Resumo em Inglês:

In this study, the conformational behavior of N-benzyl-N-(furan-2-ylmethyl) acetamide in chloroform was addressed by using a combined experimental/theoretical strategy using NMR spectroscopy and quantum chemical calculations. The 1H and 13C one-dimensional NMR spectra, as well as the two-dimensional HSQC-DEPT and HMBC-DEPT NMR spectra, evinced the presence of a hindered cis(E)-trans(Z) rotational equilibrium in solution. DFT calculations were performed at different theoretical levels using the polarizable continuum model (PCM) and predicted nine (four Z and five E structures) stable conformations. The interconversion dynamics among the different confirmations were established in terms of four different rotational equilibria in CDCl3. The chemical shifts in the 1H and 13C NMR spectra of the compound are similar to the values calculated for the two most abundant conformational equilibria at room temperature, one caused by two Z rotamers and the other by two E rotamers. The compound was also characterized for the first time by FTIR, Raman spectroscopy, and GC/MS spectrometry. Additionally, several acylation methodologies for synthesizing the title compound from N-benzyl-1-(furan-2-yl)methanamine were tested which resulted in high yields (> 90%) under very convenient conditions (10 min, at room temperature).

Resumo em Inglês:

The present work describes the chemical constituents of Odontadenia lutea (Vell.) Markgr. leaves and the toxicities of its extract and fractions against Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae). Chromatographic procedures of the ethanolic extract resulted in the identification of the triterpene β-amyrin, the flavonoid rutin, two fatty acids palmitic and linolenic, and one glyceroglycolipid 3-O-(9,12,15-octadecatrienoyl)-glyceryl-β-D-galactopyranoside, which are known compounds, but they are described for the first time in the Odontadenia genus. The known triterpenes lupeol and α-amyrin were also identified. Structural identification of the compounds was performed by analysis of IR, ESI-MS, and 1D and 2D NMR spectra. The toxicity of its extract and fractions from O. lutea leaves was tested against leaf-cutting ants Atta sexdens rubropilosa Forel by employing ingestion bioassay procedures. The hexane fraction (2 mg mL-1) decreases the average survival of ants from sixteen to six days, causing 98% mortality on the 14th day and 100% at the end of the experiment.

Resumo em Inglês:

In this work, an alternative and low-cost technique for the extraction and quantification of Fe (total) from food supplements by digital image analysis is shown. The method is based on the complexation of Fe ions in solution with the 8-hydroxyquinoline ligand, forming a colored complex that is extractable from aqueous solution to polyurethane foam, coloring this one, which was initially white, to brown. After the acquisition and treatment of the digital image generated by the foam, the quantification of Fe is performed. Interference and recovery tests show that the method is not affected by concomitants in the sample. The method was applied to 3 different types of dietary supplements, and these results were compared to those obtained by FAAS, showing statistical equivalence. The limits of quantification obtained in this work was 1.78 µmol L-1, the limit of detection was 0.53 µmol L-1, the accuracy was 97.5 + 4.8% and the precision was 8.45%. The analytical curve was linear from 2.0 to 10.0 µmol L-1, with a r2 of 0.9975.

Resumo em Inglês:

Glycerol is a plasticizer widely used due to its good plasticization efficiency, great availability, biocompatibility and low exudation. It is a renewable raw material that, when introduced in biodegradable films, promotes significant changes in its properties and, thus, guarantees a wide spectrum of application. In this work, corn straw was used to produce cellulose triacetate films from mixtures with glycerol (10%, 20% and 30%). The films were characterized by X-Ray Diffraction, Scanning Electron Microscopy, Thermogravimetric Analysis, Water Vapor Transport Rate and Water Vapor Permeation. The cellulose triacetate films produced with 20% glycerol have high barrier properties, when compared to films with concentrations 0, 10 and 30%.

Resumo em Inglês:

Biomass is a renewable energy source most used in the world, however, depending on the chemical properties and origin of the material used as biofuel, the amount of ash generated during combustion can be high, harming the energetic harnessing. The objective of this study was to characterize chemically and physically biomass: bark, sawdust, and urban pruning; used for energy generation. Also, part of the study was the physical characterization of briquettes produced from these materials. The analyzes performed to characterize the biomass were: moisture determination, higher heating value, proximate analysis and chemical composition - extractives, lignin and holocellulose contents. Subsequently, the biomass was briquetted and the mechanical properties of the briquettes were tested. The results showed that all biomass (bark, sawdust, and urban pruning) has the energy potential to be used in the industry. T1 briquettes (100% bark) showed the highest mechanical resistance. However, the formation of blends should be sought to minimize the ash content in the boiler. Thus, blends T2 and T3 can be considered as the best alternatives for the company.

Resumo em Inglês:

In recent years, research on the development of protective materials has expanded significantly in order to find efficient and economically viable solutions for application in various industrial segments. Among these materials, those aimed at protecting metallic substrates against high temperatures that end up causing corrosive processes, stand out due to the huge market demand. Advantages such as reproducibility in the process, cost reduction and reduction in environmental impact also directly contribute to the search for protective coatings as an efficient protective alternative. This article presents the characterization of a ceramic coating developed in a previous study that used silicon carbide as a filler, using potassium silicate (water glass) as a matrix (binder), and whose anti-corrosion and thermal protection properties stood out, mainly in applications in the aerospace industry. In this stage of the work, tests of thermal analysis (thermogravimetry) were carried out for the physical and chemical characterization of the material. The results corroborate those previously achieved when applying the coating on components of a hybrid rocket engine tested on a fixed-point bench.

Resumo em Inglês:

The objective of this research was to synthesize biocompatible polyurethanes, with suitable mechanical properties to be used as biomaterials. Polyurethanes were synthesized with polyols derived from castor oil and isophorone diisocyanate (IPDI), hexamethylene diisocyanate and 4,4’-methylenebis (cyclohexyl isocyanate), with the addition of polycaprolactone/chitosan (PCL/Ch). The materials were evaluated for their mechanical properties by determining the stress-strain curves, thermogravimetric analysis, differential scanning calorimetry analysis and contact angle. The biological response of the materials was evaluated by measuring in vitro cell viability on the L-929 mouse fibroblast cell line. The mechanical properties of polyurethanes vary according to the type of polyol and diisocyanate used. The best results were obtained with transesterification-modified polyols with cycloaliphatic diisocyanates. The best results were found for polyurethane synthesized with IPDI and the modified polyol (P.3): 17 MPa of maximum stress at break, 0.937 MPa of Young’s modulus, elongation greater than 250%. Polyurethanes do not have toxic effects and cell viability values exceed 70% on the L-929 fibroblast line. The addition of PCL/Ch improves the cell viability of polyurethanes. The results indicate that the polyurethanes synthesized with polyols derived from castor oil can be used in the design of biomaterials due to the mechanical and biological properties obtained.

Resumo em Inglês:

Qualitative and quantitative assessment of total sulfur and sulfur species in solid phase is necessarily important for development of effective desulfurization methods, reduction of environmental pollution, and prevention of catalyst poisoned. In this work, TPO-IR (Temperature Programmed Oxidation- Infrared) method was used for rapid determination of sulfur species in solid minerals. The high purity of Ag2S was used as the calibration materials at the fixed temperature of 1100 °C, and the TPO experimental runs were performed on the solid minerals of phosphorite and coal. The results show that pyrite sulfur with Tmax of 426 °C, and two thiophene sulfurs with Tmax of 450 °C and 481 °C were found in Kaiyang phosphorite by fitting the TPO-IR curves; while pyrite sulfur with Tmax of 432 °C, complex sulfide with Tmax of 679 °C and sulfate sulfur with Tmax of 939 °C were found in Weng’an phosphorite. For Gas coal, the TPO-IR curves of sulfur release can be deconvoluted into seven individual curves, while that of Anthracite deconvoluted into four individual curves. In conclusion, the TPO-IR method has many advantages for determination of sulfur species in solid phase systems, such as less sample consumption, simple pretreatment, convenient operation and low cost, etc.

Resumo em Inglês:

This study compares the techniques cold vapour atomic fluorescence spectrometry (CV-AFS) and inductively coupled plasma mass spectrometry (ICP-MS) for the determination of Hg in biological samples (hepatic tissue from marine tetrapods). Acid digestions were performed for the samples and aliquots of them were analysed by ICP-MS and CV-AFS. To minimize the Hg memory effect in its determination by ICP-MS, gold (200 µg L-1 in 5% v v-1 HCl) was added to the sample digests. The detection limits were 0.02 mg kg-1 for ICP-MS and 0.01 mg kg-1 for CV-AFS. Accuracy was assessed by the calculation of the recovery obtained from TORT-3 (lobster hepatopancreas) certified reference material analysis. Accurate results were obtained for both CV-AFS and ICP-MS. The comparison of the results obtained for hepatic tissue with and without lyophilization showed a significant difference among them (at 95% of confidence level), evidencing losses of Hg in the lyophilization process.

Resumo em Inglês:

Coffee is one of the most popular beverages in the world, however, little information is found regarding the mineral composition of commercial roasted and ground coffees (RG) and its correlation with organic bioactive compounds. 21 commercial Brazilian RG coffee brands - 9 traditional (T) and 12 extra strong (ES) roasted ones - were analyzed for the Cu, Ca, Mn, Mg, K, Zn, and Fe minerals, caffeine, 5-caffeoylquinic acid (5-CQA) and melanoidins contents. For minerals determination by flame atomic absorption spectrometry (FAAS), the samples were decomposed by microwave-assisted wet digestion. Caffeine and 5-CQA were determined by liquid chromatography and melanoidins by molecular absorption spectrometry. The minerals and organic compounds contents association in RG coffee was observed by a principal component analysis. The thermostable compounds (minerals and caffeine) were related to dimension 1 and 2, while 5-CQA and melanoidins were related to dimension 3, allowing for the T coffees segmentation from ES ones.

Resumo em Inglês:

Rotaxanes are currently one of the most promising objects of study in the field of artificial molecular machines. A rotaxane molecule is composed by two or more molecular components that are connected by a mechanical bond. 51 years ago, the first synthesis of this type of molecules was performed, since then, there has been a great effort in obtaining new models to study its molecular movements and application as molecular machines. Here, we present an overview of intercomponent interactions in rotaxanes and how these interactions affect the major movements presented by this class of molecules. For this, different approaches to assess these interactions are discussed, both in solution and solid state.

Resumo em Inglês:

This paper presents a comprehensive interface and electrochemical phenomena review of different anodes for SOFC. In this way, it was possible to select some mixed electronic and ionic conductor materials alternatives to the conventional anode, Ni-YSZ conductor. New materials must present a satisfactory electronic and ionic conductivity at intermediate temperatures, be able to operate under different types of hydrocarbon fuels without deactivation, present stability under redox cycles and thermal expansion compatible with the other materials. Among all new materials, Sr0.86Y0.08TiO3, a Y-doped strontium titanate (YST), presented the highest measured conductivity, of 82 S cm-1 at 800 °C. In addition, this material showed excellent stability time and coefficient of thermal expansion compatible with materials used as cathode, strontium-doped lanthanum manganite and electrolyte, yttria stabilized zirconia. SrTiO3 (ST) compounds synthesized by solid-state reaction method, calcined, and sintered to obtain undoped (ST), 4% (YST04) and 8% (YST08) of Y-dopant and as a heterojunction with yttria-stabilized zirconia (YST08/YSZ). It was observed that calcination under Ar/5%H2 atmosphere has increased the dopant maximum concentration in the SrTiO3 cubic crystal structure when compared to inert atmosphere. When the Y solubility limit was exceeded, a pyrochlore phase Y2Ti2O7 was formed on the intergranular region due to the deficiency of oxygen vacancies, especially in the presence of inert atmosphere.

Resumo em Inglês:

In order to increase the specific surface area of Pt-Rh-Pd / Al2O3 automotive three-way catalyst and improve its low-temperature reduction performance, Ce, Zr, and La were added to the Pt-Rh-Pd / Al2O3 catalyst to prepare the fibrous Pt-Rh-Pd / CeO2-ZrO2-La2O3-Al2O3 catalyst via an electrospinning technique. The fibrous catalysts were characterized by XRD, FT-IR, SEM-EDS, H2-TPR and BET analysis. The catalytic effect of the catalyst on automobile exhaust was also studied. Results revealed that the surface of catalysts is mainly mesoporous. Ce, Zr and La can remarkably increase the specific surface area of the Pt-Rh-Pd / Al2O3 catalyst. The specific surface area of the catalyst prepared with Pt Rh Pd molar ratio of 0.75:0.01:1 is 301.5816 m2 g-1, and the average diameter of which is 790 nm. In addition, the reaction temperature of the catalyst is approximately 220 °C, which shows good low-temperature reduction performance. Moreover, the Pt-Rh-Pd / CeO2-ZrO2-La2O3-Al2O3 catalyst has a catalytic conversion efficiency for NOX of 90.0% in automobile exhaust, a catalytic conversion efficiency for CO of 88.8%, and a catalytic conversion efficiency for SO2 of 75%.

Resumo em Inglês:

Spectrophotometry and potentiometry techniques were used to quantify silver in an ophthalmic solution. A standard solution of silver nanoparticles was synthesized, from which an analytical method was developed to quantify silver in the sample. Potentiometric titrations of three samples were made, using an electrochemical cell containing an alternative metallic indicator electrode and an Ag|AgCl double junction reference electrode, connected to a potentiometer. A digital burette containing a standard solution 5.00 x 10-3 mol L-1 NaCl was used. Characterization of the ophthalmic solution by spectrophotometry showed that Ag in this medicine is in the form of nanoparticles. The sample preparation for potentiometric measurements was carried out using a mixture of 50 µL of the ophthalmic solution and 2.00 mL of nitric acid. The average concentrations of Ag obtained were 1.65 ± 0.03% (w/v) by spectrophotometry, and 1.73 ± 0.06% (w/v) by potentiometry. The relative standard deviations were 2% and 4%, respectively. The precision of the measurements obtained by the cited methods showed no significant differences (f test). It was also observed that average silver concentrations obtained by the two methods were not statistically different (t test). Both tests were made at a 95% confidence level.

Resumo em Inglês:

A very simple, but rich experiment, encompassing a classical Galileo’s pendulum, has been devised to be performed at home, especially during the Covid-19 pandemics. The experiment uses a miniature supermagnet rod as the pendulum oscillating element suspended from a fixed sewing thread. Its physics can be fully investigated, allowing to study the oscillation movements and to extract the gravity acceleration constant. The interaction with chemical substances can be accurately monitored by equilibrating the magnetic attraction of the probe as it opposes the gravity restoring force. Magnetic susceptibilities can be precisely measured in this way, allowing to access the number of unpaired electrons in the compounds, while stimulating discussions in the light of the ligand field theory. The simplicity and the opportunity of joining physics and chemistry are the most relevant aspects of the experiment. Curiously, the pendulum performance also implies a meditation like posture, requiring complete silence and confinement. In this sense it can also help relaxing our mind during the pandemics.

Resumo em Inglês:

The proposal addresses the electrochemical experimentation as a pedagogical instrument for the integral and dynamic student involvement, facilitating the teaching-learning process. The experimental proposal focuses on the conversion of electrical energy to chemical energy and vice versa. The experiments for the two simultaneous energy conversions were designed with simple, easily accessible and inexpensive reagents and materials. The production of hydrogen and oxygen gases in the electrolytic cell, and the consumption of these same gases in the fuel cell, exploits the non-spontaneous and spontaneous electrochemical semi-reactions, respectively, that occur at the anode and cathode. Hydrogen gas production is crucial to the development of fuel cell technology. To facilitate the identification of anodic and cathodic reaction, and the monitoring of electrochemical decomposition of water, black bean extract was used as an alternative indicator. The electrochemical reactions involved in energy conversions are considered fundamental in the teaching-learning process of basic concepts related to water electrolysis and the recombination of hydrogen and oxygen gases. The experiment also corroborates the elucidation of alternative ways to generate electricity to meet the current needs of modern society.

Resumo em Inglês:

Currently, the public and private organizations resort to Intellectual Property mechanisms to protect their innovations and ensure their rights, with patents being the main form of protection of generated products and processes. In the Brazilian chemical sector, where there is the intensive use of new technologies which provide the basis for several other industrial sectors, having a direct impact on the country’s economy, the use of patents as a source of information can assist in the strategic management of companies in the segment. Considering the economic and social relevance of the patenting activity and the chemical industry for the country, the present study performed a systemic analysis of patenting on the Brazilian chemical industry, evaluating the patent applications by the leading companies in the sector. The results showed that these companies have a great interest on patenting, mostly products, prevailing the invention patent type, and a low interest on the protection of their products and processes in different geographical regions through deposits via Patent Cooperation Treaty (PCT). Also, a great interest on the use of externals sources of knowledge, mostly federal educational institutes, and a low index of granted patents, even with individual backlogs lower than the national average.