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991.
Let C be a treelike curve, that is, a reduced curve whose irreducible components meet transversally at disconnecting points ofC. AssumeC has planar singularities. In this note we prove an Autoduality Theorem for C. More precisely, in [6] a natural Abel map A: C → $\bar J$ to a certain compactification $\bar J$ of the generalized Jacobian of C has been constructed. In this note we prove that the pullback map $A^* :Pic^0 (\bar J) \to Pic^0 (C)$ is an isomorphism. 相似文献
992.
Francisca M. Albertí Juan J. Fiol Angel García-Raso Marta Torres A. Terrón Miquel Barceló-Oliver María J. Prieto Virtudes Moreno Elies Molins 《Polyhedron》2010
A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[RuIIICl4(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[IrIIICl4(DMSO)2] (2), trans-[IrIIICl4(DMSO)[H-(Nicotine)]] (3) and mer-[IrIIICl3(DMSO)(Nicotine)2] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[IrIIICl4(DMSO)2]¯ complex. 相似文献
993.
Gustavo Von Poelhsitz André L. Bogado Luciano M. Lião Antonio G. Ferreira Eduardo E. Castellano Javier Ellena Alzir A. Batista 《Polyhedron》2010
This study presents the syntheses and characterization of 2-mercaptopyridine (pyS−) complexes containing ruthenium(II) with the following general formula [Ru(pyS)2(P–P)], P–P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl3(NO)(P–P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P–P ligand. The reaction of pyS− with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)2(NO)(η1-dppbO-P)]PF6(5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1–5, and report the X-ray structures for 1 and 5. 相似文献
994.
José M. Santiuste Rosa Lebrón-Aguilar Jesús Eduardo Quintanilla-López 《Chromatographia》2010,72(5-6):511-522
Retention indices, RI, of 55 solutes belonging to eight chemical monofunctional group series were computed at 373 K from retention factors measurements on 14 capillary columns coated with stationary phases, SP, spanning almost the whole polarity range. RI-values of some of these analytes were validated by comparison with literature values. Positive slope straight lines were obtained for the isothermal RI versus Z plots for the eight chemical functions. For a given series the slope (A) is rather insensitive to RP, while the intercept (FF) clearly increases linearly with increasing RP. For a given stationary phase A does not show any clear trend with increasing solute polarity, while FF increases clearly from the less polar to the most polar series. 相似文献
995.
Irede Dalmolin Marcio A. Mazutti Eduardo A.C. Batista M. Angela A. Meireles J. Vladimir Oliveira 《The Journal of chemical thermodynamics》2010,42(6):797-801
The aim of this work is to report phase equilibrium experimental results for the systems grape oil/carbon dioxide and (grape oil/carbon dioxide + ethanol). The oil was obtained by supercritical extraction from the grape seed residue from wine production. The static synthetic method using a variable-volume view cell was employed for obtaining the experimental bubble and dew (cloud) points transition data over the temperature range of (313.15 to 343.15) K and pressures up to 20.6 MPa. The experiments were carried out using (ethanol + CO2) overall mass fractions ranging from 0.50 to 0.99, keeping a fixed ethanol to carbon dioxide molar ratio at 1:3. Results indicate the existence of complex phase behaviour for all temperatures investigated with the occurrence of vapour–liquid, liquid–liquid and vapour–liquid–liquid phase transitions observed. 相似文献
996.
Minerva Gamboa Myriam Campos Luis Alfonso Torres 《The Journal of chemical thermodynamics》2010,42(5):666-674
In this work, the stability of 5,10,15,20-tetraphenylporphine (TPP) and its metallic derivatives, NiTPP, CoTPP, CuTPP, and ZnTPP has been studied through differential scanning calorimetry and thermogravimetry. The decomposition temperatures are (712, 710, 708, 702, and 671) K for NiTPP, CoTPP, CuTPP, ZnTPP, and TPP, respectively. These values are in correspondence with the N–M bond length dM–N, of the metalloporphyrins. The corresponding molar enthalpies of melting ΔfusHm, were determined as (58, 57, 55, 52, and 44) kJ · mol?1 for the same series. These values are discussed in terms of the crystallographic features in the solid state. 相似文献
997.
Maria das Dores M.C. Ribeiro da Silva Manuel A.V. Ribeiro da Silva Vera L.S. Freitas Maria Victoria Roux Pilar Jiménez Juan Z. Dávalos Pilar Cabildo Rosa M. Claramunt Elena Pinilla M. Rosario Torres José Elguero 《The Journal of chemical thermodynamics》2010,42(4):536-544
Thermochemical and thermophysical studies have been carried out for crystalline 3,4,4′-trichlorocarbanilide. The standard (p° = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, for the crystalline 3,4,4′-trichlorocarbanilide (TCC) was experimentally determined using rotating-bomb combustion calorimetry, as ?(234.6 ± 8.3) kJ · mol?1. The standard enthalpy of sublimation, at the reference temperature of 298.15 K, was measured by the vacuum drop microcalorimetric technique, using a High Temperature Calvet Microcalorimeter as (182.1 ± 1.7) kJ · mol?1. These two thermochemical parameters yielded the standard molar enthalpy of formation of the studied compound, in the gaseous phase, at T = 298.15 K, as ?(52.5 ± 8.5) kJ · mol?1. This parameter was also calculated by computational thermochemistry at M05-2X/6-311++G7 and B3LYP/6-311++G(3df, 2p) levels, with a deviation less than 4.5 kJ · mol?1 from experimental value. Moreover, the thermophysical study was made by differential scanning calorimetry, DSC, over the temperature interval between T = 263 K and its onset fusion temperature, T = (527.5 ± 0.4) K. A solid–solid phase transition was found at T = (428 ± 1) K, with the enthalpy of transition of (6.1 ± 0.1) kJ · mol?1. The X-ray crystal structure of TCC was determined and the three-centred N–H?OC hydrogen bonds present analyzed. 相似文献
998.
A. Cruz‐Torres F. DE L. Castillo‐Alvarado J. Ortíz‐López J. S. Arellano 《International journal of quantum chemistry》2010,110(13):2495-2508
Ab initio density functional calculations were performed for a toroidal carbon C120 nanostructure. Hydrogen molecules, n = 1–15, were added inside the nanotorus and for each one of these systems a geometry optimization was obtained. The cohesive energy shows that these structures are energetically stable. For example, the binding energies are ?34.95 and ?36.19 Hartrees and the interatomic distances H? H are 0.753 and 0.772 Å for 1 and 14 molecules, respectively. Considering only molecular hydrogen, we have always seen so far weak physisorption into the C120 nanotorus. There is no chemisorption until the number oh hydrogen molecules are increased to 14. In this case, four hydrogen atoms are chemisorbed. With 15 molecules, there are 10 hydrogen atoms chemisorbed just at the inner nanotorus surface forming 10 H? C bondings with bond length close to that in methane. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2495–2508, 2010 相似文献
999.
Alessandro Zanardi Dr. Jose A. Mata Prof. Eduardo Peris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10502-10506
A new tandem catalytic process has been studied for a heterodimetallic complex containing both iridium and palladium fragments connected by a 1,2,4‐trimethyltriazolyldiylidene ligand. The process implies the unprecedented preparation of imines from the direct reaction of nitroarenes and primary alcohols. The global process comprises the following steps: 1) reduction of the nitroarene to an amine, 2) oxidation of the alcohol to aldehyde, and 3) condensation of the aldehyde and the amine to form the corresponding imine. The oxidation of the alcohol to aldehyde is promoted by the iridium fragment, while the reduction of the nitro group to amine is facilitated by palladium. A wide set of different catalytic systems has been studied, showing that the Ir/Pd complex 1 is a highly active and stable catalyst in the preparation of imines. 相似文献
1000.
Daniel Pellico Mar Gómez‐Gallego Prof. Pedro Ramírez‐López Dr. María José Mancheño Prof. Miguel A. Sierra Prof. M. Rosario Torres Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1592-1600
A novel approach for the synthesis of macrocyclic bis‐β‐lactams based on the Cu‐catalyzed alkyne–azide cycloaddition (CuAAC) is reported. The procedure is general and allows access to a full range of diastereomerically or enantiomerically pure macrocyclic cavities in good yields. The incorporation of chiral oxazolidinone fragments at C3 in the β‐lactam rings allows the total enantiocontrol of the process. 相似文献