Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 53-01, Section: B, page: 0308. Supervisor: John Warkentin.

Orientador: Liliane Maria Ferrareso Lona / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T01:46:35Z (GMT). No. of bitstreams: 1 Malere_CarolinePaganuccidosReis_M.pdf: 1568071 bytes, checksum: 720e59aec25863d529bde7e649b7ece7 (MD5) Previous issue date: 2011 / Resumo: A Cromatografia de Permeação em Gel ou "Gel Permeation Chromatography (GPC), também conhecida como Cromatografia de Exclusão por Tamanho ou "Size Exclusion Chromatography" (SEC) é uma das técnicas analíticas mais utilizadas para separação e caracterização de polímeros naturais e sintéticos, copolímeros e proteínas, fornecendo informações distribuição de massa molar (MWD), viscosidade intrínseca (IV) e polidispersividade (PDI). A importância de sua resposta na análise de determinado polímero se reflete em termos de sua processabilidade, uma vez que as propriedades mecânicas e químicas são drasticamente afetadas por sua massa molar média, tamanho da cadeia e distribuição. Na técnica de GPC os padrões utilizados são de primordial importância para obtenção de resultados confiáveis, pois são utilizados nas construções de curvas de calibrações necessárias para aquisição dos resultados quanti e qualitativos na técnica. Apesar da vasta utilização da técnica de GPC no Brasil, tanto em centros de pesquisa como em indústrias químicas e petroquímicas, os padrões disponíveis para comercialização são todos adquiridos no exterior, por meio de importação a altos custos. Visto a necessidade de mudança desse paradigma, este trabalho tem como objetivo desenvolver um produto nacional utilizando a polimerização via radical livre mediada por radicais nitróxidos (NMRP), também chamada "living free radical polymerization (LFRP)". O padrão escolhido para o estudo foi o poliestireno (PS), por ser ele um dos padrões mais utilizados na calibração de análise de GPC orgânico. Um dos desafios enfrentados neste trabalho foi a obtenção de polímeros com índices de polidispersividade (PDI) variando de 1 a 1,10, distribuição de massa molar (MWD) estreita e alto grau de pureza, utilizando pela primeira vez uma mistura de iniciadores no processo NMRP. A NMRP é uma técnica robusta e inovadora comparada com a polimerização iônica que é atualmente o processo empregado para obtenção de polímeros com valores de PDI muito baixos. O processo NMRP possui vantagens frente à polimerização iônica para produção de polímeros com estrutura controlada, pois nele não são necessários etapas de purificações complexas, sendo que as reações requerem menos condições estritas em relação a impurezas e temperaturas de trabalho. Este é um processo simples e barato, na qual as reações podem ser realizadas em ampolas de vidros / Abstract: Gel Permeation Chromatography, also known as Size Exclusion Chromatography, is the most employed technique to characterize macromolecules such as proteins, copolymers, natural and synthetic polymers. It provides information such as molecular weight distribution (MWD), intrinsic viscosity (IV) and polydispersity (PDI). The importance of its response reflects in terms of polymer processability once the mechanic and chemicals properties are drastically affected by the polymer average molecular weight, chain size and distribution. The standards in the GPC technique have a great importance to obtain reliable results because they are employed in calibration curves needed to acquire the quantitative and qualitative data. Despite the wide use of GPC in Brazil at research centers, chemical and petrochemical industries, all the standards available are obtained outside the country through high importation costs. To change this paradigm, this work aims to develop a national product using the pseudo-living radical polymerization or living free radical polymerization (LFRP), which is a robust and innovative technique in the polymerization science area. The standard chosen was the polystyrene, which is the most used polymer in calibration curves of organic GPC analysis. Our challenge in this work was to obtain a controlled structure polymer with polydispersity index (PDI) between 1 and 1.10, narrow molecular weight distribution (MWD) and high purity degree, using to the best of our knowledge for the first time a mixture of initiators in a NMRP process. The NMRP is a robust and innovative technique compared with the ionic polymerization that is the currently employed process to obtain polymers with very low PDI. The advantages of NMRP process over ionic polymerization to produce controlled structure polymers are that no complicated purification steps are needed, controlled radical reactions require less stringent conditions for impurities and working temperatures, it is a simple and cheaper process, where the reactions can be carried out into glass ampoules / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

The chemical evolution with respect to time of complex macroscopic mixtures such as interstellar clouds and Titan’s atmosphere is governed via a mutual competition between thousands of simultaneous processes, including thousands of chemical reactions. Chemical kinetic modeling, which attempts to understand their macroscopic observables as well as their overall reaction mechanism through a detailed understanding of their microscopic reactions and processes, thus require thousands of rate coefficients and product distributions. At present, however, just a small fraction of these have been well-studied and measured; in addition, at the relevant low temperatures, such information becomes even more scarce. Due to the recent developments in both theoretical kinetics as well as in ab initio electronic structure calculations, it is now possible to predict accurate reaction rate coefficients and product distributions from first-principles at various temperatures, often in less time, than through the running of an experiment. Here, the results of a first principles theoretical investigation into both the reaction rate coefficients as well as the final product distributions for the reactions between the ground state CH radical (X2Π) and various C1-C3 hydrocarbons is presented; together, these constitute a set of reactions important to modeling efforts relevant to mixtures such as interstellar clouds and Titan’s atmosphere.

Free radicals are produced in lignin during mechanical treatment and irradiation with light of various wavelengths. During mechanical treatment, the lignin macromolecule is degraded severely as revealed by ESR and viscosity measurements. Several types of mechano-radicals are produced in lignin during the mechanical process. Among these the phenoxy radicals are rather stable, where carbon-radicals are labile at ambient conditions. Transient mechano-radicals reacted readily with oxygen molecules to produce peroxy radicals even at 77°K, but they decayed rapidly at ambient temperature. Photodegradation of lignin was observed when macromolecule was irradiated with light of λ<3500 Å as revealed by ESR, viscosity, and weight loss. Phenoxy radicals are the predominant intermediates in the photoirradiated lignin as shown by ESR studies. Elimination of side chains of lignin phenyl propane units took effect in α-carbonyl group bearing molecules. By contrast, β aryl ether substituents adjacent to α-carbonyl groups caused ether cleavage under identical conditions of photoirradiation. This is attributed to energy transferred from excited α-carbonyl groups to the ether bonds. The α-carbonyl groups also functioned as photosensitizers accelerating photochemical reactions of lignin. Termination and decomposition reactions of mechano-radicals and photoinduced free radicals in lignin ultimately lead to the formation of para- and ortho-quinones, carbonyl groups, and double bonds which cause the color of lignin. These potential choromophoric groups can be partially removed from lignin by using ultraviolet light of λ> 4000 Å; and they can be completely removed by irradiation of lignin in the presence of dioxane-water with light of λ>3500 Å. Experimental findings suggest chat chromophoric groups in lignin were being trapped or blocked by dioxanyl radicals resulting in brightening. However, the photoreduced lignin-adduct suffered color reversion. This adverse effect can be prevented by using 2-hydroxy-4-methoxy-benzophenone as a photostabilizer. The feasibility of applying photoreduction techniques to high- yield pulps was demonstrated. However, optimal experimental conditions for photoreduction of lignin in high-yield pulps have not been established yet. / Ph. D.

This work seeks to develop new solvents for environmentally benign chemical synthesis. Switchable solvents are a new class of compounds that change properties upon the application of some stimulus such as heat, UV light, or pH. We have developed the use of a new solvent, thiirane oxide, that has chemical properties similar to DMSO. Thiirane oxide, however, undergoes facile decomposition to two gases at temperatures above 100 C, which is much lower than the temperature required for removing DMSO. Thus we have a solvent with excellent solvation properties, but with a built-in switch for easier removal. However, thiirane oxide leaves behind sulfurous products which make the reverse reaction to reform the solvent unfeasible. We are also developing the use of another solvent, piperylene sulfone, which is expected to have good solvent properties, yet with decomposition products that can be reacted to reform the solvent. This thesis also details the work to date on piperylene sulfone. Gas-expanded liquids (GXLs) also show promise as a new reaction medium. In order to design solvent systems that take full advantage of this medium, we desire to understand the microstructure of these fluids. To that end, we are using cage reactions to probe solute-solvent and solvent-solvent interactions at the molecular level. This thesis discusses the current research on using cage reactions to probe the structure of GXLs.

Radical reactions play central roles in regulating regional air quality and global climate. Some potentially important gas phase radical reactions are being investigated in this research project, including Cl reactions with acetone, butanone, 3-pentanone, pyridine, and dimethyl selenide (DMSe), HO2 complex formation and dissociation with formic and acetic acids, and reactive and non-reactive quenching of O(1D) by the potent greenhouse gases SO2F2, NF3, and SF5CF3. The involved radicals are generated by laser flash photolysis (LFP). Temporal profiles of either the radical reactant or a product are monitored in "real time" using atomic resonance fluorescence spectroscopy (RF), time-resolved UV-visible absorption spectroscopy (TRUVVAS), or tunable diode laser absorption spectroscopy (TDLAS), allowing kinetic and mechanistic information of these reactions to be obtained. These studies provide new knowledge of the investigated radical reactions and facilitate a better understanding of their significance in atmospheric chemistry.

Made available in DSpace on 2014-06-11T19:25:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-01-15Bitstream added on 2014-06-13T18:26:25Z : No. of bitstreams: 1 almeida_mgj_me_arafcf_parcial.pdf: 82683 bytes, checksum: 49424d5182616aaa8e926f756efd65e1 (MD5) Bitstreams deleted on 2015-02-09T14:35:42Z: almeida_mgj_me_arafcf_parcial.pdf,Bitstream added on 2015-02-09T14:36:22Z : No. of bitstreams: 1 000710077.pdf: 903439 bytes, checksum: 7ad6ad625787ddd4aff6f1d6cad4169e (MD5) Bitstreams deleted on 2015-02-09T17:15:05Z: 000710077.pdf,Bitstream added on 2015-02-09T17:15:41Z : No. of bitstreams: 1 000710077.pdf: 903439 bytes, checksum: 7ad6ad625787ddd4aff6f1d6cad4169e (MD5) / A tendência atual na indústria cosmética é o desenvolvimento de produtos multifuncionais, ou seja, aqueles com capacidade de apresentar diferentes funções, possibilitando diferentes resultados para o consumidor. Seguindo esta tendência, ativos naturais são alternativas interessantes como substitutos a um único composto ativo, uma vez que são matrizes complexas e apresentam diversos componentes que podem possuir diferentes mecanismos de ação e, assim, conferir ao produto mais de uma função. Por este motivo, nos últimos anos o uso de extratos naturais tem crescido muito nesta área. Com o aumento da aplicação de extratos naturais em produtos cosméticos, há também a necessidade de estudos que comprovem sua eficácia e segurança. Uma das principais funções buscadas em produtos cosméticos é a ação antienvelhecimento, ou seja, a capacidade dos produtos em atuar neutralizando radicais livres. Neste contexto, o objetivo deste trabalho foi avaliar a eficácia e segurança do extrato de Ascophyllum nodosum, além de desenvolver um sistema emulsionado para sua incorporação e verificar a eficácia deste sistema. Os resultados de citotoxicidade mostraram que este extrato pode ser utilizado com segurança na concentração proposta (1,2% m/m). Além disso, foi avaliado, por metodologias in vitro, o potencial antioxidante e o potencial de inibir a atividade da tirosinase, sendo verificado que o extrato de A. nodosum apresenta a capacidade de atuar neutralizando radicais livres e inibindo a atividade enzimática da tirosinase no processo de melanogênese. Apesar de serem necessários estudos complementares para garantir a eficácia, o fitocosmético desenvolvido com o extrato aquoso de A. nodosum apresenta enorme potencial de aplicação podendo resultar em preparações cosméticas multifuncionais / The current trend in the cosmetic industry is the development of multifunctional products, or, those with the ability to have different functions, facilitating the results to the consumer. Following this trend, natural actives are interesting alternatives as substitutes for a single active compound, since they are complex matrices and present various components that may have different mechanisms of action and thereby give the product more than one function. For this reason, in recent years the use of natural extracts has grown a lot in this area. With the increased use of natural extracts in cosmetic products, there is also a need for studies to prove its effectiveness and safety. A major function is sought in cosmetic anti-aging action, for instance, the ability of the products act by neutralizing free radicals. In this context, the aim of this study was to evaluate the effectiveness and safety of the extract of Ascophyllum nodosum, and develop a system for incorporation emulsified and verify the effectiveness of this system. The results of cytotoxicity have shown that this extract can be safely used in the proposed concentration (1.2% w/w). Furthermore, it was evaluated by in vitro methods, the antioxidant potential and the potential to inhibit the activity of tyrosinase, and found that the extract of A. nodosum has the ability to act by neutralizing free radicals and inhibiting the enzymatic activity of tyrosinase in the process of melanogenesis. Although additional studies are needed to ensure effectiveness, phytocosmetic developed with aqueous extract of A. nodosum has enormous potential application may result in multifunctional cosmetic preparations

Orientador: Chung Man Chin / Coorientador: Vera Lucia Borges Isaac / Banca: Marcos Antônio Correa / Banca: Helena Margarida Ribeiro / Resumo: A tendência atual na indústria cosmética é o desenvolvimento de produtos multifuncionais, ou seja, aqueles com capacidade de apresentar diferentes funções, possibilitando diferentes resultados para o consumidor. Seguindo esta tendência, ativos naturais são alternativas interessantes como substitutos a um único composto ativo, uma vez que são matrizes complexas e apresentam diversos componentes que podem possuir diferentes mecanismos de ação e, assim, conferir ao produto mais de uma função. Por este motivo, nos últimos anos o uso de extratos naturais tem crescido muito nesta área. Com o aumento da aplicação de extratos naturais em produtos cosméticos, há também a necessidade de estudos que comprovem sua eficácia e segurança. Uma das principais funções buscadas em produtos cosméticos é a ação antienvelhecimento, ou seja, a capacidade dos produtos em atuar neutralizando radicais livres. Neste contexto, o objetivo deste trabalho foi avaliar a eficácia e segurança do extrato de Ascophyllum nodosum, além de desenvolver um sistema emulsionado para sua incorporação e verificar a eficácia deste sistema. Os resultados de citotoxicidade mostraram que este extrato pode ser utilizado com segurança na concentração proposta (1,2% m/m). Além disso, foi avaliado, por metodologias in vitro, o potencial antioxidante e o potencial de inibir a atividade da tirosinase, sendo verificado que o extrato de A. nodosum apresenta a capacidade de atuar neutralizando radicais livres e inibindo a atividade enzimática da tirosinase no processo de melanogênese. Apesar de serem necessários estudos complementares para garantir a eficácia, o fitocosmético desenvolvido com o extrato aquoso de A. nodosum apresenta enorme potencial de aplicação podendo resultar em preparações cosméticas multifuncionais / Abstract: The current trend in the cosmetic industry is the development of multifunctional products, or, those with the ability to have different functions, facilitating the results to the consumer. Following this trend, natural actives are interesting alternatives as substitutes for a single active compound, since they are complex matrices and present various components that may have different mechanisms of action and thereby give the product more than one function. For this reason, in recent years the use of natural extracts has grown a lot in this area. With the increased use of natural extracts in cosmetic products, there is also a need for studies to prove its effectiveness and safety. A major function is sought in cosmetic anti-aging action, for instance, the ability of the products act by neutralizing free radicals. In this context, the aim of this study was to evaluate the effectiveness and safety of the extract of Ascophyllum nodosum, and develop a system for incorporation emulsified and verify the effectiveness of this system. The results of cytotoxicity have shown that this extract can be safely used in the proposed concentration (1.2% w/w). Furthermore, it was evaluated by in vitro methods, the antioxidant potential and the potential to inhibit the activity of tyrosinase, and found that the extract of A. nodosum has the ability to act by neutralizing free radicals and inhibiting the enzymatic activity of tyrosinase in the process of melanogenesis. Although additional studies are needed to ensure effectiveness, phytocosmetic developed with aqueous extract of A. nodosum has enormous potential application may result in multifunctional cosmetic preparations / Mestre

This study extends the work we have previously done by reporting on both gas-phase and particulate phase PCB concentrations in Chicago air as well as giving a first report on airborne OH-PCBs in Chicago. Gas phase PCB concentrations ranged from 43.1 pg/m³ to 2250 pg/m³, with an average concentration of 594 pg/m³ ± 445 pg/m³, and exhibited strong temporal trends. Particulate phase PCBs accounted on average for 4.3% of total PCBs in a sample. OH-PCBs were detected in both the gas and particulate phase and exhibit characteristics of either emission sources or atmospheric reactions depending on the congener.

This thesis deals with single-electron transfer (SET) radical processes mediated by ferrocenium hexafluorophosphate and TEMPO and their application in the total synthesis of natural products. Asymmetric aminooxygenation methodology for the synthesis of anti-β-amino-α-hydroxy acid derivatives has been developed by utilizing a highly diastereoselective aza-Michael addition of chiral lithium amides to various α,β-unsaturated esters or amides/SET oxidation/radical α-oxygenation. The potential of this methodology was demonstrated in short total syntheses of the anti-β-amino-α-hydroxy acid fragments of the macrocyclic (depsi)peptides perthamide C and largamide H, and (-)-cytoxazone, which is a selective modulator of TH2 cytokine secretion. The SET-catalyzed asymmetric tandem lithium amide conjugate addition/5-exo radical cyclization/oxygenation reactions were applied in the synthesis of highly substituted pyrrolidines, azabicyclo[n.3.0]alkanes and spiropyrrolidines. An enantioselective total synthesis of the pyrrolidine alkaloid (-)-α-kainic acid was accomplished by employing the SET-catalyzed 5-exo radical cyclization/oxygenation.