Collection of Czechoslovak Chemical Communications, 2011
ABSTRACT The nitration of eugenol was investigated by using density functional theory (DFT) calcu... more ABSTRACT The nitration of eugenol was investigated by using density functional theory (DFT) calculations. Potential energy surface and molecular electrostatic potential of eugenol was constructed in order to find, respectively, the minimum energy conformers and the possible sites for electrophilic attack. Stationary points were located and characterized at the B3LYP/6-311++G(2d,2p) level of theory. A strongly bound pi-complex was found, in which the distance between the nitrogen atom of the NO2 moiety and the C-1 carbon atom of the aromatic ring is 2.15 angstrom in the gas phase and 2.06 angstrom in dichloromethane. The most favorable sigma-complex or Wheland intermediate is the result from the interaction between the nitrogen and the C-6 ring carbon atom. The transition state that connects both complexes is more resembling the sigma-complex. The nitronium ion exothermically reacts with eugenol to give the pi-complex without an energy barrier. The next stage of the reaction pathway, pi-complex -> sigma-complex, is endothermic and involves a Gibbs energy of activation of 7.9-8.0 kcal mol(-1) (gas phase) and 8.3-8.9 kcal mol(-1) (CH2Cl2).
ABSTRACT Arsenic species can be removed from aqueous solutions using the liquid-phase polymer-bas... more ABSTRACT Arsenic species can be removed from aqueous solutions using the liquid-phase polymer-based retention, LPR, technique. The LPR technique removes ionic species by functional groups of water-soluble polyelectrolytes (WSP) and then using a ultrafiltration membrane that does not let them pass through the membrane, thus separating them from the solution. The ability of WSP with groups (R)4N+X− to remove arsenate ions using LPR was studied. The interaction and arsenate anion retention capacity depended on: pH, the quaternary ammonium group's counter ion, and the ratio polymer: As(V), using different concentrations of As(V). Water-soluble polychelates were also used for one-step retention of As(III) in solution. The complex of poly(acrylic acid)-Sn, 10 and 20 wt-% of metal gave a high retention of As(III) species at pH 8, although the molar ratio polychelate: As(III) was 400:1. The enrichment method was used to determine the maximum retention capacity (C) for arsenate anions in aqueous solutions at pH 8. In similar conditions, the values of C were 142 mg g−1 for P(ClAETA) and 75 mg g−1 for P(SAETA). The combined treatment of arsenic aqueous solutions by electrocatalytic oxidation (EO) to convert the species of As(III) to As(V) with the LPR technique quantitatively removed arsenic.
Summary Using capillary zone electrophoresis has made characterizations of different copolymers... more Summary Using capillary zone electrophoresis has made characterizations of different copolymers obtained via zwitterionic polymerization. Results demonstrate that this technique is able to put into evidence the molecular heterogeneity of the different copolymers. Analyses were performed in less than 10 minutes using a borate buffer. To our knowledge this the first time that free-zone capillary electrophoresis has been applied to
ABSTRACT In this publication we are reporting for the first time on examples of the redox behavio... more ABSTRACT 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.
... Stock solutions 1.Ox1O -3 mol L -1 D (Laboratory Chile) and CM (Sigma-Aldrich®) were prepared... more ... Stock solutions 1.Ox1O -3 mol L -1 D (Laboratory Chile) and CM (Sigma-Aldrich®) were prepared by dissolving 16.7 and 22.7 mg of each compound in a 50 niL volumetric flask in different solvents, respectively. ... (12) IM Palabiyik; F. Onur, Chromatographia, 66, S93, (2007). ...
... IVAN M. PERIC 1* , BERNABE L. RIVAS 2 , AMALIA POOLEY 2 , ELIZARDO RIFFFO 1 AND LUISA. BASAEZ... more ... IVAN M. PERIC 1* , BERNABE L. RIVAS 2 , AMALIA POOLEY 2 , ELIZARDO RIFFFO 1 AND LUISA. BASAEZ 1 1 Departamento de Química Analítica e Inorgánica. ... [ Links ]. 13. BL Rivas, SA Pooley, M. Soto, KE Geckeler. J. Polym. Sci.: Part A: Polym. Chem., 35, 2461 (1997). ...
... From the standpoint of possible effects associated with the semiconducting character of chalc... more ... From the standpoint of possible effects associated with the semiconducting character of chalcocite, we also considered it of interest to conduct some photovoltammetric experiments. ... Chalcocite character increase from top to bottom. ...
Abstract The oxidative electropolymerization of the (3-pyrrol-1-ylpropyl)malonic acid monomer 1 i... more Abstract The oxidative electropolymerization of the (3-pyrrol-1-ylpropyl)malonic acid monomer 1 is a simple and reproducible one-step procedure for the synthesis of complexing polymer film modified electrodes, which have been applied to the electroanalysis of Cu(II), Pb(II), Cd(II) ...
Collection of Czechoslovak Chemical Communications, 2011
ABSTRACT The nitration of eugenol was investigated by using density functional theory (DFT) calcu... more ABSTRACT The nitration of eugenol was investigated by using density functional theory (DFT) calculations. Potential energy surface and molecular electrostatic potential of eugenol was constructed in order to find, respectively, the minimum energy conformers and the possible sites for electrophilic attack. Stationary points were located and characterized at the B3LYP/6-311++G(2d,2p) level of theory. A strongly bound pi-complex was found, in which the distance between the nitrogen atom of the NO2 moiety and the C-1 carbon atom of the aromatic ring is 2.15 angstrom in the gas phase and 2.06 angstrom in dichloromethane. The most favorable sigma-complex or Wheland intermediate is the result from the interaction between the nitrogen and the C-6 ring carbon atom. The transition state that connects both complexes is more resembling the sigma-complex. The nitronium ion exothermically reacts with eugenol to give the pi-complex without an energy barrier. The next stage of the reaction pathway, pi-complex -> sigma-complex, is endothermic and involves a Gibbs energy of activation of 7.9-8.0 kcal mol(-1) (gas phase) and 8.3-8.9 kcal mol(-1) (CH2Cl2).
ABSTRACT Arsenic species can be removed from aqueous solutions using the liquid-phase polymer-bas... more ABSTRACT Arsenic species can be removed from aqueous solutions using the liquid-phase polymer-based retention, LPR, technique. The LPR technique removes ionic species by functional groups of water-soluble polyelectrolytes (WSP) and then using a ultrafiltration membrane that does not let them pass through the membrane, thus separating them from the solution. The ability of WSP with groups (R)4N+X− to remove arsenate ions using LPR was studied. The interaction and arsenate anion retention capacity depended on: pH, the quaternary ammonium group's counter ion, and the ratio polymer: As(V), using different concentrations of As(V). Water-soluble polychelates were also used for one-step retention of As(III) in solution. The complex of poly(acrylic acid)-Sn, 10 and 20 wt-% of metal gave a high retention of As(III) species at pH 8, although the molar ratio polychelate: As(III) was 400:1. The enrichment method was used to determine the maximum retention capacity (C) for arsenate anions in aqueous solutions at pH 8. In similar conditions, the values of C were 142 mg g−1 for P(ClAETA) and 75 mg g−1 for P(SAETA). The combined treatment of arsenic aqueous solutions by electrocatalytic oxidation (EO) to convert the species of As(III) to As(V) with the LPR technique quantitatively removed arsenic.
Summary Using capillary zone electrophoresis has made characterizations of different copolymers... more Summary Using capillary zone electrophoresis has made characterizations of different copolymers obtained via zwitterionic polymerization. Results demonstrate that this technique is able to put into evidence the molecular heterogeneity of the different copolymers. Analyses were performed in less than 10 minutes using a borate buffer. To our knowledge this the first time that free-zone capillary electrophoresis has been applied to
ABSTRACT In this publication we are reporting for the first time on examples of the redox behavio... more ABSTRACT 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.
... Stock solutions 1.Ox1O -3 mol L -1 D (Laboratory Chile) and CM (Sigma-Aldrich®) were prepared... more ... Stock solutions 1.Ox1O -3 mol L -1 D (Laboratory Chile) and CM (Sigma-Aldrich®) were prepared by dissolving 16.7 and 22.7 mg of each compound in a 50 niL volumetric flask in different solvents, respectively. ... (12) IM Palabiyik; F. Onur, Chromatographia, 66, S93, (2007). ...
... IVAN M. PERIC 1* , BERNABE L. RIVAS 2 , AMALIA POOLEY 2 , ELIZARDO RIFFFO 1 AND LUISA. BASAEZ... more ... IVAN M. PERIC 1* , BERNABE L. RIVAS 2 , AMALIA POOLEY 2 , ELIZARDO RIFFFO 1 AND LUISA. BASAEZ 1 1 Departamento de Química Analítica e Inorgánica. ... [ Links ]. 13. BL Rivas, SA Pooley, M. Soto, KE Geckeler. J. Polym. Sci.: Part A: Polym. Chem., 35, 2461 (1997). ...
... From the standpoint of possible effects associated with the semiconducting character of chalc... more ... From the standpoint of possible effects associated with the semiconducting character of chalcocite, we also considered it of interest to conduct some photovoltammetric experiments. ... Chalcocite character increase from top to bottom. ...
Abstract The oxidative electropolymerization of the (3-pyrrol-1-ylpropyl)malonic acid monomer 1 i... more Abstract The oxidative electropolymerization of the (3-pyrrol-1-ylpropyl)malonic acid monomer 1 is a simple and reproducible one-step procedure for the synthesis of complexing polymer film modified electrodes, which have been applied to the electroanalysis of Cu(II), Pb(II), Cd(II) ...
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