Resumo em Inglês:

The aldol condensation between furfural and acetone was studied in the presence of organic bases, such as Piperazine (PIP), 3-Aminopropyltriethoxysilane (APTES) and 1,5,7-Triazabicyclo [4.4.0] dec-5-ene (TBD), as basic catalysts. The latter base showed the highest conversion rates of furfural and high selectivity to the single-condensation product 4-(2-Furyl)-3-buten-2-on (F-Ac). These data are consistent with the greater basicity of TBD in relation to the other amines. This study was carried out aiming at the future anchoring of the bases in inorganic supports for the production of heterogeneous catalysts.

Resumo em Inglês:

Improving the development of modified release matrix systems strictly depends on selecting an appropriate agent capable of controlling the drug's release. In this study, Adenanthera pavonina galactomannan was investigated as a potential basis for developing a controlled release of rutin. This galactomannan was extracted, purified and characterized by GPC, NMR and FT-IR spectroscopy. The mannose/galactose ratio (M/G) of 1.46 was calculated by the relative area from signals of the anomeric region of 1H-NMR spectrum. The main chain of this galactomannan consists of β(1®4)-D-mannose and α(1®6)-D-galactose linked units (1H-decoupled 13C NMR, 13C DEPT 135º NMR and HSQC spectra). The sustained-release tablets containing rutin and galactomannan were compared with the extensively investigated hydrophilic matrix HPMC. Drug release analysis revealed similar release mechanism for both matrices. A new formulation for controlled drug delivery from water-swellable matrix systems is proposed.

Resumo em Inglês:

The polystyrene sulfonic acid resin catalysts were fabricated, containing elements of Cl and Mg through oxidization and impregnation, and they were characterized by EDS, FT-IR spectra, Py-IR spectra, UV spectra, XPS and TGA to investigate their physiochemical properties. The catalytic performances of these catalysts were examined in the esterification reaction of succinic acid with n-butanol, and the catalytic results showed that modified resins exhibited the highest catalytic activity and achieved a high yield of dibutyl succinate (91.6%) in addition, the modified resin generated new Lewis acid sites and showed significantly higher thermal stability. The experimental results demonstrated that the Mg2+ coordinated with a sulfonic acid group to form stable active sites, which effectively decreased the deactivation caused by the thermal degradation of sulfonic acid. Moreover, the monomer structures of polystyrene sulfonic acid resin and modified polystyrene sulfonic acid resin have been modelled using B3LYP/6-311G(d,p) approximation.

Resumo em Inglês:

A phytochemical investigation from aerial parts of Casearia arborea (Rich.) Urb. (Salicaceae) led to isolation and identification of: sitosterol, 4-en-stigmast-3-one, 13-hydroxy-trans-ent-cleroda-3,14-diene,3-hydroxy-2-oxo-trans-ent-cleroda-3,14-diene (kolavelone), a mixture of 13-hydroxy-trans-ent-cleroda-3,14-diene and an ester ethyl hexadecanoate, kaempferol-3-O-a-L-arabinofuranoside and 4',5,7-trihydroxy-3',5'-dimethoxyflavone (tricin). The compounds have been described for the first time in this species. Five trihydroxy-flavone-hexoside derivatives have been identified by LC-ESI-HR-MS. The antimicrobial activity of kolavelone was evaluated against strains of Staphylococcus, Bacillus, Pseudomonas, Shigella and Candida spores, and its minimum inhibitory concentration (MIC) was determined. The results showed the antimicrobial activity of kolavelone against several bacteria and Candida tropicalis indicating its potential use as antimicrobial agent.

Resumo em Inglês:

A simple and easily synthesized fluorescent sensor L, based on condensation reaction of 1-Naphthylamine and terephthalaldehyde, was synthesized and characterized systemically. Both UV-vis and fluorescence spectroscopic studies indicated that the sensor L showed good selectivity toward trivalent metal ions (such as Al3+, Fe3+, Cr3+, La3+ and Ce3+) over other monovalent or divalent metal ions. The sensing mechanism was suggested that the trivalent ion promoted the hydrolysis of Schiff base. Meanwhile, took the common trivalent ions Al3+, Fe3+ and Cr3+ as examples, limit of detection (LOD) values of sensor L were calculated to be 1.23, 0.94 and 1.14 nM for Al3+, Cr3+ and Fe3+, respectively, suggesting very high sensitivity towards the cations which could make it attractive in trivalent metal ions detection.

Resumo em Inglês:

Finding the most efficient solvent for a chemical reaction can demand costly experimental procedure and the screening is usually limited to few solvents. The use of theoretical methods could accelerate the search for the best solvent, able to promote most effective kinetics and thermodynamics of a reaction. In this work, it was proposed an automated procedure that calculates the solvent effect for a chemical reaction using all the 179 solvents available in SMD (solvation model density). The reaction of 2-bromoacetophenone with pyridine was used as a test. The SMD model correctly predicts the reactivity trends for five solvents, which experimental data are available. We have found that sulfolane, a less usual solvent, is the best one for this reaction. The present study points out that computational screening of large set of solvents using the SMD model is a viable approach and could be useful for chemical reactions optimization.

Resumo em Inglês:

There are many processes capable of decontamination of polychlorinated biphenyls in several matrixes. The set of inputs, materials, operation conditions and efficiencies are wide. The base catalyzed dechlorination process shows application potential in great scale, mainly due mild chemical reaction conditions and low cost raw materials. The KPEG is a familiar process of base catalyzed dechlorination. This decontamination treatment was developed mainly on mineral insulating oil. Few information is found related to process residues, usually in reaction sludge means, limited to inform that its destination must fulfill specific territorial laws. In these work KPEG treatment process was performed on decontamination of mineral insulating oils containing between 200 and 330 ppm of polychlorinated biphenyls to evaluation of reaction residues and of the decontamination percentage. Chemical characterization of these residual material allows achievement of important information to explore procedures for recovery, regeneration and/or right disposal. The analysis performed on the residues showed the presence of reaction products containing unsaturation, absents on neat polyethylene glycol, possible organic complexes products with alkali metal as also the presence of chloride ions. In oil was verified the presence of less chlorinated biphenyls, probably formed by partial dechlorination of highly chlorinated biphenyls.

Resumo em Inglês:

Solid phase extraction (SPE) is one of the main sample preparation techniques. However, the cost of cartridges and the strong retention of hydrophobic compounds in traditional solid phases are limiting factors for their use. This paper describes the application of lab-made SPE cartridges with low retention material as solid phase, Si(PDAS) - poly(dimethyl-co-alkylmethylsiloxane) thermally immobilized on silica, in the determination of pesticide residues in surface water samples. The extraction method of three pesticides: carbendazim, diurom and methyl parathion in water samples was developed, optimized and validated using Si(PDAS) cartridges and HPLC-UV for quantification. The optimized method required a small organic solvent volume for the elution of pesticides from Si(PDAS), producing a concentration factor of 1000 times and allowing limits of detection like those obtained with hyphenated techniques. The validated method for extraction of pesticides in water samples presented: accuracy, with pesticide recoveries between 70-110%; precision, with RSD < 20%, and; high detectability, resulting in LOQ < 0.4 µg L-1 for all compounds. Si(PDAS) cartridges showed similar efficiency to those commercial C18 for the extraction of pesticides in surface water samples, with additional advantages such as ease, simplicity and low cost of preparation, up to six times cheaper than commercial cartridges.

Resumo em Inglês:

Biodiesel is an alternative fuel obtained from different biomass sources and processes. Nowadays, this biofuel has gained importance due to environmental concerns and rising energy demand. In the biodiesel production chain, stability is a critical issue, as it is linked to the maintenance of its original properties. This work performed a study evaluating the influence of storage conditions on the quality aspects of biodiesel. Thus, different samples of biodiesel obtained from soybean and frying oils were produced and placed in containers made by plastic, glass and tin, and stored in presence or absence of an oxidative atmosphere, moisture and light. These samples were analyzed to evaluate the ester content, acidity, iodine value, kinematic viscosity and oxidative stability. The characterization with GC-MS and GC/FID were done aiming to determine the chemical composition. Blends with frying biodiesel into soybean biodiesel have also been produced in concentrations ranging from 1%, 5% and 10% (m/m) in order to evaluate the mixing effect. In the initial storage time, all tested parameters were in accordance to the legislation. Distinct behaviors were identified for each sample according to the container type, being the glass the most effective of them in maintenance of biodiesel characteristics.

Resumo em Inglês:

The study of environmentally friendly CO2 sorption agents are growing due to the need of mitigate this gas from atmosphere. Ionic Liquids (ILs) present the advantage of having low vapor pressures and being chemically and thermally stable. Besides, their properties can be designed by varying the groups of the cation or anion. Yet, these compounds present a lower desorption energy when compared to amines based chemical solvents. These characteristics make ILs potentially important for the development of new processes focused on the mitigation of global warming. However, ILs have high viscosity and high cost, making them economically unfeasible. To minimize these problems, bubble glass can be used as an additive in ionic liquids to reduce cost and viscosity. Bubble glass has several applications in industry, presenting low cost and high chemical and mechanical resistance. This work evaluated the CO2 solubility in [bmim][BF4] and [mbmim][Tf2N] pure and mixed with boron silicate bubble glass in volumetric concentrations of 5% to 50%. Data are reported at 27 bar of pressure and temperatures of 303 and 323 K. Mixed systems with 50% concentration of bubble glass showed the best sorption results for both ionic liquids.

Resumo em Inglês:

The search and use of bioactive compounds for different applications have been investigated, since ancient time. Virtual screening (VS) has emerged as alternative methodological approach to the Combinatory Chemistry and High-Throughput Screening (HTS) in identifying novel drug candidates. In VS, only compounds that are selected applying different computational tools to huge virtual libraries of compounds are further tested in vitro. However, the effective use of VS model applications have some challenges such as the inherent complexity of the ligand-receptor interactions as well as by other factors such as ligand and receptor multiple conformations and also ligand metabolic stabilities and toxicities. Altogether these difficulties are hardly overcome using only one computational tool. Therefore, in the literature, it has been suggested to apply a sequence of different filters, such as filters that select compounds through similarity, pharmacophore and docking. In this review, we describe the advantages, limitations and examples of recent successful applications of some of these filters, including drug-like properties, structural properties, 2D similarity, pharmacophore, shape and docking filters. Moreover, we present the main steps involved in the preparation of virtual libraries of compounds that can be used in the VS.

Resumo em Inglês:

Lanthanoid organic frameworks (LOFs) stand out as an important class of functional materials. The possibility to employ a great range of metals and ligands lead to the formation of varied and highly porous structures, with diverse applications. The presence of lanthanoid ions favours the improvement of the optical, magnetic and redox properties of MOFs. This review aims to demonstrate the state of the art of LOFs, emphasizing the chemical properties of trivalent lanthanoid ions and the carboxylic based-ligands used in their construction, as well as the main characterization methods and outstanding applications as gas storage, permanent magnets, catalysis, luminescence, drug delivery and so on.

Resumo em Inglês:

An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH3OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.

Resumo em Inglês:

In this work is proposed a didactic alternative vision to teach pericyclic reactions. To this end, they were classified according to the connectivity of reactants systems, as connected atom reactions (CAR) and the other possibility, as not connected atom reactions (NOCAR). Electrocyclic reactions and sigmatropic rearrangements are examples of CAR categorization, and the cycloadditions being NOCAR. With these two categories, a pedagogical alternative description is proposed to the orbital topology in reactants to explain the pericyclic reactions. According to this classification, the HOMO's topology is adequate to all CAR, while the traditional HOMO-LUMO's topology is adequate to NOCAR. All issues typically deduced by the traditional treatment, such as allowed and forbidden reactions, and stereochemical aspects are also explained by the alternative approach.

Resumo em Inglês:

A simple and low cost experiment is proposed to chemistry students associating the Photodynamic Activity involving Chemical and Biochemical concepts. The inclusion of this experiment in undergraduate courses in Chemistry promotes interdisciplinarity and contextualization, combining current and relevant topics to the teaching of program content. The experiment used the Methylene Blue and Erythrosine B as dyes to demonstrate the photodynamic action of these photosensitizers in the inhibition of microbial growth. Both dyes presented satisfactory results against environmental microorganisms. The growth inhibition was caused exclusively by the photochemical processes undergone by the dye/light/oxygen, with LED light exposure.

Resumo em Inglês:

1,2,4-Oxadiazoles are heterocyclic compounds that have a remarkable range of applications. This overview focused on investigating the potential and scientific and technological evolution of these compounds through an analysis of patent databases and scientific papers. Prospecting technology using patent databases is an important tool for mapping technologies or technological areas, allowing the identification of such things as trends and investments. The mapping of 1,2,4-oxadiazoles patents and patent applications was facilitated by using different key word from scientific papers found in the INPI, Esp@cenet, WIPO, LATIPAT databases and in the Web of ScienceTM database. The majority of the patent records related to the researched technology had been filed in the Esp@cenet database. A constant linear growth in the number of records of patents granted could be observed over the years, with a remarkable dominance of patents recorded in the USA (24.7%). In addition, when the search through scientific papers was performed, the USA was also the country that had produced the largest number of publications. On the other hand, Brazil presented only two patent grant records (0.2%) and fifty-four published papers related to the technology being researched. In summary, there is great scientific and technological interest in the 1,2,4-oxadiazoles.