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161.
Selenoacetals derived from 1,3-propanediselenol and 1,2-ethanediselenol are much less prone to be cleaved by butyllithiums than their open chain analogues. The stereochemistry of the products resulting from these reactions as well as from the cleavage of the C---Se bond under radical conditions is disclosed. 相似文献
162.
Thomas E. Renau Joseph R. Sanchez John M. Domagala 《Journal of heterocyclic chemistry》1996,33(4):1407-1411
A series of 8-bromo-4-oxo-3-quinolinecarboxylic acids was prepared via the borate ester, 8 . The key intermediate in the synthesis of the final products 10a-10d was 3-bromo-2,4,5-trifluorobenzoic acid ( 3 ), conveniently prepared in two steps from the known oxazoline, 1 . The preparation of 10a-10d is a significant improvement of the literature procedure currently available for the synthesis of these compounds. 相似文献
163.
L. Znaidi G.J.A.A. Soler Illia R. Le Guennic C. Sanchez A. Kanaev 《Journal of Sol-Gel Science and Technology》2003,26(1-3):817-821
Microcrystalline ZnO films presenting well-defined and tunable orientation were obtained by spin coating of alcoholic sols by two different approaches, based on controlled hydrolysis-condensation of Zn-ethanolamine complexes. As-deposited films are formed by amorphous zinc oxide-acetate submicronic particles, which are transformed into oriented ZnO after thermal treatment. The orientation of ZnO depends on the synthesis method, and the solvent. While in ethanol and [Zn] = 0.05 mol·L–1, films consist of rectangular platelets oriented with the (100) planes parallel to the substrate (a//n), the orientation of the particles changes to (c//n) for systems in 2-methoxyethanol (2-ME) and [Zn] = 0.75 mol·L–1. A study of chemical factors that influence the orientation (precursor, solvent, MEA/Zn ratio, concentration, coating parameters, heat treatment) is presented. 相似文献
164.
165.
L. Rosenthaler P. Krumholz J. Vasquez Sanchez F. Feigl A. S. Komarowsky N. S. Poluektoff J. V. Dubský J. Trtilek A. Oká G. Hellsing K. Heumann F. Emich Olga S. Fedorova Georges Glomaud J. Trtílek VI. Stanék T. Nemes Carl Urbach R. Baril und J. H. Yoe 《Fresenius' Journal of Analytical Chemistry》1935,102(7-8):280-289
Ohne Zusammenfassung 相似文献
166.
Monika Kuemmel Cédric Boissière Lionel Nicole Christel Laberty-Robert Clément Sanchez David Grosso 《Journal of Sol-Gel Science and Technology》2008,48(1-2):102-112
TiO2, Al2O3, and ZrO2 patterns composed of ordered nano motifs of various morphologies (i.e. perforations (craters), rings, canyons, wires, dots, or channels) with typical lateral dimensions of less than 40 nm and thickness below 15 nm are presented. Simple chemical solution deposition (CSD) of molecular inorganic precursors and commercial block copolymers was used to create patterns on several substrate surfaces (bare, hydrophobized or gold covered silicon wafers and ITO). Self-assembly during evaporation and subsequent stabilization at 500 °C leads to the various nanostructures. Compared to other techniques for surface nano patterning, the present method has the advantage of being cheap, reproducible and easy to scale up and does not require specialized equipment. The type, dimension, and organization of these motifs were assessed by AFM, FE-SEM, spectroscopic ellipsometry, and GI-SAXS and are shown to depend on the conditions of preparation. Usage as model surfaces for modelling of wetting properties and as nanoelectrode arrays were investigated. 相似文献
167.
Marcos Ghislandi Luis Antonio Sanchez de A. Prado Alejandra de la Vega Oyerviedes Hans Wittich Karl Schulte Ana Barros‐Timmons 《Journal of polymer science. Part A, Polymer chemistry》2008,46(10):3326-3335
Vapor‐grown carbon nanofibers (CNFs) were oxidized and functionalized for atom transfer radical polymerization (ATRP) of tert‐butyl acrylate (t‐BA) from the surface of the CNFs. The materials were characterized by solubility tests, Fourier‐transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and scanning electron microscopy. The FTIR and electron microscopy results suggest that ATRP process was successfully used to graft poly(tert‐butyl acrylate) (poly(t‐BA)) chains from the surface of the fibers. Raman results strongly indicate the partial degradation of the graphitic layer of CNFs because of the chemical treatments. TGA results suggest that the presence of poly(t‐BA) leads to a decrease of the initial degradation temperature of the fibers. XRD and electron microscopy results indicate that the microstructure of fibers was not destroyed because of the oxidation and functionalization processes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3326–3335, 2008 相似文献
168.
Magnetic susceptibilities play a very important part in NMR spectra, but their values are not always known; here, the authors give a method for the measurement of paramagnetic susceptibilities and suggest an explanation about linear dependence of magnetic susceptibility vs. observed shift. 相似文献
169.
C. Gonzalez Perez L. Polo Diez A. Sanchez Perez F. Lucena Conde 《Mikrochimica acta》1977,67(1-2):29-35
Summary A simple and direct method for the spectrophotometric determination of chloride, based on the formation of chromyl chloride and its extraction into carbon tetrachloride has been developed. The absorption spectrum of the organic extract shows two bands at 300 and 415 nm; Beer's law is obeyed at both wavelengths over the range 20–320g of chloride. The best conditions for the spectrophotometric determination of chloride are determined and a procedure is recommended. Interferences from some of the most common anions are studied.
Zusammenfassung Eine neue Methode für die Bestimmung von Chloridionen wurde angegeben. Sie beruht auf der Bildung von Chromylchlorid und dessen Extraktion mit Tetrachlorkohlenstoff. Der Extrakt hat spektrale Maxima bei 300 und 415 nm. Das Beersche Gesetz ist zwischen 20 und 320g Chlorid erfüllt. Die besten Bedingungen für die spektrophotometrische Bestimmung wurden ermittelt und ein Verfahren empfohlen. Störungsmöglichkeiten einiger üblicher Anionen wurden untersucht.相似文献
170.
D. Grosso F. Babonneau C. Sanchez G.J. de A.A. Soler-Illia E.L. Crepaldi P.A. Albouy H. Amenitsch A.R. Balkenende A. Brunet-Bruneau 《Journal of Sol-Gel Science and Technology》2003,26(1-3):561-565
Since mesoporous materials can be prepared by combining the sol-gel chemistry and the structuring effect of surfactants, they have attracted attention for application in various high technology fields. The present work deals with the analyses of the mechanisms involved in the formation of SiO2 and TiO2 highly organised 2D-hexagonal meso-structured films using Brij 58 as surfactant. The preparation of such films by dip-coating involves rapid evaporation which makes the different steps difficult to control. Simultaneous in-situ SAXS (synchrotron) and interferometry analyses have been performed to get a first understanding of the self-assembly process. SiO2 and TiO2 materials have a different chemical reactivity (kinetics and coordination aspects). However, we show that the mechanisms involved during dip-coating are quite similar : the self-assembly leading to the organised phase takes place at a final stage of the drying process, involves the formation of a disorganised intermediate phase and depends also on the presence of micellar interfaces in addition to film/air and film/substrate interfaces. 相似文献