Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> http://www.scielo.cl/rss.php?pid=0717-970720140004&lang=en vol. 59 num. 4 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>Editorial</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400001&lng=en&nrm=iso&tlng=en <![CDATA[<b>SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL ACTIVITY OF COBALT(III) COMPLEX WITH PHENANTHROLINE AND MALTOSE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400002&lng=en&nrm=iso&tlng=en The mononuclear cobalt(III) complex derived from 1,10-phenanthroline and maltose ([Co(phen)2maltose]Cl2∙3H2O) (1) has been synthesized and characterized in aqueous solution. Its characterization was based on its optical and spectroscopic properties. The antimicrobial activity of this complex was screened in vitro against the microorganisms Escherichia coli DH5a, Salmonella enterica sv Enteritidis ISP/953, Klebsiella pneumoniae RYC492, Pseudomonas aeruginosa PAO1, Enterococcus faecalis ATCC 29212, Bacillus cereus GCA234, Micrococcus sp. Staphylococcus aureus ATCC25923. Complex (1) showed antibacterial activity with a bacteriostatic effect over Gram positive and negative bacteria. The cytotoxicity of complex (1) was tested in vitro on human embryonic kidney cells. <![CDATA[<b>CRYSTAL STRUCTURE AND DFT STUDIES OF 4-(1-BENZYL-5-METHYL-1H-1,2,3-TRIAZOL-4-YL)-6-(3- METHOXYPHENYL)PYRIMIDIN-2-AMINE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400003&lng=en&nrm=iso&tlng=en The title compound 1, 4-(1-benzyl-5-methyl-1H-1,2,3-triazol-4-yl)-6-(3-methoxyphenyl)pyrimidin-2-amine (C21H20N6O), was synthesized and structurally characterized by elemental analysis, ¹H NMR, 13C NMR and single crystal X-ray diffraction. The molecular conformation is stabilized by an intramolecular C-H...N hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked by two pairs of inversion-related amine N-H...N and C-H... N hydrogen bonds, each generating alternate R2²(8) ring motifs in a zigzag supramolecular chain that runs along c-axis. These chains stack along a-axis via amine N-H...O hydrogen bonds forming a two-dimensional supramolecular network. Density functional theory calculations of the structure, Mulliken population analyses on atomic charges and thermodynamic functions of the title compound were performed by using (DFT/B3LYP) method with the 6-311G(d,p) basis set level. The charge energy distribution and site of chemical reactivity of molecules were obtained by mapping electron density isosurface with electrostatic potential surfaces. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. <![CDATA[<b>SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURES OF BENZOHYDRAZONE COMPOUNDS DERIVED FROM 5-METHYLSALICYLALDEHYDE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400004&lng=en&nrm=iso&tlng=en A series of three new benzohydrazone derivatives, N'-(2-hydroxy-5-methylbenzylidene)-4-methylbenzohydrazide (1), N'-(2-hydroxy-5-methylbenzylidene)-4-hydroxybenzohydrazide (2), and N'-(2-hydroxy-5-methylbenzylidene)-4-dimethylaminobenzohydrazide (3), were prepared and characterized by elemental analysis, Ή and 13C NMR, and single crystal X-ray diffraction. Compound (1) crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 27.421(1) Å, b = 9.9843(4) Å, c = 24.302(1) Å, β = 119.416(2)°, V = 5795.7(5) ų, Z = 16, R1 = 0.0520, and wR2 = 0.1172. Compound (2) crystallizes in the orthorhombic space group Pna2(1) with unit cell dimensions a = 9.511(2) Å, b = 9.866(2) Å, c = 13.871(3) Å, V = 1301.6(5) ų, Z = 4, R1 = 0.0342, and wR2 = 0.0912. Compound (3) crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 26.957(2) Å, b = 10.0612(9) Å, c = 25.526(2) Å, β = 114.405(3)°, V= 6304.5(10) ų, Z = 16, R1 = 0.0532, and wR2 = 0.1079. X-ray diffraction indicated that the benzohydrazone molecules of the compounds display trans configuration with respect to the C=N double bonds. The crystal structures of the compounds are stabilized by hydrogen bonds and weak π···π interactions. <![CDATA[<b>ENHANCED PROPERTIES OF HYPERBRANCHED POLYURETHANE ELASTOMERS BASED ON POLYDIMETHYLSILOXANE/POLYETHER MIXED SOFT SEGMENTS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400005&lng=en&nrm=iso&tlng=en A novel hydroxyl-terminated polymer HPMS-APE was synthesized by introducing allyl polyethylene oxide (APE) into hydrogen-terminated polydimethylsiloxane (HPMS) backbone by hydrosilylation reaction. A series of hyperbranched polyurethane elastomers (HBPUs) based on HMPS-APE and polypropylene glycol (PPG) mixed soft segments were successfully synthesized with trimethylolpropane (TMP) as a chain extender. The effect of HPMS-APE segments content on enhanced properties of HBPUs were characterized by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), atomic force microscopy (AFM), thermogravimetric analysis (TGA), mechanical testing and water absorption. It was found that incorporating HPMS-APE in polyurethanes made substantial changes in their morphology, thermal properties, mechanical properties and water absorption. When 5 wt% HPMS-APE was incorporated in HBPUs, the extent of microphase separation between hard and soft segments was the best, resulting in polyurethanes without significant compromise in tensile strength and elasticity. Furthermore, HBPUs derived from HPMS-APE presented excellent thermal stability and unique water resistance. <![CDATA[<b>A SENSITIVE SEQUENTIAL INJECTION ANALYSIS (SIA) DETERMINATION OF MEMANTINE HYDROCHLORIDE USING LUMINOL-HYDROGEN PEROXIDE INDUCED CHEMILUMINESCENCE DETECTION</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400006&lng=en&nrm=iso&tlng=en A fully automated sequential injection analysis (SIA) method for chemiluminescence (CL) determination of Al-zheimer's drug memantine hydrochloride was developed and presented. The employing of SIA injection analysis facilitates fluidic handling and lowering the consumption of sample and reagents. The basic CL reaction was based on the emission of CL radiation due to the reaction of luminol with hydrogen peroxide in basic medium. The CL emission has been monitored using FIAlab system. The optimum conditions and characterizations were optimized using a computer-aided simplex method. Under the optimal conditions the linear calibration graph was obtained within the range of 0.0001-1.0 μg mL-1, (r=0.9996) with detection limit of 3.3x10-5 μg mL-1 along with relative standard deviation 1.8 % (n). The flow rates were 120 μL s-1, for the aspiration into the holding coil and 80 μL s-1 for detection. The sample frequency throughput was 103 h-1. The proposed CL method was successfully applied for determination of the tested drug in pure form and its pharmaceutical formulations. The interference of some common additive compounds such as glucose, lactose, starch, talc and magnesium stearate was investigated. No interference was recorded. The obtained SIA results were statistically compared with those obtained from a reported method and did not show any significant difference. <![CDATA[<b>DEVELOPMENT AND VALIDATION OF A REVERSED-PHASE HPLC METHOD FOR THE SIMULTANEOUS ESTIMATION OF DICYCLOMINE HYDROCHLORIDE AND FAMOTIDINE IN BULK AND TABLETS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400007&lng=en&nrm=iso&tlng=en In the present study an isocratic reverse phase-high performance liquid chromatography (RP-HPLC) method was developed and validated for simultaneous estimation of dicyclomine hydrochloride (DCY) and famotidine (FAM) in bulk and pharmaceutical dosage forms. The separation was achieved on a Phenomex Gemini C column (4.6 x 250 mm, 5μ particle size) using a mixture of methanol and 0.1% triethylamine (TEA) pH 3.0 (adjusted with orthophosphoric acid) in the ratio of 40:60 (v/v) as a mobile phase. The flow rate was 1.0 mL min-1, column temperature was kept at 28 0 C and detection was monitored at 270 nm. The retention time of dicyclomine hydrochloride and famotidine was found to be 10.72 and 2.72 min respectively. Recovery studies were satisfactory and the correlation coefficient for FAM and DCY were 0.9947 and 0.9935 respectively, indicates linearity of the methods within the limits. The developed method can be used for routine quality control simultaneous analysis of DCY and FAM in tablet dosage form without any interference of excipients. <![CDATA[<b>A DENSITY FUNCTIONAL THEORY STUDY ON STRUCTURE AND PROPERTIES OF BENZENE AND BORAZINE-BASED CHROMOPHORES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400008&lng=en&nrm=iso&tlng=en Density functional theory (DFT) calculations were employed to investigate the structural characteristics, electronic properties, and nonlinear optical properties of borazine-based chromophores at B3LYP/ 6-311G(d,p) level. We studied the effects of various donor and acceptor substituents (H, F, Cl, Br, Me, NH2, OH, COOH, CHO, CN, NO2) on the stability, dipole moment, polarizability, frontier orbitals, structure, the most intense electronic transition, and hyperpolarizabilities. These calculations indicate B-isomer is more stable than N-isomer. On the other hand, the most stable isomer confirms the minimum polarizability and maximum hardness principles in the most molecules. Also, we obtained good linear relations between some of the studied properties. The predicted first hyperpolarizability also shows that the substituted molecules might have a reasonably good nonlinear optical (NLO) behavior. <![CDATA[<b>SYNTHESIS OF TRI-ARM STAR SHAPED 1, 3, 5-TRIAZINES CATALYZED BY 1,5,7-TRIAZABICYCLO[4.4.0] DEC-5-ENE (TBD)</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400009&lng=en&nrm=iso&tlng=en Facile solution method for the synthesis of tri-arm star shaped 1,3,5-triazines was developed using 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) by reaction of cyanuric chloride with O-nucleophiles. <![CDATA[<b><i>IN VIVO</i></b><b> AND IN VITRO INTERACTION STUDIES OF ENALAPRIL WITH FLURBIPROFEN ON CARRAGEENAN INDUCED INFLAMMATION RATS (CIIR)</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400010&lng=en&nrm=iso&tlng=en Both ACE inhibitors and non steroidal anti-inflammatory drugs (NSAIDs) are prescribed together in the elderly as different diseases may occur together. In vivo and in vitro interaction studies of ACE inhibitor (enalapril) was carried out with commonly used NSAID, flurbiprofen in carrageenan induced inflammation (CIIR) rats to check the anti-inflammatory response of NSAIDs in presence of enalapril and alone. In present study, altered anti-inflammatory response was observed for flurbiprofen when given simultaneously with enalapril by comparing decrease in paw size. Results were expressed in % reduction in paw size for every hour and were calculated for edema rate and percentage reduction. In vitro interaction studies carried out using HPLC and both the drugs were analyzed by assaying both drugs alone and in combination.The combination of enalapril and flurbiprofen showed increased activity of flurbiprofen as depicted by increase of % reduction and decrease in edema rate. It was also proved from AUC of the chromatogram of combine drugs. Since this study has certain limitation as a number of tested animals were small and the duration of anti-inflammatory response was checked for flurbiprofen alone and in combination with enalapril for few hours, further studies may be required to establish the strong relationship. <![CDATA[<b>EFFECT OF ORGANOCLAY INCORPORATION ON THERMAL, PHYSICAL AND MORPHOLOGICAL PROPERTIES OF LLDPE NANOCOMPOSITES FOR ACTIVE FOOD PACKAGING APPLICATIONS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400011&lng=en&nrm=iso&tlng=en Active films based on nanocomposites from linear low-density polyethylene (LLDPE) were prepared by melting extrusion incorporating Cloisite 30B (5 wt.%) and thymol as active compound at two different concentrations: 2 and 4 wt.%. A complete thermal, structural characterization and antioxidant capacity of all blends was carried out. Extraction procedures revealed final concentrations of thymol in the film between 40-80 % of the thymol that was initially included in the films formulation. Materials with 2 and 4 % of thymol presented similar antioxidant capacity. XRD results indicated a slightly lower degree of intercalation in the nanocomposites with thymol, due probably to the lower compatibility between the hydrophilic character of the clays, and the hydrophobic thymol substance. The addition of the antioxidant improved slightly the thermal stability of the polymer. <![CDATA[<b>AN EMPIRICAL MODEL FOR ADSORPTION THERMODYNAMICS OF COPPER (II) FROM SOLUTIONS ONTO ILLITE CLAY-BATCH PROCESS DESIGN</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400012&lng=en&nrm=iso&tlng=en The copper causes important health problems risk when it exists at high concentrations in drinking waters and daily feeds. Therefore, in this study, copper adsorption from solutions onto illite clay was investigated in batch mode as a function of the initial solution pH (3-6), temperature (30-60 °C) and ionic strength (0-0.1 mol/L-1 NaCl). The equilibrium was attained within 24 hours. Optimum conditions were determined as pH 6, temperature 60 °C and 0 mol/L-1 NaCl concentration. The isotherm data followed the S-class isotherm. The reason of this S-class isotherm was either solute-solute attractive forces at the surface causing cooperative adsorption or a competing reaction such as complexation with a ligand. Mathematically, the isotherm data were explained with the sum of several single Freundlich models. Also, the thermodynamic parameters of the process were calculated. Positive values of Gibbs free energy change (ΔGº) indicated that the adsorption process was unspontaneous. As the enthalpy change (ΔH°) had positive value for all the parameter intervals, copper adsorption was concluded to be physical and endothermic process. The positive entropy values indicated that the randomness at solid-liquid interface increased with concentration decrease. Maximum copper adsorption capacity of illite clay was calculated at 60 ºC as 1.823×10-5 mol/g. Furthermore, an empirical model was developed to determine the thermodynamic parameters of the process and operation conditions of the batch reactor as follows. <![CDATA[<b>SIMULTANEOUS VOLTAMMETRIC DETERMINATION OF N-ACETYL-L-CYSTEINE, URIC ACID AND TRYPTOPHAN AT SURFACE OF GLASSY CARBON ELECTRODE IN THE PRESENT OF 4-CHLOROCATECHOL AS A HOMOGENEOUS ELECTROCHEMICAL CATALYST</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400013&lng=en&nrm=iso&tlng=en Simultaneous determination of N-acetyl-L-cysteine (NAC), uric acid (UA) and tryptophan (Trp) has been studied at the surface of glassy carbon electrode (GCE) in the present of 4-chlorocatechol as a homogenous electrochemical catalyst in aqueous media. The electrocatalytic properties of GCE in the present of 4-chlorocatechol toward the electrocatalytic oxidation of NAC, UA and Trp was studied using cyclic voltammetry (CV), double-step potential chronoamperometry and differential pulse voltammetry (DPV). The results show that NAC participates in the reaction with electrogenerated quinone from electrooxidation of 4-chlorocatechol at surface of GCE to form the corresponding thioquinone derivative. The reoxidation of the adduct leads to increase in the oxidative current which is proportional to the concentration of NAC. Differential pulse voltammogram peak currents of NAC, UA and Trp increased linearly with their concentrations in the ranges of 5.0 - 45.0 μM, 10.0 - 50.0 μM and 5.0 - 55.0 μM, respectively and the detection limits for NAC, UA and Trp were sequentially 3.55 μM, 6.96 μM and 4.41 μM. The proposed method was employed for simultaneous determination of NAC, UA and Trp in the pharmaceutical and biological samples and the obtained results were found to be satisfactory. <![CDATA[<b>LIGAND FREE Pd CATALYZED CYCLIZATION-INFLUENCE OF STERIC HINDRANCE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400014&lng=en&nrm=iso&tlng=en Synthesis of sultams was performed using ligand free palladium catalyst following Heck cyclization. The diverse synthesized intermediates in this strategy includes halogenated sulfonyl chloride, alkyl/aryl sulfonamides, N-alkylation using halogenated alkenyl reagents followed by improved Heck cyclization with Pd(OAc)2/DIPA in 1-methyl-pyrolidin-2-one/toluene. In this way, isomeric six membered sultams with endocyclic & exocyclic double bonds (benzothiazine) and seven membered (thiazipene) were obtained. Endocyclic double bond isomer was dominates in respect of yield over the exocyclic double bond isomer. The isolated amounts of endocyclic sultams and thiazipene were almost equal in amounts. The intermediates and final products were characterized using IR, ¹H-NMR, 13C-NMR and EI-MS techniques. <![CDATA[<b>ION PAIR METHOD TO DETERMINE THE CTAB CONTENT IN GOLD NANORODS SAMPLES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400015&lng=en&nrm=iso&tlng=en In this work, we report a fast and accessible method for quantification of cetyltrimethylammonium bromide (CTAB) in solutions of gold nanorods (GNRs) by bromophenol blue (BPB) ion-paring formation and spectrophotometric detection. The ion-par method used to quantify CTAB exhibited adequate figures of merit and was applied to the quantification of CTAB present in solutions of GNRs-CTAB and in GNRs-CLPFFD samples obtained by the seed growth method. This type of methodology could be extensive to others surfactants employed for the synthesis of nanoparticles. In addition, this method allows screening CTAB in GNRs samples and consequently would help to know if CTAB concentration is lower than an acceptable cut-off for cell viability analysis. <![CDATA[<b>DEVELOPMENT AND VALIDATION OF SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION AND SPECTROSCOPIC CHARACTERIZATION OF VILDAGLIPTIN USING II -ACCEPTORS IN PHARMACEUTICAL PREPARATIONS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400016&lng=en&nrm=iso&tlng=en Three simple, quick and sensitive methods are described for the spectrophotometric determination of vildagliptin (VLD) in pharmaceutical preparations. The methods are based on formation of colored charge transfer (CT) complexes between VLD as n-electron donor and chloranilic acid (CA), tetrachloro-1,4-benzoquinone (p-chloranil), 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors. The colored products were quantitated spectrophotometrically at 520, 535 and 842 nm for CA, p-chloranil and TCNQ methods, respectively. Optimization of different experimental conditions were investigated. Beer's law was obeyed in the concentration range of 20-250 μg mL-1, 25-400 μg mL-1 and 20-500 μg mL-1 for CA, p-chloranil and TCNQ methods, respectively. The formation of the CT-complexes and the sites of interactions were confirmed by elemental analysis using IR, ¹H NMR spectroscopy. Validity of the methods in terms of specificity, linearity, accuracy, precision, robustness, limit of detection and limit of quantitation were evaluated. Good recoveries were obtained for all of the methods indicating that no interference was observed from concomitants usually present in dosage forms. The methods were applied successfully to the determination of VLD in pharmaceutical preparations. <![CDATA[<b>IMPROVEMENT OF PREFERENTIAL CO OXIDATION ACTIVITY OVER CUO/CO<sub>3</sub>O<sub>4</sub>-CEO<sub>2</sub> CATALYSTS</b>: <b>EFFECT OF CO/CE RATIO</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400017&lng=en&nrm=iso&tlng=en A series of Co3O4-CeO2 supports with different Co/Ce ratio have been synthesized by using polyethyleneglycol (PEG) as a surfactant. The catalytic performance tests indicated the activity of the catalysts is better than the corresponding support. In addition, CuO/(0.7)Co3O4-CeO2 displayed the best activity with 100% CO conversion and 93% O2 selectivity at 120 °C. Furthermore, the stability test of CuO/(0.7)Co3O4-CeO2 expressed the activity can be retained at 80% for 80h at 100 °C. Catalysts and supports were characterized by BET, XRD, TPR and TPD techniques. Discussion of the results showed that the strongest lattice distortion and the best reducibility of Co3O4-CeO2 supports were both negative factors for the catalytic activity. More precisely, an appropriate Co/Ce ratio can restrain the stronger interaction between cobalt oxide and ceria to promote the formation of reducible copper species. <![CDATA[<b>SUZUKI-MIYAURA CROSS-COUPLING REACTION OF DICHLORO-HETEROAROMATICS</b>: <b>SYNTHESIS OF FUNCTIONALIZED DINUCLEOPHILIC FRAGMENTS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400018&lng=en&nrm=iso&tlng=en The Suzuki-Miyaura cross-coupling reaction has successfully been applied for the synthesis of 4,4'- [6-(diethylamino)-1,3,5-triazine-2,4-diyl]diphenol (4a), 4,4'-(pyrimidine-4,6-diyl)diphenol (4b), 4,4'-(pyridine-2,6-diyl)diphenol (4c). The reaction of 4,6-dichloro-N,N-diethyl-1,3,5-triazin-2-amine (1a), 4,6-dichloropyrimidine (1b) and 2,6-dichloropyridine (1c) with p-methoxyphenylboronic acid (2) in the presence of palladium catalyst followed by demethylation reaction furnished the desired products in good to excellent yields. To test the reactivity of these nucleophiles, the compound 4a was further reacted with cyanuric chloride to get trimeric fragment (5a). All the compounds were characterized by their physical, spectral (¹H and 13C NMR and Mass) and microanalytical data. These dinucleophilic fragments (4a-4c) having triazine, pyrimidine and pyridine rings, respectively, are excellent future candidates for the construction of large functional hetero-atom bridged macrocycles for diverse applications in host-guest chemistry, supramolecular catalysis, self-assembly and other related fields of supramolecular chemistry in addition to their potential in medicinal chemistry. <![CDATA[<b>EMQAL</b>: <b>ERASMUS MUNDUS MASTER IN QUALITY IN ANALYTICAL LABORATORIES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400019&lng=en&nrm=iso&tlng=en The Erasmus Mundus Master in Quality in Analytical Laboratories (EMQAL) is a two-year Joint Master Degree. The course is funded by the European Commission through the Erasmus Mundus Programme, providing a number of attractive scholarships for European and non-European students. EMQAL prepares professionals for analytical laboratories, focusing on laboratory management and quality systems, along with complementing their technical knowledge. The EMQAL aims at training students in the most relevant issues concerning quality systems and management in analytical laboratories, and to become an expert in: Quality management, Analytical methods and Data Analysis. EMQAL promotes mobility. The students will attend one academic year of lectures in one of the European universities of the EMQAL consortium, and a 12 months master thesis at other European university, with the possibility to spend three-months in one of the non-EU partners. The language of instruction and examination is English. Further information is available at www.emqal.org. <![CDATA[<b>CATALYTIC COMBUSTION OF SOOT ON Ce-DOPED LANTHANUM COBALTITES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400020&lng=en&nrm=iso&tlng=en Substituted La1-xCe xCoO3 perovskite-type oxides (0.0≤x≤0.9), prepared by the self-combustion method, have been investigated as catalysts in soot combustion. The characterization results indicate modification in the specific surface area, crystal structure, oxygen mobility and reducibility of cobaltite upon cerium substitution. Cobaltite structure does not tolerate more than 50% substitution of La by Ce. For higher Ce substitution the perovskite structure is lost and mixed oxides are detected. Further destruction of the perovskite structure in a reductive process indicates a lower catalytic role of the perovskite structure in the catalytic combustion of soot regarding to the chemical composition of the La1-xCe xCoO3 system. After the reductive process, only a slight increase in the catalytic activity of the samples with low Ce content (x≤0.3) while a larger increased was detected for those with larger amount of Ce(x≥0.5). These results suggest that the activity of these materials for soot combustion is improved by two factors: i) the increasing of CeO2 content, closely related to higher material capacity for oxygen transfer from catalyst to carbonaceous surface and ii) the formation of larger CeO2 crystals in the higher-Ce-content samples after H2 reduction, responsible of the improvement of the oxygen exchange and number of contact points between catalyst and soot. <![CDATA[<b>PREPARATION OF MOLECULARLY IMPRINTED POLYMERS FOR DIPHENYLAMINE REMOVAL FROM ORGANIC GUNSHOT RESIDUES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400021&lng=en&nrm=iso&tlng=en In order to obtain a better tool for collecting forensic evidence at the crime scene and the subsequent analysis of gunshot residue in laboratories, we propose the development of Molecularly Imprinted Polymers (MIPs) for the retention of diphenylamine (DPA), an organic compound coming from gunshot residues. This technique aims to achieve molecular recognition of a particular organic molecule, called target molecule. Once occurred recognition, this organic molecule may be removed, separated, and preconcentrated for further analysis. For this, a series of MIPs and their analogs Non Molecularly Imprinted Polymers (NIPs) following a non-covalent strategy was synthesized. This was carried out by solution radical polymerization, using 1-vinyl-2-pyrrolidone (VP) as monomer, and diphenylamine as imprinting and target molecule. The retention capacity of MIPs was studied by HPLC and UV-VIS spectroscopy, meanwhile adsorption mechanism was studied by isothermal and kinetic assays. Resin yields ranged from 25% to 100%. The results show that the variable that has more influence on DPA retention is the amount of crosslinking, wherein a greater amount of crosslinking results in higher retention of DPA, achieving values up to 90%. There is a clear difference in adsorption capacity between MIPs and NIPs, where MIPs show higher adsorption capacity reaching a double or triple retention value. Kinetic studies show that it is achieved a high retention capacity within 5 min of contact. The results show that the fundamental mechanism for molecular recognition displayed by the imprinting effect can be attributed at two processes: the pre-organization of complementary functional groups present in the polymer and the template and selective cavity formation which complement the template size. Binding factors and selectivity combined effects contributing to molecular recognition of diphenylamine (DPA) by MIPs. <![CDATA[<b>FUNCTIONAL ION MEMBRANES SUPPORTED INSIDE MICROPOROUS POLYPROPYLENE MEMBRANES TO TRANSPORT CHROMIUM IONS</b>: <b>DETERMINATION OF MASS TRANSPORT COEFFICIENT</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400022&lng=en&nrm=iso&tlng=en Polypropylene (PP) membranes incorporating interpenetrating polymer networks of poly[(ar-vinylbenzyl) trimethylammonium chloride](P(ClVBTA)) and poly[sodium (styrenesulfonate)] P(SSNa) were modified via an "in-situ" radical polymerization synthesis inside the pores. The modified polypropylene membranes were characterized using SEM, ATR/FTIR, DRX, TGA, and Donnan dialysis for the transport of chromium ions. The modified membranes exhibited a percent modification between 2.5% and 4.0% in weight gain and a hydrophilic character with a water uptake capacity between 15% and 20%. The mass transport coefficient was determined using the non-linear fit of the experimental data to the exponential equation. Hexavalent chromium ions were efficiently transported by the modified membranes containing P(ClVBTA). At pH 3.0, the M4Cl.PEI (11.0x10-6 m s-1), and at pH 9.0, the M3Cl (14.4x10-6 m s-1) could transport hexavalent chromium ions efficiently using a 1 mol L-1 NaCl extraction agent. In the same way, the transport of trivalent chromium could be performed using membranes modified with P(SSNa). At pH 3.0 and 4.0x10-2 mol L-1 trivalent chromium in the food chamber, the M9Na.PVA (16.3x10-6 m s-1) performed efficient transport using 1x10-3mol L-1 HNO3 as the extraction agent. <![CDATA[<b>EXPERIMENTAL ACTIVITIES IN THE LABORATORY OF ANALYTICAL CHEMISTRY UNDER AN INQUIRY APPROACH</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400023&lng=en&nrm=iso&tlng=en This study analyzes the perception, development and improvement of the cognitive abilities of undergraduate students (of biochemistry and industrial chemistry) through the application of an inquiry methodology in the laboratory of analytical chemistry. The study was conducted during one semester. The instruments for data collection were a Test of Critical Thinking and a Questionnaire to determine the perception of the inquiry methodology and the traditional methodology, applied at the beginning and at the end of the semester. The results show an improvement in cognitive strategies and in the students' perception of the inquiry methodology. This is consistent with future job performance. <![CDATA[<b>SYNTHESIS, STRUCTURAL CHARACTERIZATION AND CATALYTIC OXIDATION PROPERTY OF SCHIFF BASE COPPER(II) COMPLEXES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400024&lng=en&nrm=iso&tlng=en Two new square planar mononuclear copper(II) complexes, [CuL¹] (1) and [CuL²(NCS)] (2), where L¹ is the dianionic form of the bis-Schiff base N,N'-bis(2-hydroxynaphthylmethylidene)-l,3-pentanediamine (H2L¹), and L² is the monoanionic form of 1-[(2-diethylaminoethylimino)methyl]naphthalen-2-ol (HL²), have been synthesized and characterized by physico-chemical methods and single-crystal X-ray diffraction. Complex (1) (C27H24CuN2O2) crystallizes as the orthorhombic space group Pbca, with unit cell dimensions a = 18.284(1) Å, b = 12.2373(7) Å, c = 19.775(1) Å, V = 4424.6(4) ų, Z = 8, R1 = 0.0421, wR2 = 0.0975, S = 1.054. Complex (2) (C18H21CuN3OS) crystallizes as the monoclinic space group P2/c, with unit cell dimensions a = 12.776(1) Å, b = 24.181(2) Å, c = 11.743(1) Å, β = 98.621(1)°, V = 3586.7(7) ų, Z = 8, R1 = 0.0520, wR2 = 0.1183, S = 1.012. X-ray analysis indicates that the Cu atoms in the complexes are in square planar coordination. The complexes were evaluated for their catalytic oxidation of cyclooctene and styrene with tert-butylhydroperoxide. <![CDATA[<b>THEORETICAL STUDY ON INTERACTIONS BETWEEN CU-BASED IONIC LIQUID AND PROPANE/PROPYLENE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072014000400025&lng=en&nrm=iso&tlng=en Density functional theory has been employed to investigate the interactions between copper(I) bis(trifluoromethylsulfonyl)imide (Cu[Tf2N]) and C3H8/C3H6. The calculations were based on the model of Cu[Tf2N], and performed at X3LYP/6-31++G** level. The calculated interaction energies indicated that the adsorption ability of Cu[Tf2N] for C3H8/C3H6 followed the order of C3H8 < C3H6. The noncovalent interactions in real space, based on the electron density and its derivatives, reveal the nature of interactions between Cu[Tf2N] and C3H8AC3H6. The natural bond orbital (NBO) analysis of the second-order perturbation energy has been performed to investigate the interaction mechanism of C3H8/C3H6 on ionic liquid Cu[Tf2N].