https://repositorio.ufba.br/handle/ri/6415 Sun, 03 May 2026 03:58:00 GMT 2026-05-03T03:58:00Z https://repositorio.ufba.br/handle/ri/38053 Título: Efeito de grupamentos éster e cinamato na obtenção de cristais líquidos termotrópicos. Autor(es): Jesus, Eunice Cerqueira de Primeiro Orientador: Vieira, André Alexandre Abstract: In this work, a homologous series of eight (08) liquid crystals derived from aryloxycinnamates with a wide range of mesomorphism will be presented. The molecules investigated in this study were synthesized from the Wittig olefination reaction, carried out by researchers at Quaid-i-Azam University in Pakistan. The characterization was carried out by infrared spectroscopic techniques, 1H and 13C NMR, which demonstrated the effectiveness of the reactions. These materials were designed with architecture suitable to exhibit liquid-crystalline properties. In our group, the objective was to study the structure-property relationship of the compounds of the series, and for that, the size of the terminal alkoxy chain was varied between three and twelve carbon atoms, to verify its influence on the mesomorphic properties of the compounds. Mesomorphic properties were investigated by MOLP, DSC, and XRD techniques. All molecules exhibited characteristic textures by MOLP as a result of the organizational defects of the liquid-crystalline phase, being, therefore, possible to prove the birefringence of the analyzed anisotropic materials. The different structural arrangements revealed the type of mesophase present, thus, the nematic phase was confirmed by the Schlieren-type texture and the smectic phase by the focal-conical and fan-shaped textures. The transition temperatures of the mesophases and the energies involved in the processes were determined by DSC, in the second heating and cooling cycle. These experiments confirmed that all compounds in the series exhibited a wide range of mesomorphism between 64 °C and 80 °C. The mesomorphism of the samples was shown to be dependent on the length of the alkoxy chain for the organization and stability of the liquid-crystalline phase, where smaller carbon chains exhibited the nematic phase, while larger chains presented exclusively the smectic phase. It was possible to observe that the increase in the chain length resulted in the appearance of more organized phases, as well as reflected in the reduction of melting points and lightening of the compounds. The confirmation of the molecular organization in the mesophase was made through XRD analysis, which showed interference sequences through the Bragg reflection peaks (d001 and d002). The relationship between the diffractions evidences the lamellar packing of the molecules, pointing to the presence of type A smectic mesophase, due to the inexistence of folding, interdigitalization, and inclination of the layers. The decomposition temperatures of the samples were investigated by TGA and the results denoted that all were thermally stable up to 230 ºC. The decomposition values were found to ensure that there is no decomposition of the compounds during heating and obtaining the mesophases. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação Fri, 27 May 2022 00:00:00 GMT https://repositorio.ufba.br/handle/ri/38053 2022-05-27T00:00:00Z https://repositorio.ufba.br/handle/ri/37985 Título: Reatividade de 2-amino-heterociclos frente ao etoxi-metilenomalonato de dietila na síntese tricomponente de β-enaminodicarbonílicos e síntese telescópica de piridopirimidinonas. Autor(es): Cerqueira, Bruna Costa Primeiro Orientador: Cunha, Silvio do Desterro Abstract: Synthetic strategies play an important role in the development of sustainable methodologies, aiming to reach important molecules. Thus, the use of multicomponent reactions, one pot and telescopic syntheses, can be applied in this aspect. Diethyl ethoxy-methylene malonate is an important electrophile for the synthesis of polyfunctionalized heterocycles, and can be used in different types of chemical transformations, as well as it is an attractive building block in the synthesis of carbonyl compounds. The present work had as purpose to investigate the reactivity of 2-amino-heterocycles against diethyl ethoxy-methylene malonate, precursors of β-enaminodicarbonyl compounds via a three-component reaction. The β-enaminodicarbonyl compounds were synthesized with yields ranging from 75% to 90%, beginning with 2-aminopyridines derivatives, diethyl malonate and triethyl orthoformate, an unprecedented condition for the synthesis of these molecules. Furthermore, cyclic products were accessed using these reactants under mild conditions, reaching pyrido-pyrimidinone nuclei via telescopic reaction. Hence, the tricomponent and telescopic reactions were more efficient and more environmentally sustainable methodologies being useful to achieve new molecules without the need to synthesize, isolate and purify intermediates. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação Fri, 11 Feb 2022 00:00:00 GMT https://repositorio.ufba.br/handle/ri/37985 2022-02-11T00:00:00Z https://repositorio.ufba.br/handle/ri/37927 Título: A metabolômica na compreensão de doenças neurológicas: análise untargeted de amostras de soro de bebês com microcefalia. Autor(es): Nunes, Estéfane da Cruz Primeiro Orientador: Canuto, Gisele André Baptista Abstract: Zika is a disease caused by the Zika virus (ZIKV), whose main form of transmission is through the bite of Aedes aegypti and Aedes albopictus mosquitoes. The disease has been registered in more than 80 countries worldwide. ZIKV infection has been associated with several neurological disorders and auditory and vision abnormalities. A concern in the medical community revolves around infection during the gestation period, as ZIKV affects fetal development and can lead to pregnancy complications. One of the main consequences is congenital microcephaly, a neurological anomaly that causes a reduction in the newborn's head circumference. The knowledge of the impact of ZIKV on metabolism is scarce and is essential for the development of treatments and understanding of pathogenesis. Metabolomics, a comprehensive and quantitative analysis of the metabolites present in a biological system, is an interesting tool to obtain information about the metabolic alterations of several diseases, including ZIKV infection. In this work, the metabolic profile of serum samples from newborns with positive diagnoses for ZIKV, with and without microcephaly was evaluated using untargeted metabolomics. Sample treatment involved protein precipitation, followed by derivatization, using oximation and silylation reactions for subsequent analysis by gas chromatography hyphenated to mass spectrometry (GC-MS). Data were processed in XCMS software and metabolites identified in AMDIS. Statistical analysis using univariate and multivariate methods was applied to find discriminating metabolites. The results showed significant changes in metabolic pathways of amino acids, organic acids, carbohydrates and derivatives. The biological interpretation of these alterations indicates that microcephaly is associated with a reduction in carbohydrate levels caused by virus replication. The increase of amino acid in patients with microcephaly reinforces this relationship due to the involvement of glycolysis intermediaries in amino acid synthesis. Little is known about the metabolic changes caused by infection with ZIKV, especially in newborns. Thus, the results obtained in this study provide relevant information on the association between Zika and cases of microcephaly. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação Thu, 16 Dec 2021 00:00:00 GMT https://repositorio.ufba.br/handle/ri/37927 2021-12-16T00:00:00Z https://repositorio.ufba.br/handle/ri/27714 Título: Avaliação da atividade fotocatalítica de compósitos (CDS)x/(ZNO)y na geração de hidrogênio preparados pelo método Citrato seguido de troca iônica Autor(es): Araújo, Rodrigo de Jesus Abstract: Combustíveis fósseis são os maiores responsáveis pelo atendimento à demanda energética mundial. Além dos problemas ambientais, como emissão de gases poluentes e mudança climática, outra preocupação relacionada ao consumo de combustíveis fósseis é o fato destes não serem renováveis. O hidrogênio é um vetor energético promissor, visto que pode ser obtido de fontes renováveis e mais abundantes, a exemplo da água, além de não ser poluente. A proposta deste trabalho é o desenvolvimento de um método de síntese de compósitos do tipo (CdS) x/(ZnO)y, com o objetivo de gerar hidrogênio a partir da decomposição fotocatalítica da água em meio básico, utilizando como reagentes de sacrifício sulfeto e sulfito de sódio, sob irradiação de luz visível. Estes semicondutores foram sintetizados com base no método dos precursores poliméricos seguido de troca iônica, variando o teor de zinco em cada amostra. Os resultados das análises de difração de raios-X permitiram identificar a composição de cada amostra sintetizada, as fases de sulfetos e óxido presentes, e confirmou a formação dos compósitos esperados. A microscopia eletrônica de varredura mostrou tamanhos e formas de cristais bastante heterogêneos. Também foram realizadas caracterizações por EDX e DRS. Todas as amostras sintetizadas apresentaram atividade fotocatalítica, sendo a amostra com a relação y/x = 0,3, a de melhor desempenho, com uma taxa de produção de hidrogênio igual a 1,54 mmol gcat-1h-1. Apesar de não ter havido uma relação linear entre o teor de zinco e a taxa de produção de hidrogênio, este trabalho mostra a vantagem de adicionar zinco na forma de óxido na estrutura do fotocatalisador.; ABSTRACT- Fossil fuels are the major responsible for customer service to the world energy demand. In addition to the environmental problems, such as emissions of polluting gases and climate change, another concern related to the consumption of fossil fuels is the fact that those not being renewable. Hydrogen is a promising energy vector, since it can be obtained from renewable and more abundant sources, such as water, besides not be pollutant. The proposal of this work is the development of a method of synthesis of type composite (CdS)x/(ZnO)y, with the objective of generating hydrogen from the photocatalytic decomposition of water in basic solution, using as sacrifical reagents sulfide and sodium sulphite, under irradiation of visible light. These semiconductors were synthesized based on the polymeric precursors method followed by ionic exchange, varying the zinc content in each sample. The results of analysis of X-ray diffraction, allowed to identify the composition of each sample synthesized, the phases of sulfide and oxide present, and confirmed the formation of expected composites The scanning electron microscopy showed very much heterogeneous sizes and forms of crystals. Were also performed characterizations by EDX and DRS. All synthesized samples presented photocatalytic activity, being the sample with the ratio y/x = 0.3, for best performance, with a production rate of hydrogen equal to 1.54 mmol gcat-1h-1. Although there was a linear relationship between the zinc content and the rate of production of hydrogen, this work shows the advantage of adding zinc oxide in the structure of photocatalyst. Tipo: Dissertação Tue, 16 Oct 2018 00:00:00 GMT https://repositorio.ufba.br/handle/ri/27714 2018-10-16T00:00:00Z