Preparação e propriedades de zeólitas faujasita contendo cátions amônio

Sodium faujasite zeolites with Si/Al ratio of 1.4 and 2.5 were exchanged with methylammonium cations. The influence of framework aluminum and ion exchange degree in their basic properties were evaluated. These properties were assessed in the Knoevenagel catalytic condensation. The sodium ion exchange was restricted to the supercavity and the exchange degree depended on the cation volume and on the Si/Al ratio. The higher catalytic activity is achieved for the zeolite with the lower Si/Al ratio exchanged with the monomethylammonium cation. The best performance of this catalyst is attributed to the higher basicity in combination with elevated micropore volume.

Síntese de fotoprotetores e sua imobilização em poli(metacrilato de metilo): um projeto integrado de química orgânica, química de polímeros e fotoquímica

Dibenzalacetone and other aldol condensation products are known sunscreens commonly used in cosmetics. This type of compounds can easily be prepared in an Organic Chemistry Lab by reaction of aldehydes with ketones in basic medium. These compounds can be incorporated in poly(methyl methacrylate) and used as UV light absorbers, for example in sunglasses. This project has the advantage of using inexpensive reagents which are readily available in Chemistry Laboratories. This experiment can also be a base starting point for discussions of organic, polymer and photochemistry topics.

Síntese e avaliação da atividade antimicrobiana de furanonas halogenadas e de compostos análogos aos nostoclídeos

Considering the broad spectrum of biological activity of gamma-butyrolactone derivatives, we presented the synthesis of 3,4-dihalo-5-arylidenefuran-2(5H)-ones (17-21) and analogues (24-28) of the natural product nostoclide (7,8). Furanones 17-21 were synthesized from the condensation of aromatic aldehydes with lactones 14 and 15, that were obtained from mucobromic and mucochloric acids. Lactone 15 was converted into the intermediate 23 in 36% overall yield. Compound 23 was then transformed into the nostoclide analogues 24-28. Some of the compounds prepared showed antimicrobial activities against Escherichia coli, Staphylococcus aureus and Bacillus cereus comparable to commercial antibiotics.

Síntese e avaliação preliminar da atividade antinociceptiva de novas isoxazolil-aril-hidrazonas

New 2-isoxazoline aldehydes were synthesized, in good yields, from cycloadduct of the 1,3-dipolar cycloaddition reaction between endocyclic enecarbamate and carboethoxyformonitrile oxide (CEFNO). Condensation of these 2-isoxazoline aldehydes with several phenyl-hydrazines produced new isoxazolyl-aryl-hydrazones, which showed low toxicity and excellent antinociceptive activity, when compared to dipyrone. The antinociceptive activity of isoxazolyl-aryl-hydrazones was performed using the acetic acid-induced mice abdominal constrictions test.

Determinação de constituintes químicos em madeira de eucalipto por Pi-CG/EM e calibração multivariada: comparação entre redes neurais artificiais e máquinas de vetor suporte

Multivariate models were developed using Artificial Neural Network (ANN) and Least Square - Support Vector Machines (LS-SVM) for estimating lignin siringyl/guaiacyl ratio and the contents of cellulose, hemicelluloses and lignin in eucalyptus wood by pyrolysis associated to gaseous chromatography and mass spectrometry (Py-GC/MS). The results obtained by two calibration methods were in agreement with those of reference methods. However a comparison indicated that the LS-SVM model presented better predictive capacity for the cellulose and lignin contents, while the ANN model presented was more adequate for estimating the hemicelluloses content and lignin siringyl/guaiacyl ratio.

A green synthesis of α,β-unsaturated carbonyl compounds from glyceraldehyde acetonide

The catalytic behavior of Cs-exchanged and Cs-impregnated zeolites (X and Y) was studied using the Knoevenagel condensation between glyceraldehyde acetonide and ethyl acetoacetate in order to produce the corresponding α,β-unsaturated carbonyl compound that is an important intermediate for fine chemicals. The influence of reaction temperature, type of zeolite, and basicity of the sites on the catalytic behavior of the samples was evaluated. All zeolites were active for the studied reaction. The formation of the main condensation product was favored at lower reaction temperatures. Products of further condensations were also observed especially for samples that were only dried before catalytic test.

Polimerização do glicerol: uma reação simples e versátil para produzir diferentes materiais a partir do coproduto do biodiesel

In this work, it is proposed a simple experiment in polymer science for undergraduates, involving the glycerol polymerization catalyzed by H2SO4 to produce different materials, e.g. from oligomers to crosslinked polymer. The students can investigate the reaction conditions such as time, temperature and catalyst concentration, thus controlling the extent of polymerization and its kinetics. This experiment stimulates students to see polymer science in a broader context, involving diverse topics, such as biodiesel, and processing of a co-product of low value in polymeric materials with potential industrial application.

Síntese, caracterização e estudo da atividade inibitória de novas dialquilfosforilarilidrazonas sobre o crescimento de tripanossomatídeos

A new series of dialkylphosphorylhydrazones was synthesized through the condensation of aromatic aldehydes with different phosphorylhydrazines. All synthesized compounds were characterized by IR, ¹H-NMR, 13C-NMR and 31P-NMR spectroscopies. The in vitro investigation of the activity of these compounds against Leishmania amazonensis promastigotes and epimastigotes of T. cruzi, showed an efficient inhibition of proliferation, at non toxic concentrations to mammalian cells. The results have shown some derivatives as potential antiparasitic agents against trypanosomatids.

Uso de aditivos na biodegradação de madeira pelo fungo Ceriporiopsis subvermispora: efeito na peroxidação de lipídios dependente de manganês-peroxidase

Ceriporiopsis subvermispora is a selective fungus in the wood delignification and the most promising in biopulping. Through the lipid peroxidation initiated by manganese peroxidase (MnP), free radicals can be generated, which can act in the degradation of lignin nonphenolic structures. This work evaluated the prooxidant activity (based in lipid peroxidation) of enzymatic extracts from wood biodegradation by this fungus in cultures containing exogenous calcium, oxalic acid or soybean oil. It was observed that MnP significant activity is required to promote lipid peroxidation and wood delignification. Positive correlation between prooxidant activity x MnP was observed up to 300 IU kg-1 of wood.

Synthesis, characterization, and biological activity of a new class of dialkylphosphorylhydrazone derivatives of isatin

Sixteen dialkylphosphorylhydrazones were synthesized by condensation of phosphorylhydrazines with substituted isatins. Products were characterized by FTIR, ¹H-NMR, 13C-NMR, and 31P-NMR. Fungicidal activities of these compounds against Rhizoctonia solani and Fusarium oxysporum were also evaluated. Some compounds inhibited the growth of Rhizoctonia solani and Fusarium oxysporum by 43% and 51%, respectively. These compounds exhibited no effects on germination of lettuce seeds (Lactuca sativa L).

EFEITO DOS TRATAMENTOS SUPERFICIAIS NAS PROPRIEDADES DO BAGAÇO DA FIBRA DE PIAÇAVA Attalea funifera Martius

The aim of this study was to investigate the effect of surface treatment on the properties of waste piassava fiber with the goal of aggregating additional business value. The fiber surface was subjected to four different treatments. In the present work, it was found that washing the fibers with water partially removed impurities from the surface rendering it rougher. Alkaline treatment removed impurities from the surface, hemicellulose and lignin, improving the flexibility of the fibers. Increasing the concentration of washing agents, times and temperature of treatment promoted intense defibrillation on the fiber surface, reducing its strength.

PARÂMETROS TERMODINÂMICOS DA CASCA DE LARANJA DESIDRATADA

The global energy scenario is currently a widely discussed topic, with growing concern about the future supplies. Thus, much attention has been dedicated to the utilization of biomass as an energy resource. In this respect, orange peel has become a material of great interest, especially to Brazil, which generates around 9.5 million tons of this waste per year. To this end, the authors studied the kinetics of the thermal processing of dried orange peel in inert and oxidizing atmosphere. The thermodynamic parameters were determined by the Ozawa-Flynn-Wall method for the global process observed during heating from the 25°C up to 800°C. The thermal analysis in air and nitrogen showed 3-2 stages of mass loss, respectively, with approximately 20% residual mass under a nitrogen atmosphere. The increase in the values of activation energy for the conversion points between 20% and 60% for thermal effects in air and nitrogen atmosphere was observed. The activation energy obtained in an oxidizing atmosphere was higher than that obtained under a nitrogen atmosphere. The fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that the material has a high level of complexity with the presence of alkali and alkaline earth groups as well as phosphate, plus substances such as pectin, cellulose and lignin.

REAÇÃO DE CONDENSAÇÃO DO GLICEROL COM COMPOSTOS CARBONÍLICOS. SÍNTESE, CARACTERIZAÇÃO E APLICAÇÃO EM CRISTAIS LÍQUIDOS

Condensation reactions of glycerol with aldehydes and ketones were performed under thermal heating and microwave irradiation regimes. Homogeneous and heterogeneous catalysts were tested in both conditions. A silica sulfated (SiO2-SO3H) heterogeneous catalyst demonstrated the best performance relative to a selectivity of >95% in favor of 5-membered ketals. For acetals, preference in favor of 5-membered or 6-membered functional groups depends on the nature of the catalyst. Homogenous catalysts favor the more stable 6-membered acetals, whereas heterogeneous catalysts favor the less stable 5-membered acetals. However, the isomer ratios in the acetalization reaction are too low, and hence the reaction cannot be used in a synthetic plan for functional materials. Ketalization processes mediated by SiO2-SO3H show a high selectivity in favor of a 5-membered ring (1,3-dioxolane). The scope of condensation was tested with different ketones. A mechanism for heterogeneous catalysis related to the selectivity in the cyclization process is presented herein. Solketal, a commercial product, was also obtained by a condensation reaction of glycerol and propanone, and showed a high selectivity in favor of 1,3-dioxolane. It was transformed to potential allylic and chiral intermediates. A mesogenic core was connected to the organic framework of glycerol to produce a monomer liquid crystal material with a stable smectic-C mesophase.

PYROLIGNEOUS LIQUOR PRODUCED FROM ACACIA MEARNSII DE WILD WOOD UNDER CONTROLLED CONDITIONS AS A RENEWABLE SOURCE OF CHEMICALS

Acacia mearnsii de Wild (black wattle) is one of the most important trees planted in Southern Brazil for tannin extraction and charcoal production. The pyrolysis of the black wattle wood used for obtaining charcoal is performed in brick ovens, with the gas fraction being sent directly into the environment. The present study examines the condensable compounds present in the liquor produced from black wattle wood at different thermal degradation conditions, using gas chromatography coupled with mass spectrometry (GC/MS). Branches of black wattle were thermally degraded at controlled ambient and temperature conditions. Overall, a higher variety of compounds were obtained under atmospheric air pressure than under synthetic air pressure. Most of the tentatively identified compounds, such as carboxylic acids, phenols, aldehydes, and low molecular mass lignin fragments, such as guayacol, syringol, and eugenol, were products of lignin thermoconversion. Substituted aromatic compounds, such as vanillin, ethyl vanillin, and 2-methoxy-4-propeny-phenol, were also identified. At temperatures above 200 ºC, furan, 2-acetylfuran, methyl-2-furoate, and furfural, amongst others, were identified as polysaccharide derivatives from cellulose and hemicellulose depolymerization. This study evidences the need for adequate management of the condensable by-products of charcoal production, both for economic reasons and for controlling their potential environmental impact.

Spectrophotometric determination of metronidazole through Schiff's base system using vanillin and PDAB reagents in pharmaceutical preparations

Two simple sensitive and reproducible spectrophotometric methods have been developed for the determination of metronidazole either in pure form or in their tablets. The proposed methods are based on the reduction of the nitro group to amino group of the drug. The reduction of metronidazole was carried out with zinc powder and 5 N hydrochloric acid at room temperature in methanol. The resulting amine was then subjected to a condensation reaction with aromatic aldehyde namely, vanillin and p-dimethyl amino benzaldehyde (PDAB) to yield yellow colored Schiff's bases. The formed Schiff's bases are quantified spectrophotometrically at their absorption maxima at 422 nm for vanillin and 494 nm for PDAB. Beer's law was obeyed in the concentration ranges 10 to 65 µg mL-1 and 5 to 40 µg mL-1 with a limit of detection (LOD) of 0.080 µg mL-1 and 0.090 µg mL-1 for vanillin and PDAB, respectively. The mean percentage recoveries were found to be 100.05 ± 0.37 and 99.01 ± 0.76 for the two methods respectively. The proposed methods were successfully applied to determine the metronidazole in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis.