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101.
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103.
Jaber Jahanbin Sardroodi Jafar Azamat Maryam Atabay 《The Journal of chemical thermodynamics》2011,43(12):1886-1892
Osmotic coefficients of the binary solutions of two room-temperature ionic liquids (1-butyl-3-methylimidazolium chloride and bromide) in methanol and ethanol have been measured at T = 298.15 K by the isopiestic method. The experimental osmotic coefficient data have been correlated using a forth-order polynomial in terms of (molality)0.5, with both, ion interaction model of Pitzer and electrolyte non-random two liquid (e-NRTL) model of Chen. The values of vapor pressures of above-mentioned solutions have been calculated from the osmotic coefficients. The model parameters fitted to the experimental osmotic coefficients have been used for prediction of the mean ionic activity coefficients of those ionic liquids in methanol and ethanol. 相似文献
104.
Rifai A Bourcier S Arquier D Charvet Y Jaber F Bouchoux G 《Journal of mass spectrometry : JMS》2011,46(10):1079-1088
Dinoterb (6-t-butyl-2,4-dinitrophenol), 1, Dinoseb (6-secbutyl-2,4-dinitrophenol), 2, TBP (2-t-butylphenol), 3, and DNP (2,4-dinitrophenol), 4, have been analyzed by electrospray ionization in the negative mode (ESI-N) - tandem mass spectrometry. Nominal laboratory collision energy was varied from zero to 60 eV during the experiments. Apparent fragmentation energies were estimated from a parametric fitting of the collision efficiency curves. In parallel, fragmentation mechanisms of the deprotonated molecules [M-H](-) were explored using quantum chemistry modeling at the B3LYP/6-31 + G(d,p) level. A major fragmentation of the [M-H](-) ions of Dinoterb and Dinoseb is elimination of an alcohol molecule. This reaction is shown to involve one oxygen atom originating from a nitro group rather than the phenoxide moiety. Eliminations of NO, C(4) and CH(2) = C(CH(3))(2), i.e. reactions involving significant rearrangements, constitute the major part of the other fragmentation pathways observed from [3-H](-) and [4-H](-) ions. 相似文献
105.
Abbas FA Al-Massarany SM Khan S Al-Howiriny TA Mossa JS Abourashed EA 《Natural product research》2007,21(5):383-391
The aerial part of Commiphora opobalsamum L. (Burseraceae) growing in Saudi Arabia was subjected to a phytopharmacological investigation in order to identify its major chemical constituents and to evaluate its extracts and isolated compounds in preliminary in vitro assays for antimicrobial, antimalarial, antitumor, anti-inflammatory (COX-2 inhibition), antioxidant and estrogenic activity. Six compounds were isolated and identified as the triterpenes friedelin, canophyllal, and oleanonic acid; the flavonols mearnsetin and quercetin; and syringic acid. The ethyl acetate extract was moderately active against Staphylococcus aureus, Pseudomonas aeruginosa, and Plasmodium falciparum; while the petroleum ether and chloroform extracts inhibited COX-2 at 5 and 10 microg mL(-1), respectively. Of the isolated compounds, syringic acid showed moderate antimalarial, anticandidal, and antimycobacterial activity; while mearnsetin and quercetin exhibited antioxidant activity comparable to ascorbic acid and trolox. This is the first detailed phytochemical investigation of C. opobalsamum L. growing in Saudi Arabia and elsewhere. The isolated compounds are reported from this plant for the first time and their full (1)H and (13)C NMR assignments are included. 相似文献
106.
Jaber F Schummer C Al Chami J Mirabel P Millet M 《Analytical and bioanalytical chemistry》2007,387(7):2527-2535
Solid-phase microextraction (SPME) coupled with gas chromatography–mass spectrometry has been used for analysis of four phenols
and sixteen nitrophenols in rainwater samples. Analytes were extracted from the water in the immersion mode and derivatised
for 5 min during direct desorption in the GC injector. Before desorption, 2 μL N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MDBSTFA) was introduced into the injector, which was maintained at 280 °C. Different conditions
affecting extraction efficiency were studied, including temperature, type of microextraction fibre, and effect of pH and ionic
strength. Five different fibre coatings were tested: 85-μm polyacrylate (PA), 100-μm polydimethylsiloxane (PDMS), 65-μm Carbowax–divinylbenzene
(CW–DVB), 75-μm Carboxen–polydimethylsiloxane (CAR–PDMS), and 65-μm polydimethylsiloxane–divinylbenzene (PDMS–DVB). The best
conditions were use of PA fibres for 40 min at ambient temperature (75 g NaCl per 100 mL, pH 3.0). MDBSTFA was used as derivatising
agent because it enables analysis of phenols derivatives with high confidence in identification, because in electron-impact
mode TBDMS–phenol derivatives produce the specific M–57 ion. Quantification was achieved by using 4-nitrophenol-d4, at 1 mg
L−1, as internal standard. Linearity was good, with correlation coefficients in the range 0.9888 (o-cresol) to 0.9987 (dinitro-o-cresol, DNOC). Detection limits varied between 0.208 and 99.3 μg L−1 and quantification limits between 0.693 and 331 μg L−1. Uncertainties varied between 8.7% (phenol) and 17.9% (4-methyl-2-nitrophenol). The method was successfully applied to the
analysis of rainwater collected at urban and rural sites in Alsace (East of France). Because of derivatisation in the injector
and the associated high temperature, the lifetime of the fibre is severely reduced. 相似文献
107.
Esmaeilpour Mohsen Javidi Jaber Mokhtari Abarghoui Mehdi Nowroozi Dodeji Fatemeh 《Journal of the Iranian Chemical Society》2014,11(2):499-510
We demonstrate herein the modification of magnetic nanoparticles and their use as a magnetic nanocatalyst in direct coupling reactions of aryl halides with terminal alkynes. Magnetite particles were prepared by simple co-precipitation method in aqueous medium, and then Fe3O4@ SiO2 nanosphere was synthesized by using nano-Fe3O4 as the core, TEOS as the silica source and PVA as the surfactant. Fe3O4@SiO2 was coated with polymeric N-heterocyclic carbene/Pd. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, thermogravimetric analysis, vibration sample magnetometer and N2 adsorption–desorption isotherm analysis. Poly (N-vinyl imidazole) functionalized Fe3O4@SiO2 nanoparticle was found to be an efficient nanocatalyst in Sonogashira–Hagihara cross-coupling reactions. The nanocatalyst can be easily recovered by a magnetic field and reused for six runs without appreciable loss of its catalytic activity. 相似文献
108.
Farah Ibrahim Houssein Nasrallah Xiang Hong Mohamed Mellah Ali HachemGhassan Ibrahim Nada Jaber Emmanuelle Schulz 《Tetrahedron》2012,68(48):9954-9961
Polycondensation reactions between various modified disalicylaldehyde derivatives and two chiral diamines afforded in each case macrocyclic structures, named calix-salen. Mixtures of oligomers (dimers to pentamers) were qualitatively analyzed by Maldi-Tof and 1H NMR DOSY experiments allowed their easy quantitative investigation. Tuning the reaction conditions and namely the concentration of both monomeric partners led interestingly to the selective preparation of the dimer or the tetramer as main products, in diluted or concentrated media, respectively. 相似文献
109.
Recent developments in the properties and applications of polyelectrolyte multilayers 总被引:1,自引:0,他引:1
Complexity and innovation in the application of layer-by-layer adsorbed polyelectrolyte systems continues to grow. In this review, we will recap recent findings on the application of multilayers at the biological interface, and as thin films for controlling wetting properties. We also review recent experiments on determining the mechanical properties of polyelectrolyte multilayers. 相似文献
110.
This paper addresses the managerial and economic impacts of improving delivery performance in a serial supply chain when delivery performance is evaluated with respect to a delivery window. Building on contemporary management theories that advocate variance reduction as the critical step in improving the overall performance of a system, we model the variance of delivery time to the final customer as a function of the investment to reduce delivery variance and the costs associated with untimely delivery (expected earliness and lateness). A logarithmic investment function is used and the model solution involves the minimization of a convex–concave total cost function. A numerical example is provided to illustrate the model and the solution procedure. The model presented provides guidelines for determining the optimal level of financial investment for reducing delivery variance. The managerial implications as well as the economic aspects of delivery variance reduction in supply chain management are discussed. 相似文献