Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> http://www.scielo.cl/rss.php?pid=0717-970720050003&lang=es vol. 50 num. 3 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>CHARACTERIZATION OF HUMIC ACIDS ORIGINATED FROM ARGENTINEAN COMPOST AND SOIL BY CAPILLARY ELECTROPHORESIS AND MASS SPECTROMETRY</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300001&lng=es&nrm=iso&tlng=es Humic acids (HAs) extracted from different organic compost and soil from Argentina have been characterized by capillary electrophoresis (CE) and mass spectrometry. The chemical properties of HAs show changes depending on their origin (compost, soil). Capillary electrophoresis analyses were carried out using a background electrolyte consisting of boric acid, TRIS and EDTA (BTE). BTE was also modified with cyclodextrins. After optimization of BTE, the best results were obtained when b-cyclodextrin was used. Under optimized separation conditions, the characteristics CE fingerprints of compost derived HAs (CHAs) were studied. CE fingerprints show differences in the composition of the different CHAs. Mass spectra obtained by laser desorption ionization time of flight mass spectrometry show differences between the CHAs and HAs extracted from Argentinean soil. A comparison with the soil standard HAs (International Humic Substances Society) was made. CHAs show mostly compounds in the mass spectra with low m/z values. The typical patterns exhibited in soil HAs of different origin are present in the Argentinean soil HA, i.e. groups of peaks around mass-to-charge (m/z) 800 <![CDATA[<b>SYNTHESIS OF CONDENSATION POLYMERS DERIVED FROM SILYLATED MONOMERS UNDER PHASE TRANSFER CATALYSIS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300002&lng=es&nrm=iso&tlng=es The synthesis of the poly(carbonate) and poly(thiocarbonate) derived from the diphenol bis(4-hydroxyphenyl)-phenylmethylsilane and the poly(ester) derived from the same diphenol and the acid dichloride bis(4-chloroformylphenyl)-phenylmethylsilane are described. Polymers were synthesized under phase transfer conditions and the results were evaluated by the yields and inherent viscosity values. The phase transfer process was effective, but the results were affected by the increase of the NaOH concentration in the aqueous phase, in the sense that it was possible to see hydrolytic processes that decrease the yields and the inherent viscosity values. Also there was an influence of the nature of the catalysts, with BTEAC being efficient due to it hydrophilic nature <![CDATA[<b>EVALUATION OF b-DIKETONATE TIN AND INDIUM COMPLEXES AS PRECURSORS FOR THE PHOTODEPOSITION OF SnO<sub>2</sub> AND In<sub>2</sub>O<sub>3</sub> THIN FILMS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300003&lng=es&nrm=iso&tlng=es SnO2 and In2O3 thin films have been succesfully prepared by direct UV irradiation of amorphous films of b-diketonate complexes on Si(100) substrates. The as-deposited films were analyzed by Auger electron spectroscopy (AES), whereas annealing was required in order to get X-ray diffraction spectra, indicating the amorphous nature of the films. The surface morphology of the films examined by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) revealed that In2O3 films are much smoother than SnO2 films, with average surface roughness (Ra) of 3 nm and 11 nm respectively. The low resistivity values determined for these metal oxide films (3-4 x 10-4 W cm) demonstrate the potential use of these deposited films in gas-sensing devices for detection of environmentally significant concentrations of oxidizing species such as NO2 and O3 <![CDATA[<b>A RAPID ESTIMATION OF METAL CONTENTS IN WASTEWATER TREATMENT FOR CONDUCTIVITY MEASUREMENTS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300004&lng=es&nrm=iso&tlng=es An efficient wastewater treatment for metal removal is based on the precipitation of metal ferrites by addition of iron(II) in alkaline and oxidizing conditions. The maximum efficiency is achieved for an iron(II)/total metal ratio of 15:1 (w:w) (Barrado et al., 1996a) which implies that the total metal concentration must be known. It has been established a linear empirical correlation (R²=0.997) between wastewater conductivity and the total metal concentration that allows a rapid estimation of the amount of iron(II) to be added for metal precipitation with no need of time-consuming metal analysis. The empirical correlation obtained overestimates the total metal concentration, and therefore the added iron(II), thus assuring maximum efficiency of metal removal. The occurrence of metal complexing substances modifies the wastewater ionic composition decreasing the conductivity measurements and the estimated metal concentration. However, it has been demonstrated that the estimated amount of iron(II) is still in excess to assure maximum metal precipitation <![CDATA[<b>A CONVENIENT, RENEWABLE SOURCE OF THE ANXIOLYTIC PROAPORPHINE ALKALOID GLAZIOVINE</b>: <b><i>DUGUETIA VALLICOLA</i></b><b> LEAVES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300005&lng=es&nrm=iso&tlng=es The leaves of Duguetia vallicola, a fairly common, large evergreen tree from the coastal regions of Panama, Colombia and Venezuela, contain (6aS)-glaziovine (1) as a major constituent. The abundance and renewable character of the plant material make it an attractive source for this rare, psychoactive alkaloid. The availability of glaziovine and its O-methyl derivative pronuciferine (2) has made complete ¹H and 13C NMR assignments of proaporphines possible for the first time <![CDATA[<b>N-FUNCTIONALIZATION OF DIHYDROCARVONE</b>: <b>OBTAINING AMINOCYCLOHEXANE DERIVATIVES AND THEIR SPECTROMETRIC STUDY</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300006&lng=es&nrm=iso&tlng=es The easy N-functionalization of dihydrocarvone was achieved through the preparation of its imine derivatives. Secondary amines were obtained by the reduction and allylation of ketimines derived from dihydrocarvone. It was established that these amines represent mixtures of four stereoisomers which were analyzed by capillary gas chromatographic-mass spectrometry (GC-MS) (EI, 70 eV). Total energy and heat of formation for diastereoisomeric amines were calculated using AM1 and PM3 semi-empiric methods <![CDATA[<b>ESTIMATING DENSITY AND PULPING YIELD OF <i>E.</i> <i>globulus </i>WOOD</b>: <b>COMPARISON OF NEAR-INFRARED (NIR) AND MID-INFRARED (MIR)</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300007&lng=es&nrm=iso&tlng=es The application of near-infrared (NIR) spectroscopy as a tool for the rapid determination of pulp yield and basic density of Eucalyptus globulus wood is described. Previously, we had examined these properties using mid-infrared (MIR) spectroscopy. More precise results were obtained based on NIR spectra where the calibrations models were more robust and better predictors than obtained for the MIR spectra. Twenty-seven samples were used for establishing the correlations (calibration) and three for making predictions based on the calibration (validation). Quant+ chemometrics software was used to obtain the calibration and prediction through principal components regression (PCR). A PCR model based on NIR spectra gave fits with a standard error of prediction (SEP) of 14.3 kg m-3 and 1.57% for basic density and pulping yield, respectively. Using PCR-MIR, the SEP values obtained were 21.44 kg m-3 and 1.73%. The method readily predicts yield (correlation coefficient: R²= 0.51), and density (correlation coefficient: R² = 0.94) from spectral NIR measurement. Both NIR and MIR performed better in the analysis of the density property than for the pulp yield of the hardwood samples <![CDATA[<b>ELECTROTOPOLOGICAL STATE MODELING OF STABILITY CONSTANTS OF BINARY AND TERNARY COPPER(II) COMPLEXES WITH A-AMINO ACIDS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300008&lng=es&nrm=iso&tlng=es The second stepwise formation constants of binary and ternary copper(II) complexes with a-amino acidate ligands are modeled by using four-descriptor sets consisting of three indexes defined as linear combinations of the E-states of some skeletal groups of the different species involved in the formation equilibria, and the logarithm of the statistical factor. Hydrophobicity and basicity properties of the ligands are also described. Results indicate that both hydrophobic interactions and ligand basicities, as differential factors over the sequence of copper(II) complexes, would operate mainly through changes in the stability of the copper(II)-carboxylate bonds <![CDATA[<b>CYCLIC VOLTAMMETRY OF 1-(<i>n</i>-HEXYL)-3-METHYL-5-PYRAZOLONE-BASED ENAMINES AND THEIR CHLOROMANGANESE(III) AND NITRIDOMANGANESE(V) COMPLEXES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300009&lng=es&nrm=iso&tlng=es In this publication we are reporting for the first time on examples of the redox behavior of enamines and complexes derived from 1-alkylpyrazolones. Cyclic voltammetry experiment was performed on three enamines derived from 4-acyl-1-(n-hexyl)-3-methylpyrazol-5-ol and their chloromanganese(III) and nitridomanganese(V) complexes. The ligands have an irreversible oxidation potential of 1.1 V. Chloromanganese(III) complexes are quasi-reversible with an E1/2 of ­ 0.1 V. Nitridomanganese(V) complexes are also quasi-reversible, with E1/2 potentials of 0.95 V. However, for nitridomanganese(V) complexes reversibility increases as the scan speed raises from 100 to 3000 mV·s-1 <![CDATA[<b>SYNTHESIS AND CHARACTERIZATION OF FUNCTIONALIZED VINYL COPOLYMERS I</b>: <b>STRUCTURE-MONOMER REACTIVITY RELATIONSHIP IN COPOLYMERS CONTAINING N-VINYL-2-PYRROLIDONE MOIETIES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300010&lng=es&nrm=iso&tlng=es Copolymers containing N-vinyl-2-pyrrolidone as a common monomer with acrylic acid, 4-methyl styrene and vinyltrichlorosilane of different comonomer compositions were synthesized and characterized. Copolymer composition was determined by elemental analysis, from which monomer reactivity ratios (MRR, r) were estimated using straight line intersection procedures, such as Fineman-Ross and Kelen-Tüdõs methods, and a nonlinear one, the Reactivity Ratios Error in Variables Model. In this case, the values of MRR are rVP = 0.1 and rAA = 1.1 (for VP-co-AA), rVP = 0.8 and r4MS = 14.6 (for VP-co-4MS), and rVP = 0.0 and rVTCS = 0.3 (for VP-co-VTCS). Copolymers containing blocks of one of the monomer units and another tending to the alternation were obtained, with the product depending on the chemical nature of the comonomers. The different proposed comonomer distributions are analyzed in terms of the obtained MRR values and compared with related systems. The MRR are discussed in terms of monomer structural properties such as electronegativity and electron delocalization <![CDATA[<b>PENTACYCLIC TRITERPENES FROM <i>Cirsium pascuarense</i> </b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300011&lng=es&nrm=iso&tlng=es Copolymers containing N-vinyl-2-pyrrolidone as a common monomer with acrylic acid, 4-methyl styrene and vinyltrichlorosilane of different comonomer compositions were synthesized and characterized. Copolymer composition was determined by elemental analysis, from which monomer reactivity ratios (MRR, r) were estimated using straight line intersection procedures, such as Fineman-Ross and Kelen-Tüdõs methods, and a nonlinear one, the Reactivity Ratios Error in Variables Model. In this case, the values of MRR are rVP = 0.1 and rAA = 1.1 (for VP-co-AA), rVP = 0.8 and r4MS = 14.6 (for VP-co-4MS), and rVP = 0.0 and rVTCS = 0.3 (for VP-co-VTCS). Copolymers containing blocks of one of the monomer units and another tending to the alternation were obtained, with the product depending on the chemical nature of the comonomers. The different proposed comonomer distributions are analyzed in terms of the obtained MRR values and compared with related systems. The MRR are discussed in terms of monomer structural properties such as electronegativity and electron delocalization <![CDATA[<b>PHYSICO-CHEMICAL CHARACTERIZATION OF THE INCLUSION COMPLEX BETWEEN A 2-PROPEN-1-AMINE DERIVATIVE AND </b>b<b>-CYCLODEXTRIN</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300012&lng=es&nrm=iso&tlng=es Inclusion complexes and physical mixtures were prepared with isomeric mixture of E/Z (50:50) of 3-(4'-bromo-[1,1'-biphenyl]-4-yl)-3-(4-bromophenyl)-N,N-dimethyl-2-propen-1-amine (BBAP) and b-cyclodextrin (b-CD) in different proportions. In this study, theoretical calculations using Molecular Mechanics MM+ force field were applied to predict the structures of the inclusion complexes formed by interaction of BBAP and b-cyclodextrin. Circular dichroism, differential thermal analysis (DTA), X-ray diffraction and 13C CP/MAS NMRmethods were used to characterize the inclusion complexes and provide information about the stoichiometry of the inclusion complexes. The combined spectroscopy techniques indicate the formation of a complex of BBAP/b-CD in the molar proportion of 1:1 and 1:2 by co-evaporation and no complexation was detected in the physical mixture of the compounds <![CDATA[<b>ELECTROPOLYMERIZATION OF HETEROARYLENE AZOMETHINES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300013&lng=es&nrm=iso&tlng=es Organic diodes were obtained using a thiophene and furan azomethines derivative polymer electrochemically synthesized in nonaqueous media. The polymers were deposited on indium tin oxide (ITO) coated glass substrates. The films obtained were physicochemically characterized by electron probe microanalysis and X-ray photoelectron spectroscopy. The current­voltage (I­V) characteristics exhibit a turn-on voltage at about 2.5-3.5 V depending on the heterocycle nature. The electroluminescence­voltage (EL­V) curve has a similar shape but a shift of 1-2 V toward higher voltage. The charge injection mechanism is related with Fowler-Nordheim tunneling effect <![CDATA[<b>CHEMICAL REACTIONS AT NANOMETAL PARTICLES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300014&lng=es&nrm=iso&tlng=es The concept of nanochemistry and the reactions involved are discussed. The work is focused on nanoparticles obtained from colloidal dispersions. The colloidal particles by transmission electron microscopy of low and high resolution were analyzed. The high resolution electron miscroscopy (HRTEM) allow us to classify the nanostructure of the metal particles in some polyhedral models: cubooctahedron, truncated octahedron, tetracai decahedron and icosahedron. Some HRTEM of Pd-2 propanol and Ge-2-propanol are analyzed. The Pd atoms exhibit a high crystalline nanoparticles, cubooctahedral arrangement in the [001] orientation. On the other hand , the Ge atoms are ordered in a pseudohexagonal arrangement. The spacing in the last system are typical of a diamond cubic Ge structure. The structure of nanometals and also some relevant properties of nanoclusters are discussed. Some heterogeneous catalysis applications of supported metal clusters are discussed. Selective hydrogenation of a, b-unsaturated aldehydes are based on Pd, Rh, Ru, Os, Ir, Ni, Co and Pd.. In particular the crotonaldehyde hydrogenation in the presence of Pd/SiO2, Pd/Al2O3, PdSn/SiO2 and PdSn/Al2O3 was measured. The influence of the organic fragments incorporated on the surface of the particles in the systems mentioned above was studied. Finally, some remarks of the advantage of this technique in order to obtain nanoclusters are summarized <![CDATA[<b>ELECTRODIC POLYMER MATERIALS BASED IN ANILINE</b>: <b>INFLUENCE OF Ni<sup>2+</sup>, Co<sup>2+</sup>, AND Cu<sup>2+</sup> IONS ON ITS FORMATION</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300015&lng=es&nrm=iso&tlng=es Behaviour of aniline when voltametrically electropolymerized in the presence of Ni2+, Co2+, and Cu2+ cations has been studies 0.1 mol ·L-1 aniline in the presence of 0.01 mol·L-1 copper(II), nickel(II), and cobalt(II) ions and of three inorganic acids: HCl, HNO3, and H2SO4, was used. Aniline shows that polymerizes in all strong acids and metal ions selected, the reversibility and clarity of the redox processes in the presence of metal ions, indicate that the most accurate conditions for electrosynthesizing polyaniline (Pani) was CuCl2 in 1.0 M HCl; Ni(NO3)2 in 1.0 M HNO3 and in HNO3 1.0 M Co(NO3)2. In all cases, similar voltamograms were obtained and polymer growing changes according to the metal ion used. For Co(II), is more favorable in the following order: H2SO4 > HCl > HNO3. For Ni(II) is H2SO4 > HCl @ HNO3, and for Cu(II) is H2SO4 > HCl @ HNO3. The aim of this work is to study the effects of metal ions on aniline and their electropolymerization in acid media <![CDATA[<b>Magnetic properties of spinel-type oxides NiMn<sub>2-x</sub><i>Me</i><sub>x</sub>O<sub>4</sub></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000300016&lng=es&nrm=iso&tlng=es New materials, based on the well-known spinel compound NiMn2O4, have been synthesized and characterized from the magnetic point of view. The manganese cation was partially substituted in the general formula NiMn2-xMe xO4 , by nonmagnetic and magnetic elements, such as Me = Ga, Zn, Ni and Cr (0 x 1). Prior to the determination of their magnetic properties, the non-substituted spinel NiMn2O4 was carefully characterized and studied as a function of the oxygen stoichiometry, based on the influence of the annealing atmosphere and quenching rate. The ferrimagnetic character was observed in all samples, with a paramagnetic-to-ferromagnetic transition temperature Tc stabilized at 110 K, and well defined long-range antiferromagnetic interactions at lower temperatures, which depend on the applied field and the substitute concentration