Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> http://www.scielo.br/rss.php?pid=0103-505320150006&lang=es vol. 26 num. 6 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[The Multiple Faces of Eugenol. A Versatile Starting Material and Building Block for Organic and Bio-Organic Synthesis and a Convenient Precursor Toward Bio-Based Fine Chemicals]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601055&lng=es&nrm=iso&tlng=es Phenylpropenes are produced by plants as part of their defense strategy against microorganisms and animals, and also as floral attractants of pollinators. Eugenol, the main component of clove’s essential oil, is an inexpensive and easily available phenylpropene that has been known by humankind since antiquity, and used as a medicinal agent, but also for food flavoring and preservation. The review includes the most relevant results obtained during the last 15 years with regard to the synthetic uses of eugenol. Discussed here are the multiple applications of eugenol in organic synthesis, including its use as starting material or building block for the total synthesis of natural products, their analogs and derivatives, as well as other structurally interesting or bioactive compounds. The preparation technologically relevant macrocycles and polymeric derivatives of eugenol, is included, and the impact of biotechnology on the use of eugenol as feedstock for biotransformations, leading to other valuable small molecules is also addressed. <![CDATA[Synthesis and Antitumor Evaluation of New Heterocycles Derived from 3-Methyl-2-benzothiazolinone Hydrazone]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601086&lng=es&nrm=iso&tlng=es 3-Methyl-2-benzothiazolinone hydrazone condensed with some selected aldehydes to give the corresponding Schiff bases. Cyclizing the obtained Schiff base derivatives with thioglycolic acid afforded the respective thiazolylideneaminothiazolidenones. Condensation of 3-methyl-2-benzothiazolinone hydrazone with ethyl cyanoacetate yielded a mixture of the bishydrazine and the cyanoacetohydrazide derivatives. Meanwhile, its condensation with ethyl acetoacetate produced a mixture of the monoketone and the β-diketone derivatives. Besides, the reaction of the starting hydrazone with malononitrile afforded a mixture of the cyanomethylylidene and cyanomethyl hydrazone derivatives beside the bishydrazine derivative. Elementary and spectroscopic measurements were in good accord with the structures postulated for the new compounds. The antitumor activities of certain selected new compounds were screened, in vitro, against a panel of four (liver, HepG2; breast, MCF-7; lung, A549; and colon; HCT116) human solid tumor cell lines. The cells that showed better activity were HepG2 and MCF-7. Structure-activity relationship (SAR) was also discussed. <![CDATA[Separation, Concentration and Determination of Trace Thiamphenicol in Egg, Milk and Honey Using Polyoxyethylene Lauryl Ether-Salt Aqueous Two-Phase System Coupled with High Performance Liquid Chromatography]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601098&lng=es&nrm=iso&tlng=es As a pretreatment technique to trace analysis, polyoxyethylene lauryl ether (POELE10)- salt aqueous two-phase extraction system (ATPES) is coupled with high performance liquid chromatography to analyse thiamphenicol (TAP) in egg, milk and honey. The analysis of the phase behaviors of the ATPES found that the extraction efficiency and enrichment factor of TAP was influenced by the types of salts, the concentration of salt, the concentration of POELE10, the concentration of 1-propanol and the temperature. The optimized conditions of experiment were determined in the multi-factor experiment by using response surface methodology. The extraction efficiency of TAP is up to 99.59% and the optimal values of enrichment factor of TAP was 27 under the optimized conditions. The limit of detection and the limit of quantification of TAP are 0.5 µg kg−1 and 1.5 µg kg−1, which meet the needs of determination of trace or ultratrace TAP in food. <![CDATA[Interrelation Between the Interaction Parameter and the Width of the Adsorption Voltammetric Peak]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601111&lng=es&nrm=iso&tlng=es It is known that the width of adsorption of a voltammetric peak is defined by lateral interactions in adsorption layer, so the peak width may be a key to intensity of these interactions. Correlation between the width of the peak and interaction parameter G has been examined in details. It is impossible to find the exact equation setting G as a direct function of peak width. Approximate equations are proposed to calculate G from the peak width with high accuracy in a wide range of G values. G value can be useful not only for characterization of lateral interactions in adsorbed layer (for finding adsorption isotherm parameters), but also for quick estimation of adsorption of electroactive substance. <![CDATA[Effect of Applied Voltage on Slow-Release of Cu(II) Ions on the Synthesis of Copper(II) Stearate Complex by Electrochemical Technique]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601115&lng=es&nrm=iso&tlng=es An electrochemical technique based on the slow-release of Cu2+ ion from electrochemical oxidation of a Cu anode in the presence of stearic acid (HSt) and an aqueous solution of ammonium acetate (CH3COONH4) (0.1 mol L-1) as supporting electrolyte has been used to synthesize Cu(II) stearate (Cu(II)St) complex. Different values of applied voltages (1, 5 and 10 V) were used during the synthesis to study the effect of applied voltage on the particle size of the Cu nanoparticles and morphology of the synthesized Cu(II)St complex. By using 1 V of applied voltage, small Cu nanoparticle was produced with an average particle size of 2.49 ± 0.82 nm, followed by 5 V (3.61 ± 1.18 nm) and 10 V (6.64 ± 2.72 nm). Another advantage of using 1 V of the applied voltage is the formation of well-shaped petal-like structures of the Cu(II)St complex compared to the synthesis using 5 V and 10 V which inhibit the formation of well-shaped petal-like structure. This proves that the slow-release electrochemical synthesis using lower value of applied voltage has successfully resulted in the formation of small size Cu nanoparticles. <![CDATA[Investigation of the Environmental Transport of Human Pharmaceuticals to Surface Water: A Case Study of Persistence of Pharmaceuticals in Effluent of Sewage Treatment Plants and Hospitals in Malaysia]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601124&lng=es&nrm=iso&tlng=es The present work reports the occurrence and monitoring of 11 pharmaceuticals (i.e., caffeine, prazosin, enalapril, carbamazepine, nifedipine, gliclazide, levonorgestrel, simvastatin, hydrochlorothiazide, diclofenac-Na and mefenamic acid) in surface water and in the influent and effluent of sewage treatment plants (STPs) and hospitals (HSPs). A total of 105 water samples were analyzed using solid-phase extraction combined with liquid chromatography-time-of-flight/mass spectrometry (SPE-LC-TOF/MS). The mean concentrations of the detected pharmaceuticals in STP influent and effluent ranged from &lt; limit of quantification (LOQ) to 3909 ng L−1 and 12 to 577 ng L−1, respectively. The mean concentrations of the detected pharmaceuticals in the hospital influent and effluent ranged from 28 to 1644 ng L−1 and 20 to 1540 ng L−1, respectively. The highest concentration detected in the sampling points was 9099 ng L−1 for caffeine in influent STP. The presence of prazosin has never been reported before in literature. In this study, prazosin was detected in all studied samples, and the highest concentration was 525 ng L−1 in influent STP. Chemometric analysis was used to assess the presence of pharmaceuticals in samples. <![CDATA[Structure of Humic Substances from Some Regions of the Amazon Assessed Coupling 3D Fluorescence Spectroscopy and CP/PARAFAC]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601136&lng=es&nrm=iso&tlng=es The Amazon rainforest presents one of the greater biodiversity in the world and a huge and dynamic carbon reservoir, both in the vegetation and in the soil pools, so it is an attractive subject of study. In the present paper, humic acids from a toposequence of an Oxisol-Spodosol system associated with kaolin was studied using fluorescence emission-excitation matrix combined with parallel factor analysis. The combined techniques allowed to assess the intensities of the two different fluorophores associated with humic acid with core consistency diagnoses of 84.2%. The results for the Humiluvic Spodosol seem to corroborate the model of the supramolecular structure of humic acid, because the intensity ratio of fluorophores does not remain in the profile. Therefore, the use of these combined techniques can provide information about the transformation processes of humic substances in soils, becoming an interesting analytical tool for studying these substances of different soils. <![CDATA[Recovery Process Development for the Rare Earths from Permanent Magnet Scraps Leach Liquors]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601143&lng=es&nrm=iso&tlng=es The current study deals with the recovery process development for the rare earths (REs), i.e., dysprosium (Dy) and neodymium (Nd), metals from permanent magnet scraps leach liquors. Its main objective is the recovery of the rare earths (Dy and Nd) from permanent magnet scraps (PMSs). Introdutory experiments were carried out to get leach liquor solution: oxidation/roasting, acid leaching, and precipitation methods implemented for PMSs dissolution. The obtained PMSs leach liquor was diluted ten times and used for present study. Di-2-ethylhexyl phosphoric acid (D2EHPA) was used as an extractant for recovery of the REs and kerosene as diluent system. The present study optimized the various experimental parameters such as the time influence on extraction process, influence of pH, extractant concentration, separation factors calculated, scrubbing, stripping, maximum loading capacity of the extractant, and various phase ratios as well as phase ratios influence on present metals separations. Loading capacity of D2EHPA and selective stripping process were developed for targeted metal ions by using various mineral acids such as hydrochloric, sulfuric and nitric acids. The metal content analysis in the aqueous samples was determined with inductively coupled plasma optical emission spectrometer (ICP OES) for sensitive and accurate data. <![CDATA[New Alkaloids from <em>Margaritopsis carrascoana</em> (Rubiaceae)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601152&lng=es&nrm=iso&tlng=es Two new alkaloids containing Nb-methyl-triptamine units linked to bis-quinoline moieties, N-8”-formyl-calycosidine and N-8”-methyl-N-1’-demethyl-iso-calycosidine, were isolated from the aerial part of Margaritopsis carrascoana, along with known calycosidine and hodgkinsine. The cytotoxicity of the isolated alkaloids has been evaluated against cancer cell lines. The first two compounds showed only weak activity against HL-60 cell line, while hodgkinsine was the most active compound against HCT-116, OVCAR-8, HL-60 and SF-295 cancer cell lines. The structures of the isolated compounds were established by spectroscopic and molecular mechanical methods. <![CDATA[Adsorption of Transition Metal Chlorides by Silica with Grafted 1-<em>n</em>-Propyl-3-Methylimidazolium Chloride]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601160&lng=es&nrm=iso&tlng=es Silica with grafted 1-n-propyl-3-methylimidazolium chloride was investigated as adsorbent for the removal of cobalt(II), copper(II), zinc(II), cadmium(II) and mercury(II) chlorides from alcoholic and aqueous solutions. The adsorption proceeds via the formation of metal-chloride anionic complexes detained near the grafted organic cations as counterions. This conclusion is corroborated by the electronic and Raman spectra. The high removal degrees of the metal chlorides from solutions are easily reached. The adequate models of adsorption equilibria consider dissociation and auto-complexation of chlorides in solutions and formation of tri- and tetrachlorometallate anions in the solid phase. Also, the equilibrium constants for the CoCl2 and CuCl2 adsorption by several materials containing grafted organic cations and chloride counterions were recalculated in the framework of this model. The weak dependence of equilibrium constants on the nature of immobilized cations and carriers agrees with the established chemistry of metal chlorides fixation. <![CDATA[Optimization of Auxiliary Solvent Demulsification Microextraction for Determination of Cyanide in Environmental Water and Biological Samples by Microvolume UV-Vis Spectrophotometry]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601171&lng=es&nrm=iso&tlng=es A new, simple, rapid and efficient solvent terminated-auxiliary solvent-dispersive liquid-liquid microextraction (ST-AS-DLLME) technique for determination of cyanide ions by microvolume UV-Vis spectrophotometry was developed. Effective parameters on the extraction and absorbance of cyanide were optimized using two optimization methods: fractional factorial design (FFD) and central composite design (CCD). Zinc(II) tetraphenylporphyrine (ZnTPP) was used as a selective cyanide receptor agent. Methyl isobutyl ketone (MIBK), ethanol and 1-butanol were used as extraction solvent, dispersive solvent and demulsifier solvent, respectively. The method shows very good selectivity in presence of other species. The analytical curve was linear in the range of 4.0-130 µg L-1 with a limit of detection of 1.0 µg L-1. Relative standard deviation (RSD) of the method for ten replicate measurements of 100 µg L-1 of cyanide was 1.1%. The method was successfully applied for determination of cyanide in natural water and plasma samples with good spike recoveries. <![CDATA[Synthesis of Nano-Pore Size Ag(I)-Imprinted Polymer for the Extraction and Preconcentration of Silver Ions Followed by Its Determination with Flame Atomic Absorption Spectrometry and Spectrophotometry Using Localized Surface Plasmon Resonance Peak of Silver Nanoparticles]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601180&lng=es&nrm=iso&tlng=es Silver ion imprinted polymer (IIP) was synthesized in the presence of Ag(I)-N,N’‑bis(salicylidene)ethylenediamine (salen) complex using 4-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, and 2,2-azobis(isobutyronitrile) (AIBN) as the initiator. The Ag(I)-imprinted polymer (IIP) particles were characterized by SEM (scanning electron microscope), FTIR (Fourier transform infrared spectroscopy) and BET/BJH (Brunauer-Emmett-Teller/Barrett-Joyner-Halenda) analysis. The imprinted Ag(I) ions were completely removed by leaching the IIP with thiourea (0.5 mol L-1). The polymer was employed as a selective sorbent for extraction and separation of the trace amounts of the Ag(I) ions. The preconcentrated ion was determined via the flame atomic absorption spectrometry (FAAS) or it was reduced to silver nanoparticles and quantified by spectrophotometry based on its localized surface plasmon resonance peak (LSPRP). The figures of merit of both methods were compared. Under the optimized conditions, a sample volume of 80 mL resulted in an enhancement factor of 312. The detection limit (3Sb/m) and the relative standard deviation (n = 10) at 10 µg L-1 level for FAAS were found to be 0.06 µg L-1, 2.9%, whereas for the LSPRP method they were 0.5 µg L-1 and 10.3%, respectively. The methods were successfully applied to the determination of silver in radiology film, hair, nails, and water samples. <![CDATA[TiO<sub>2</sub> Supported on HZSM-11 Zeolite as Efficient Catalyst for the Photodegradation of Chlorobenzoic Acids]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601191&lng=es&nrm=iso&tlng=es The photocatalytic decomposition of 2-, 3- and 4-chlorobenzoic acids (2CB, 3CB and 4CB, respectively) with TiO2 loaded on HZSM-11 zeolite was investigated. The optimum decomposition rate of 2CB was obtained with TiO2/HZSM-11(30%) (TiO2 30 wt.%) catalyst at a concentration of 1 mg mL-1. 2CB and 3CB decompose at similar rates, but 4CB remains adsorbed on TiO2/HZSM-11(30%) without further degradation. This absorption is attributed to the relative positions of Cl and COOH groups on 4CB. However, this compound can be partially degraded and/or removed from aqueous solutions by TiO2/HZSM-11(50%) catalyst or HZSM-11 zeolite. TiO2/HZSM-11(30%) is stable; it retains its photocatalytic properties after nine cycles, can be easily removed and immediately reused. These are important advantages of TiO2/HZSM-11(30%) over unsupported TiO2, making it a good photocatalyst for the treatment of polluted water. On the other hand, HZSM-11 could be used to selectively adsorb 4CB, thus becoming an alternative method of environmental remediation. <![CDATA[Green Synthesis of Chalcones and Microbiological Evaluation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601201&lng=es&nrm=iso&tlng=es A green method was developed for the synthesis of chalcones using glycerin as solvent. Subsequently, the potential microbiology activity of these molecules was evaluated by testing them against the Gram-positive bacteria Staphylococcus aureus (S. aureus) ATCC 19095 and Enterococcus faecalis (E. faecalis) ATCC 4083, the Gram-negative bacteria Escherichia coli (E. coli) ATCC 29214 and Pseudomonas aeruginosa (P. aeruginosa) ATCC 9027, and the fungus Candida albicans (C. albicans), which includes ATCC 62342 and three clinical strains of C. albicans from human oral cavities. The results showed that some chalcones exhibited moderate inhibitory activity, the most prominent being those acting against the fluconazole-resistant strains of C. albicans. <![CDATA[Evaluation of Direct Analysis for Trace Elements in Tea and Herbal Beverages by ICP-MS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601211&lng=es&nrm=iso&tlng=es In general, inductively coupled plasma mass spectrometry (ICP-MS) food analysis requires numerous sample treatment steps that imply an increase of analysis time and the use of chemicals. In this study, the main objective was to evaluate the applicability of the direct analysis by ICP-MS to determine twelve elements (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se and Zn) in tea and herbal beverages. Direct analysis method was compared with two other sample treatments: minimum treatment (acid dilution) and using a destructive method (microwave assisted digestion). Besides the lowest time of analysis, direct analysis provides a reliable response and agrees with the “green chemistry” principles. High sensitivity was also observed by low values of limits of detection and quantification, in general, below 2.5 µg L-1. The method accuracy was evaluated by spiked experiments and values ranged between 82 and 120%. Low values of coefficient of variation were also observed, 2 to 17%, for all analytes. The method exhibited applicability for commercial tea samples as well as for drinks made by herb infusion. <![CDATA[<em>In silico</em> Antibacterial Activity Modeling Based on the TOMOCOMD-CARDD Approach]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601218&lng=es&nrm=iso&tlng=es In the recent times, the race to cope with the increasing multidrug resistance of pathogenic bacteria has lost much of its momentum and health professionals are grasping for solutions to deal with the unprecedented resistance levels. As a result, there is an urgent need for a concerted effort towards the development of new antimicrobial drugs to stay ahead in the fight against the ever adapting bacteria. In the present report, antibacterial classification functions (models) based on the topological molecular computational design-computer aided ‘‘rational’’ drug design (TOMOCOMD-CARDD) atom-based non-stochastic and stochastic bilinear indices are presented. These models were built using the linear discriminant analysis (LDA) method over a balanced chemical compounds dataset of 2230 molecular structures, with a diverse range of structural and molecular mechanism modes. The results of this study indicated that the non-stochastic and stochastic bilinear indices provided excellent classification of the chemical compounds (with accuracies of 86.31% and 84.92%, respectively, in the training set). These models were further externally validated yielding correct classification percentages of 86.55% and 87.91% for the non-stochastic and stochastic bilinear models, respectively. Additionally, the obtained models were compared with those reported in the literature and demonstrated comparable results, although the latter were built over much smaller datasets and with much higher degrees of freedom. Finally, simulated ligand-based virtual screening of 116 compounds, recently identified as potential antibacterials, was performed yielding 86.21% and 83.62% of correct classification, respectively, and thus demonstrating the utility of the obtained TOMOCOMD-CARDD models in the search of novel compounds with desirable antibacterial activity. <![CDATA[Brazilian Federal District Cocaine Chemical Profiling - Mass Balance Approach and New Adulterant Routinely Quantified (Aminopyrine)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601227&lng=es&nrm=iso&tlng=es From a set of 159 samples seized by Brazilian Federal Police between 2010 to 2013 in the Federal District, the major component chemical profiling routine analyses revealed the presence of cocaine with purity range of 5.5 to 99.9% (mean 69.8%). Most cocaine base samples show moderately and not oxidized levels, whereas cocaine hydrochloride samples exhibit moderate to high oxidation degrees. More than 40% of the analyzed samples did not have any adulterant. Phenacetin was the most abundant adulterant (24% average purity). Aminopyrine, a new adulterant, was identified and quantified only in cocaine base samples, mainly as a trace adulterant but also as a major compound. In most samples adulterated with aminopyrine, phenacetin was also identified as a major adulterant, suggesting a possible association of the two pharmaceuticals in the cutting process. Aminopyrine was not detected in 2010 seizures, but became a common adulterant throughout the years of 2011 to 2013. A mass balance approach analysis also established that adulterants are responsible for only 12% of the mass of all seizures (i.e., 84 kg), whereas 77% (i.e., 553 kg) is due to alkaloids (cocaine and cis/trans-cinnamoylcocaine), contributing to provide forensic intelligence information to police investigators. <![CDATA[Preliminary Investigation of Medicinal Herb Adulteration Using Comprehensive Two-Dimensional Gas Chromatography and Chemometric Analysis]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601232&lng=es&nrm=iso&tlng=es Anise is frequently found among the ingredients described in the label of cosmetic products. However, the use of fennel instead of anise may occur due to the lower price of fennel. The main differences in volatile profile of anise and fennel fruits were, for the first time, evaluated using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC×GC/TOFMS) and chemometric analysis. Aproximately 950 peaks were found in chromatograms of each sample and Fisher ratio appointed 31 volatile analytes as the most discriminating between anise and fennel samples. These 31 compounds were used in principal component analysis and canonical discriminant analysis that designated seven compounds (estragole, methyl eugenol, 4,5-dehydro-isolongifolene, calamenene, linalool, β-ocimene and fenchol) as the most important to verify the use of fennel or anise in personal care products. Among these seven compounds, thrree coeluted with other compounds and were correctly identified only with the use of GC×GC/TOFMS. <![CDATA[Synthesis, Vibrational Spectroscopic and Thermal Properties of Oxocarbon Cross‑Linked Chitosan]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601247&lng=es&nrm=iso&tlng=es In this work specimens of chitosan which have been cross-linked covalently and ionically with different oxocarbon and pseudo-oxocarbon anions have been synthesised and characterized using infrared and Raman spectroscopic techniques, solid state 13C nuclear magnetic resonance (NMR) and by thermogravimetry. According to the spectroscopic and thermal results, ionically crosslinked chitosans are obtained with squarate, croconate and rhodizonate ions as crosslinking agents, whereas covalently crosslinked chitosan can be obtained when squaric acid is used as the crosslinking agent; the same products are not observed when the pseudo-oxocarbon anion croconate violet is used, which can be attributed to the low basic strength of the crosslinking species. <![CDATA[<sup>1</sup>H qNMR and Chemometric Analyses of Urban Wastewater]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601257&lng=es&nrm=iso&tlng=es The industrial development, urbanization and agriculture play a major role in the degradation of the global environmental. Thus, the wastewater treatments need to be monitored continuously to ensure efficient operation. This manuscript presents an application of 1H nuclear magnetic resonance (NMR) associated with chemometric and quantitative analyses to study the wastewater before and after the sewage treatment plant (STP). The concentration of compounds related to organic matter degradation ranged with treatment and seasonality. Anomalous discharges and the influence of stormwater on the sewage composition were further identified. All the variations indicated that the employed procedure might be useful to enhance the effectiveness of STPs, plan prevention actions for equipment protection and preserve the environment. <![CDATA[Multiple Dynamics of Hydrazone Based Compounds]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601265&lng=es&nrm=iso&tlng=es Hydrazone derivatives of 2-quinolinecarboxaldehyde and 6-bromo-2-pyridinecarboxaldehyde were synthesized by sequence reactions with hydrazine derivatives. These compounds exhibited E/Z isomerization upon irradiation using a mercury lamp (250 W). The configurational changes were monitored by 1H nuclear magnetic resonance (NMR), UV-Vis and fluorescence spectroscopy. Data of concentration of the E/Z isomers versus time showed first order kinetics with constants ranging from 0.024 to 0.0799 min-1. The Z isomers were isolated by chromatographic methods and characterized by 1H NMR, UV-Vis and fluorescence spectroscopy and X-ray diffraction. The Z compounds are stable even in solution for several months. Such stability is due to a thermodynamic stabilization by the formation of an intramolecular hydrogen bond in the Z structure, which is not seen in the E configuration. Furthermore, some of the compounds were used as ligands for various metal centers (Zn2+, Co2+ and Hg2+) and their electronic properties were studied including measurements of cyclic voltammetry. The compounds studied herein allow their use as dynamic systems in dynamic combinatorial chemistry as their properties can be modulated by light, heat and the presence of metal centers. Besides, obtaining a metastable state (Z-isomer) allows the use of these compounds as photo-brakes, and therefore they can be implemented as molecular machines. <![CDATA[Novel and Fast Microwave-Assisted Synthesis of Carbon Quantum Dots from Raw Cashew Gum]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601274&lng=es&nrm=iso&tlng=es Carbon quantum dots (C-dots) with average size of 9 nm were synthesized from an aqueous solution of raw cashew gum (RCG) using a novel and fast microwave-assisted technique which involves two steps. In the first step (partial depolymerization in solution) some monomer units are formed through the autohydrolysis of CG and a small amount of 5-hydroxymethyl furfural can be obtained. The second step involves polycondensation/polymerization to give rise to a polyfuranic structure followed by aromatization/carbonization and nuclear burst. At the end of the process a composite of partially depolymerized CG and C-dot was formed. A mechanism involved in microwave-assisted two-steps synthesis was suggested. Although no passivation reagent was used, an intensely blue photoluminescent material in UV light was obtained. C-dot was characterized by spectroscopy in the medium infrared, thermal analysis, gel permeation chromatography, transmission electron microscopy, zeta potential, and photoluminescence. <![CDATA[Mapping Ethanol Production Sources in Brazil Through Stable Isotopes]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601283&lng=es&nrm=iso&tlng=es Ethanol is a biofuel produced in Brazil through fermentation of sugarcane, requiring vast plantation areas and water availability. The present work aimed at testing isotopic markers as tools for ethanol source appointment or certification of origin. For this, oxygen and hydrogen isotopic patterns were determined in plant-water, soil-water, rainwater, and water from reservoirs and some rivers in four sugarcane crop areas. The isotopic fingerprint of carbon and hydrogen in ethanol produced in the respective mills was also determined. Samples were collected in 2011 and 2012 in crop areas of the state of Amazonas (North), Mato Grosso (Center-West), São Paulo (Southeast) and Rio Grande do Sul (South). The substantial and complex influence of the hydrological cycle on the ethanol δD and the small δ13C variations constrain the use of isotopes for the intended objectives. <![CDATA[Exploratory Analysis of the Distribution of Lignin and Cellulose in Woods by Raman Imaging and Chemometrics]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601297&lng=es&nrm=iso&tlng=es The determinations of cellulose and lignin are important in wood analysis from both perspectives: chemistry composition, commercial and industrial application of woods. In this context, Raman image spectroscopy was applied in the determination of cellulose and lignin distribution in wood surfaces of Swietenia macrophylla King (Mahogany) and Eucalyptus hybrid (E. urophylla × E. camaldulensis). The relative concentration maps were obtained by applying a multivariate curve resolution procedure. The estimated Raman spectra for cellulose and lignin agrees with the ones available in the literature. The cellulose concentration maps showed similar variations for both studied species with an average value of nearly 85% as obtained by the reference method. The lignin concentration maps were somewhat different. The Eucalyptus hybrid presents a broader distribution (20 to 45%) while for Mahogany it is nearly constant, around 25%, with localized regions presenting contents of 45 to 65% of lignin. The reference method showed that the mean lignin content of both species is 27%. The cellulose and lignin concentration maps agree with the biological functions of the anatomic structures observed in the images. <![CDATA[Straightforward and Clean Ultrasound-Promoted Synthesis of 2-(4,5-Dihydro‑1<em>H</em>‑pyrazol-1-yl)pyrimidines]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015000601306&lng=es&nrm=iso&tlng=es A series of twelve novel 2-(pyrazol-1-yl)pyrimidine derivatives was easily obtained under ultrasonic conditions by the cyclocondensation reaction of 1-carboxamidino-pyrazoles with 4-methoxyvinyl-trifluoromethyl ketones using ethanol as an environment-friendly solvent in the presence of potassium hydroxide. Comparison of the ultrasound-promoted reaction with classical methodology shows that the former is faster and gives better yield. The products were isolated in excellent purity grades without purification by chromatography or recrystalization.