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151.
152.
[structure: see text] Dicobalt-beta-pinene hybrids of types I and II have been prepared using a Nicholas reaction between propargyl derivatives, obtained from commercial (1R)-(-)-myrtenal, and different aromatic nucleophiles. The method is suitable for the preparation of densely functionalized bio-organometallic natural product-based hybrids, as demonstrated by the preparation of a beta-pinene-neoclerodane hybrid. 相似文献
153.
Antunes FE Lindman B Miguel MG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(22):10188-10196
Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification, and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separately can give high viscosities and a gel-like behavior, a pronounced maximum in viscosity and storage modulus with the mixing ratio of the polyelectrolytes is observed; the maximum is located between the points of charge and hydrophobe stoichiometry and reflects a combination of hydrophobic and electrostatic association. Lowering the charge density of the anionic polymer leads to a strengthened association at first, but at lower charge densities there is a weakened association due to the onset of phase separation. The strength of the electrostatic interaction was modified by adding salt. Increased ionic strength can lead to phase separation and to increased or decreased viscosity depending on the polyelectrolyte mixing ratio. 相似文献
154.
Wang Mei Miguel Daniel Riera Víctor Bois Claudette Jeannin Yves 《Transition Metal Chemistry》2001,26(4-5):566-569
A novel dimolybdenum complex [(3-C3H5)(CO)2Mo(-S2CPCy3)Mo(3-CH2CMeCH2)(CO)2], obtained by reacting the [(CO)2(3-C3H5)Mo(-S2CPCy3)Mo(CO)3]– anion with an excess of ClCH2CMe=CH2, has been characterized by i.r., 31P{1H}, 1H- and 13C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S2CPCy3 bridge to bind to the Mo(2) atom coordinated by 3-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted 3-allyl ligand. 相似文献
155.
R. Usón L.A. Oro D. Carmona M.A. Esteruelas C. Foces-Foces F.H. Cano S. García-Blanco A.Vázquez De Miguel 《Journal of organometallic chemistry》1984,273(1):111-128
A new series of cationic areneiridium(I) complexes of formula [Ir(barrelene)(arene)]+ or [Ir(barrelene)(PhNRPh)]+ (R= Ph or H) have been synthesized from neutral iridium complexes of the type [IrY(barrelene)]x (barrelene = Me3TFB, Y = Cl or OMe (x = 2), Y = acac (x = 1); barrelene = TFB, Y = OMe (x = 2), Y = acac (x = 1)). The crystal structures of [Ir(Me3TFB)(1,4-C6H4Me2)]ClO4 and [Ir(TFB)(PhNPh2)]BF4·CH2Cl2 have been determined by X-ray diffraction. They crystallize in the space groups Pbca and Pna21 respectively with lattice constants of 17.6947(11), 15.8072(10), 16.0019(11) Å and 9.8059(2), 20.8097(9), 14.3367(4) Å. Final R factors were 0.063 and 0.042 for the observed data. Both complexes show a staggered arrangement between the arene and the TFB moieties and deviation from planarity of the coordinated arene ligands. In the second complex the IrC and NC distances, the CNC angle, the type of arene puckering, and the spectroscopic data indicate a distortion of the coordinated arene towards a η5-coordinated iminocyclohexadienyl form. 相似文献
156.
Miguel F. Braa María L. Lpez Rodríguez Concepcin Rodríguez Amando Garrido-Pertierra 《Journal of heterocyclic chemistry》1986,23(4):1019-1022
Reaction of N-(4-pyridylmethyl)benzamide N-oxides 2a-f with ethyl cyanoacetate in the presence of acetic anhydride yield dimerization compounds 3a-f and (E)-ethyl 2-cyano-3-(4-pyridyl)-3(benzoylamino)acrylates 4a-f , which react with hydrazine to give 4-cyano-3-(4-pyridyl)-3-pyrazolin-5-one 9 and the corresponding benzamides 10a-f . 相似文献
157.
Miguel A. Esteso Luis Fernandez-Merida Felipe F. Hernandez-Luis 《Journal of Electroanalytical Chemistry》1987,230(1-2)
Values of the emf for the cell: Na-glass|Na2Succ(m), Hg2Succ|Hg, have been measured. These values of E have been used with Hückel's extended Debye and Hückel equation to obtain the mean ionic activity coefficient values for Na2Succ in aqueous solutions of several concentrations, m. The values of γ± thus obtained have been adjusted to Pitzer's equation, with b = 1.2 and α = 2.0 to find Pitzer's parameters and then the values for both the osmotic coefficients and the activity of water. Finally, the standard potential of the Hg2Succ|Hg electrode has been determined and from this value the solubility-product equilibrium constant for mercurous succinate has also been calculated. 相似文献
158.
The three-dimensional structure of a complex tubular uranyl phosphonate, (UO(2))(3)(HO(3)PC(6)H(5))(2)(O(3)PC(6)H(5))(2).H(2)O, was determined ab initio from laboratory X-ray powder diffraction data and refined by the Rietveld method. The crystals belong to the space group P2(1)2(1)2(1), with a = 17.1966(2) ?, b = 7.2125(2) ?, c = 27.8282(4) ?, and Z = 4. The structure consists of three independent uranium atoms, among which two are seven-coordinated and the third is eight-coordinated. These metal atoms are connected by four different phosphonate groups to form a one-dimensional channel structure along the b axis. The phenyl groups are arranged on the outer periphery of the channels, and their stacking forces keep the channels intact in the lattice. The determination of this structure which contains 50 non-hydrogen atoms in the asymmetric unit, from conventional X-ray powder data, represents significant progress in the application of powder techniques to structure solution of complex inorganic compounds, including organometallic compounds. 相似文献
159.
Maldonado-Valderrama J Fainerman VB Galvez-Ruiz MJ Martín-Rodriguez A Cabrerizo-Vílchez MA Miller R 《The journal of physical chemistry. B》2005,109(37):17608-17616
The rheological behavior of beta-casein adsorption layers formed at the air-water and tetradecane-water interfaces is studied in detail by means of pendant drop tensiometry. First, its adsorption behavior is briefly summarized at both interfaces, experimentally and also theoretically. Subsequently, the experimental dilatational results obtained for a wide range of frequencies are presented for both interfaces. An interesting dependence with the oscillation frequency is observed via the comparative analysis of the interfacial elasticity (storage part) and the interfacial viscosity (loss part) for the two interfaces. The analysis of the interfacial elasticities provides information on the conformational transitions undergone by the protein upon adsorption at both interfaces. The air-water interface shows a complex behavior in which two maxima merge into one as the frequency increases, whereas only a single maximum is found at the tetradecane interface within the range of frequencies studied. This is interpreted in terms of a decisive interaction between the oil and the protein molecules. Furthermore, the analysis of the interfacial viscosities provides information on the relaxation processes occurring at both interfaces. Similarly, substantial differences arise between the gaseous and liquid interfaces and various possible relaxation mechanisms are discussed. Finally, the experimental elasticities obtained for frequencies higher than 0.1 Hz are further analyzed on the basis of a thermodynamic model. Accordingly, the nature of the conformational transition given by the maximum at these frequencies is discussed in terms of different theoretical considerations. The formation of a protein bilayer at the interface or the limited compressibility of the protein in the adsorbed state are regarded as possible explanations of the maximum. 相似文献
160.
The acid-catalysed esterification of myristic acid with isopropanol was studied by using near-infrared spectroscopy (NIR) in combination with soft-modeling curve resolution (MCR) methodology with a view to establishing the effect of experimental variables on the reaction kinetics. The reaction was conducted at temperatures above the boiling point of the alcohol, with continuous addition of an isopropanol/water mixture to the reactor. Spectral and concentration profiles were determined by applying soft-modeling curve resolution methodology to a column-wise augmented data matrix containing the spectra for the pure components. MCR profiles were compared with reference values and found to depart from then by less than 3% as %RSE for concentrations and to exhibit correlation above 0.999 for spectra.The reaction kinetics as estimated from the concentration profiles was found to be pseudo-first-order. Also, the pseudo-first-order rate constant was found to depend on the flow-rate of the isopropanol/water mixture and its water content; although the constant decreased with increase in the proportion of water, a content of ca. 15% could be used without important retarding effects on the kinetics. The proposed NIR-MCR method allows the rate constant and the influence of the initial water content to be determined with a view to minimizing consumption of the raw materials and optimizing the experimental conditions. 相似文献