Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> vol. 60 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>ULTRASOUND-ASSISTED EXTRACTION AND CHARACTERIZATION OF POLYSACCHARIDE FROM MARYLAND TOBACCO LEAVES</b>]]> Ultrasound-assisted extraction (UAE) of polysaccharide from Maryland tobacco leaves was studied by response surface methodology. Furthermore, the crude polysaccharide was purified and two components (Fr-I and Fr-II) were obtained. FT-IR spectral analysis of the purified polysaccharide revealed prominent characteristic groups. The monosaccharide composition analysis by gas chromatography-mass spectrometry (GC/MS) indicated the main composition between Fr-I and Fr-II was different. Furthermore, thermo gravimetric analysis (TGA) indicated the degradation temperature (Td) of the Fr-I (241 ºC) was higher than those of Fr-II (216 ºC). Detected by the pyrolysis gas chromatography-mass spectrometry (py-GC/MS), it was found that the main kinds of pyrolysis products from both Fr-I and Fr-II were similar. Finally, On the basis of hydroxyl and DPPH radical scavenging assay, Fr-II has stronger antioxidant activities than Fr-I. The thermal behavior and antioxidant activity might be attributed to the configuration of the chemical compositions. <![CDATA[<b>DEVELOPMENT OF AN EFFICIENT HPLC METHOD WITH PRE-COLUMN DERIVATIZATION FOR DETERMINATION OF ENANTIOMERIC PURITY OF 2-(AMINOMETHYL)-1-ETHYLPYRROLIDINE</b>]]> The development of a simple and efficient analytical method for determination of enantiomeric purity of 2-(aminomethyl)-1-ethylpyrrolidine was presented. The method was based on pre-column derivatization of 2-(aminomethyl)-1-ethylpyrrolidine with 4-nitrobenzoic acid completing separation of the enantiomers on high performance liquid chromatographic (HPLC) chiral stationary phase (CSP). After optimizing all the effective parameters, the best performances were achieved on a Chiralcel OD-H analytical column (250 × 4.6 mm) using n-hexane: ethanol (98:2, v/v) containing 0.2% triethylamine as mobile phase with a flow rate of 1.0 mL min-1 at 25°C. Online UV and optical rotation (OR) detection was performed at 254 nm. The parameters which have an effect on chiral separation were investigated, including mobile phase additive, organic modifier type and concentration, column temperature and flow rate. The method was tested for precision, accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ) and robustness. The present method is expected to be accurate, stable, rapid and sensitive and can be used for the determination of the enantiomeric purity of 2-(aminomethyl)-1-ethylpyrrolidine in bulk samples. <![CDATA[<b>NEW AZO-SCHIFF BASE DERIVED WITH Ni(II), Co(II), Cu(II), Pd(II) AND Pt(II) COMPLEXES</b>: <b>PREPARATION, SPECTROSCOPIC INVESTIGATION, STRUCTURAL STUDIES AND BIOLOGICAL ACTIVITY</b>]]> The coordination ability of the azo-Schiff base 2-[1,5-Dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethyl imino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylazo]-5-hydroxy-benzoic acid has been proven in complexation reactions with Co(II), Ni(II), Cu(II), Pd(II) and Pt(II) ions. The free ligand (LH) and its complexes were characterized using elemental analysis, determination of metal concentration, magnetic susceptibility, molar conductivity, FTIR, Uv-Vis, (1H, 13C) NMR spectra, mass spectra and thermal analysis (TGA). The results confirmed the coordination of the ligand through the nitrogen of the azomethine, Azo group (Azo) and the carboxylate ion with the metal ions. The activation thermodynamic parameters, such as ΔE*, ΔH*, ΔS*, ΔG*and K are calculated from the TGA curves using Coats-Redfern method. Hyper Chem-8 program has been used to predict structural geometries of compounds in the gas phase. The synthesized ligands and their metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aereuguinosa). <![CDATA[<b>STUDY OF CORROSION INHIBITION PROPERTIES OF NOVEL SEMICARBAZONES ON MILD STEEL IN ACIDIC SOLUTIONS</b>]]> The inhibition efficiency of corrosion on mild steel using acids by three different novel Semicarbazones as inhibitors have been studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy methods. The inhibition efficiency, corrosion rate, the nature of anchoring sites and the adsorption characteristics have been determined from the results. It was found that the newly synthesized compounds behaved as mixed type inhibitors with high inhibition efficiency. The inhibition efficiency increases with increasing the inhibitors concentration but decreases with increasing the temperature. Addition of halide ion enhances the inhibition efficiency. The adsorption of the inhibitors on the mild steel surface obey Langmuir adsorption isotherm. Scanning Electron Spectroscopy is used to examine the surface morphology of mild steel samples both in the presence and absence of inhibitors at optimum conditions. Scanning Electron Microscope reveals the formation of a smooth, dense protective layer in the presence of inhibitor. <![CDATA[<b>A LOW-COST AND HIGH-YIELD PRODUCTION OF MAGNETITE NANORODS WITH HIGH SATURATION MAGNETIZATION</b>]]> Nanopowders of single-crystalline rod-like magnetite have been synthesized in a glycerol-water system under hydrothermal condition by using the goethite (α-FeOOH) precursor. The influence of different reaction parameters on the morphology and composition of the products have been investigated. The structure, morphology and magnetic properties of the products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and superconducting quantum interference device (SQUID). The results show that every as-prepared Fe3O4 nanorod with diameter ca.70nm grows along the [110] direction which is one of easy magnetic axes of magnetite. The ratio of glycerol to water has a great effect on the purity at given temperature. Magnetic measurements indicated that the specific saturation magnetization (Ms) and coercivity values (Hc) of magnetite nanorods were 90 emu/g and 172Oe, respectively. An in situ dissolution-reduction-reassembling formation mechanism is recommended for as-synthesized magnetite nanorods. <![CDATA[<b>CHEMOMETRIC OPTIMIZATION OF AN EXTRACTION PROCEDURE USING TARTARIC ACID FOR BUTYLTIN COMPOUNDS FROM SEDIMENT SAMPLES BY GC-PFPD</b>]]> In this study a simple extraction procedure was developed to minimize the sulfur interferences on the determination of butyltin in sediment samples based on extraction with tartaric acid solution. The optimal conditions were determined using an experimental design methodology and these were achieved using a solution of tartaric acid (0.5 M) with methanol (30 % v/v) for 12 hours in an orbital shaker. This protocol could be followed by a liquid-liquid extraction and this organic phase can be analyzed directly by gas chromatography with pulsed flame photometric detection (GC-PFPD) without any further cleanup due to interferences from elemental sulfur were completely eliminated. The accuracy of the procedure was verified analyzing two reference materials (CRM) (BCR-646, freshwater sediment and PACS-2, marine sediment) and comparing the results to the certified values, the optimized method produced satisfactory results certified values in the CRMs. Finally, harbour sediment samples were analyzed in order to evaluate the suitability of the method for organotin control in complex environmental samples containing high concentrations of sulfur compounds. <![CDATA[<b>SYNTHESIS, CRYSTAL STRUCTURE, AND THERMAL DECOMPOSITION KINETICS OF HOLMIUM WITH BENZOATE AND 2, 2'-BIPYRIDINE COMPLEX</b>]]> The complex [Ho(BA)3bipy]2 (BA=benzoate; bipy=2,2'-bipyridine) was synthesized and characterized by elemental analysis, infrared spectra, ultraviolet spectra, single-crystal X-ray diffraction, thermogravimetry and differential thermogravimetry (TG-DTG) techniques. The crystal is monoclinic with space group P2/n. The unit cell parameters are: a=14.1114(8) Å, b=15.3743(9) Å, c=25.8887(14) Å, β=103.555(2)°. Two Ho3+ ions are connected by four carboxylic groups through a bridging bidentate mode. The thermal decomposition behavior of the title complex under nitrogenous atmosphere was studied using the TG-DTG, and IR techniques. The non-isothermal kinetics was investigated by using the Popescu method and the integral iso-conversional non-linear method (NL-INT). The mechanism function of the first decomposition step was determined. The thermodynamic parameters (ΔG≠, ΔH≠ and ΔS≠) were also calculated, and kinetic parameters (activation energy E and the pre-exponential factor A) were also obtained. <![CDATA[<b>STUDIES ON THE ALKYLATION OF QUINOLIN-2(1<i>H</i>)-ONE DERIVATIVES</b>]]> Alkylation of quinolin-2(1H)-one (1) and its C(6) and C(7) substituted dervatives (OMe, OBn, and Cl) with 2-bromoacetophenone or chloroacetone under basic condition (K2CO3 in DMF) gave a mixture of N1- and O2- alkylated products with the former one as a major product. However, alkylation of 8-methoxy-, 8-benzyloxy-, and 8-chloro- quinolin-2(1H)-ones under the same reaction conditions gave exclusively O2-alkylated products. <![CDATA[<b>ADSORPTION OF 4,6-DIMETHYLDIBENZOTHIOPHENE OVER <i>Cu/ZrO<sub>2</sub></i></b>]]> The adsorption of refractory sulfur molecule 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over copper supported on zirconia, using different copper loadings (2-10% w/w) and a zirconia support with a high specific surface area, was studied. The results showed that the adsorption capacity of 4,6-DMDBT over Cu/ZrO2 increased with copper content, reaching a maximum at around 8% Cu (0.58 mmol 4,6-DMDBT per gram of adsorbent). The results of characterizations with H2-TPR, Electrophoretic Migration, and XRD demonstrated that this Cu loading (8%) also corresponds to a maximum copper dispersion capacity for ZrO2 support. Also, these absorbents showed considerable selectivity toward the adsorption of 4,6-DMDBT in a feed stream also containing Quinoline, decreasing adsorption capacity of 4,6-DMDBT by only 35%, despite both molecules being present in the same concentrations. The results of this work showed that desulfurization adsorption using Cu/ZrO2 adsorbents can be an effective method to remove this type of refractory sulfur molecules, and an excellent alternative as a complementary process for deep desulfurization in the fuel industry. <![CDATA[<b><i>IN SITU</i></b><b> X-RAY FLUORESCENCE ANALYSIS OF ROCK ART PAINTINGS ALONG THE COAST AND VALLEYS OF THE ATACAMA DESERT, NORTHERN CHILE</b>]]> Results of exploratory in situ analyses with a portable X-Ray Fluorescence (XRF) applied to six rock painting sites, located from Lluta to Camarones coastal valleys in the Atacama Desert, northern Chile, are presented. The results indicate the use of iron oxide as a main component in all paintings, alone or combined with aluminum silicate. Arsenic, a component highly present in water in the region, was also identified, indicating the use of water as a possible binder or thinner. These output allow unraveling painting technology, a step forward to define and understand the stylistic variability of rock art (engravings and paintings) in the context of the social changes and continuities of prehistoric communities. Additionally, it illustrates the effectiveness of portable XRF, a non-destructive analytical tool, applied for the first time in the Atacama Desert. <![CDATA[<b>ONE-POT SYNTHESIS OF ISOBENZOFURAN-1(3<i>H</i>)-ONES USING SULFURIC ACID IMMOBILIZED ON SILICA UNDER SOLVENT-FREE CONDITIONS AND SURVEY OF THIRD-ORDER NONLINEAR OPTICAL PROPERTIES</b>]]> Solvent-free synthesis of isobenzofuran-1(3H)-ones have been described via reaction of phthalaldehydic acid (2-carboxybenzaldehyde) with methylaryl or cyclic ketones using sulfuric acid immobilized on silica (H2SO4-SiO2) in excellent yields (70-88%). The catalyst can be recovered by simple filtration and reused. Also, some of these compounds has been studied the third-order nonlinear optical properties by laser Gaussian z-scan techniques. <![CDATA[<b>SULFAMIC ACID CATALYZED FIVE COMPONENT REACTION FOR EFFICIENT AND ONE-POT SYNTHESIS OF DENSELY FUNCTIONALIZED TETRAHYDROPYRIDINE SCAFFOLD</b>]]> The utility of sulfamic acid in One-pot assembling of aromatic aldehydes, aromatic amines and β-keto esters to afford densely functionalized tetrahydropyridines in 70-89% yield has been presented. The advantage of sulfamic acid against other catalysts in terms of yield has been studied. The effect of different solvents on reaction time and yield has also been studied. Easy work up and mild reaction condition are the advantages of the proposed method. <![CDATA[<b>CHEMICAL STUDY AND ANTIMICROBIAL ACTIVITIES OF <i>Piper arboreum</i> (PIPERACEAE)</b>]]> This study evaluated the antifungal and antibacterial activities of the extracts and their fractions, essential oils, and major constituents of Piper arboreum tissues. The chemical compositions of P. arborem tissues and major constituent were identified using GC/MS, Ή and 13C NMR. All the botanic material tested proved to be specific bactericidal agents against Staphylococcus aureus, with MBC/MIC = 2, including the amide piperetine, the major compound isolated of P. arboreum for the first time. The essential oil of leaves showed antifungal activity against Microsporum gypseum and Epidermophyton floccosum, with MFC values of 312.5 and 125 μg/mL, respectively. <![CDATA[<b>SIMPLE AND SENSITIVE DETECTION FOR TRACE CHROMIUM (VI) USING ALBUMIN AS FLUORESCENCE PROBES</b>]]> We have developed a novel method for fast determination of chromium(VI) using egg albumin(EAB) as fluorescence probe. The influence factors, including pH, reaction time, concentration of EAB, were investigated on the performance of the method and the optimum experimental conditions were determined. Under the optimum conditions, the relative fluorescence intensity of albumin was linearly proportional to Cr(VI) over a concentration range from 1.0x10-7 to 6.0x10-5 mol L-1 with a correlation coefficient of 0.9936 and a detection limit of 5.2 nmol L-1. This is a fast, simple, high selective and environment-friendly method, which has been employed to detect trace Cr(VI) in drinking water samples with satisfactory. The infrared spectral information indicated that the possible mechanism of fluorescence quenched may be the change of the secondary structures of EAB in the presence of Cr(VI). <![CDATA[<b>A BODIPY-PHENOL-BASED SENSOR FOR SELECTIVELY RECOGNIZING THREE BASIC ANIONS</b>]]> A novel BODIPY-based anion sensor 1 bearing di-tert-butyl phenol unit was designed and prepared. In the presence of three basic anions F-, AcO- or H2PO4-, 1 exhibited two novel partially overlapped red-shift absorption bands at 718 nm and 757 nm, respectively. The formation of allotropie structures, after deprotonation of phenol OH, is responsible for these two emerging bands. Fluorescence quenching was also observed due to intramolecular charge transfer (ICT) from phenolate to BODIPY core. As results revealed, the anion affinity mainly depended on the acidity of binding site OH and the basicity of the target anion. Moreover, two bulky tert-butyl groups cannot effectively exclude the approach of large anions to phenol OH, but can facilitate the formation of allotropic resonance structures. <![CDATA[<b>AN EFFICIENT AND GREEN PROTOCOL FOR THE SYNTHESIS OF DIHYDROPYRANO [<i>2,3-C</i>] PYRAZOLES IN AQUEOUS MEDIUM USING THIAMINE HYDROCHLORIDE AS A CATALYST</b>]]> A green and expedient approach for the synthesis of dihydropyrano[2,3-c] pyrazoles via four-component reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and malononitrile at room temperature under ultrasound irradiation is described. The reaction has been catalyzed by thiamine hydrochloride in aqueous medium. This protocol afforded several advantages such as inexpensive, easily available catalyst, simple operational procedure, excellent yield, use of aqueous medium and ultrasound irradiation that is considered to be relatively eco-friendly. <![CDATA[<b>NANO SbCl<sub>5</sub>.SiO<sub>2</sub></b>: <b>AN EFFICIENT CATALYST FOR THE SYNTHESIS OF QUINOXALINE DERIVATIVES AT ROOM TEMPERATURE UNDER SOLVENTLESS CONDITION</b>]]> Nano SbCl5.SiO2 as an eco-friendly and efficient nanocatalyst was applied for quinoxaline derivatives preparation with improved yield. In this protocol, α-diketones and 1,2-diamines were condensed in the presence of nanocatalyst at room temperature under solventless conditions. The method gave good yields of quinoxaline derivatives in short reaction times in comparison with earlier methods. Using nontoxic and inexpensive materials, simple work-up, short reaction times and high yields of the products are the advantages of this method. <![CDATA[<b>SYNTHESIS AND ANTI-MICROBIAL ACTIVITIES OF 1,3,5-TRISUBSTITUTED-PYRAZOLE DERIVATIVES CONTAINING A PYRIDYL MOIETY</b>]]> Claisen condensation of ethyl isonicotinate with different acetophenones gave the corresponding pyridyl-ß-diketones, while the treatment with hydrazine hydrate yielded 3,5-disubstituted-1H-pyrazoles, which then converted 1,3,5-trisubstituted-pyrazole derivatives containing a pyridyl moiety by N-acylation with acyl chloride. The structures of all newly synthesized compounds are established by FTIR, ¹H NMR, mass spectroscopy and elemental analysis, and in the case of compound 2e, analyzed by single-crystal X-ray diffraction further. The anti-microbial activities of the title compounds have been tested by disc diffusion method against Escherichia coli, Staphylococcus aureus, Pyricularia oryzae and Rhizoctnia solani. The results showed that compounds 3c and 4c exhibited good inhibitory activity against all the tested organisms. <![CDATA[<b>PHYTOSYNTHESIS OF SILVER NANOPARTICLES USING E. CAMALDULENSIS LEAF EXTRACT AND THEIR CHARACTERIZATION</b>]]> Herein, we report a simple green synthesis of silver nanoparticles (Ag NPs) by the reduction of aqueous silver salt solution using leaf broth of Eucalyptus camaldulensis. The profile of synthesized silver nanoparticles was evaluated by using UV-visible spectrophotometer, X-ray diffractometer, atomic force microscope, energy-dispersive X-ray spectroscope and scanning electron microscope. Surface plasmon resonance peak of silver nanoparticles appeared at 425 nm in UV-vis spectra of silver nanoparticles. XRD studies clearly confirmed the crystalline nature of the synthesized nanoparticles. The EDX analysis disclosed the arranged inorganic composition of the synthesized Ag NPs. Atomic force microscopy investigation revealed 3D surface profile of nanoparticles. From the SEM images, the silver nanoparticles were found to be more or less spherical with an average diameter range of 110-250 nanometers. <![CDATA[<b>A NON-CENTROSYMMETRIC POLYMORPH OF 5-HYDROXY-7-METHOXY-2-PHENYLCHROMAN-4-ONE</b>]]> The bioactive compound 5-hydroxy-7-methoxy-2-phenylchroman-4-one (pinostrobin, I), was isolated from aerial parts of Nolana ramossisima I.M. Johnst., a Chilean endemic species, using a combination of medium pressure column chromatography and high speed countercurrent liquid-liquid chromatography (HSCCC). The compound crystallized as a non-centrosymmetric polymorph in the orthorhombic chiral space group P2(1)2(1)2(1). Its structure had been previously reported by Shoja (Acta Cryst. C45, 828, 1989) and Yamovoi et al. (Khim. Prir. Soedin (5), 361, 2001) in the centrosymmetric space groups Pbca and P21/c, respectively. <![CDATA[<b>EFFECT OF THE AMOUNT OF WATER ON THE SYNTHESIS OF LiMn<sub>2</sub>O<sub>4</sub>, USED AS CATHODE MATERIAL IN LITHIUM-ION BATTERIES</b>]]> LiMn2O4 with nanostructured morphologies possess rapid kinetics which is favorable for the intercalation of lithium ions in battery electrodes¹. In this work, we have studied the effect of varying the amount of water in the hydrothermal synthesis of nanostructured LiMn2O4 spinel. It was found that three distinct nanostructured morphologies of this compound are obtained when the volume of water used during the synthesis is varied. The powders were morphologically and structurally characterized using TEM, XRD, and BET yielding particle sizes ranging from 1 to 50 nm, with 90 % of the sample possessing a particle size of 21.7 nm. X-ray diffraction analysis show characteristic peaks and confirm the compound's identity and crystalline structure. Furthermore, the electrochemical behavior of this material in lithium ion batteries was studied. The results indicate that the electrochemical performance is strongly influenced by the size and shape of the (α-LiMn2O4 nanoparticles.