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51.
Adriana F. Ibaez Andrea R. Martinez Graciela Y. Moltrasio Iglesias 《Journal of heterocyclic chemistry》1993,30(4):1047-1049
A novel approach to the title compound 10 starting with a conveniently available cinnamic acid is proposed. It involves a Friedel-Crafts reaction followed by the synthesis of the amide and subsequent cyclodehydration via a Bischler-Napieralski reaction. 相似文献
52.
Gina Pecchi Patricio Reyes M. Graciela Jiliberto T. López J. L. G. Fierro 《Journal of Sol-Gel Science and Technology》2006,37(3):169-174
Platinum-supported catalysts prepared by impregnation of mixed CeO2/Al2O3 and CeO2/ZrO2 oxides using the sol-gel method were characterized and used in the combustion of ethyl acetate. In each series, the effect
of CeO2 loading (3 and 5 wt%) was studied. Characterization data from the studied catalysts (specific area measurements, hydrogen
chemisorption, programmed temperature reduction (TPR), X-ray diffraction (XRD), photoelectron spectra (XPS) and transmission
electron microscopy (TEM)) revealed significant changes in porosity and metal dispersion in each series. The catalytic activity
of the solids, evaluated in the total combustion of ethyl acetate, exhibited a positive effect with the addition of Ce in
the zirconia series whereas no significant changes was observed in the alumina series. 相似文献
53.
Adriana F. Ibaez Graciela Y. Moltrasio Iglesias Jos M. Delfino 《Journal of heterocyclic chemistry》1996,33(2):265-270
Ring and nitrogen inversion account for the conformational equilibria of 3-phenyl-1, 2,3, 4-tetrahydroiso-quinolines. In order to quantitate the relative contribution of each conformer to the equilibrium, we undertook a molecular mechanics study on several substituted 3-phenyl-1, 2, 3, 4-tetrahydroisoquinolines. Predictions from calculations were checked against cmr chemical shift data. No boat conformation contributed significantly to the equilibrium. A general result of our calculations is that in all cases the 3-phenyl group in the equatorial position is strongly favored (by at least 2.50 kcal/mole). For 3-phenyl-1, 2, 3, 4-tetrahydroisoquinolines without substitution at nitrogen, N-H in equatorial position is preferred over the axial conformer, although the energy difference between both is always small (0.30–1.10 kcal/mole). For the cis-1,3-disubstituted compounds the le'3e conformers are the only species present (at least 99.8%). The calculated energy differences between the la′3a conformer and the le′3e conformer are always large (3.80–6.10 kcal/mole for the NHe conformers and 3.60–3.80 kcal/mole for the NHa conformers). The lack of a γ1a upfield shift at C3 also points to the preference for the pseudoequatorial-equatorial conformer. For N-methyl-3-phenyl-1,2,3,4-tetrahydroisoquinoline a preference for the NMe group in the equatorial position is predicted (0.60–2.00 kcal/mole). The small downfield shift at C4 (γNa = 0.5 ppm) is consistent with the equatorial NMe preference. For the cis-1,2,3-trisubstituted compounds no significant γ1a effect at C3 (γ1a = -0.2 and 1.0 ppm) or γNa effect at C4 (γNa = 0.1 and 0.4 ppm) is observed. For these compounds, deformations due to steric congestion are evidenced by the deviation from the values of the C4a-C8a-Cl-N and C4a-C4-C3-N torsional angles, as compared to less crowded 3-phenyl-1,2,3,4-tetrahydroisoquinolines. Here the heterocyclic ring adopts a distorted half-chair conformation. 相似文献
54.
Alexander V. Briceño Graciela Díaz de Delgado Belkis V. Ramírez William O. Velásquez Alí B. Bahsas 《Journal of chemical crystallography》1999,29(7):785-791
[Ba(C5H5O4)2(OH2)] is monoclinic, C2/c, with a = 4.472(1), b = 13.312(3), c = 22.236(5) Å, = 92.90(1)°, Z = 4, and D
m = 2.06 g cm–3. The barium atom is 10-coordinate with Ba—O distances in the range 2.749(2)–2.989(2) Å. The material suffers a complex decomposition process upon heating at temperatures between 25 and 600°C in dynamic nitrogen and static air atmospheres. FT-IR and gas chromatography analyses indicate that water, CO, CO2, methane, ethane, ethylene, propane, propylene, and butane, are evolved during the heating process, leaving a residue of BaCO3. 1H-NMR spectra of a sample heated at 200°C, showed isomerization of barium itaconate to barium methylmaleate. 相似文献
55.
Graciela Díaz de Delgado Pedro P. Parra Alexander Briceño José Miguel Delgado 《Journal of chemical crystallography》1995,25(5):241-244
[Sr(C4H2O4)(OH2)3]·H2O is monoclinic, P21/n, witha=11.476(2),b=7.027(1),c=12.344(2) Å, =115.74(3)°,V=896.67 Å3,Z=4. The Sr atom is surrounded by nine oxygen atoms which come from four different maleate anions and three water molecules. The Sr–O distances range from 2.546(2) to 2.808(2) Å. The C–O distances are equal within the standard deviation 1.263(3) to 1.258(3) Å). In the maleate anion, the planes that contain the carboxylate groups form an angle of 74.44(9)°. Both carboxylate groups deviate significantly from planarity. The different coordination modes of the carboxylate group and the extensive hydrogen bonding present are responsible for the polymeric nature of the structure. 相似文献
56.
Alejandra Salemo Graciela Buldain Isabel A. Perillo 《Journal of heterocyclic chemistry》2001,38(4):849-852
1H NMR spectra of a series of 1,2 and 1,3‐diarylimidazolidines are analyzed and correlated with their conformational features. Results were interpreted on the basis of chemical shifts and coupling constants of hydrogen atoms and confirmed by ID nOe difference experiments. 1,3‐Diarylimidazolidines ( 1–7 ) show a fast inversion of the N‐aryl nitrogen in all studied cases. 1,2‐Diaryl‐3‐methyl (or benzyl) imidazolidines ( 8–13 ) display a preferential conformation with a transoid orientation of N3 and C2 substituents. 相似文献
57.
Jaime Baeza Juanita Freer Graciela Palma 《Monatshefte für Chemie / Chemical Monthly》1984,115(11):1369-1371
The oxidative addition of benzenethiol to indene in the presence of ovoalbumin produces only one isomer on the surface of the protein,trans-anti-2-phenylsulfinyl-1-indanol. This reaction may be considered as a biomimetic model of detoxification of certain hydrocarbons by the liver.
Stereoselektive oxydative Anlagerung von Thiophenol an Inden in Gegenwart von Ovoalbumin (Kurze Mitteilung)
Zusammenfassung Durch die oxydative Anlagerung von Thiophenol an Inden in Gegenwart von Ovoalbumin bildet sich nur ein Isomer an der Oberfläche des Proteins, dastrans-anti-2-Phenylsulfinyl-1-Indanol. Diese Reaktion kann als ein biomimetisches Modell der Entgiftung von gewissen Kohlenwasserstoffen durch die Leber betrachtet werden.相似文献
58.
59.
Graciela Chichilnisky 《Journal of Mathematical Analysis and Applications》1977,61(2):504-520
A problem of existence and characterization of solutions of optimal growth models in many sector economies is studied. The social utility to be optimized is a generalized form of a preference depending additively on consumption at the different dates of the planning period. The optimization is restricted to a set of admissible growth paths defined by production-investment-consumption relations described by a system of differential equations. Sufficient conditions are given for existence of a solution in a Hilbert space of paths, without convexity assumptions on either the utilities or the technology, using techniques of nonlinear functional analysis. A characterization is given of the utilities which are continuous with respect to the Hilbert space norm. Under convexity assumptions a characterization is also given of optimal and efficient solutions by competitive prices. 相似文献
60.
We present here a scenario, based on a low reheating temperature T(R)<100 MeV at the end of (the last episode of) inflation, in which the coupling of sterile neutrinos to active neutrinos can be as large as experimental bounds permit (thus making this neutrino "visible" in future experiments). In previous models this coupling was forced to be very small to prevent a cosmological overabundance of sterile neutrinos. Here the abundance depends on how low the reheating temperature is. For example, the sterile neutrino required by the Liquid Scintillator Neutrino Detector result may not have any cosmological problem within our scenario. 相似文献