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Katerina Liberkov Raymonde Touroude 《Journal of molecular catalysis. A, Chemical》2002,180(1-2):221-230
Selective hydrogenation of crotonaldehyde was performed on 5% Pt/SnO2 catalysts, in gaseous phase, at atmospheric pressure, at 353 K. Two types of catalyst were prepared using H2PtCl6 and Pt(NH3)4(NO3)2 as metallic precursors. Their performances were compared as a function of the reduction temperature and both catalysts were characterised by X-ray diffraction after different reduction treatments. Using the ex-chloride catalyst, the selectivity values to the unsaturated alcohol (UOL) resulted into a maximum of 45% while a selectivity as high as 70–77%, in 0–25% conversion range, was achieved by using ex-nitrate catalyst reduced at 443 K. The formation of Pt–Sn alloy on the metal particles of platinum was thought to be necessary to improve the activity and the selectivity on these catalysts. In the contrast, a presence of PtSn2 formed at a reduction temperature higher than 473 K led to a decrease of activity and selectivity. 相似文献
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5‐O‐Caffeoylshikimic acid from Solanum somalense leaves: Advantage of centrifugal partition chromatography over conventional column chromatography 下载免费PDF全文
Saïda Chideh Serge Pilard Jacques Attoumbré Robert Saguez Alshaimaa Hassan‐Abdallah Dominique Cailleu Anne Wadouachi Sylvie Baltora‐Rosset 《Journal of separation science》2014,37(17):2331-2339
Solanum somalense leaves, used in Djibouti for their medicinal properties, were extracted by MeOH. Because of the high polyphenol and flavonoid contents of the extract, respectively, determined at 80.80 ± 2.13 mg gallic acid equivalent/g dry weight and 24.4 ± 1.01 mg quercetin equivalent/g dry weight, the isolation and purification of the main polyphenols were carried out by silica gel column chromatography and centrifugal partition chromatography. Column chromatography led to 11 enriched fractions requiring further purification, while centrifugal partition chromatography allowed the easy recovery of the main compound of the extract. In a solvent system composed of CHCl3/MeOH/H2O (9.5:10:5), 21.8 mg of this compound at 97% purity was obtained leading to a yield of 2.63%. Its structure was established as 5‐O‐caffeoylshikimic acid by mass spectrometry and NMR spectroscopy. This work shows that S. somalense leaves contain very high level of 5‐O‐caffeoylshikimic acid (0.74% dry weight), making it a potential source of production of this secondary metabolite that is not commonly found in nature but could be partly responsible of the medicinal properties of S. somalense leaves. 相似文献
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Back Cover: Assessment of DNA Binding to Human Rad51 Protein by using Quartz Crystal Microbalance and Atomic Force Microscopy: Effects of ADP and BRC4‐28 Peptide Inhibitor (ChemPhysChem 17/2014) 下载免费PDF全文
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Michèle Barthekat Thérése Bouissou Raymonde Mathis Ferdinand Mathis 《Journal of Molecular Structure》1974,21(1):67-83
The infrared spectra of some derivatives of 2-pyrazoline have been studied in the region of the CN and N-H stretching bands.The N-H stretching frequency seems to be related to Taft's σ* constants of the substituents bound to the intracyclic carbon atoms. The “acidity” of this group seems to be considerably less than in pyrrole or in carboxylic amides.Absorption spectra of the pure compounds or of moderately concentrated solutions suggest the existence of intermolecular hydrogen bonding.The hybridization state of nitrogen atom (1) seems to be approximatively sp3, without any noticeable conjugation with the CN(2) double bond. In those cases where two conformers could be assumed to exist only one has been observed.These results are in accordance with those of a molecular orbital calculation by the CNDO/2 method. This calculation suggests that in 5-methyl-2-pyrazoline, the hydrogen atom bound to N(1) is trans with respect to the methyl group. 相似文献
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C. Vanga Bouanga K. Fatyeyeva P.-Y. Baillif C. Khaokong J.-F. Pilard M. Tabellout 《Macromolecular Symposia》2010,290(1):175-184
Summary: Composite polyurethane/polyaniline (PU/PANI) films have been chemically prepared by oxidative in-situ polymerization of aniline inside the previously swelled PU film. Swelling kinetic studies have shown that for PU films the swelling degree of aniline is 25 wt.%. The dielectric and electrical properties of the composite films were measured using dielectric relaxation spectroscopy and four-probe method. Dielectric measurements as a function of temperature and frequency revealed the presence of a relaxation process for the composite PU/PANI-HCl film. This relaxation was explained in terms of interfacial polarization due to the double-layered structure of the composite film. The activation energy values found by dielectric and electrical measurements are close and this result confirms the conducting character of the PANI containing layer. 相似文献
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The complex formation of gallium with benzohydroxamic acid has been studied by potentiometry and spectrophotometry. Three successive complexes, GaL2+, GaL2+, and GaL3, are formed. The stability constants, log β1, β2, and β3 , are 9.2 ± 0.1, 18.0 ± 0.1 and 25.3 ± 0.1, respectively, in 3 M NaClO4 at 25°C. 相似文献
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Lesur D Gassama A Moreau V Djedaïni-Pilard F Brique A Pilard S 《Rapid communications in mass spectrometry : RCM》2006,20(5):747-754
The development of natural cyclodextrins (CDs) for various industrial applications (agroalimentary, cosmetic or pharmaceutical) constitutes a continuous challenge. For the integration of these agricultural plant products in the creation of super-absorbent biodegradable and hypoallergenic materials (water-retaining agents, cosmetic hydrating and texturing, pharmaceutical and horticultural products) to replace synthetic polymers, we have developed chemical methods to access regioselectively C-6-derivatized maltooligosaccharides starting from CDs. These compounds are highly suitable for further chemical modifications and are expected to give access to a new class of polymeric materials with potential applications such as water-retaining agents in the disposable nappies industry. For the structural analysis of carbohydrates, electrospray ionization mass spectrometry (ESI-MS) offers precise results, analytical versatility and very high sensitivity. We report herein the rapid and convenient follow-up of chemical reactions, the purity evaluation of intermediates and final products, and the structural characterization of derivatized maltooligosaccharides, obtained by acidic cleavage (acetolysis) of halogenated and esterified CDs, using ESI-MS in combination with the high-resolution (HRMS) and tandem mass spectrometry (MS/MS) capabilities of a quadrupole orthogonal time-of-flight (Q-TOF) mass spectrometer. 相似文献