Orientador: Marcos Nogueira Eberlin / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-14T13:08:08Z (GMT). No. of bitstreams: 1 Corilo_YuriEberlimde_M.pdf: 973329 bytes, checksum: 0e8a6362dd2a94d8ce4185376aa8bde3 (MD5) Previous issue date: 2009 / Resumo: A técnica de ionização a pressão atmosférica por electrospray (ESI) se tornou rapidamente a mais utilizada nas áreas de química e bioquímica, em estudos mecanísticos e em análises por ¿fingerprinting¿. ESI é versátil devido a sua alta sensibilidade e capacidade de transferir espécies iônicas da solução para a fase gasosa de forma branda, permitindo inclusive que espécies de alto peso molecular fracamente ligadas permaneçam intactas. Entre os líquidos iônicos (LI) já conhecidos, destacam-se os compostos heterocíclicos da classe dos cátions imidazólios. A espectrometria de massas não era capaz de detectar e analisar essa classe de compostos devido à baixa volatilidade que estes LI apresentam. Entretanto, com o desenvolvimento da técnica de ESI tornou-se possível à transferência desses compostos para a fase gasosa de uma forma bastante branda e eficaz. Estas espécies, podem ser detectadas por espectrometria de massas mesmo sofrendo modificações como fragmentações, rearranjos e reações, pelo fato de um ou dois anéis imidazóis funcionarem como uma ¿âncora¿ de carga, permitindo o estudo de propriedades intrínsecas destes compostos, como reatividade bimolecular. Através de experimentos com ESI em tandem (ESI-pseudo-MS, e ESIMS/ MS) utilizando a técnica de dissociação induzida por colisão (CID), foi possível formar, selecionar e identificar várias novas espécies de carbenos e radicais com sítios afastados de cargas múltiplas e arinos imidazólios / Abstract: The ionization technique, atmospheric pressure electrospray (ESI) has become rapidly the most used in the fields of chemistry and biochemistry, mechanistic studies and in analysis by fingerprint. ESI is versatile due to its high sensibility and capability to transfer ionic species from the solution to the gas phase in a soft way, allowing, inclusively, that species of high molecular weight weakly bonded remain intact. Among the ionic liquids (IL¿s) known, heterocyclic imidazolium cations stand out. Mass spectrometry was not able to detect and analyze this class of compounds due to the low volatility of these compounds. However, with the development of the ESI technique has become possible the transfer of these compounds to the gas phase. These species may be detected by mass spectrometry even when they suffer modifications such as fragmentations, rearrangements or other reactions, due to the fact that one or two imidazolium rings work as a charge ¿anchor¿, allowing the study of intrinsic proprieties of these compounds, such as bimolecular reactivity. Through tandem ESI experiments (ESI-psedo-MS, and ESI-MS/MS) using the collision induced dissociation (CID) technique, it was possible to form, select and identify several new species of multiply charged carbenes, radicals and arynes / Mestrado / Quimica Organica / Mestre em Química

Large chemical reaction networks often exhibit distinctive features that can be interpreted as higher-level structures. Prime examples are metabolic pathways in a biochemical context. We review mathematical approaches that exploit the stoichiometric structure, which can be seen as a particular directed hypergraph, to derive an algebraic picture of chemical organizations. We then give an alternative interpretation in terms of set-valued set functions that encapsulate the production rules of the individual reactions. From the mathematical point of view, these functions define generalized topological spaces on the set of chemical species. We show that organization-theoretic concepts also appear in a natural way in the topological language. This abstract representation in turn suggests the exploration of the chemical meaning of well-established topological concepts. As an example, we consider connectedness in some detail.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24634号 / 工博第5140号 / 新制||工||1982(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 佐藤 啓文, 教授 佐藤 徹, 教授 松田 建児 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Yes / The production of a number of methyl esters such as methyl decanoate (MeDC), methyl salicylate (MeSC), and methyl benzoate (MeBZ) by esterification reactions of several carboxylic acids such as decanoic acid (DeC), salicylic acid (ScA), and benzoic acid (BeZ) with methanol, respectively, through a reactive distillation system (batch or continuous) is cost-intensive and operationally challenging operation. It is difficult to keep the reaction species together in the reaction section due to wide boiling point differences between the reactants. Methanol (in those esterification processes) having the lowest boiling temperature in the reaction mixture can separate easily from carboxylic acid as the distillation progresses, resulting in a severe drop in the reaction conversion ratio of the acid employing batch/continuous distillation system. In order to overcome this type of challenge and to increase the overall reaction conversion, a novel split-reflux conventional batch reactive distillation configuration (sr-BRD) is proposed/studied in detail in this investigation. The optimal performance of BRD/ sr-BRD column is determined in terms of maximum achievable conversion of acids, and highest concentration of the esters produced for each chemical reaction scheme. The results for given separation tasks are compared with those obtained using conventional batch distillation (BRD) process. The optimization results clearly show that the sr-BRD process significantly improves the process efficiency, the conversion ratio of acid, and the product purity of methyl esters compared to that obtained via the BRD process.

<p><br></p><p dir="ltr">Algorithmic reaction explorations based on transition state searches can now routinely predict relatively short reaction sequences involving small molecules across a variety of chemical domains, including materials degradation, combustion chemistry, battery performance, and biomass conversion. Mature quantum chemistry tools can comprehensively characterize the reactivity of species with efficiency and broad coverage, but consecutive characterizations quickly encounter prohibitive costs of reactant proliferation, spurious characterization of irrelevant intermediates, and compounding uncertainties of quantum chemical calculations deep in a network. Application of these algorithms to deeper chemical reaction network (CRN) exploration still requires the development of more effective, comprehensive, and automated exploration policies. </p><p><br></p><p dir="ltr">This dissertation addresses the challenge of exploring deep chemical reaction networks (CRNs) in complex and chemically diverse systems by introducing Yet Another Kinetic Strategy (YAKS), an automated algorithm designed to minimize the computational costs of deep exploration and maximize coverage of important reaction channels. YAKS demonstrates that microkinetic simulations of the nascent network are cost-effective and able to iteratively build deep networks. Key features of the algorithm are the automatic incorporation of expanded elementary reaction steps, compatibility with short-lived but kinetically important species, and the incorporation of rate uncertainty into the exploration policy. The automatically induced expansion of reaction mechanisms gives YAKS access to important chemistries that other algorithms ignore, while also maintaining the ability to limit expensive forays into kinetically irrelevant regions of the CRN that would stymie previous methods. Instead of conducting a greedy exploration, YAKS biases network topography to probe beyond short-lived but kinetically important species, which enables YAKS to explore important endergonic reactions deep into the CRN. YAKS further induces rate uncertainty into an ensemble of microkinetic simulations, which positively influences intermediate prioritization deep in a network. </p><p><br></p><p dir="ltr">Algorithm effectiveness was validated in a case study of glucose pyrolysis, where the algorithm rediscovers reaction pathways previously discovered by heuristic exploration policies and also elucidates new reaction pathways to experimentally obtained products. The resulting CRN is the first to connect all major experimental pyrolysis products to glucose. Additional case studies are presented that investigate the role of reaction rules, rate uncertainty, and bimolecular reactions. These case studies show that na\"ive exponential growth estimates can vastly overestimate the actual number of kinetically relevant pathways in physical reaction networks. The excellent performance of YAKS demonstrates the ability of automated algorithmic methods to address the gaps outlined above.</p><p><br></p><p dir="ltr">The power of YAKS was then demonstrated on radically distinct chemistry from the validation study, chemical warfare agents (CWAs). Despite the almost uniform ban on the use of chemical agents and the widespread neutralization of stockpiles due to treaties, CWAs continue to pose a grave threat around the world. Rogue states, terrorist organizations, and lone wolf terrorists have all conducted CWA attacks within the past few decades. These circumstances make it necessary to prepare against and forensically evaluate the use of CWAs without direct experimentation. YAKS was applied to elucidate degradation reaction networks of three prominent CWAs, mustard gas (SM, HD), sarin (GB), and VX, and identified a range of possible degradant products of real world use cases. This dissertation also computationally interpreted the most common mechanism of action (MoA) associated with each CWA and examined their hydrolysis networks as a method to neutralize these agents. Additionally, agent stability was evaluated during extended microkinetic modeling in arid and humid scenarios, highlighting the potential for computational simulation approaches to fill a capability gap in the broader field of chemical defense. </p><p><br></p><p dir="ltr">This dissertation advanced automated CRN exploration, but considerable gaps remain. Future research directions include the accuracy gaps of both density functional theory and conformational sampling on energy calculations. Incorporation of machine learning (ML) methods can accelerate the costly reactivity characterization process, but ML models still require vast amounts of data. A recently released dataset comprehensively explored over 175,000 graphically defined reactions of moderately-sized C, H, O, and N containing molecules. While models trained on such data could readily be applied to glucose pyrolysis systems, chemical agents involve a much wider array of chemistry including Cl, S, P, and considerable quantities of radical and charged species. More comprehensive datasets are required to train a general ML model capable of accelerating geometry or energy calculations. Additionally, microkinetic modeling is hindered by software implementations that are unable to explore diverse chemistry such as multiphase reactions. In light of this, further improvements in exploration policies, reaction prediction algorithms, and simulation software make it feasible that CRNs might soon be routinely predictable in many additional contexts.</p>

Notre contribution porte sur les processus de conceptualisation et de modélisation de la matière et de ses transformations en chimie. Elle s'articule autour de deux parties. Une première partie consistant en une analyse du type sémioépistémologique de ce processus pendant la période fin XVIIIe - début XIXe siècles. Nous mobilisons pour cela la théorie sémiotique de C.S. Peirce comme cadre d'analyse. Elle a permis de resituer l'expérimental de la chimie comme étant un ensemble de signes qui prolonge le théorique en même temps qu'il le fonde. Le signe iconique loin d'être signe d'une pensée primitive apparait comme une véritable néo écriture, un instrument heuristique privilégié utilisé par les chimistes pour sonder la matière à la recherche d'indices sur une structure pouvant rendre compte de son comportement, il leur a permis, après de nombreuses controverses, d'aboutir à une structure particulaire, et de construire les concepts d'atome, la molécule et son atomicité. Une deuxième partie où l'analyse sémio-épistémologique a constitué notre cadre théorique pour une transposition didactique de ce contexte. Notre question de recherche est de savoir si le signe iconique, comme défini au sens peircien, peut être mobilisé de manière spontanée par les élèves de 13-15 ans pour construire un raisonnement en chimie, et s'il peut les aider à accéder à l'infiniment petit sur la base de ce contexte transposé ? Nous avons alors élaboré un corpus de 20 séquences d'enseignement engageant les élèves dans une démarche qui nécessite la construction de modèles évolutifs. Nos résultats permettent de dire que le signe iconique loin d'être un moyen pédagogique de transmission facilité, un auxiliaire didactique est au contraire un instrument heuristique privilégié dans la construction des connaissances par les élèves, comme il l'est chez le chimiste / Our contribution focuses on the process of conceptualization and modeling of matter and its transformations in chemistry. It consists of two parts. A first part consisting of an analysis of the semio-epistemological type of this process during the late 18th - early 19th centuries. We mobilize for this semiotic theory of C.S. Peirce as a framework for analysis. It allowed to relocate the experimental chemistry as being a set of signs that extends the theoretical at the same time that he founded. The iconic sign far from signs of a primitive thought appears as a true neo writing, a privileged heuristic instrument used by chemists to probe the matter for clues on a structure that can make account of his behavior, he allowed them, after much controversy, lead to a particulate structure, and build the concepts of atom, the molecule and its atomicity. A second part where the semio-epistemological analysis was our theoretical framework for a didactic transposition of this context. Our research question is to know if the sign iconic, as defined in the peircien sense, can be mobilized spontaneously by students from ages 13-15 to build reasoning in chemistry, and if he can help in accessing the infinitely small on the basis of this converted context? We then developed a corpus of 20 sequences of teaching engaging students in a process that requires the construction of evolutionary models. Our results to say that the iconic sign far from a pedagogical means of transmission facilitated, a teaching assistant is instead a heuristic instrument in the construction of knowledge by students, as it is at the chemist

We report here the development of very efficient sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), to accelerate the rate of nucleophilic substitution reactions involving poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. Indeed NALGs have shown exceptional ability in improving rate of nucleophilic substitution reactions. New very mild stereoretentive halogenations and azidation reactions have also been developed for secondary cyclic alcohols using NALGs involving titanium(IV) reagents. This reaction is particularly significant since the carbon-halogen bond is found widely in natural products and is used extensively as a synthesis intermediate. Azide is also a synthetically important functional group from which a variety of biologically important functional groups are conveniently obtained. Though stereoretentive chlorination and bromination reactions are known, we have developed, for the first time, a stereoretentive azidation reaction using titanium(IV) azide, a reagent not previously used in organic synthesis. During our development of stereoretentive reactions, we eventually developed very efficient, mild, two-step one-pot stereoretentive halogenations (chlorination and bromination) using titanium(IV) halides as catalysts or stoichiometric reagents. These reactions were found to be particularly efficient for cyclic alcohols. An efficient one pot stereoretentive amidation reaction for secondary cyclic alcohols is also reported. The important features of this reaction are that, for the first time, chlorosulfite (prepared in situ from alcohol using thionylchloride) has been used as a leaving group and titanium(IV) fluoride as an activator. / Utilization of those two reagents is unique as thionylchloride has never been used for nucleophilic substitution reactions except in chlorination procedures. In addition, this work has found new and creative applications for titanium (IV) fluoride, a reactant rarely used in organic synthesis. Further exploiting the unique reactivity of titanium(IV), reactions of alkenes with various nucleophiles have been developed with this reagent in both catalytic and stoichiometric quantities. It was observed that a-substituted aromatic conjugated alkenes dimerize to generate important indan class of compounds which are very important in the polymer industry. In addition, non conjugated unactivated alkenes react with various nucleophiles to yield the adduct. / by Deboprosad Mondal. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

We report here the development of very efficient aryl- and quinolinyl- sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), which substantially accelerate the rate of nucleophilic substitution reactions with metal halides. Detailed synthesis and kinetics study are described herein. Our synthesized NALGs have shown great reactivity towards poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. The abundant existence of halide, azide and amine in natural products demands new synthetic pathway. To fulfill this requirement, new mild stereoretentive halogenations (chlorination, bromination and iodination) reactions have also been developed for secondary cyclic alcohols using NALGs involving titanium (IV) reagents. The novel methodology can be extended to Azidation reactions as well with titanium (IV) azide, in which Ti (N3)4 is the first time being engaged in organic synthesis. Beased on the NALGs theory we discover the chlorosulfite can be a simplest NALG and applied as the intermediate in mild one-pot stereoretentive halogenations (chlorination and bromination) using titanium (IV) halides as catalysts or stoichiometric reagents. These reactions were found to be particularly efficient for cyclic alcohols. Finally, an efficient mild bromination and iodination reaction for primary and secondary alcohols with Grignard reagents is also reported. This reaction exhibits the generality with substrates with various leaving groups. The important features of this reaction are that, for the first time, bromide formation using Grignard reagents without the Cu (I) catalysts. / by Songye Li. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

La théorie de la dynamique des processus chimiques élementaires cherche à décrire quantitativement les collisions réactives à l'échelle atomique. Les mouvements des noyaux étant extrêmement difficiles à traiter dans le formalisme quantique, les tomes sont souvent considérés comme des objets classiques. Cepandant, les effets purement quantiques jouent un rôle majeur dans certaines situations, alors que la description classique les néglige. Cette thèse apporte de nouvelles perspectives sur l'inclusion, dans le formalisme clasique, de forts effets quantiques, à savoir la quantification des mouvements internes des réactifs et produits. / The goal of chemical reaction dynamics theory is the quantitative description of reactive molecular collistions at the atomic scale. Since nuclear motions are difficult to study quantum mechanically, nuclei are often considered as classical object. However, quantum effects may play a major role in some situation, and the standard classical description does not take them into account. This thesis brings new perspectives on the inclusion into the classical treatment of one of the strongest qunatum effects, the quantization of reagents and products.

"December 2004" / Includes bibliographical references. / 2 v. (various pagings) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Sc.)--University of Adelaide, School of Chemistry and Physics, Discipline of Chemistry, 2005