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Abstract(s)
A síntese de compostos quirais, a partir de produtos naturais, é uma área da investigação que há muito está em desenvolvimento. O uso de catalisadores heterogéneos em reações traz vantagens a nível ambiental e prático a nível laboratorial. Apesar do estudo das nanopartículas de ouro como catalisador não ser muito antigo, alguns avanços já foram feitos.
Esta dissertação corresponde à descrição de um estudo da influência do conteúdo de nanopartículas de ouro suportadas em hidrotalcite do tipo MgAl-CO3.
Foi feita a síntese do suporte hidrotalcite por coprecipitação e imobilizamos nanopartículas de ouro entre as lâminas. Esta imobilização foi feita em diferentes percentagens de massa (1% e 5%) e a diferentes condições de temperatura. Os suportes hidrotalcite com partículas de ouro imobilizadas foram utilizados como catalisador em reações de epoxidação da Carvona e do Citral, e halogenação da Carvona.
Verificou-se a tendência que maior quantidade de ouro demonstra maior eficácia catalítica.
Obtivemos vários compostos de síntese, entre eles a 6-bromocarvona, as (5R,7R)-8-Bromo-7-(2-nitrobenzoato)-carvona e (5R,7S)-8-Bromo-7-(2-nitrobenzoato)-carvona, p-menta-1,8-dien-3-ona e 2,3-epoxicarvona. Tentamos a epoxidação dos bromoésteres da Carvona com peróxido de hidrogénio em meio alcalino e com ácido meta-cloroperbenzóico, contudo apenas um deles é possível epoxidar.
Neste trabalho foram utilizadas técnicas de Microscopia eletrónica de transmissão (MET), Energia dispersiva de Raio-X (EDX), Difração de Raio-X (DRX) e Espetroscopia de Ressonância Magnética de Protão e de Carbono para a caracterização das hidrotalcites e dos compostos de síntese obtidos.
The synthesis of chiral compounds from natural products is an area of research that has long been under development. The use of heterogeneous catalysts in reactions brings environmental and practical advantages at laboratory level. Although the study of the gold nanoparticles as a catalyst is not very old, some advances have already been made. This dissertation corresponds to the description of a study of the influence of the content of gold nanoparticles supported on hydrotalcite of the MgAl-CO3 type. The hydrotalcite support was synthesized by coprecipitation and immobilized gold nanoparticles on its surface. This immobilization was done in different percentages of mass (1% and 5%) and at different temperature conditions. The hydrotalcite supports immobilized with gold were used as catalysts in epoxidation reactions of Carvona and Citral, and halogenation of Carvona. It was possible to prove that the size and arrangement of the gold nanoparticles in the support are two very important factors for the catalytic function of the material and that manipulation of the conditions can help obtaining better results. We obtained several synthetic compounds, including 6-bromocarvone, (5R, 7R) -8-Bromo-7- (2-nitrobenzoate) -carvone and (5R, 7S) -8-Bromo-7- (2-nitrobenzoate) -carvone, p-menthyl-1,8-dien-3-one and 2,3-epoxycarvone. We try to epoxidate the bromoesters of Carvone with hydrogen peroxide in alkaline medium and with meta-chloroperbenzoic acid, however only one of them is possible to epoxidate. In this work, the techniques of Transmission Electron Microscopy, X-ray Dispersive Energy, X-Ray Diffraction and Proton and Carbon Magnetic Resonance Spectroscopy were used for the characterization of hydrotalcites and the synthesis compounds obtained
The synthesis of chiral compounds from natural products is an area of research that has long been under development. The use of heterogeneous catalysts in reactions brings environmental and practical advantages at laboratory level. Although the study of the gold nanoparticles as a catalyst is not very old, some advances have already been made. This dissertation corresponds to the description of a study of the influence of the content of gold nanoparticles supported on hydrotalcite of the MgAl-CO3 type. The hydrotalcite support was synthesized by coprecipitation and immobilized gold nanoparticles on its surface. This immobilization was done in different percentages of mass (1% and 5%) and at different temperature conditions. The hydrotalcite supports immobilized with gold were used as catalysts in epoxidation reactions of Carvona and Citral, and halogenation of Carvona. It was possible to prove that the size and arrangement of the gold nanoparticles in the support are two very important factors for the catalytic function of the material and that manipulation of the conditions can help obtaining better results. We obtained several synthetic compounds, including 6-bromocarvone, (5R, 7R) -8-Bromo-7- (2-nitrobenzoate) -carvone and (5R, 7S) -8-Bromo-7- (2-nitrobenzoate) -carvone, p-menthyl-1,8-dien-3-one and 2,3-epoxycarvone. We try to epoxidate the bromoesters of Carvone with hydrogen peroxide in alkaline medium and with meta-chloroperbenzoic acid, however only one of them is possible to epoxidate. In this work, the techniques of Transmission Electron Microscopy, X-ray Dispersive Energy, X-Ray Diffraction and Proton and Carbon Magnetic Resonance Spectroscopy were used for the characterization of hydrotalcites and the synthesis compounds obtained
Description
Keywords
Carvona Catálise Heterogénea Citral Hidrotalcites Nanopartículas de Ouro