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101.
Abdelfetah Mounir Mohamed El Guendouzi Abderrahim Dinane 《Journal of solution chemistry》2002,31(10):793-799
Ternary aqueous solutions of MgSO4 and K2SO4 have been studied by the hygrometric method at 25°C. The relative humidity of this system is measured at total molalities from 0.35 mol-kg–1 to about saturation for three ionic-strength fractions (y = 0.25, 0.50, and 0.80 of MgSO4. The data allow calculation of water activities and osmotic coefficients. From these measurements, the Pitzer ionic mixing parameters are determined and used to predict the solute activity coefficients in the mixture. The results are used to calculate the excess Gibbs energy at total molalities for ionic-strength fraction y. 相似文献
102.
Houda Marouani Mohamed Rzaigui Muriel Bagieu‐Beucher 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):356-357
In hexakis(m‐toluidinium) cyclohexaphosphate, 6C7H10N+·P6O186?, the atomic arrangement is typical of a layer structure. Layers including the centrosymmetric P6O18 ring anions develop around the (100) planes at x = . The hydrogen‐bond distribution is described. 相似文献
103.
Lamia T. Abou El-Kassem Usama W. Hawas Mohamed S. Abdelfattah Ayat A. Mostafa 《Natural product research》2020,34(5):613-620
AbstractA new rotenoid named 12-O-methylrotenolol along with five known rotenoid and isoflavone metabolites were isolated from the seeds of Dalbergia lanceolaria subsp. paniculata, collected from Egypt. The structures of these compounds were identified by physical and spectroscopic data measurements ([α]D, UV, 1D- and 2D-NMR and MS). The methanol extract of the seeds exhibited strong antioxidant activity with IC50 value 0.7?µg/µl against DPPH radical, in respect to quercetin as antioxidant reference (IC50 1.5?μM), while the tested compounds from this extract showed weak activities with IC50 values ranged from 19.6 to 33.0?µM. 相似文献
104.
Gibbs ensemble Monte Carlo simulations were used to calculate the vapor-liquid and vapor-solid coexistence curves for benzene using two simple united-atom models. An extension of the Gibbs ensemble method that makes use of an elongated box containing a slab of the condensed phase with a vapor phase along one axis was employed for the simulations of the vapor-solid equilibria and the vapor-liquid equilibria at very low reduced temperatures. Configurational-bias and aggregation-volume-bias Monte Carlo techniques were applied to improve the sampling of particle transfers between the two simulation boxes and between the vapor and condensed-phase regions of the elongated box. An isotropic united-atom representation with six Lennard-Jones sites at the positions of the carbon atoms was used for both force fields, but one model contained three additional out-of-plane partial charge sites to explicitly represent benzene's quadrupolar interactions. Both models were fitted to reproduce the critical temperature and density of benzene and yield a fair representation of the vapor-liquid coexistence curve. In contrast, differences between the models are very large for the vapor-solid coexistence curve. In particular, the lack of explicit quadrupolar interactions for the 6-site model greatly reduces the energetic differences between liquid and solid phases, and this model yields a triple point temperature that is about a factor of 2 too low. In contrast, the 9-site model predicts a triple point of benzene at T = 253 +/- 6 K and p = 2.3 +/- 0.8 kPa in satisfactory agreement with the experimental data (T = 278.7 K and p = 4.785 kPa). 相似文献
105.
The syntheses and the X-ray structures of the tetranuclear gold(I) benzamidinate, Au4[PhNC(Ph)NPh]4, and the tetranuclear gold(I) acetamidinate, Au4[PhNC(CH3)NPh]4, clusters are reported. The clusters are produced by the reaction of the sodium salt of an amidine ligand with the gold precursor
Au(THT)Cl in a (1:1) stoichiometry. The average Au...Au distance between adjacent Au(I) atoms is ∼2.9 ?, typical of compounds
having an aurophilic interaction. The four gold atoms are arranged in a square (Au...Au...Au... = 88–91°) in the acetamidinate
and in a distorted square (Au...Au...Au... = 82–97°) in the benzamidinate derivative. Electrochemical oxidation of the tetranuclear
complex Au4[PhNC(Ph)NPh]4 show three reversible waves at 0.87, 1.19, 1.42 V vs. Ag/AgCl at a scan rate of 100 mV/s in CH2Cl2 similar to the three reversible waves seen before from the tetranuclear complexes Au4[ArNC(H)NAr]4, Ar = C6H4-4-OMe, Ar = C6H4-4-Me, and Ar = C6H3-3,5-Cl. A summary of the chemistry of the tetranuclear Au(I) amidinate complexes Au4[ArNC(H)NAr]4, Ar = C6H4-4-OMe, C6H3-3,5-Cl, C6H4-4-Me, C6H4-3-CF3, C6F5, C10H7 also is presented. The tetranuclear clusters Au4[ArNC(H)NAr]4, Ar = C6H4-4-OMe, Ar = C6H4-3-CF3, Ar = C6H4-4-Me and Ar = C6H4-3,5-Cl are the first tetranuclear gold(I) cluster species from group 11 elements to show fluorescence at room temperature.
The lifetimes of the naphthyl and trifluoromethylphenyl complexes are in the millisecond range indicating phosphorescent processes.
Recently it has been shown that Au4[ArNC(H)NAr]4 are very effective catalysts upon calcination for room temperature CO oxidation.
Congratulations to Dieter Fenske, a superb synthetic chemist with exceptional talents in cluster chemistry, on the occasion
of his 65th birthday. 相似文献
106.
Mohamed Hilmy Elnagdi Mohamed Riffaat Hamza Elmoghayer Hassan Attia Elfaham Mohamed Mohamed Sallam Hikmat Hussein Alnima 《Journal of heterocyclic chemistry》1980,17(2):209-212
The 4-bromo-3-phenylpyrazol-5-ylhydrazonyl chlorides (Ia,b) and 1,2,4-triazol-5-ylhydrazonyl chlorides (IIa,b) were prepared via coupling of diazotized 4-bromo-3-phenyl-5-aminopyrazole (III) and 5-amino-1,2,4-triazole (IV) with α-chloro derivatives of acetylacetone and of ethyl aceto-acetate. Compounds Ia and IIa,b were utilised for the synthesis of several new heterocyclic derivatives. 相似文献
107.
Mohamed Ariff Md. Jainuddin V. Gopalan K. Venkata Rao 《Journal of polymer science. Part A, Polymer chemistry》1985,23(7):2063-2071
The polymerization of acrylonitrile initiated by an ascorbic acid–peroxodisulfate redox system was studied in an aqueous solution at 35°C in the presence of air. Molecular oxygen was found to have no effect on the polymerization reaction. An increase in ionic strength slightly increased the rate. The overall rate of polymerization, Rp, showed a square dependence on [monomer] and a half-order dependence on [peroxodisulfate]. A first-order dependence on [ascorbic acid] at low concentrations (<3.0 × 10?3 mol L?1) followed by a decrease in Rp at higher concentrations of ascorbic acid (>3.0 × 10?3 mol L?1) was also noted. Rp remained unchanged up to 40°C and showed a decline thereafter. Addition of catalytic amounts of cupric ions decreased the rate whereas ferric ions were found to increase the rate. Added sulfuric acid in the range (6.0?50.0) × 10?5 mol L?1 decreased the Rp. 相似文献
108.
Mohammed A. Suliman Mohammed A. Gondal Mohamed A. Dastageer Gaik‐Khuan Chuah Chanbasha Basheer 《Photochemistry and photobiology》2019,95(6):1485-1494
An efficient method of photocatalytic degradation of methylparaben in water using Ag nanoparticles (NPs) loaded AgBr‐mesoporous‐WO3 composite photocatalyst (Ag/AgBr@m‐WO3), under visible light is presented. In this process, quantification of methylparaben in water was carried out by high‐performance liquid chromatography (HPLC) and the HPLC results showed a significant reduction of methylparaben in water due to the enhanced of photocatalytic degradation efficiency of Ag/AgBr@m‐WO3. For the material synthesis, highly ordered mesoporous‐WO3 (m‐WO3) was initially synthesized by sol–gel method and AgBr nanoparticles (NPs) were subsequently introduced in the pores of m‐WO3, and finally, the Ag nanoparticles were introduced by light irradiation. The enhanced photocatalytic degradation of methylparaben in water is attributed to the formation of surface plasmonic resonance (SPR) due to the introduction of Ag NPs on the surface of the catalyst. Also, the formation of heterojunction between AgBr and mesoporous‐WO3 in Ag/AgBr@m‐WO3 significantly inhibited the recombination of light‐induced electron‐hole pairs in the semiconductor composite. The morphological and optical characterizations of the synthesized photocatalysts (Ag/AgBr@m‐WO3) were carried out using SEM, TEM, XDR, N2 adsorption–desorption, UV‐VIS diffuse reflectance spectroscopy (DRS). Also, the photocatalytic studies using radical scavengers were carried out and the results indicated that is the main reactive species. 相似文献
109.
Adahchour M Wiewel J Verdel R Vreuls RJ Brinkman UA 《Journal of chromatography. A》2005,1086(1-2):99-106
The practicability and potential of comprehensive two-dimensional gas chromatography (GC x GC) coupled to both conventional flame ionisation (FID) and time-of-flight mass spectrometric (TOF-MS) detection, were compared with those of conventional one-dimensional (1D) GC, with the determination of flavour compounds in butter as an application. For polar flavour compounds, which were collected from the aqueous fraction of butter by means of solid-phase extraction (SPE), it was found that GC x GC dramatically improves the overall separation. Consequently, quantification and preliminary identification based on the use of ordered structures, can be performed more reliably. The improvement effected by replacing 1D-GC by GC x GC is considerable also in the case of TOF-MS detection, as illustrated by the high match factors generally obtained during identification. GC x GC was also used successfully for the characterisation of volatile flavour compounds in the headspace of butter collected by solid-phase microextraction (SPME) and to study the effect of heat treatment on the composition of butter samples in more detail. 相似文献
110.
Sabry K. Mohamed 《Analytica chimica acta》2006,562(2):204-209
A poly(vinyl chloride)-based membrane of 2,9-dimethyl-4,11-diphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene (DDTCT) with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dibutyl butylphosphonate (DBBP), tris(2-ethylhexyl) phosphate (TEP) and tributyl phosphate (TBP) as plasticizing solvent mediators was prepared and investigated as a Ga(III)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-DBP-STB composition 1:4:1:1, which worked well over a wide concentration range (1.45 × 10−6 to 0.1 mol L−1) with a Nernstian slope of 28.7 mV per decade of activity between pH 4.0 and 10.0. This electrode showed a fast response time of 12 s and was used over a period of 100 days with good reproducibility (s = 0.3 mV). The selectivity coefficients for monovalent, divalent and trivalent cations indicate excellent selectivity for Ga(III) ions over a large number of cations. Anions such as Cl− and SO42− do not interfere and the electrode also works satisfactorily in partially water-alcohol medium. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents, i.e., cetyltrimethylammonium bromide and sodium dodecyl sulfate and used for the determination of gallium in nickel alloy, fly-ash and biological samples. 相似文献