Inaug.-diss.--Basel. / Cover title. Vita.

Inaug.-diss.--Basel. / Cover title. Vita.

Malaria is still the most important parasitic disease in humans with most cases occurring in Sub-Saharan Africa (90% cases). It is transmitted via anopheles mosquitoes. Several vector control methods are available, e.g. long lasting insecticidal mosquito nets (LLINs), insecticide-treated nets (ITNs) and indoor residual spraying (IRS). However, they are effective only when a person is in-doors. Outdoor protection can be obtained for short periods (48-72 hours) using topical repellents. This preliminary study investigated the possibility to develop longer acting delivery forms based on polymer technology. The viability of two different approaches were considered for the controlled release of the natural repellent 3,7-dimethyloct-6-en-1-al (citronellal). The first idea was to dissolve the repellent in the polymer while controlling the rate of release by clay nanoplatelets dispersed in the matrix. Towards this, ethylene vinyl acetate (EVA) copolymer (18% VA) was modified with organically modified nanoclay. Release tests showed that this approach was not viable as only a small amount of repellent could be incorporated and it was lost within a day or two from thin polymer strands. The second approach targeted the use of a polymer in which the repellent is not soluble at ordinary temperature but where solubility is achieved at high temperatures. In this case polyethylene was used as host polymer. It was shown that large quantities of repellent can be trapped inside the polymer matrix using the temperature induced phase separation method (TIPS). Scanning electron microscopy revealed that a microporous co-continuous phase structure was obtained by shock cooling homogeneous mixtures to temperatures well below the spinodal phase boundary curve. The phase behaviour of the LLDPE-citronellal system was studied using cloud point determinations in a microscope fitted with a hot stage and by differential scanning calorimetry. The experimental data points on the bimodal phase envelope were used to fix parameter values of the Flory-Huggins equation. The latter was then used to predict the location of the spinodal lines. At 40 wt.% polymer the spinodal boundary is located at 96 C. However, experiments showed that quenching temperature of 5°C (i.e. the temperature of typical cooling baths used during filament extrusion) is sufficient to generate the desired microporous structure. / Dissertation (MSc)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / MSc / Unrestricted

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-07-10T12:16:42Z No. of bitstreams: 1 arquivototal.pdf: 1661395 bytes, checksum: 3b90c7dae81a55f752093bd4865ac20e (MD5) / Made available in DSpace on 2017-07-10T12:16:42Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1661395 bytes, checksum: 3b90c7dae81a55f752093bd4865ac20e (MD5) Previous issue date: 2016-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Serious infections caused by opportunistic fungal pathogens such as Candida genus, have been increasingly common in immunocompromised patients. The spread of drug-resistant fungi is one of the most serious threats to the successful treatment of fungal diseases, in addition, some drugs are very toxic, hindering adherence to therapy. In this context, the monoterpenes have stood out for having various pharmacological activities such as fungicide and bactericide. It also stands out the antioxidant activity of these compounds by being able to react and inactivate the different reactive species produced during a cellular oxidative stress. Based on this, the antifungal, cytotoxic and antioxidant effect of the monoterpenes (R)-(+)-citronellal (RC), (S)-(-)-citronellal (SC) and 7-hydroxycitronellal (7-OH) were studied. For the analysis of the antimicrobial potential of monoterpenes was used with the in silico analysis software Pass online. For the realization of antifungal studies used the microdilution test with different fungal strains of Candida for evaluation of minimum inhibitory concentration (MIC). In addition, it was determined the Minimum Fungicidal Concentration (MFC) for seeding on plates. In carrying out cytotoxicity studies and antioxidant was used human red blood cells obtained from the transfusion unit of the University Hospital Lauro Wanderley/UFPB. For the antioxidant studies used the techniques with phenylhydrazine and hydrogen peroxide. The study showed that the in silico monoterpenes RC, SC and 7-OH were more likely to be active in percentage, compared to fungal microorganisms. The antifungal activity of experiments revealed that the RC and SC monoterpenes promoted strong antifungal effect with MIC50 of 256 μg/mL for strains of Candida albicans and Candida tropicalis and fungicidal action for presenting CFM50 512 μg/mL. The monoterpene 7-OH showed strong antifungal effect for both strains of Candida albicans and for Candida tropicalis strains with MIC50 of 256 μg/mL and MIC50 512 μg/mL, respectively, and fungicidal action with CFM50 512 μg/mL and 1024 μg/mL. The monoterpenes RC, SC and 7-OH showed no oxidant opposite effect to human erythrocytes. Furthermore, the front monoterpenes had antioxidant effect against phenylhydrazine and hydrogen peroxide. RC analysis of cytotoxicity, SC and 7-OH front of haemolysis erythrocytes showed values below 25% for all blood types tested at a concentration of 256 μg/mL. Given these results, it was possible to infer that the stereoisomerism of RC and SC monoterpenes did not interfere in the tested activities. In conclusion, these results suggest that the RC, SC-OH and 7 show antifungal and antioxidant effect with low cytotoxic effect. / As infecções graves causadas por fungos patogênicos oportunistas, tais como do gênero Candida, têm sido cada vez mais comuns em pacientes imunocomprometidos. A disseminação de fungos resistentes aos medicamentos é uma das mais graves ameaças para o sucesso do tratamento das doenças fúngicas, além disso, algumas drogas são muito tóxicas, dificultando a adesão a terapêutica. Nesse contexto, os monoterpenos têm se destacado por apresentarem diversas atividades farmacológicas tais como: fungicida e bactericida, além da atividade antioxidante, por serem capazes de reagir e inativar as diferentes espécies reativas produzidas durante um estresse oxidativo celular. Com base nisto, foram estudados os efeitos antifúngico, citotóxico e antioxidante dos monoterpenos (R)-(+)-citronelal (RC), (S)-(-)-citronelal (SC) e 7-hidroxicitronelal (7-OH). Para a análise do potencial antimicrobiano dos monoterpenos foi utilizado a análise in silico com o software Pass online. Para a realização dos estudos antifúngicos utilizou-se o teste de microdiluição com diferentes cepas fúngicas do gênero Candida para avaliação da Concentração Inibitória Mínima (CIM). Além disso, determinou-se a Concentração Fungicida Mínima (CFM) por semeio em placas. Na realização dos estudos de atividade citotóxica e antioxidante utilizou-se hemácias humanas obtidas da unidade transfusional do Hospital Universitário Lauro Wanderley/UFPB. Para os estudos antioxidantes utilizou-se as técnicas com fenilhidrazina e peróxido de hidrogênio. O estudo in silico demonstrou que os monoterpenos RC, SC e 7-OH apresentaram uma maior probabilidade de serem ativos, expressa em porcentagem, frente aos microrganismos fúngicos. Os experimentos de atividade antifúngica revelaram que os monoterpenos RC e SC promoveram efeito antifúngico forte com CIM50 de 256 μg/mL para as cepas de Candida albicans e Candida tropicalis, bem como ação fungicida por apresentarem CFM50 512 μg/mL. O monoterpeno 7-OH apresentou forte efeito antifúngico tanto para as cepas de Candida albicans como para as cepas de Candida tropicalis, com CIM50 de 256 μg/mL e CIM50 512 μg/mL, respectivamente, bem como ação fungicida com CFM50 de 512 μg/mL e 1024 μg/mL. Os monoterpenos RC, SC e 7-OH não demonstraram efeito oxidante frente a eritrócitos humanos. Além disso, os monoterpenos apresentaram efeito antioxidante frente a fenilhidrazina e ao peróxido de hidrogênio. A análise da citotoxicidade de RC, SC e 7-OH frente a eritrócitos revelou valores de hemólise abaixo de 25% para todos os tipos sanguíneos testados, na concentração de 256 μg/mL. Diante desses resultados, foi possível inferir que a estereoisomeria dos monoterpenos RC e SC não interferiu nas atividades testadas. Em conclusão, estes resultados sugerem que o RC, SC e 7-OH apresentam efeito antifúngico e antioxidante, com baixo efeito citotóxico.

Made available in DSpace on 2015-05-14T12:56:04Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1501652 bytes, checksum: 4c9d4fada2cc41f87661b7f25404ae20 (MD5) Previous issue date: 2014-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The study aimed to evaluate the biological activity of the essential oil of Cymbopogon nardus and citronellal phytochemical on Candida strains, checking the possible inhibition of adhesion to dental implants and cover screws. Initially, a screening was performed by the disk diffusion technique in Sabouraud Dextrose Agar (SDA) for the essential oils of Cinnamomum camphora (White Camphor), Melissa officinalis (Lemon Balm), Ocimum basilicum (Basil) and Cymbopogon nardus (citronella), as well as phytochemicals alpha pinene, citral, citronellal and carvacrol. After screening, the essential oil of C. nardus and citronellal were selected because they displayed significant antifungal activity. Then, essential oil was analyzed by Gas chromatography mass spectrometry (GC-MS). Subsequently, were determined MIC and MFC of essential oil and citronellal against 12 strains of Candida and tests of inhibition of adhesion to dental implants and cover screws, using the MIC of substances evaluated, followed by analysis on a Scanning Electron Microscope (SEM). Assays were performed in triplicate and chlorhexidine and nystatin were used as positive control. The data were analyzed on the software GraphPad Prism 4. Analysis of variance (ANOVA) with Tukey s post-test was carried out, with a confidence interval of 95%. The GC-MS analysis of the essential oil identified the major substance as citronellal terpenoid. The essential oil, citronellal, chlorhexidine and nystatin able to inhibit 100% of the strains was 64 &#956;g/mL, 512 &#956;g/mL, 64 &#956;g/mL, 32 &#956;g/mL, respectively. The essential oil inhibited the adhesion of C. albicans in the dental implants and cover screws (p <0.001). Citronellal only inhibited the growth of the strain in dental implants (p <0.001) with no significant results in the cover screws (p> 0.05) compared to the growth control. We conclude that the essential oil of C. nardus and citronellal have antifungal activity and are able to inhibit the in vitro adherence of C. abicans. / O estudo teve como objetivo avaliar a atividade biológica do óleo essencial de Cymbopogon nardus e do fitoconstituinte citronelal sobre cepas de Candida, verificando a possível inibição da aderência aos implantes dentários e cover screws. Inicialmente, foi realizado uma triagem por meio da técnica de disco-difusão em Agar Sabouraud Dextrose (ASD), para os óleos essenciais de Cinnamomum camphora (Cânfora Branca), Melissa officinalis (Erva Cidreira), Ocimum basilicum (Manjericão) e Cymbopogon nardus (Citronela), bem como dos fitoconstituintes alfa pineno, citral, citronelal e carvacrol. Após a triagem, o óleo essencial de C. nardus e o citronelal foram selecionados por terem apresentado expressiva atividade antifúngica. Em seguida, o óleo essencial foi analisado por cromatografia gasosa acoplada ao espectro de massa (GC-MS). Posteriormente, foram determinadas a CIM e CFM do óleo essencial e citronelal frente a 12 cepas de Candida e realizados testes de inibição da aderência aos implantes dentários e cover screws, utilizando-se a CIM das substâncias avaliadas, seguida de análise em Microscópio Eletrônico de Varredura (MEV). Os ensaios foram realizados em triplicata e a nistatina e clorexidina foram utilizadas como controle positivo. Os dados foram analisados no software GraphPad Prism 4. Foi realizada uma análise de variância (ANOVA) com pós-teste de Tukey ao nível de confiança de 95%. A análise por GC-MS do óleo essencial permitiu a identificação do terpenoide citronelal como substância majoritária. A CIM do óleo essencial, citronelal, clorexidina e nistatina capaz de inibir 100% das cepas foi 64 &#956;g/mL; 512 &#956;g/mL; 64 &#956;g/mL; 32 &#956;g/mL, respectivamente. O óleo essencial inibiu a aderência de C. albicans nos implantes dentários e cover screws (p<0,001). O citronelal inibiu apenas o crescimento da cepa nos implantes dentários (p<0,001), não apresentando resultados significantes nos cover screws (p>0,05) em relação ao controle de crescimento. Conclui-se que o óleo essencial de C. nardus e citronelal possuem atividade antifúngica e são capazes de inibir a aderência in vitro de C. abicans.

Hauptaufgabe dieser Promotionsarbeit war es, eine neue Sol-Gel basierte Syntheseroute zur Darstellung edelmetallbeladener (Pd, Pt, Ag und Au) Aluminiumhydroxidfluoride zu entwickeln. Derartige Katalysatoren besitzen sowohl Lewis- als auch Brønsted-saure, sowie hydrogenierungsaktive Zentren. Solche multifunktionellen Katalysatoren können für mehrstufige Umsetzungen von Substraten in Eintopfverfahren eingesetzt werden. Das Potential der dargestellten Katalysatoren wurde in der zweistufigen Umsetzung von Citronellal zu Mentholen und der dreistufigen Reaktion von Citral zu Mentholen gezeigt. / The main aim of this thesis was to develop a new sol gel based synthesis route to noble metal loaded (Pd, Pt, Ag and Au) aluminium hydroxide fluorides. These catalysts provide Lewis as well as Brønsted acidity and hydrogenation ability. Those multifunctional catalysts can be used for multi step conversions of substrates performed in a one pot process. The potential of the synthesized catalysts was shown in the two step conversion of citronellal to menthols and in the three step conversion of citral to menthols.

Submitted by Márcio Maia (marciokjmaia@gmail.com) on 2016-09-08T19:00:34Z No. of bitstreams: 1 arquivototal.pdf: 1813229 bytes, checksum: 9baf431a2df59a0cbf6ce91d58a3ce3c (MD5) / Made available in DSpace on 2016-09-08T19:00:34Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1813229 bytes, checksum: 9baf431a2df59a0cbf6ce91d58a3ce3c (MD5) Previous issue date: 2015-02-23 / Dematiaceous, demaceous or dark fungi comprise a large, heterogeneous group of fungi that cause a variety of diseases, including feohifomycoses, cromoblastomycoses, mycetoma and allergies. Species of the genus Cladosporium are relevant in developing cromoblatomycoses, and stand out as plant contaminants. The toxicity of conventional antifungal and increased resistance to therapeutic regimens, driving the study of the antifungal activity of new alternatives, including natural sources. Given this context, the aim of this study was to evaluate the In vitro antifungal activity of seven essential oils (Laurus nobilis L., Mentha arvensis, Mentha X piperita L., Mentha spicata, Ocimum basilicum L., Cymbopogon nardus L. Rendle e Origanum vulgare) and the phytoconstituent citronellal on strains of dematiaceous fungi. In this study, the following methods were used: microbiological screening, determining the minimum inhibitory concentration (MIC) and Minimum Fungicidal Concentration (MFC), kinetics of microbial death, inhibition of conidial germination and evaluation of morphological changes. Among the essential oils tested, the C. nardus essential oil demonstrated potent antifungal activity, inhibiting the growth of 83,3% of strains used. The Cymbopogon Nardus L. Rendle (citronella grass) belongs to the family Poaceae, subfamily Panicoideae. The Cymbopogon genus consists of eighty-five species. C. nardus presents constitution of essential oil with two major compounds: the citronellal and geraniol. Citronellal is a monoterpene, predominantly formed by the secondary metabolism of plants. The essential oil of C. nardus had its MIC and MFC established at 64 mg / mL and the citronellal in 32 mg / mL. Both the essential oil of C. nardus as citronellal significantly inhibited the radial mycelial growth of the tested strains, the MIC concentrations, MICx2 and MICx4 after 12 days of exposure. In MIC50 concentrations (64 ug / ml- essential oil and 32μg / ml -citronellal) and MIC90 (128 ug / ml - 512μg essential oil and / ml - citronellal), were able to significantly inhibit the germination of fungal conidia from both strains tested. The determination of the effect of the essential oil of C. nardus and citronellal on the morphogenesis of C. carrionii strains showed that both were capable of inducing morphological changes, as development tortuous hyphae, fine and decreased conidiation in MIC concentrations, MICx2 and MICx4. Thus, it is concluded that the essential oil of C. nardus and its phytoconstituent citronellal showed pronounced antifungal activity against the strains of C. carrionii tested, what drives the study of its In vivo antifungal activity, as well as the search for pharmaceutical formulations to be used for the therapy of certain mycoses, especially those caused by dematiaceous fungi. / Fungos dematiáceos, demáceos ou escuros compõem um grupo grande e heterogêneo de fungos que causam uma variedade de doenças, incluindo feohifomicoses, cromoblastomicoses, micetomas e alergias. Espécies do gênero Cladosporium são relevantes no desenvolvimento de cromoblatomicoses, e se destacam como contaminantes de plantas. A toxicidade dos antifúngicos convencionais e o aumento da resistência aos esquemas terapêuticos utilizados impulsionam o estudo da atividade antifúngica de novas alternativas, incluindo as de fonte natural. Diante desse contexto, o objetivo deste trabalho foi avaliar a atividade antifúngica In vitro de sete óleos essenciais (Laurus nobilis L., Mentha arvensis, Mentha X piperita L., Mentha spicata, Ocimum basilicum L., Cymbopogon nardus L. Rendle e Origanum vulgare) e do fitoconstituinte citronelal sobre cepas de fungos dematiáceos. Neste estudo, os seguintes métodos foram utilizados: triagem microbiológica, determinação da Concentração Inibitória Mínima (CIM) e Concentração Fungicida Mínima (CFM), cinética de morte microbiana, inibição da germinação de conídios e avaliação de alterações morfológicas. Dentre os óleos essenciais testados, o de C. nardus demonstrou uma potente atividade antifúngica, inibindo o crescimento de 83,3% das cepas de fungos demáceos utilizadas. O Cymbopogon nardus L. Rendle (capim-citronela) pertence à família Poaceae, subfamília Panicoideae. O gênero Cymbopogon é constituído de oitenta e cinco espécies. O C. nardus apresenta constituição do óleo essencial com dois compostos majoritários: o citronelal e o geraniol. Citronelal é um monoterpeno, predominantemente formado pelo metabolismo secundário de plantas. O óleo essencial de C. nardus teve sua CIM e CFM estabelecidas em 64 μg/ mL e o citronelal em 32 μg/ mL. Tanto o óleo essencial de C. nardus quanto o citronelal inibiram de forma significativa o crescimento micelial radial das cepas testadas, nas concentrações CIM, CIMx2 e CIMx4, após 12 dias de exposição. Nas concentrações CIM50 (64 μg/ mL- óleo essencial e 32μg/mL -citronelal) e CIM90 (128 μg/mL - óleo essencial e 512μg/mL - citronelal), foram capazes de inibir de forma significativa a germinação dos conídios fúngicos de ambas as cepas testadas. A determinação do efeito do óleo essencial de C. nardus e do citronelal sobre a morfogênese das cepas de C. carrionii demonstrou que ambos foram capazes de induzir alterações morfológicas, como desenvolvimento de hifas tortuosas, finas e diminuição da conidiação, nas concentrações CIM, CIMx2 e CIMx4. Dessa forma, conclui-se que o óleo essencial de C. nardus e o seu fitoconstituinte citronelal mostraram pronunciada atividade antifúngica sobre as cepas de C. carrionii testadas, o que impulsiona o estudo de suas atividades antifúngicas In vivo, bem como a busca por formulações farmacêuticas a serem utilizadas para a terapia de algumas micoses, especialmente aquelas causadas por fungos demáceos.

Made available in DSpace on 2014-08-20T13:42:06Z (GMT). No. of bitstreams: 1 Dissertacao_Francine_ Novack_ Victoria.pdf: 1036234 bytes, checksum: 1fea71545d5ff3ff1e433c5ceaff9a37 (MD5) Previous issue date: 2010-02-26 / Java citronella (Cymbopogon nardus (L) Rendle) belongs to the genus Cymbopogon and the essential oil extracted from the plant is constituted mainly by the (+)-R-citronellal (3,7-dimethyl-6-octenal), formed by the secondary metabolism plants. Essential oils and plant extracts have a growing interest to industry and scientific research due to its antimicrobial activity, and as well as compounds organosselênios that are of great interest for scientific research because of its wide spectrum of biological activity. Thus, we performed a study of α-selenation of aldehydes and ketones, including the (+)-( R)-citronellal, as a major component of essential oil of citronella, using PEG/KF/Al2O3, as a recyclable medium. Derivatives of (+)- (R)-citronellal containing organoselenium were assessed for their potential antimicrobial, the antimicrobial activity was determined by the techniques of disk diffusion and minimum inhibitory concentration. The 2-phenylseleno citronellal and 2 phenylseleno citronellol provided yields of 71 and 73% respectively. The antimicrobial activity of 2- phenylseleno citronellal showed the best results, soon the addition of a organoselenium to (+)-R-citronellal increased the antimicrobial activity of (+)-R-citronellal against foodborne pathogenic bacteria Listeria monocytogenes, Staphylococcus aureus and Salmonella Typhimurium. / O capim citronela (Cymbopogon nardus(L) Rendle) pertence ao gênero Cymbopogon, o óleo essencial extraído da planta tem como principal constituinte o (+)-R-citronelal (3,7-dimetil-oct-6-enal), predominantemente formado pelo metabolismo secundário das plantas. Os óleos essenciais e os extratos das plantas possuem um interesse crescente para a indústria e para a pesquisa científica devido a sua atividade antimicrobiana, assim como os compostos organosselênios que são de grande interesse para a pesquisa científica devido ao seu grande espectro de atividade biológica. Desta forma, foi realizado um estudo da α-selenização de aldeídos e cetonas, incluindo o (+)-(R)-citronelal, principal componente do óleo essencial de citronela, utilizando PEG/KF/Al2O3, como meio reciclável. Os derivados do (+)-(R)-citronelal contendo organosselênio foram avaliados em relação aos seus potenciais antimicrobianos, determinados pelas técnicas de difusão do disco e concentração inibitória mínima. Os produtos 2-fenilselenocitronelal e 2-fenilselencitronelol apresentaram rendimentos de 71 e 73%, respectivamente. Nos ensaios de atividade antimicrobiana o produto 2-fenilselenocitronelal apresentou os melhores resultados, inclusive melhores que o (+)-R-citronelal. Logo, a adição de um grupamento de selênio ao composto (+)-R-citronelal aumentou sua atividade antimicrobiana contra Listeria monocytogenes, Staphylococcus aureus e Salmonella Typhimurium.

A determinação do excesso enantiomérico (ee) em compostos quirais por ressonância magnética nuclear (RMN) foi descoberta há mais de meio século por Raban e Mislow e permanece bastante atual e importante. Uma das formas de quantificar o ee consiste em formar diastereoisômeros através de agentes quirais de derivação (AQD). AQDs com a função aldeído tem sido amplamente usados na discriminação de aminas quirais devido a fácil formação de iminas em condições brandas. Existe uma preferência pelo uso de aldeídos cíclicos como AQD, uma vez que sua menor flexibilidade conformacional favorece a diferenciação dos derivados diastereoisoméricos. Até o momento, não havia estudos de AQD utilizando compostos acíclicos. Desta forma, o objetivo desse trabalho foi utilizar o terpeno acíclico (S)-citronelal como AQD para a determinação do excesso enantiomérico de aminas primárias, através da RMN de 1H e 13C. Inicialmente, nós conseguimos observar uma preferência por conformações dobradas do (S)-citronelal por NOE e pela comparação entre os deslocamentos químicos teóricos, obtidos a partir da otimização com a correção de dispersão D3, e experimentais de RMN de 1H. Em seguida, nossos resultados sugeriram que a causa do dobramento molecular do citronelal estaria baseada em interações de London e HOMO-LUMO. Após a análise conformacional do (S)-citronelal, nós reagimos este composto dentro do tubo de RMN (\"mix and shake\") com misturas racêmica e escalêmicas das aminas sec-butilamina, 1-(fenil)etanamina e anfetamina, do amino-álcool 2-aminobutan-1-ol e dos amino-ácidos metionina e fenilalanina. Em todos os casos foi possivel fazer a determinação do ee e da configuração absoluta com grande eficácia. Os resultados mostraram que a metila ligada ao centro estereogênico do (S)-citronelal é um sinal conveniente para se determinar o ee de aminas quirais por ser facilmente reconhecido no espectro, uma vez que esse sinal já faz parte do agente quiral de derivação e também por estar em uma região bastante blindada do espectro tanto no RMN de 1H como no de 13C. Com isso, a completa e minuciosa elucidação estrutural torna-se desnecessária. Posteriormente, as conformações das iminas formadas mostraram, através de estudos teórico e experimental (NOE), um dobramento molecular semelhante ao encontrado no citronelal. O motivo para esse efeito também se encontra nas interações de London e nas interações de orbitais moleculares adequadas. / The determination of enantiomeric excess (ee) in chiral compounds by nuclear magnetic resonance (NMR) was discovered more than half a century ago by Raban and Mislow and remains quite current and important. One of the ways of quantify the ee is to form diastereoisomers via chiral derivatizing agents (CDA). CDA with the aldehyde function has been widely used in discriminating chiral amines because of easy formation of the imines under mild conditions. There is a preference for the use of cyclic aldehydes as CDA since their lower conformational flexibility favors the differentiation of the diastereoisomeric derivatives. As far as we are aware, there were no studies of CDA using acylic compounds. Thus, the goal of this work was to use acylic terpene (S)-citronellal as CDA for the determination of the ee of primary amines, through 1H and 13C NMR. Initially, we observed the preference for a folded conformations of the (S)-citronellal by NOE and by comparing the theoretical chemical shifts obtained from the optimization with the D3 dispersion correction, and experimental 1H NMR. Next, our results suggested that the cause of the citronelal molecular folding could be attributed to London and HOMO-LUMO interactions. After the conformational analysis of the (S)-citronellal, we reacted this compound within the NMR tube (\"mix and shake\") with racemic and scalemic mixtures of the sec-butylamine, 1-(phenyl) ethanamine, amphetamine, 2-aminobutan-1-ol, methionine and phenylalanine. In all cases, it was possible to make the determination of the ee and absolute configuration with great effectiveness. The results showed that methyl group attached to the stereogenic center of the (S)-citronelal is a convenient signal to determine the ee of chiral amines, because it is easily recognized in the spectrum, since that signal is already part of the CDA and also for being in a fairly shielded region of the spectrum in both 1H and 13C NMR. With this, complete and rigorous structural elucidation becomes unnecessary. Subsequently, the conformations of the imines formed showed, by theoretical and experimental (NOE) studies, the same molecular folding similar to that found in citronellal. The reason for this effect is also found in the interactions of London and in the interactions of suitable molecular orbitals.

The work described in this thesis focuses on the effects that adsorption processes on catalytic surfaces pose in controlling key steps that can affect and control reaction pathways. To that, the development of Nuclear Magnetic Resonance (NMR) relaxometry methods and the comparison with traditional catalytic was performed with a series of C5 and C6 unsaturated hydrocarbons on two different alumina supports, γ- and θ-Al2O3. The developed techniques were applied in the study of liquid phase selective hydrogenation of citral on 5% Pt/SiO2. Infrared (IR) spectroscopy, volumetric adsorption isotherms, dynamic isotherms via a Tapered Element Oscillating Microbalance (TEOM), temperature programmed desorption (TPD) as well as 13C T1 NMR and 1H 2D T1-T2 relaxometry methods were employed. Energies of adsorption as a function of coverage were obtained via adsorption isotherms and the particular surface adsorbate interactions were described with IR spectroscopy. For example, 1-pentyne showed the strongest interaction with the alumina (94 kJ mol-1) while 1-pentene presented a weaker interaction (46 kJ mol-1) on θ-Al2O3. Desorption energies obtained from TPD ranged 85 – 130 kJ mol-1, irrespective of the adsorbate. Reactivity of the aluminas was captured with TPD, TEOM and NMR relaxometry. Interaction of adsorbates with hydrocarbon occurred predominantly on weak adsorption sites. 13C NMR T1 relaxometry provided in addition atom-specific adsorbate-adsorbent interaction strengths, showing the molecular geometry of adsorption, and applied in co adsorption measurements. The selective hydrogenation of citral as a model α,β-unsaturated aldehyde and the effect of different solvents on the activity and product distribution was studied at 298 and 373 K. A series of polar protic, polar aprotic and non polar solvents was investigated. Results showed higher initial reaction rates in non polar solvents but higher selectivities towards desired products on polar protic solvents. Solvent used also affected by product formation. The strong variations in reaction rates and selectivities reported were related with adsorbate catalyst interactions, as well as solvent reactant interactions. For example, adsorption isotherms showed that ethanol notably reduced the adsorption capacity of citral as compared with hexane, related with the rate differences observed. ATR-IR measurements indicated solvent citral interactions were solely present in polar protic solvents in line with higher yields of geraniol and nerol. Finally, 13C T1 NMR and 1H 2D T1-T2 correlation experiments determined that the geometry of adsorption of citral, influenced by solvent, affected product selectivity, and that product adsorption affected selectivity and deactivation.