Resumo em Inglês:

This review contains experimental values of polar tensors and generalized atomic polar tensor (GAPT) charges determined since the publication of the polar tensor formulism for infrared intensity interpretation in 1961. GAPT charges, also called mean dipole moment derivatives, for 167 atoms of 67 molecules are discussed and compared with infrared charges also determined completely from experimental intensities. The importance of the charge transfer and polarization dynamic contributions to the GAPT charge are emphasized as they differentiate this charge from most theoretically calculated charges. The inclusion of these dynamic contributions is shown to be necessary to provide adequate numerical descriptions of core electron ionization energy processes. These contributions are expected to be important in studies of chemical reactivity.

Resumo em Inglês:

In recent years, the production, distribution and consumption of so-called new psychoactive substances, such as synthetic cannabinoids, synthetic cathinones, and phenethylamines, have increased worldwide. The present work reports the identification of such substances found in samples of blotter papers that were seized in the city of Bogotá in accordance with the analytical method implemented in the chemistry laboratories of the Attorney General of Colombia. Using gas chromatography coupled to a selective mass ion trap detector, the presence of phenethylamine derivatives, mainly from the 2,5-dimethoxy- N-(2-methoxybenzyl) phenethylamine series, was detected. Among them, 2-(4-chloro-2,5-dimethoxy- N-(2-methoxybenzyl)) phenethylamine, 2-(4-bromo-2,5-dimethoxy- N-(2-methoxybenzyl)) phenethylamine, and 2-(4-iodo-2,5-dimethoxy- N-(2-methoxybenzyl)) phenethylamine ( m/z 150, 121, 91) were prevalent. The 2,5-dimethoxy- N-(2-methoxybenzyl) phenethylamine series derivatives correspond to proved powerful hallucinogens that have not yet been subjected to international control and supervision.

Resumo em Inglês:

In this work, desulfurization of real fluidized catalytic cracking (FCC) gasoline was investigated in dual steps; first in oxidative desulfurization (ODS) using imidazolium and pyrrolidonium based Brønsted acidic ionic liquids (ILs) as solvent and catalyst and hydrogen peroxide as oxidant. In second step, extractive desulfurization took place using organic solvents of furfural, furfural alcohol and ethylene glycol. Variety of factors such as temperature, time, mass ratio of oil/ILs and regeneration and recycling of ILs, multiple-step desulfurization of ILs and organic solvents and solvent/oil ratio were also investigated. The S-content was significantly decreased to ca. 18 ppm from initial S-content of 260 ppm with a total S-removal of ca. 95% in one-step ODS using pyrrolidonium based ILs coupled with five-step extraction desulfurization (EDS) using furfural alcohol as extractant. This work shows that oxidative desulfurization using ionic liquids coupled with extractive desulfurization using organic solvents is a potential method to produce clean gasoline.

Resumo em Inglês:

A novel 12-molybdophosphoric acid (HPM)-based complex (H2PI)2(H3O)[PMo12O40][Mo2O5(H2O)2(PI)2]·11H2O (PI-HPM) was prepared by modification with picolinic acid (HPI) and characterized by the methods of Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG), X-ray powder and single crystal diffraction. The complex retained the classical Keggin structure of bulk HPM, there were some strong hydrogen bonds existing between the [PMo12O40]3- polyanion, the [Mo2O5(H2O)2(PI)2] coordination moiety, the protonated HPI and the lattice water molecules. Then PI-HPM was employed as heterogeneous catalyst for esterification reaction to evaluate its acid-catalytic activity. The complex exhibited high activity and good durability in reaction mixtures, indicating that it was a promising heterogeneous acid catalyst for esterification that including the conversion of oleic acid to oleates.

Resumo em Inglês:

The decomposition of the solid solution of potassium jarosite with chromium(VI) in Ca(OH)2 media was studied in the present work. According to experimental results, the incorporation of CrO42- into the crystal structure of jarosite resulted in a solid solution with the following approximate formula: [K0.86(H3O)0.14]Fe2.67[(SO4)1.23(CrO4)0.77][(OH)5.01(H2O)0.99]. The experimental data describe a reaction based on the shrinking core model with chemical control for spherical particles. A reaction order of n = 0.67 and an activation energy (Ea) of 63.75 kJ mol-1 were obtained in the induction period (tind). The progressive conversion period is characterized by the diffusion of K+, SO42- and CrO42- ions into the solution. In this stage, n = 1.99 with respect to OH-, and Ea = 51.56 kJ mol-1. The CrO42- diffusion is slower compared to that of sulfate, a slight amount of chromate is adsorbed in the layer of the solid residue consisting on Fe(OH)3. Finally, the equations that satisfactorily describe the reaction process were established from the data obtained.

Resumo em Inglês:

For the first time, the isotope ratio of lead is reported in Brazilian red wines. The lead concentration and the ratios of 204Pb/206Pb, 207Pb/206Pb and 208Pb/206Pb were determined in 94 red wines produced in Campanha Gaúcha, Serra Gaúcha, Vale dos Vinhedos in Southern Brazil and Vale do São Francisco in Northeastern Brazil. The values observed for the isotopic ratios were consistent with those reported in the literature for wines of South America. The lead isotopic ratios showed no statistically significant differences among the vineyards of the Southern region; on the other hand, the vineyard from the Northeastern region showed large variations in its ratios. The 204Pb/206Pb ratio data demonstrated that the wines of the Southern region have radiogenic features, whereas the wines of the Northeastern region ranged from slightly to very radiogenic. These results indicated that the lead concentrations in the wines from these Brazilian regions are influenced both by agricultural practices and by natural occurrences. Isotope ratios allowed for differentiation among the wines produced in these two important wine producing areas in Brazil and are emerging as a promising tool in the study of the geographical origin of Brazilian wines.

Resumo em Inglês:

The present study describes the antiprotozoal activities of four cyclopalladated compounds, [Pd(dmba)(μ-Cl)]2, [Pd(dmba)(NCO)(isn)], [Pd(dmba)(N3)(isn)] and [Pd(dmba)(μ-NCO)]2, (dmba: N,N'-dimethylbenzylamine and isn: isonicotinamide), against the diseases leishmaniasis (Leishmania amazonensis and Leishmania infantum), Chagas disease (Trypanosoma cruzi) and human African trypanosomiasis (Trypanosoma brucei). [Pd(dmba)(μ-NCO)]2 exhibited good leishmanicidal and trypanocidal activities against L. amazonensis and T. cruzi intracellular amastigote forms, with a 50% inhibitory concentration (IC50) value of less than 9 µM and selectivity indexes of 14.47 and 28.42, respectively. Stability essays were conducted in phosphate buffer saline (PBS) pH 7.0 and showed that [Pd(dmba)(μ-NCO)]2 is the most stable molecule. These findings indicate that this compound presented higher selectivity for these parasites than the other tested compounds. The data presented here suggest that this compound should be considered in the development of new and more potent drugs for the treatment of leishmaniasis and Chagas disease.

Resumo em Inglês:

An electrochemical immunosensor for detection of aflatoxin B1 (AFB1) in food samples was developed. The sensor is composed by cysteine monolayer immobilized on gold electrode surface with subsequent bind to monoclonal antibody (MAb-Cys-modified electrode). The AFB1 detection was evaluated by cyclic voltammetry and impedance spectroscopy in the frequency range of 100 mHz-100 kHz. Samples of rice were spiked with AFB1 to evaluate the sensitivity of the sensor. Impedance spectra could be fitted to a Randles equivalent circuit containing a constant phase element. Atomic force microscope (AFM) images showed MAb-AFB1 complex immobilized across the electrode surface. The electron transfer resistance (Rct) increase was attributed to a decrease in the charge permeability of the MAb-AFB1-Au surface to a redox probe K4[Fe(CN)6]4-/K3[Fe(CN)6]3-. The surface coverage exhibited a linear relationship as function of toxin concentration and is found to be 0.75 at 30 µg mL-1. The obtained sensor is a promising candidate for detection of AFB1 in rice with sensitivity and specificity.

Resumo em Inglês:

In this study, fifteen endophytic fungi were isolated from Paepalanthus planifolius (Eriocaulaceae). From the capitula, seven endophytes were screened and evaluated for their metabolomic profile and radical scavenging activity (2,2-diphenyl-1-picrylhydrazyl (DPPH) assay). Chemical investigation of ethyl acetate extract of the endophytic fungus Anthostomella brabeji resulted in the isolation of one new compound, (+)-(6R*,7S*,8R*)-6,7,8-trihydroxy-2,2-dimethyl-5,6,7,8-tetrahydro-chroman-4-one, and three known compounds: 6-hydroxy-2,2-dimethyl-5,6,7,8-tetrahydro-7,8-epoxycroman-4-one, siccayne and eutypinol. All of the compound structures were elucidated using 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. The antimicrobial activity of the compounds and A. brabeji extract were assayed against the microorganisms Staphylococcus aureus, Escherichia coli, Salmonella setubal and Candida albicans. Measured minimal inhibitory concentration (MIC) values ranged from 31.25 to 1000.0 µg mL-1.

Resumo em Inglês:

This work describes a method for the determination of gallic, caffeic and p-coumaric acids, as well as quercetin, in Brazilian red wines by employing reverse phase high performance liquid chromatography (RP HPLC) coupled to diode array and mass detectors. The method was performed using a sample volume of 10 µL. The limits of detections were 0.36, 0.27, 0.33 and 0.59 mg L-1 for gallic acid, caffeic acid, p-coumaric acid and quercetin, respectively. The precision, as estimated by the relative standard deviation, was between 1.0 and 2.0% for different concentrations of gallic acid, caffeic acid, p-coumaric acid and quercetin. The accuracy was evaluated by addition and recovery experiments, and the obtained values were between approximately 92 and 117% recovery. The method was then applied to the analysis of red wine samples that were collected from the São Francisco region, Bahia State, Brazil. The concentrations of analytes were determined in ten Brazilian wines and varied from 5.26 to 10.22 mg L-1 for quercetin, 6.65 to 43.92 mg L-1 for gallic acid, 3.58 to 7.83 mg L-1 for p-coumaric acid, and 3.59 to 10.5 mg L-1 for caffeic acid.

Resumo em Inglês:

A series of highly dispersed Pd/Al2O3 catalysts were prepared via the polyol method. The catalysts were characterized by nitrogen adsorption, X-ray diffraction (XRD), UV-Vis spectrophotometry, temperature programmed reduction (TPR) and transmission electron microscopy (TEM). The influence of Pd particle size on the hydrogenation of 2-amyl anthraquinone (AAQ) was investigated in a trickle-bed reactor. The turnover frequency (TOF) showed antipathetic size dependence while the space time yield (STY) peaked at 4 nm. Also, the selectivity and deactivation rate were affected by the size of palladium particles. The structure-sensitivity relations for the catalysts may be ascribed to the necessities of specific Pd cluster structure for the activation of π-bond.

Resumo em Inglês:

This paper describes the use of digital imaging acquired from a conventional desktop scanner for characterization of newly synthesized amino-nitroquinoxaline dyes. The synthetic protocol was based on reactions of building block 2,3-dichloro-6,7-dinitroquinoxaline with aliphatic amines and experiments based on image analysis were carried out with compounds in solution (96-microwell plates) and/or adsorbed on silica (thin-layer chromatography (TLC) plates). Three main goals were achieved: firstly, compounds 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline and 6,7-dinitro-2,3-dipyrrolidinoquinoxaline had their concentration predicted in dimethyl sulfoxide (DMSO) solution, as a mixture. Secondly, TLC studies were performed to build a kinetic profile in attempt to monitor reaction involving conversion of 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline into 6,7-dinitro-2,3-dipyrrolidinoquinoxaline. Lastly, image analysis and UV-Vis spectroscopy were applied to study the interaction of 2,3-di-n-butylamino-6,7-dinitroquinoxaline with hydroxide anion in DMSO. These approaches based on digital image characterization were successfully implemented in qualitative and quantitative analysis of organic dyes.

Resumo em Inglês:

Cardanol is an alkyl/alkenyl phenolic material obtained from cashew nut shell liquid (CNSL), which is a byproduct of cashew nut processing. In an effort to develop new uses, cardanol was derivatized for the first time with diethyl azodicarboxylate (DEAD) through the ene reaction. The reaction was facile and required only the application of heat without a catalyst. Both conventional heating and microwave heating were shown to be effective; the latter entailed much shorter reaction time and substantial energy savings. The reaction product (a hydrazino-ester derivative of cardanol) was characterized by nuclear magnetic resonance (NMR). The product increased in viscosity with time and may be useful as a viscosifier in oil-based commercial formulations and as a synthon for further organic reactions.

Resumo em Inglês:

Considering the high interest and commercial value of pigments from microalgae, this study aimed to stablish the best lutein and β-carotene extraction method for Desmodesmus sp., a microalgae with high biomass production. The evaluation was done considering the best solvent or solvent mixture, number of extractions, pre-treatment of dry biomass with acetone, saponification in methanol and ethanol and stability evaluation of the obtained extract. Among achieved results, the best solvent extractor was a hexane:ethanol mixture in a 1:1 (v/v) proportion. In order to obtain maximum yield, the pattern stablished includes six extractions performed for 40 minutes. Stability tests presented that xanthophylls and carotenes pigments were more stable in methanol and that xanthophylls and carotenes pigments were less negatively affected than chlorophylls in the methanolic extract. Chromatographic identification and quantification of pigments from Desmodesmus sp. microalgae revealed that its major constituents are trans-zeaxanthin, chlorophyll b, β-carotene and trans-lutein.

Resumo em Inglês:

The photocatalytic performance of a composite based on the association of TiO2 and 2.5 wt.% of zinc(II) phthalocyanine (TiO2/ZnPc) was evaluated towards the mineralization of paracetamol and compared to that observed for the bare oxide in different pH and H2O2 concentrations. The results show that the photocatalytic performances were influenced by the pH, with maximum efficiency around the isoelectric point. Mineralization efficiencies between 86-91% was obtained using TiO2/ZnPc in pH 5.5-6.8, with 33 mg L-1 of H2O2, ca. 15% higher than that observed with TiO2. The mineralization efficiencies using bare TiO2 and TiO2/ZnPc were respectively 112 and 18% lower in the absence of H2O2. The better performance of TiO2/ZnPc is related to its extended light absorption and non-uniform coating of the TiO2 surface by ZnPc aggregates. Above pH 6.8, the mineralization efficiencies decrease for both photocatalysts, although the consumption of H2O2 remains above 90%, due to its decomposition in alkaline pH.

Resumo em Inglês:

Hexanitrohexaazaisowurtzitane (CL-20) is the most powerful non-nuclear explosive in the world. Herein, a greener and safer new one-pot method for the synthesis of CL-20 from tetraacetyldibenzylhexaazaisowurtzitane (TADB) has been developed through zeolite/98% HNO3. The H-ZSM-5 catalyst, with both Brønsted and Lewis acid sites, indicated higher catalytic activity. The reaction using H-ZSM-5 has been optimized with respect to reaction temperature, reaction time, amount of acid and amount of catalyst to substrate ratio.

Resumo em Inglês:

This study describes the synthesis of fourteen thiazinanones from a multicomponent reaction of 2-morpholinoehtylamine (as primary amine), arenealdehydes (as carbonyl compound) and the mercaptopropionic acid using both conventional (thermal heating) and ultrasound methodologies. Through thermal heating methodology, the thiazinanones were obtained in 49 to 97% yields for 16 hours and through sonochemistry methodology, the reaction time was reduced for 25 minutes with yields 41 to 88%. The full identification and characterization of unpublished heterocycles were achieved by proton (1H) and carbon 13 (13C) nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry and infrared. Some of them were also characterized by elemental analysis.

Resumo em Inglês:

The chiral separation of sibutramine enantiomers was resolved succesfully by capillary zone electrophoresis using cyclodextrins (CDs) as chiral selectors. A complex screening of several different native and derivatized, neutral and ionized cyclodextrine derivatives was performed. The effects of buffer type, concentration and pH, cyclodextrin type and concentration, applied voltage, capillary temperature and injection parameters on the chiral resolution were examined. The best results on a very short fused silica capillary of 30 cm × 50 μm were obtained using a 50 mmol L-1 phosphate buffer containing 10 mmol L-1 randomly methylated β-CD at a pH of 4.5, 15 kV of voltage, temperature of 15 °C, injection parameters of 30 mbar s−1 and ultraviolet (UV) detection at 220 nm. The analytical performances of the optimized method were verified in terms of linearity, precision and robustness, and limit of detection and quantification were calculated.

Resumo em Inglês:

Propacetamol is an acetaminophen prodrug of intravenous administration used to control fever and pain of perioperative period in multimodal analgesia therapy. After injection, it is completely converted by plasma esterases into N,N-diethylglycine and acetaminophen, its active metabolite whose mechanism of action is the inhibition of prostaglandin synthesis. Herein, we report an improved protocol for the synthesis of propacetamol hydrochloride that allows the isolation of the active pharmaceutical ingredient (API) with high purity and yield. In addition, the in vitro metabolism of propacetamol in a microssomal reaction was evaluated by ion trap tandem mass spectrometry.

Resumo em Inglês:

A facile and efficient method for esterification and amidation of carboxylic acids under neutral conditions has been developed. Esters and amides can be prepared by reacting a carboxylic acid (1 mmol) with tribromoisocyanuric acid (0.37 mmol) and triphenylphosphine (1 mmol) in dichloromethane at room temperature, followed by addition of an alcohol or an amine, respectively.