsaturated hydrocarbons are found to display negative temperature dependence over the window investigated, and are thought to proceed through an addition mechanism. Finally, the flow reactor was also coupled to a tunable vacuum and extreme ultraviolet frequency source based on four wave frequency mixing to allow for studies of radical species with their first electronic transitions in this frequency range. A discussion of the development, implementation, and future directions is included.

New dynamical applications of quantum beat spectroscopy (QBS) to molecular dynamics are employed to probe the angular momentum polarization effects in photodissociation and molecular collisions. The magnitude and the dynamical behaviour of angular momentum alignment and orientation, two types of polarization, can be measured via QBS technique on a shot-by-shot basis. The first part of this thesis describes the experimental studies of collisional angular momentum depolarization for the electronically excited state radicals in the presence of the collider partners. Depolarization accompanies both inelastic collisions, giving rise to rotational energy transfer (RET), and elastic collisions. Experimental results also have a fairly good agreement with the results of quasi-classical trajectory scattering calculations. Chapter 1 provides the brief theories about the application of the QBS technique and collisional depolarization. Chapter 2 describes the method and instrumentation employed in the experiments of this work. In Chapter 3, the QBS technique is used to measure the total elastic plus elastic depolarization rate constants under thermal conditions for NO(A,v=0) in the presence of He, Ar, N2, and O2. In the case of NO(A) with Ar, and particularly with He, collisional depolarization is significantly smaller than RET, reflecting the weak long-range forces in these systems. In the case of NO(A)+N2/O2, collisional depolarization and RET are comparable, reflecting the relatively strong long-range forces in these systems. In Chapter 4, the QBS technique is used to measure the elastic and inelastic depolarization and total RET rate constants for OH(A,v=0) under thermal conditions in the presence of He and Ar, as well as the total depolarization rate constants under superthermal conditions. In the case of OH(A)+He, elastic depolarization is sensitive to the N rotational state, and inelastic depolarization is strongly dependent on the collision energy. In the case of OH(A)+Ar, elastic depolarization is insensitive to N, and inelastic depolarization is less sensitive to the collision energy, reflecting that the relatively strong long-range force in OH(A)+Ar system. The second part of this thesis describes the experimental studies of photodissociation under thermal conditions. Chapter 5 provides a brief introduction about several polarization parameter formalisms used for photodissociation, and the incorporation of the QBS technique to measure these polarization parameters. In this thesis, most polarization parameters of the molecular photofragments are measured using the LIF method, and the QBS technique is used as a complementary tool to probe these polarization parameters. In Chapter 6, rotational orientation in the OH(X,v=0) photofragments from H2O2 photodissociation using circularly polarized light at 193 nm is observed. Although H2O2 can be excited to both the A and B electronic states by 193 nm, the observed orientation is only related to the A state dynamics. A proposed mechanism about the coupling between a polarized photon and the H2O2 parent rotation is simulated, and the good agreement between the experimental and simulation results further confirms the validity of this mechanism. In Chapter 7, rotational orientation in the NO(X,v) photofragments from NO2 photodissociation using circularly polarized light at 306 nm (v=0,1,2) and at 355 nm (v=0,1) is observed. Two possible mechanisms, the parent molecular rotation and the coherent effect between multiple electronic states, are discussed. NOCl is photodissociated using circularly polarized light at 306 nm, and NO(X,v) rotational distributions (v=0,1) and rotational orientation (v=0) are measured. For the case of NOCl, the generation of orientation is attributed to the coherent effect.

This thesis reports on the study of elementary reactions of the carbon radicals C, C2 and C3 at combustion temperatures. The shockwave technologie was used to generate the necessary gas temperatures of 2500 K up to 5000 K. Fast optical measurement techniques were applied for the time resolved observation of radical reactions. For the detection of C2-radicals, a highly sensitive diagnostic was developed, based on a ring-dye-laser spectrograph. The radicals C3 and CN and the atomic species C, N, and O were measured with a CCD-Camera spectrograph and with the atomic-resonance-absorption spectroscopy. The thermal decomposition (pyrolysis) of acetylene (C2H2) was used as a source for Carbon radicals. Results of this thesis are an extension and a verification of reaction mechanisms for the pyrolysis of acetylene as well as the determination of rate coefficients for the decompostion reactions of C2H2, C2H and C2 and for the bimolecular reactions of C2 with H2, O, O2, N2 and NO.

Etude théorique de la réactivité photochimique mono- et poly moléculaire des états de Rydberg infèrieurs de NH::(3), H::(2)O, CH::(4), alkylamines, alcools, radicaux méthyle, éthyle et ammonium de petits agrégats de NH::(3) ET NH::(3)-H::(2)O, de la photocyclodimèrisation de C::(2)H::(4), de l'extinction de l'état singulet excité de H::(2) par H::(2) à l'état fondamental, de la solvatation du radical NH::(4) dans un état de Rydberg par NH::(3), de l'interaction de H::(2) et HE avec NH::(3) excité, par la détermination des surfaces d'énergie potentielle par des méthodes ab initio quantitatives et des diagrammes de corrélation qualitatifs étendus aux états de Rydberg, en réunissant les différents concepts contenus dans les diagrammes de corrélation de l'atome unifié, dans le diagramme de Woodward Hoffmann, dans les règles de "topicité" et le concept de "rydbergnisation".

Ce travail a pour motivation de fournir des données expérimentales importantes pour l'interprétation de la chimie des ionosphère planétaires, en particulier pour le plus grand satellite de Saturne, Titan. On s'intéresse spécifiquement à la réactivité des espèces ioniques excitées. Cette thèse porte, d'une part, sur des expériences de préparation des cations (CH3+ et CF3+) sélectionnés en énergie interne par photoionisation VUV d'espèces neutres, et d'autre part, sur des réactions de cations sélectionnés en énergie interne avec des molécules, O+ avec CH4 et N+(3P) avec C3H4, C3H6 et C3H8.L'étude de la préparation des cations CH3+ et CF3+ sélectionnés dans des niveaux vibrationnels a été réalisée par la technique de coïncidence TPEPICO et du rayonnement VUV synchrotron à SOLEIL. Un spectromètre de type PFI-ZEKE qui permet d'atteindre une résolution de 0.84 cm-1 a été construit pour la réalisation d'études complémentaires avec le rayonnement laser VUV du Centre Laser de l'Université Paris Sud (CLUPS), à Orsay en France.Les expériences pour la détermination de l'influence de l'excitation du cation O+ (2S,2D,2P) sur sa réactivité avec le méthane ont été réalisées par les techniques de coïncidence TPEPICO et de guides d'ions. Elles ont été réalisées sur la ligne de rayonnement VUV DESIRS du synchrotron SOLEIL. Les études pour déterminer la constante de vitesse et les rapports de branchement entre produits des réactions de N+(3P) avec C3H4, C3H6 et C3H8 ont été réalisées par l'utilisation de la technique SIFT sur un montage de type commercial de petite taille à l'Institut de Physico-Chimie J. Heyrovský à Prague, en République Tchèque
This work has the motivation to provide experimental data relevant to the interpretation of the chemistry of planetary ionospheres, particularly for the largest satellite of Saturn, Titan. Here we have a particular interest in studying the reactivity of excited ionic species. The first part of this work concerns the production of CH3+ and CF3+ state selected cations by VUV photoionization of neutral species and the second part, the reactions of state selected cations with molecules: O+ with methane and N+(3P) with C3H4, C3H6 and C3H8.The study of the preparation of the CH3+ and CF3+ cations in selected vibrational levels was performed by using the TPEPICO coincidence technique and VUV radiation at the french synchrotron, SOLEIL. A PFI-ZEKE spectrometer, that allowed us to obtain a resolution down to 0.84 cm-1, was constructed to conduct additional studies involving laser VUV radiation at the Laser Center of the University Paris Sud XI, at Orsay in France.Experiments to determine the influence of the O+ (2S,2D,2P) cation excitation on its reaction with methane were performed using the TPEPICO coincidence and the guide ion beam technique. These experiments were performed on the VUV DESIRS beamline at the synchrotron SOLEIL. Rate constants and products branching ratio for the reacion of N+(3P) with C3H4, C3H6 and C3H8 were measured with the SIFT technique in a small commercial apparatus at the Institute of Physical Chemistry J. Heyrovský in Prague, Czech Republic
Este trabalho tem como motivação fornecer dados experimentais importantes para a interpretação da química de ionosferas planetárias, em particular para o maior Satélite de Saturno, Titan. Aqui temos o interesse específico pelo estudo de reatividades de espécies iônicas excitadas. Uma parte deste trabalho consistiu de experiências de preparação de cátions (CH3+ e CF3+) selecionados em energia interna via a fotoionização VUV de espécies neutras e de reações de cátions selecionados em massa e energia interna com moléculas (O+ com metano e N+(3P) com C3H4, C3H6 e C3H8).O estudo de preparação dos cátions CH3+ e CF3+ selecionados energia interna (vibracional) foi realizado pela utilização da técnica de coincidência TPEPICO com a radiação VUV do síncrotron SOLEIL. Um espectrômetro do tipo PFI-ZEKE que nos permite obter uma resolução de até 0.84 cm-1 foi construído para a realização de estudos complementares envolvendo a radiação VUV laser do Centro de Laser da Universidade Paris Sud XI, em Orsay na França.Experiências para determinar a influência da excitação do cátion O+ (2S,2D,2P) na produção de íons devido a sua reação com o metano foram realizadas com a utilização da técnica de coincidência TPEPICO e da técnica de guia de íons. Estes experimentos foram realizados na linha de radiação VUV DESIRS do síncrotron SOLEIL. Estudos de determinação de constantes de velocidade e dos produtos formados da reação N+(3P) com C3H4, C3H6 e C3H8 foram realizados a partir da utilização da técnica SIFT em uma montagem do tipo comercial de pequeno porte no Instituto de Físico-Química J. Heyrovský em Praga, na República Checa

Calcul des géométries du points de sille et des barrières d'activation pour les réactions d'abstraction (HO::(2) + H->H::(2) + O::(2)) et d'approche concertée (HO::(2) + H->H::(2)O + O) pour la méthode SDCI à l'ordre d'une base DZ dans la région de valence, augmentée par des orbitales de polarisation de type D sur chaque atome O. Evaluation des paramètres cinétiques dans le cadre de la théorie de l'état de transition : énergies d'activation et constantes de vitesse. Faible probabilité du mécanisme de réaction concertée

This Ph.D. thesis describes the versatility of metal complexes with tris(2-pyridylmethyl)amine (TPMA) based ligands to be used either as self-assembling molecular scaffolds with application on molecular recognition and chiroptical probing, or as active catalysts in atom transfer radical polymerization and hydrogen evolving catalysis reactions. Quantitative chirality determination is fundamental due to the broad effect that stereochemistry has in many different scientific fields. Within this subject, there is a strong urge to develop fast and effective methods to perform stereochemical analysis to couple with high throughput screening methods for production or analysis of biological samples. Chiroptical methods are able to provide the speed and accuracy that enantiomeric excess determination measurement needs. Within that scope, three molecular probes for amino acids have been developed allowing to perform enantiomeric determination and absolute configuration by measuring the induced circular dichroism (CD), vibrational circular dichroism (VDC) or circularly polarized luminescence (CPL). The reported systems were able to provide reliable information about the chirality of the studied analytes. In this dissertation the mechanistic investigation for the elucidation of the self-assembly process of TPMA with amino acids and metals is described. The complex equilibrium that yields the dimeric supramolecular architectures responsible for the chiroptical signals is exposed. The main factor that affects the final products of the reaction as well. Then the effects on the chiroptical response when changing the metal ions on the main structure are reported. Some impressive results were obtained by using Co (II) instead of Zn (II) on the VCD measurements. It was actually possible to enhance the signal intensity by two orders of magnitude. Furthermore, after modifying the initial ligand structure to add a quinolinic moiety in order to give fluorescent properties to the system, it was possible to obtain CPL bands. Moreover, the versatility of the studied ligands was assessed in other areas like catalysis. Eight novel copper complexes were synthesized and applied as active catalysts in atom transfer radical polymerization (ATRP). Hidroxyquinolinic based cobalt, nickel and iron complexes were evaluated as potential catalysts for hydrogen evolving reactions with positive results.
Questa tesi di dottorato descrive la versatilità dei complessi metallici con leganti tris(2-piridilmetil)amminici (TPMA) da utilizzare come scaffold molecolari autoassemblanti con applicazione sul riconoscimento molecolare e sonde chiroptiche, o come catalizzatori attivi nella polimerizzazione radicale a trasferimento atomico e reazioni di catalisi di sviluppo di idrogeno. La determinazione quantitativa della chiralità è fondamentale a causa dell'ampio effetto che la stereochimica ha in molti campi scientifici diversi. All'interno di quest’area, esiste una grande necessità di sviluppare metodi rapidi ed efficaci per eseguire analisi stereochimiche da abbinare a metodi di screening ad alto rendimento per la produzione o l'analisi di campioni biologici. I metodi chiropici sono in grado di fornire la velocità e la precisione necessarie per la determinazione dell’eccesso enantiomerico. Con questo obiettivo sono state sviluppate tre sonde molecolari per amminoacidi che consentono di eseguire la determinazione enantiomerica e la configurazione assoluta misurando il dicroismo circolare indotto (CD), il dicroismo circolare vibrazionale (VDC) o la luminescenza circolare polarizzata (CPL). I sistemi riportati sono stati in grado di fornire informazioni affidabili sulla chiralità degli analiti studiati. In questa dissertazione viene descritta l'indagine meccanicistica per la delucidazione del processo di auto-assemblaggio di TPMA con amminoacidi e metalli. Viene esposto il complesso equilibrio che produce le architetture supramolecolari dimeriche responsabili dei segnali chiropici. Il fattore principale che influisce anche sui prodotti finali della reazione. Quindi vengono riportati gli effetti sulla risposta chiropica al cambiare degli ioni metallici sulla struttura principale. Alcuni risultati significativi sono stati ottenuti utilizzando Co (II) invece di Zn (II) sulle misurazioni VCD. In realtà è stato possibile aumentare l'intensità del segnale di due ordini di grandezza. Inoltre, dopo aver modificare la struttura del legante iniziale per aggiungere un gruppo chinolinico al fine di conferire proprietà fluorescenti al sistema, è stato possibile ottenere le bande CPL. In aggiunta, la versatilità dei leganti studiati è stata valutata in altre aree come la catalisi. Otto nuovi complessi di rame sono stati sintetizzati e applicati come catalizzatori attivi nella polimerizzazione radicale a trasferimento atomico (ATRP). I complessi cobalto, nichel e ferro idrossichinolinici sono stati valutati come potenziali catalizzatori per reazioni di sviluppo di idrogeno con risultati positivi.

Doutoramento em Bioquímica
Os polissacarídeos são os componentes maioritários dos grãos de café verde e torrado e da bebida de café. Os mais abundantes são as galactomananas, seguindo-se as arabinogalactanas. Durante o processo de torra, as galactomananas e arabinogalactanas sofrem modificações estruturais, as quais estão longe de estar completamente elucidadas devido à sua diversidade e à complexidade estrutural dos compostos formados. Durante o processo de torra, as galactomananas e arabinogalactanas reagem com proteínas, ácidos clorogénicos e sacarose, originando compostos castanhos de alto peso molecular contendo nitrogénio, designados de melanoidinas. As melanoidinas do café apresentam diversas atividades biológicas e efeitos benéficos para a saúde. No entanto, a sua estrutura exata e os mecanismos envolvidos na sua formação permanecem desconhecidos, bem como a relação estrutura-atividade biológica. A utilização de sistemas modelo e a análise por espectrometria de massa permitem obter uma visão global e, simultaneamente, detalhada das modificações estruturais nos polissacarídeos do café promovidas pela torra, contribuindo para a elucidação das estruturas e mecanismos de formação das melanoidinas. Com base nesta tese, oligossacarídeos estruturalmente relacionados com a cadeia principal das galactomananas, (β1→4)-Dmanotriose (Man3), e as cadeias laterais das arabinogalactanas, (α1→5)-Larabinotriose (Ara3), isoladamente ou em misturas com ácido 5-Ocafeoilquínico (5-CQA), o ácido clorogénico mais abundante nos grãos de café verde, e péptidos compostos por tirosina e leucina, usados como modelos das proteínas, foram sujeitos a tratamento térmico a seco, mimetizando o processo de torra. A oxidação induzida por radicais hidroxilo (HO•) foi também estudada, uma vez que estes radicais parecem estar envolvidos na modificação dos polissacarídeos durante a torra. A identificação das modificações estruturais induzidas por tratamento térmico e oxidativo dos compostos modelo foi feita por estratégias analíticas baseadas principalmente em espectrometria de massa, mas também em cromatografia líquida. A cromatografia de gás foi usada na análise de açúcares neutros e ligações glicosídicas. Para validar as conclusões obtidas com os compostos modelo, foram também analisadas amostras de polissacarídeos do café obtidas a partir de resíduo de café e café instantâneo. Os resultados obtidos a partir dos oligossacarídeos modelo quando submetidos a tratamento térmico (seco), assim como à oxidação induzida por HO• (em solução), indicam a ocorrência de despolimerização, o que está de acordo com estudos anteriores que reportam a despolimerização das galactomananas e arabinogalactanas do café durante a torra. Foram ainda identificados outros compostos resultantes da quebra do anel de açúcares formados durante o tratamento térmico e oxidativo da Ara3. Por outro lado, o tratamento térmico a seco dos oligossacarídeos modelo (individualmente ou quando misturados) promoveu a formação de oligossacarídeos com um maior grau de polimerização, e também polissacarídeos com novos tipos de ligações glicosídicas, evidenciando a ocorrência de polimerização através reações de transglicosilação não enzimática induzidas por tratamento térmico a seco. As reações de transglicosilação induzidas por tratamento térmico a seco podem ocorrer entre resíduos de açúcares provenientes da mesma origem, mas também de origens diferentes com formação de estruturas híbridas, contendo arabinose e manose como observado nos casos dos compostos modelo usados. Os resultados obtidos a partir de amostras do resíduo de café e de café instantâneo sugerem a presença de polissacarídeos híbridos nestas amostras de café processado, corroborando a ocorrência de transglicosilação durante o processo de torra. Além disso, o estudo de misturas contendo diferentes proporções de cada oligossacarídeo modelo, mimetizando regiões do grão de café com composição distinta em polissacarídeos, sujeitos a diferentes períodos de tratamento térmico, permitiu inferir que diferentes estruturas híbridas e não híbridas podem ser formadas a partir das arabinogalactanas e galactomananas, dependendo da sua distribuição nas paredes celulares do grão e das condições de torra. Estes resultados podem explicar a heterogeneidade de estruturas de melanoidinas formadas durante a torra do café. Os resultados obtidos a partir de misturas modelo contendo um oligossacarídeo (Ara3 ou Man3) e 5-CQA sujeitas a tratamento térmico a seco, assim como de amostras provenientes do resíduo de café, mostraram a formação de compostos híbridos compostos por moléculas de CQA ligadas covalentemente a um número variável de resíduos de açúcar. Além disso, os resultados obtidos a partir da mistura contendo Man3 e 5-CQA mostraram que o CQA atua como catalisador das reações de transglicosilação. Por outro lado, nas misturas modelo contendo um péptido, mesmo contendo também 5-CQA e sujeitas ao mesmo tratamento, observou-se uma diminuição na extensão das reações transglicosilação. Este resultado pode explicar a baixa extensão das reações de transglicosilação não enzimáticas durante a torra nas regiões do grão de café mais ricas em proteínas, apesar dos polissacarídeos serem os componentes maioritários dos grãos de café. A diminuição das reações de transglicosilação na presença de péptidos/proteínas pode dever-se ao facto de os resíduos de açúcares redutores reagirem preferencialmente com os grupos amina de péptidos/proteínas por reação de Maillard, diminuindo o número de resíduos de açúcares redutores disponíveis para as reações de transglicosilação. Além dos compostos já descritos, uma diversidade de outros compostos foram formados a partir dos sistemas modelo, nomeadamente derivados de desidratação formados durante o tratamento térmico a seco. Em conclusão, a tipificação das modificações estruturais promovidas pela torra nos polissacarídeos do café abre o caminho para a compreensão dos mecanismos de formação das melanoidinas e da relação estrutura-atividade destes compostos.
Polysaccharides are the major components of green and roasted coffee beans, and coffee brew. The most abundant ones are galactomannans, followed by arabinogalactans. During the roasting process, galactomannans and arabinogalactans undergo structural modifications that are far to be completely elucidated due to their diversity and complexity of the compounds formed. During the roasting process, galactomannans and arabinogalactans react with proteins, chlorogenic acids, and sucrose, originating high molecular weight brown compounds containing nitrogen, known as melanoidins. Several biological activities and beneficial health effects have been attributed to coffee melanoidins. However, their exact structures and the mechanisms involved in their formation remain unknown, as well as the structure-biological activity relationship. The use of model systems and mass spectrometry analysis allow to obtain an overall view and, simultaneously, detailed, of the structural modifications in coffee polysaccharides promoted by roasting, contributing to the elucidation of the structures and formation mechanisms of melanoidins. Based on this thesis, oligosaccharides structurally related to the backbone of galactomannans, (β1→4)-D-mannotriose, and the side chains of arabinogalactans, (α1→5)-Larabinotriose, alone or in mixtures with 5-O-caffeoylquinic acid, the most abundant chlorogenic acid in green coffee beans, and dipeptides composed by tyrosine and leucine, used as models of proteins, were submitted to dry thermal treatments, mimicking the coffee roasting process. The oxidation induced by hydroxyl radicals (HO•) was also studied, since these radicals seem to be involved in the modification of the polysaccharides during roasting. The identification of the structural modifications induced by thermal and oxidative treatment of the model compounds was performed mostly by mass spectrometry-based analytical strategies, but also using liquid chromatography. Gas chromatography was used in the analysis of neutral sugars and glycosidic linkages. To validate the conclusions achieved with the model compounds, coffee polysaccharide samples obtained from spent coffee grounds and instant coffee were also analysed. The results obtained from the model oligosaccharides when submitted to thermal treatment (dry) or oxidation induced by HO• (in solution) indicate the occurrence of depolymerization, which is in line with previous studies reporting the depolymerization of coffee galactomannans and arabinogalactans during roasting. Compounds resulting from sugar ring cleavage were also formed during thermal treatment and oxidative treatment of Ara3. On the other hand, the dry thermal treatment of the model oligosaccharides (alone or when mixed) promoted the formation of oligosaccharides with a higher degree of polymerization, and also polysaccharides with new type of glycosidic linkages, evidencing the occurrence of polymerization via non-enzymatic transglycosylation reactions induced by dry thermal treatment. The transglycosylation reactions induced by dry thermal treatment can occur between sugar residues from the same origin, but also of different origins, with formation of hybrid structures, containing arabinose and mannose in the case of the model compounds used. The results obtained from spent coffee grounds and instant coffee samples suggest the presence of hybrid polysaccharides in these processed coffee samples, corroborating the occurrence of transglycosylation during the roasting process. Furthermore, the study of mixtures containing different proportions of each model oligosaccharide, mimicking coffee bean regions with distinct polysaccharide composition, subjected to different periods of thermal treatment, allowed to infer that different hybrid and non-hybrid structures may be formed from arabinogalactans and galactomannans, depending on their distribution in the bean cell walls and on roasting conditions. These results may explain the heterogeneity of melanoidins structures formed during coffee roasting. The results obtained from model mixtures containing an oligosaccharide (Ara3 or Man3) and 5-CQA and subjected to dry thermal treatment, as well as samples derived from spent coffee grounds, showed the formation of hybrid compounds composed by CQA molecules covalently linked to a variable number of sugar residues. Moreover, the results obtained from the mixture containing Man3 and 5-CQA showed that CQA acts as catalyst of transglycosylation reactions. On the other hand, in the model mixtures containing a peptide, even if containing 5-CQA and subjected to the same treatment, it was observed a decrease in the extent of transglycosylation reactions. This outcome can explain the low extent of non-enzymatic transglycosylation reactions during roasting in coffee bean regions enriched in proteins, although polysaccharides are the major components of the coffee beans. The decrease of transglycosylation reactions in the presence of peptides/proteins can be related with the preferential reactivity of reducing residues with the amino groups of peptides/proteins by Maillard reaction, decreasing the number of reducing residues available to be directly involved in the transglycosylation reactions. In addition to the compounds already described, a diversity of other compounds were formed from model systems, namely dehydrated derivatives formed during dry thermal treatment. In conclusion, the identification of the structural modifications in coffee polysaccharides promoted by roasting pave the way to the understanding of the mechanisms of formation of melanoidins and structure-activity relationship of these compounds.

Kinetic investigation of the polymerization initiation process, predictive control of average molar mass and qualitative control of composition distributions, which can be controlled by selected feed of reagents into the reactor ('semi-batch' operation) obtained with appropriate computations, and phenomenon of counterion condensation accompanying charged polymers are investigated based on detailed kinetics obtained by Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP)
acase@tulane.edu

博士
國立陽明大學
生物醫學工程學系
104
The wear of ultra-high molecular weight polyethylene (UHMWPE) is a major cause for the failure of joint arthroplasty. It is well known that crosslink induced by gamma-ray irradiation can improve the wear resistance of UHMWPE. However, gamma-ray irradiation will also cause the formation of various types of free radicals. The reactions of these free dadicals can chang the mechanical properties of the materials and the residual radicals will affect its the long term stability. Therefore it is necessary to further study the dynamic reaction behavior of these free radicals. The reactivity of various type of free radicals are different. In this research, we establish a theoretical model to describe the EPR spectrum of a free radical by a specific set of EPR parameters. By using this model together with a Matlab program for the best-fit regression with the experimental EPR spectrum, one can obtain not only the overall free radical concentration but also the dynamic behavior of various free radical types in a sample. The effects of various crosslinking treatment parameters on the physical, chemical and mechanical properties of UHMWPE are also studied. The current EPR studies indicated that the overall free radicals decay behavior can be well described by a parallel 2nd order reaction model. The slow reaction with an activation energy of 12 ~ 14 kcal/mol and the fast reactions with an activation energy of 3 ~ 4 kcal/mol represent the reactions of free radical decay in the crystalline and amorphous regions, respectively. As for the free radical type analysis, it is found that there are mainly two types of free radicals, i.e. alkyl and allyl radical, observed for UHMWPE iraadiated by gamma-ray of 25-100 kGy in vacuum at 77 K. Both of these two types of radical exhibit slow and fast reactions. The results suggest that alkyl radicals appear in both of the crystalline and amorphous regions while allyl free radicals are most likely existing in the interfacial area of the crystalline and amorphous regions. The rate constant of slow and fast reaction are 10-25 ~ 10-22 (radical/g)-1 s-1 and 10-22 ~ 10-20 (radical/g)-1 s-1 for alkyl free radicals and 10-25 ~ 10-22 (radical/g)-1 s-1 and 10-22 ~ 10-21 (radical/g)-1 s-1 for allyl free radicals, respectively. By increasing the gamma-irradiation dose, more double bond will be formed. The alkyl free radicals will then be converted into allyl free radicals by reacting with these double bonds at higher temperature. The physic-chemical property examinations show that the oxidation index and crystallinity of a crosslinked UHMWPE rise substantially after reaching a critical period of aging time. We surmise that this longterm oxidation behavior was caused by residual alkyl radicals existed in the crystalline region for UHMWPE crosslinked at 403 K and by residual allyl free radicals for UHMWPE crosslinked at 423 K. The results of mechanical tests indicated that for crosslinking treatment at 423 K, the UHMWPE becomes soft and the friction coefficient increases with the increase of annealing time, suggesting that the frictional force might be increased due to the increase of real contact area. For UHMWPE irradiated by gamma-ray of 100 kGy and annealed at 403 K for 0 to 7 days, UHMWPE annealed for 2 hr exhibits the lowest wear factor. The current results can be applied in the development of a wear-resistant crosslinking precess for UHMWPE used in joint arthroplasty.

Free radicals play a critical role in the formation of tropospheric air pollution, but current condensed chemical mechanisms used in gridded photochemical models under-predict total radical concentrations. This dissertation evaluates three hypotheses regarding radical sources and sinks using environmental chamber data and ambient data from southeast Texas. The first hypothesis, that aromatics chemistry is under-represented as a radical source in condensed chemical mechanisms, was evaluated mainly by using environmental chamber simulations and in part by using ambient simulations. Results indicate that improved characterization of aromatics chemistry in condensed chemical mechanisms will lead to more rapid and extensive free radical formation. The second hypothesis, that alkene reactions are under-represented as a radical source in condensed chemical mechanisms, was also evaluated using chamber data and TexAQS-2000 data. Results indicate that the methods used in mechanism condensation lead to lower estimates of free radical production than detailed, compound specific models. The third hypothesis, chlorine emissions and chemistry as a radical source, was also evaluated in a series of sensitivity analyses with various levels of molecular chlorine emissions. Results imply that incorporating chlorine chemistry in condensed chemical mechanisms is expected to lead to more accurate modeling of OH, HO₂ and O₃, particularly for the southeast Texas region where relatively large chlorine emissions occur from various anthropogenic sources of molecular chlorine. The relative magnitudes of these radical sources (aromatics, alkenes, and molecular chlorine) in southeast Texas were also compared using box modeling with TexAQS-2000 data. Results indicate that the relative importance of these three types of radical sources depends on the strengths of their corresponding emissions.
text

碩士
國立陽明大學
醫學工程研究所
94
The wear of ultra high molecular weight PE is the major cause for joint arthroplasty failure. Crosslinking process has been known for several years to improve wear resistance of UHMWPE. Irradiation causes both immediate and time dependent changes in the mechanical properties and there is considerable experimental evidence that the time dependent effects arise from the presence of long lived free radicals. Therefore, it is necessary to further discuss the reaction kinetics of different free radicals. There are many parameters in each type free radical. In order to understand the change of each type of free radical, the variations of parameters must be known. This study analyze the parameters of free radical by program. The effects of crosslinking process on the physico-chemical properties of UHMWPE are also studied. The program analysis indicates that after gamma irradiation, the parameters describing alkyl radical is stable. While at low temperature (273K, 298K), there might exists asymmetric free radicals which lead to center shift of allyl and polyenyl radicals. At high temperature (353K, 383K), allyl radical transform into dienyl and trienyl radicals, and, then, into polyenyl radical. Therefore, it maybe need to add other free radicals to help understanding the reaction kinetics of free radicals thoroughly. As for the crosslinking treatment, the oxidation index and crystallinity rise substantially after reaching a critical period of time. At high temperature, free radicals tend to form double bond. In the mean time, the oxidation of the material will cause chain scission. After Gamma ray irradiation, UHMWPE contracts. When UHMWPE is further annealed at 1500C, the size is changed eminently. As for the crosslinking treatment UHMWPE becomes soft and contact area goes up, which leads to the increase of friction coefficient. When UHMWPE is annealed at 1500C for 0 to 7 days, the friction coefficient of samples annealed for 7 days is the highest.

Copper-catalyzed regeneration in atom transfer radical addition (ATRA) utilizes reducing agents, which continuously regenerate the activator (CuI) from the deactivator (CuII) species. This technique was originally found for mechanistically similar atom transfer radical polymerization (ATRP) and its application in ATRA and ATRC has allowed significant reduction of catalyst loadings to ppm amounts. In order to broaden the synthetic utility of in situ catalyst regeneration technique, this was applied in copper-catalyzed atom transfer radical cascade reaction in the presence of free radical diazo initiators such as 2,2’-azobis(isobutyronitrile) (AIBN) and (2,2’-azobis(4-methoxy-2,4-dimethyl valeronitrile) (V-70), which is the first part of this dissertation. This methodology can be translated to sequential ATRA/ATRC reaction, in which the addition of CCl4 to 1,6-dienes results in the formation 5-hexenyl radical intermediate, which undergoes expedient 1,5-ring closure in the exo- mode to form 1,2-disubstituted cyclopentanes. When [CuII(TPMA)Cl][Cl] complex was used in conjunction with AIBN at 60 0C, cyclic products derived from the addition of CCl4 to 16-heptadiene, diallyl ether and N,N­-diallyl-2,2,2-trifluoroacetamide were synthesized in nearly quantitative yields using as low as 0.02 mol% of the catalyst (relative to 1,6-diene). Even more impressive were the results obtained utilizing tert­-butyl-N,N-diallylcarbamate and diallyl malonate using only 0.01 mol% of the catalyst. Cyclization was also found to be efficient at ambient temperature when V-70 was used as the radical initiator. High product yields (>80%) were obtained for mixtures having catalyst concentrations between 0.02 and 0.1 mol%. Similar strategy was also conducted utilizing unsymmetrical 1,6-diene esters. It was found out that dialkyl substituted substrates (dimethyl-2-propenyl acrylate and ethylmethyl-2-propenyl acrylate) underwent 5-exocyclization producing halogenated g-lactones after the addition of CCl4 in the presence of 0.2 mol% of [CuII(TPMA)Cl][Cl]. Based on calculations using density functional theory (DFT) and natural bond order (NBO) analysis, cyclization of 1,6-diene esters was governed by streoelectronic factors. <br>As a part of broadening the synthetic usefulness of in situ copper(I) regeneration, scope was further extended to sequential organic transformations. Based on previous studies, copper(I) catalyzed [3+2] azide-alkyne cycloaddition is commonly conducted via in situ reduction of CuII to CuI species by sodium ascorbate or ascorbic acid. At the same time, ATRA reactions have been reported to proceed efficiently via in situ reduction of CuII complex to the activator species or CuI complex has been fulfilled in the presence of ascorbic acid. Since the aforementioned reactions share similar catalyst in the form of copper(I), a logical step was taken in performing these reactions in one-pot sequential manner. Reactions involving azidopropyl methacrylate and 1-(azidomethyl)-4-vinylbenzene in the presence of a variety of alkynes and alkyl halides, catalyzed by as low as 0.5 mol-% of [CuII(TPMA)X][X] (X=Br-, Cl-) complex, proceeded efficiently to yield highly functionalized (poly)halogenated esters and aryl compounds containing triazolyl group in almost quantitative yields (>90%). Additional reactions that were carried out utilizing tri-, di- and monohalogenated alkyl halides in the ATRA step provided reasonable yields of functionalized trriazoles. A slightly different approach involving a ligand-free catalytic system (CuSO4 and ascorbic acid) in the first step followed by addition of the TPMA ligand in the second step was applied in the synthesis of polyhalogened polytriazoles. Sequential reactions involving vinylbenzyl azide, tripropargylamine and polyhalogenated methane (CCl4 and CBr4) provided the desired products in quantitative yield in the presence of 10 mol% of the catalyst. Modest yields of functionalized polytriazoles were obtained from the addition of less active tri- and dihalogenated alkyl halides utilizing the same catalyst loading. <br>The last part focuses on copper(I) complexes, which were used catalysts in cyclopropanation reaction. One class represented cationic copper(I)/2,2-bipyridine complexes with p-coordinated styrene [CuI(bpy)(p-CH2CHC6H5)][A] (A = CF3SO3- (1) and PF6- (2) and ClO4- (3). Structural data suggested that the axial coordination of the counterion in these complexes observed in the solid state weak to non-coordinating (2.4297(11) Å 1, 2.9846(12) Å 2, and 2.591(4) Å 3). When utilized in cyclopropanation, complexes 1-3 provided similar product distribution suggesting that counterions have negligible effect on catalytic activity. Furthermore, the rate of decomposition of EDA in the presence of styrene catalyzed by 3 (kobs=(7.7±0.32)´10-3 min-1) was slower than the rate observed for 1 (kobs=(1.4±0.041)´10-2 min-1) or 2 (kobs=(1.0±0.025)´10-2 min-1). On the other hand, tetrahedral copper(I) complexes with bipyridine and phenanthroline based ligands have been reported to have strongly coordinated tetraphenylborate anions. CuI(bpy)(BPh4), CuI(phen)(BPh4) and CuI(3,4,7,8-Me4phen)(BPh4) complexes are the first examples in which BPh4- counterion chelates a transition metal center in bidentate fashion through h2 p-interactions with two of its phenyl rings. The product distribution revealed that the mole percent of trans and cis cyclopropanes were very similar. The observed rate constants (kobs) shown in for decomposition of EDA in the presence of externally added styrene were determined to be kobs=(1.5±0.12)´10-3 min-1, (6.8±0.30)´10-3 min-1 and (5.1±0.19)´10-3 min-1.
Bayer School of Natural and Environmental Sciences
Chemistry and Biochemistry
PhD
Dissertation

碩士
中國文化大學
化學系應用化學碩士班
103
Abstract We calculated the RCNN (R = H, F, CI, Br, CN, NH2, CH3) radical reacted with NO molecule via Gaussian 03 program. All of the reactants, intermediates, transition states and products have also been optimized at B3LYP/6-311++G (3df, 2p) level. In our study, we found three important reaction pathway, Channel A : R  IM1  TS1  IM4  TS4  P1, Channel B : R  IM2  TS2  P2, and Channel C : R  IM3  TS3  P2, respectively. The result shown the major reaction pathways are the Channel A and Channel C. In the Channel A and C, the rate-determining step is the process of the IM4 transferring to TS4 and the process of the IM3 transferring to TS3, respectively. The furthermore, the calculated result also shown the electron donating group could decrease the energy barrier, and the CH3 group is better than others. The electron-withdrawing group would be enhance the energy barriers, and the functional group of fluorine is more strong than others.

碩士
國立陽明大學
醫學工程研究所
92
The wear of ultra high molecular weight polyethylene (UHMWPE) is the major cause for joint arthroplasty failure. Many studies have shown that γ-ray sterilization process before implication is the major factor to change the mechanical properties, generation of wear debris and aging behavior of UHMWPE. Crosslinking process has been well-known to improve wear resistance of UHMWPE. However, accompanied with crosslinking process, the mechanical properties of polymer, such as yield strength and anti-fatigue property, will decrease. Therefore, it becomes a crucial issue to fully understand the interaction betweenγ-ray irradiation and material properties in crosslinking process. This study detects the free radical decay curves by Electron Spin Resonance (EPR) method and measures the crosslinking density of the γ-ray irradiated UHMWPE to study the free radical generation, crosslinking mechanism of the material. Theoretical dynamic analysis indicates that the free radical decay in vacuum can be described by a modified second order reaction. The present research also indicates that these are two reaction rate constants for the reaction of free radical decay. To describe this feature, we propose a parallel second order reaction model to simulate the dynamic behavior of the free radical decay. The results show that the present parallel model can appropriately describe free radical decay behaviors of Gamma irradiated UHMWPE in vacuum. By analyzing EPR spectrums, we find the free radical decay is dominted by different reaction mechanisms involving the double bond formation and crosslinking in different conditions. Crosslinking density tests reveal that higher dose and temperature during irradiation increases crosslinking density, while, decreases crosslinking ratio. By increasing reaction time, both crosslinking density and crosslinking ratio increased. It reveals that UHMWPE treated by general crosslinking process cannot maintain a long-term stability during the subsequently aging process, and the mechanical properties might be changed by oxidation reaction.

碩士
國立陽明大學
醫學工程研究所
97
The wear of UHMWPE is the major cause for the failure of joint artheroplasty. It is known that the oxidation accelerated by residual free radicals induced by gamma irradiation is the main cause for the increase of wear rate. In this work, EPR and FTIR spectroscopy were applied to study the formation and the subsequent reactions of the free radical induced by gamma irradiation for Polyethylene materials with various crystallinity. Theoretical analysis on the dynamic curves of free radical decay obtained by EPR measurements suggests that the reaction kinetics of free radical decay in vacuum or in air for the gamma irradiated PE with different degree of crystallinity can be well described by a parallel second order model proposed in our lab. It also showed that regardless to its crystallinity, the absolute concentrations of various types of free radical all decrease with time. The decay rate increases with the increase of temperature. Also, the percentages of different type of free radicals gradually reach to a constant level. For both of the UHMWPE and HDPE materials, the final equilibrium concentration ratio of the free radicals with unsaturated C=C to radicals without unsaturated C=C, i.e. [allyl+polyenyl radical]/[alkyl radical]3, is higher for PE with higher crystallinity before gamma irradiation. The results of FTIR spectroscopy reveal that after annealing , the residue level of various C=C in order is: trans-vinylene > vinyl > vinyldene > trans-trans-vinylene. Among them, the concentrations of vinyldene and trans-trans- vinylene in GUR1020 (Quench) , GUR1020 and HDPE show no apparent changes with the changes of annealing/aging time and annealing/aging temperature. The formation of trans-vinylene seems to be mainly dominated by gamma ray irradiation and not transformed from the C=C present in the virgin materials. Compared to the other types of C=C, trans-vinylene is rather unstable during the annealing and aging process. The results obtained herein can be implemented to design a cross-linking process which is able to avoid the formation of long-life residue free radical and to ensure better long- term stability.

碩士
國立交通大學
應用化學系碩博士班
107
The first part: Compounds containing heteroatoms are the most prominent entities in commercially available drugs that are sold in large quantities.Among all heteroatom molecules, benzimidazole,benzoselenazole, guanidine and pyrrole are considered to be the privileged core of drug and drug discovery.In particular, these biologically important heterocyclic fused/linked heterocyclic molecules are considered to be well known scaffolds in medical and drug discovery research. Therefore, the synthesis of fused and linked heterocyclic molecules must be taken care of this paper deals with the design and synthesis of biologically interesting fused and linked heterocycles.A catalyst-controlled chemical reaction cyclization strategy was reported to obtain diazepam [1,7-a] fluorene and hydrazine from the reaction of the readily available ortho-anisidine and diazonium ester as coupling partners.And [1,2-a] quinoxaline.Under Rh(III) catalyst, the reaction is carried out by amine-assisted C2-H activation followed by amidation to obtain diazepam [1,7-a]pyrene in a highly selective manner.Under the Ru(II) catalyst, the reaction involves the formation of a Ru-carbene complex, followed by a metal-olefin reaction and a β-hydrogen removal reaction, and finally the insertion of the -NH2 group and the cascade cyclization to obtain a ruthenium. Indole [1,2-a] quinoxaline.This newly developed catalyst control strategy is broadly applicable to the construction of a series of very high yields of ruthenium diazide/quinoxaline and pyrrole fused diazapest/quinoxaline scaffolds.We believe this approach opens up new avenues in the fields of catalysis and organic synthesis. The second part: We have successfully developed a regioselective method for the synthesis of isoquinoline [1,2-a]isoquinolines.First of all, the tetrahydroisoquinoline skeleton is synthesized by a Pictet-Spengler reaction, and then reacted with allyl bromide to carry out cyclization and rearrangement of a six-membered ring in the presence of a monovalent gold catalyst.The process of this cascade involves a metal catalyzed cyclization reaction and a process in which the allyl group migrates from the nitrogen atom to ethylene. The third part: In order to obtain the biologically active 2-thiohydantoin ring (B), we perform the Pictet-Spengler reaction by radical to form a tetrahydroisoquinoline skeleton compound having antibacterial and antitumor activity, and then it will react with isothiocyanate, a biologically active heterocyclic small molecule structure is obtained.