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21.
Chiral α,ω-diesters react under high-pressure conditions (10 kbar) with α,ω-diamines to give chiral cyclic tetraamides of C2-symmetry. The complexation properties of tetraamides towards alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) were estimated on the basis of ESI-MS spectra. 相似文献
22.
Arif Ahmet Baaran hsan ali Clemens Anklin Sansei Nishibe Otto Sticher 《Helvetica chimica acta》1988,71(6):1483-1490
A new phenlypropanoid glycoside has been isolated from the methanolic extract of the aerial parts of Stachys lavandulifolia (Lamiaceae), lavandulifolioside (1) . On the basis of chemical and spectral data the structure of the new compound 1 has been elucidated as β-(3,4-dihydroxyphenyl)ethyl O-α-L -arabinopyranosyl-(1→2)-α-L -rhamnopyranosyl-(1→3)-4-O-caffeoyl-β-D -glucopyranoside. 相似文献
23.
Two polynuclear complexes, a dimer and a tetramer, involving sulfate and hydroxo bridges and ligating ascorbate were isolated from aqueous solutions. Structural formulae are proposed on the basis of microanalytical and thermal analysis results, i.r., 13C-n.m.r., mass spectral data and magnetic measurements. 相似文献
24.
A sensitive, simple method for the determination of trace amounts of samarium by spectrophotometry is described based on the formation of the samarium-chrome azurol S (CAS) complex in micellar medium. The molar absorptivities of the complexes at pH 7.5 at 505 nm were 3.6x10(4) and 1.4x10(5) l mol(-1) cm(-1) for water media and cetylpyridinium chloride (CPC), respectively. Beer's law is obeyed from 0.05-2 mg l(-1) of samarium at 505 nm as Sm-CAS-CPC complex. Optimal conditions such as reagent amounts, and pH for the samarium determination were reported. The effects of foreign ions were also investigated. The proposed method was successfully applied to the determination of samarium contents in synthetic samples. 相似文献
25.
Inverse gas chromatography (IGC) was applied to characterize the surface of sepiolite. The adsorption thermodynamic parameters (the standard enthalpy (ΔH 0), entropy (ΔS 0) and free energy of adsorption (ΔG 0)), the dispersive component of the surface energy (γ S d ), and the acid/base character of sepiolite surface were estimated by using the retention time of different non-polar and polar probes at infinite dilution region. The specific free energy of adsorption (ΔG sp ), the specific enthalpy of adsorption (ΔH sp ), and the specific entropy of adsorption (ΔS sp ) of polar probes on sepiolite were determined. ΔH sp were correlated with the donor and modified acceptor numbers of the probes to quantify the acidic K A and the basic K D parameters of the sepiolite surface. The values obtained for the parameters K A and K D indicated an acidic character for sepiolite surface. 相似文献
26.
A vinyl bis-sulfone Michael type approach towards heteroatom vinylation was applied on nitrogen derivatives. Cyclic thionocarbamates--mainly 1,3-oxazolidine-2-thiones--were converted into their N-vinyl counterparts; the procedure proved particularly efficient in the case of carbohydrate-derived complex structures. 相似文献
27.
High-resolution 17O NMR spectra have been collected for crystalline samples of lanthanum new phase, La3Si8N11O4. In conjunction with previously published 29Si and 15N spectra obtained for this phase, and in the light of the high-quality crystal structure data reported recently, a more detailed interpretation of the NMR spectra is presented than was possible in previous studies. The non-bridging oxygens in the structure are responsible for the single sharp peak seen in the 17O spectrum at 188 ppm; the remaining oxygens, occupying bridging sites shared with nitrogen, show up only weakly on the 17O spectrum as a broad diffuse band centered around zero ppm. The peak at −57.3 ppm on the 29Si spectrum is believed to correspond to an overlap of [SiN4] and [SiON3] environments, with the −68.2 ppm peak corresponding to an [SiO2N2] environment. 相似文献
28.
Abdurrahmanoğlu S Ozkaya AR Bulut M Bekaroğlu O 《Dalton transactions (Cambridge, England : 2003)》2004,(23):4022-4029
A new sandwich-tpype dilutetium tetraphthalocyanine 4 has been synthesized by the reaction of dimeric lutetium(III) phthalocyanine 3 with two equiv. of dilithium octakishexylthiophthalocyanine in amyl alcohol. Compound 3 was prepared from 4',5',4",5"-tetraiminoisoindoline(1,4,7,10-tetrathia-12-crown-4) 1, 4,5-bis(hexylthio)-1,2-diiminoisoindoline and lutetium acetate in amyl alcohol. Compounds 3 and 4 were characterized by elemental analysis, UV/visible, IR, (1)H NMR and ESR spectroscopy. The electrochemical and electrochromic properties of 3 and 4 have been examined by cyclic voltammetry. Both 3 and 4 displayed well-defined electrochromic behavior. 相似文献
29.
Surface modification of pyrophyllite with amino silane coupling agent for the removal of 4-nitrophenol from aqueous solutions 总被引:2,自引:0,他引:2
Sayilkan H Erdemoğlu S Sener S Sayilkan F Akarsu M Erdemoğlu M 《Journal of colloid and interface science》2004,275(2):530-538
The surface of naturally hydrophobic mineral pyrophyllite was modified to hydrophilic by treatment with prehydrolyzed N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (APEO) coupling agent to prepare a novel and effective adsorbent for the removal of 4-nitrophenol (4-NP) from aqueous solutions. XRD, FTIR, and SEM analyses were used to characterize the surface modification. It was found that after the grafting procedure, heat treatment at 110 degrees C results in condensation reaction between the OH groups of the APEO molecule and the hydroxyl groups and/or oxygen atoms on the pyrophyllite surface and the adsorption of 4-NP by APEO-modified pyrophyllite involves interactions between dissociated 4-NP molecules and protonated amine groups of APEO molecules attached to the mineral surface. Adsorption equilibrium data for 4-NP adsorption on APEO-treated and untreated pyrophyllite were most satisfactorily fitted using the Freundlich adsorption isotherm and adsorption capacity was found to be 0.268 mg/g for modified pyrophyllite whereas it was only 0.105 mg/g for untreated pyrophyllite. 相似文献
30.
A fast transient fluorescence technique was used to study latex film formation induced by organic solvent vapor. Mixtures of pyrene (P)- and naphthalene (N)-labeled and/or pure naphthalene-labeled latex films were prepared separately from poly(methyl methacrylate) (PMMA) particles. Then these pure and mixed latex films were exposed to vapor of various chloroform-heptane mixtures in seven different experiments. In both films, fluorescence lifetimes from N were monitored during vapor-induced film formation. It was observed that N lifetimes decreased as the vapor exposure time is increased. A Stern-Volmer kinetic analysis was used for low quenching efficiencies to interpret the decrease in N lifetimes. A Prager-Tirrell model was employed to obtain back-and-forth frequencies, nu, of reptating PMMA chains during latex film formation induced by solvent vapor. In both pure and mixed latex films, nu values were found to be correlated with the chloroform content in the vapor mixture. It was observed that polymer interdiffusion obeyed a t1/2 law during film formation. 相似文献