Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-28Bitstream added on 2014-06-13T20:26:01Z : No. of bitstreams: 1 silva_as_dr_araiq.pdf: 2860868 bytes, checksum: 0a5366c12c615d912dea72ff05ef8e46 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O produto comercial Roundup®, contendo o glifosato como principal ingrediente ativo, é vendido mundialmente por ser um herbicida sistêmico, pós-emergente e não seletivo. Além disso, a alta eficiência no processo de remoção de plantas indesejadas e o aumento de culturas transgênicas favorecem seu uso extensivo. Embora não seja considerado um sério contaminante para o homem, o controle e monitoramento destes herbicidas são muito importantes. Desta forma, o presente projeto propõe o desenvolvimento de sistemas de screening e métodos analíticos limpos que possam ser aplicados à determinação de glifosato, uma vez que a literatura dispõe de poucos métodos de análise que visam à aplicação dos princípios da Química Verde. Os métodos propostos neste estudo foram espectroscopia de reflectância difusa, espectrofotometria e sistemas em fluxo, empregando análise por injeção em fluxo (FIA) e multi-bombas (MPFS), com detecção na região do UV-Vis. Os métodos de análise propostos são baseados na reação entre glifosato e p-dimetilaminocinamaldeído (p- DAC), em meio acidificado, com um máximo de reflecção ou absorção em 495 nm. Após a otimização das condições experimentais e validação dos métodos propostos, através de parâmetros como linearidade da curva analítica, exatidão, precisão, limite de detecção, limite de quantificação, recuperação e estudos de possíveis íons interferentes, estes foram aplicados em amostras de herbicidas comerciais e águas (naturais e de consumo humano). Os resultados obtidos na determinação de glifosato nas amostras de herbicidas comerciais empregando reflectância difusa concordaram com os resultados obtidos empregando análise por injeção em fluxo, os quais apresentaram teores de 378,8 g L-1 para a amostra A, 392,4 g L-1 para a amostra... / The commercial product Roundup®, containing the glyphosate as its main active ingredient, is marketed worldwide because it is a nonsystemic, post-emergent and nonselective herbicide. Moreover, the high efficiency in the process of the removal of unwanted plants and the increase in the introduction transgenic plants favor their extensive use. Although it has not been considered a serious contaminant to humans the control and monitoring of this herbicide are very importants. The present project proposes the development of screening systems and clear analytical methods that can be applied to determine the presence of glyphosate, since in the literature there are few methods of analysis that apply Green Chemistry’s principles. The proposed methods in this study were diffuse reflectance spectroscopy, spectrophotometry and flow systems, employing flow injection analysis (FIA) and multi-pumping (MPFS), with detection in the Uv-vis region. The proposed analysis methods are based in the reaction between glyphosate and p-dimethylaminocinnamaldehyde (p-DAC), in acid medium, it presents a reflection or absorption maximum in 495 nm. After the optimization of the experimental conditions and validation of the proposed methods, through parameters such as: linearity of the analytical curve, accuracy, precision, limit of detection, limit of quantification, recovery and study of possible interference ions, these were applied to commercial herbicides and water samples (naturals and for human consumption). The results obtained in the determination of glyphosate in the commercial herbicides employing diffuse reflectance were agree with the results obtained by employing flow injection analysis, which presented levels of 378.8 g L-1 to the A sample, 392.4 g L-1 to the B sample and 330.6 g L-1 to the C sample... (Complete abstract click electronic access below)

This thesis includes NMR studies of free base meso-tetra(otolyl) porphyrin (TTP) and meso -tetraphenylporphyrin (TPP) and their dications protonated by trifluoroacetic acid (TFA). The chemical shift changes of the -NH resonance are very unusual and have never been reported. At the beginning of the titration, the N-H resonances broaden considerably but do not shift; when the ratio of [TFA]/[TTP] or [TFA]/[TPPf are over 2, the N-H resonances shift markedly to lower field by as much as 1.6 ppm. At acid levels well above the equivalence point, the NH resonances moves back to higher field. Moreover upon protonation the NH line of TTP becomes a complex multiplet which changes as a function of [TFA]/[TTP]. The NH line of TPP remains a singlet at all acid levels. We also report here a way of isolating atropisomers of mesotetra( o -tolyl)porphyrin through HPLC by using an analytical C-18 bond pack reverse phase column eluted by a 1 %THF + 99%Me0H solvent combination. A preliminary study by HPLC was also carried out on ZnTTP(II) with aliquots of 2,6-dimethylpyridine, and the retention time of the separation decreased markedly, but this study needs to be repeated and improved. TTP and TPP dications at two different acid levels were studied by VT-NMR, and the downfield shift of -NH resonance of TTP dications was more pronounced at higher temperatures than those of TPP dications.

A series of studies are presented in which fluorine tagging reagents are used to analyze complex mixtures for compounds containing active hydrogen functional groups (e.g., hydroxyl, amine, thiol, and carboxylic groups). The existence of these derivatized functional groups is determined by utilizing a number of solution and solid-state nuclear magnetic resonance (NMR) techniques. In solution NMR studies p-fluorobenzoyl chloride was the fluorine tagging reagent of choice because of a large ¹⁹F chemical shift range for the different derivatized substrates (~10 ppm) and generally good reaction yields. Various classes of sterol and amino acid p-fluorobenzoyl derivatives were characterized on the basis of their ¹⁹F NMR isotropic chemical shifts. The presence (or absence) of hydroxyl, amine, and carboxylic acid functional groups in coal extract and pyrolysis products was also determined. The versatility of the p-fluorobenzoyl chloride as the fluorine tagging reagent in ¹⁹F NMR was enhanced by: a) enriching the carbonyl carbon of the acid chloride with labeled ¹³C isotope, thus synthesizing a dual ¹⁹F and ¹³C NMR sensitive reagent and b) using the reagent in conjunction with LC-NMR. The extension to either technique added another dimension to the NMR spectral data obtained from the p-fluorobenzoyl tagging reagent in solution NMR. Finally, preliminary data is presented illustrating how fluorine tagging reagents may be used to study functional groups (and atoms present in the immediate proximity of the group) existing on solid material utilizing solid-state NMR. Functional groups on the solid material are tagged with a fluorinated reagent. The sample is then analyzed using solid-state NMR with cross-polarization (CP), magic angle spinning (MAS), and high-power proton decoupling. The ¹⁹F dipolar coupling interactions, created by the presence of the fluorine tag, attenuate signals for these nuclei in the immediate proximity of the tagged site. A series of 1-adamantanol, steroid, and silica gel fluorinated derivatives show that the effects of the ¹⁹F dipolar interactions were modulated by complex anisotropic molecular motions (i.e., solid system with little motion, exhibiting greater signal attenuations due to ¹⁹F dipolar coupling). / Ph. D. / incomplete_metadata

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2007. / Includes bibliographical references.

Thesis (Ph.D.) -- Mississippi State University. Dave C. Swalm School of Chemical Engineering. / Title from title screen. Includes bibliographical references.

Earnest carbohydrate research was initiated in the nineteenth century by several talented organic chemists. Carbohydrates, now known to play essential roles in a range of fundamental biological processes, are presently studied by a throng of scientists from many fields, including: biochemistry, molecular biology, immunology, structural biology, medicine, agriculture, pharmacology and, of course, chemistry. Organic chemistry remains as relevant to carbohydrate research as it has ever been; its practitioners, with their skills in synthesis and fundamental understanding of molecules, are truly indispensable. This thesis details various synthetic endeavours within the field of carbohydrate chemistry. It describes four projects with goals as diverse as natural product synthesis, rational inhibitor design and the development of new reagents in organic synthesis. The first chapter provides an account of the synthesis of compound 1, a potent germination stimulant present in smoke, from D-xylose. Many analogues of 1 were prepared from carbohydrates and evaluated as germination stimulants, which permitted the dissemination of several structure-activity relationships. Subsequent chapters describe the design and preparation of inhibitors for various carbohydrate-processing enzymes. Compounds 55 and 56 were sought after as putative synergistic inhibitors of a Vitis vinifera (grape) uridine diphospho-glucose:flavonoid 3-O-glucosyltransferase (VvGT1). It was hoped that crystallographic investigations of VvGT1-UDP-2/3 complexes by a collaborator, structural biologist Professor Gideon Davies, would aid in clarifying mechanistic aspects of this enzyme.Compounds 114, 115 and 118 were prepared as putative arabinanase inhibitors. Once again, this work was undertaken to assist in crystallographic studies that might provide a better understanding of how these enzymes operate. The thesis concludes by describing the development of compound 152.HCl, a novel reagent for the diazotransfer reaction. Previously, this reaction utilised trifluoromethanesulfonyl azide (TfN3), an expensive and explosive liquid with a poor shelf-life, to convert a primary amine directly into an azide. Reagent 152.HCl was developed to replace TfN3 in this useful synthetic transformation. A one-pot procedure enabled the simple and inexpensive preparation of 152.HCl, which was demonstrated to be shelf-stable, crystalline and, crucially, effective in the diazotransfer reaction.