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41.
Brahim Lakhrissi Mohamed Massoui El Mokhtar Essassi Vincent Lequart Nicolas Joly Patrick Martin Grard Goethals 《Journal of heterocyclic chemistry》2004,41(6):1011-1014
Reaction of 1,5‐benzodiazepin‐2,4‐dione with 3‐O‐substituted‐5,6‐anhydro‐1,2‐isopropylidene‐α‐D‐glucofuranose gave the unexpected N,N'‐di‐glucofuranosyl benzimidazol‐2‐one by a novel rearrangement and ring closure reaction. A mechanism is proposed. 相似文献
42.
Novel furo, thieno and pyrrolo[2,3‐b]pyrazole cyanine dyes were synthesized. The structure‐photosensitization properties correlation of the dyes were examined in 95% ethanol solution by absorption spectroscopy. The chemical structure of the starting biheterocyclic compounds and their derived cyanine dyes were confirmed by elemental analysis, IR and 1H NMR spectroscopy. 相似文献
43.
Summary The substitution of phosphine in the [RhCl(COD)(phosphine)] complex (1), where phosphine is PPh3 or 1/2 BPS-2 [bis(diphenylphosphinoethyl)tetramethyldisiloxane] and COD is cycloocta-1,5-diene, by 1-hexene is a two-step reversible reaction. All individual rate constants and equilibrium constants were determined spectrophotometrically and associative mechanism occurring via the formation of five-coordinated [RhCl(COD)(phosphine)(1-hexene)] (2) was inferred. The rate-determining step changes from the first- to the second-one as the concentration of 1-hexene increases. An excess of phosphine shifts the equilibrium towards complex (2). 相似文献
44.
Mangeney C Ferrage F Aujard I Marchi-Artzner V Jullien L Ouari O Rékaï el D Laschewsky A Vikholm I Sadowski JW 《Journal of the American Chemical Society》2002,124(20):5811-5821
Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilic polymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolved to yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations, gel permeation chromatography, or centrifugation. They do not suffer from undesirable nonspecific adsorption of proteins while allowing the diffusion of small species within the hydrogel surface coating. In addition, specific properties of the original hydrophilic polymers are retained such as a lower critical solution temperature. The latter feature could be useful to enhance optical responses of functionalized gold surfaces toward interaction with various substrates. 相似文献
45.
Menadione (vitamin K3) undergoes a reversible two-electron transfer involving the quinone structure in acidic medium. As demonstrated by using cyclic voltammetry, the reduced form is more strongly adsorbed than the oxidized one. Stripping voltammetry of an adsorbed layer has been applied to the determination of this molecule after preconcentration of the reduced compound and scanning the potential towards less negative values. Adsorption, which is highly effective when stirring is used, approaches an equilibrium process in quiescent solution, as evidenced by a loss of part of the adsorbed material when stirring is stopped. A square-wave mode has been selected owing to its high sensitivity (the current is 20 times that for the differential pulse mode), but also to its high scan-rate, which minimizes the slow desorption process occurring during the scan. A concentration range from 2 × 10−10 to 5 × 10−7 M is easily investigated, the detection limit being 1.3 × 10−10 M. The influence of several operational parameters has also been considered. 相似文献
46.
N. A. El’tekova Yu. A. El’tekov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(2):243-248
The isotherms of adsorption of benzene, anisole, benzyl alcohol, and benzaldehyde on the surface of microspherical mesoporous crosslinked cellulose were calculated from the chromatographic peaks of these compounds with consideration given to the longitudinal smearing of the analyte zone under the action of adsorption forces. The solvents were n-heptane-isopropanol mixtures containing various amounts of isopropanol (up to 2 vol %). The adsorption isotherms were described using equations of the displacement adsorption theory. The mechanism of the sorption of aromatic compounds and the physical meaning of the constants entering into the adsorption isotherm equation were discussed. 相似文献
47.
Mohamed S. A. El‐Gaby Ahmed M. Sh El‐Sharief Ahmed A. Atalla Abu‐Bakr A. A. M. El‐Adasy 《中国化学会会志》2004,51(2):327-333
The novel cyanothioformamides 2a‐d were prepared by treatment of isothiocyanatosulfonamides 1a‐d with potassium cyanide at room temperature. Cyclocondensation of compounds 2b,c with phenyl isocyanate as electrophile furnished the corresponding imidazolidines 3a,b . The reactivity of compound 3a towards some nitrogen nucleophiles was investigated. Thus, the thiosemicarbazone 4 and imidazo[4,5‐b]quinoxaline 6 were synthesized by condensation of compound 3a with thiosemicarbazide and o‐phenylenediamine, respectively. Treatment of 3a with hydrochloric acid afforded compound 7 . Our investigation was extended to include the reactivity of cyanothioformamide 2 towards o‐aminophenol, anthranilic acid, and o‐phenylenediamine and yielded the corresponding heterocycles 9 , 11 and 13 derivatives, respectively. Structures of the synthesized compounds were established by their elemental analysis and spectral data. 相似文献
48.
Namita Singh Sana Ahmed Aliyah Fakim Somayah Qutub Othman Alahmed Omar El Tall Osama Shekhah Mohamed Eddaoudi Niveen M. Khashab 《Chemical science》2020,11(41):11280
Assembling well-defined MOF superstructures remains challenging as it requires easily removable hard templates or readily available immiscible solutions for an emulsion-based soft-template approach. In this work, a single-step emulsion-free soft templating approach is reported to spontaneously prepare hollow ZIF-8 and ZIF-67 colloidosomes with no further purification. These superstructures can load different enzymes regardless of the size and charge with a high encapsulation efficiency of 99%. We envisage that this work will expand the repertoires of MOF superstructures by the judicious selection of precursors and the reaction medium.An emulsion-free approach for the preparation of hollow ZIF-8 superstructures in a single step is established based on metal sulfate hydrates in methanol. 相似文献
49.
Analysis Mathematica - 相似文献
50.
A. El Sayed S. S. Abd El Rehim H. Mansour 《Monatshefte für Chemie / Chemical Monthly》1991,122(12):1019-1027
Summary The electrochemical behaviour of pure indium in KOH solutions (1–4M) was studied at different temperatures (25–70°C) by potentiostatic techniques. Two anodic peaks corresponding to the formation of In(OH)3 and In2O3 were observed. The heights of the two peaks increased with the increase of alkali concentration. An increase of temperature increased the peak currents and shifted their corresponding potentials to more negative values. The variation of the peak currents and peak potentials with scan rate suggested that the anodic dissolution of indium was a diffusion controlled process. In cyclic voltammetry, the reverse scan consistently showed one peak which was attributed to the reduction of anodic oxidation products into indium. X-ray diffraction analysis confirmed the presence of In(OH)3 at the first anodic peak, In(OH)3 and In2O3 at the second anodic peak and In2O3 in the permanent passive region.
Zum elektrochemischen Verhalten einer Indium-Elektrode in konzentrierter Kalilauge bei verschiedenen Temperaturen
Zusammenfassung Es wurde das Verhalten von reinem Indium in 1 – 4M KOH-Lösungen bei Temperaturen zwischen 25 und 70°C mittels potentiostatischer Methoden untersucht. Zwei anodische Peaks, entsprechend der Bildung von In(OH)3 und In2O3, traten auf. Die Höhe der beiden Peaks wurde mit zunehmender Alkalikonzentration gesteigert. Eine Temperaturerhöhung verstärkte die Peakströme und verschob die entsprechenden Potentiale zu negativeren Werten. Die Abhängigkeit der Peakströme und Peakpotentiale von der Scangeschwindigkeit legte den Schluß nahe, daß die anodische Lösung von Indium in einem diffusionskontrollierten Prozeß stattfindet. Bei der cyclischen Voltammetrie zeigte der reverse Scan einheitlich einen Peak, der der Reduktion der anodischen Oxidationsprodukte zu Indium zugeschrieben wurde. Röntgendiffraktionsanalyse bestätigte die Präsenz von In(OH)3 beim ersten anodischen Peak, In(OH)3 beim zweiten Peak und In2O3 im permanent passiven Bereich.相似文献