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61.
Nabila Guechtouli Abdou Boucekkine Jean-François Halet Samia Kahlal Hacène Meghezzi Jean-Yves Saillard 《Journal of Cluster Science》2012,23(3):913-928
Four different skeletal structural arrangements with very different connectivities are known for 6-vertex/68-electron of M4E2 core (M = transition metal; E = main-group atom or ligand). DFT calculations on a large number of title model compounds allow to rationalize the preferences between these structural shapes with respect to the nature of the metal and main-group elements constituting the cluster cage. In particular, the electronegativity of M and the “size” (first-row vs. second-row element) of E play an important role in the stability preference of a particular isomer. For several compounds, although only one type of structure is known, other low-energy isomeric forms are also likely to exist. Moreover, two structural types, so far unreported, are predicted to be stable enough for being synthesized. 相似文献
62.
Mohamed Ali Mahjoub Samia Ammar Kaouther Majouli Zine Mighri 《Chemistry of Natural Compounds》2012,47(6):955-958
Two new alkaloid derivatives of the 3-benzazocine skeleton (cotuzine A and B) and a new polyphenolic substance (3-(1,3-dihydroxyprop-2-yl)-4-hydroxyanisol)
(corimen) have been isolated from the aerial part (stems, leaves) of the plant Cotula coronopifolia (L.). These three new
structures were established by spectroscopic procedures (1H, 13C, one- and two-dimensional NMR). The stereochemistry of the new alkaloids was established based on different NOE effects
revealed on the NOESY spectrum. Mass spectrometry and IR spectroscopy were used to confirm these structures. 相似文献
63.
The oxidation of methyl ester of pectic acid (pectin) (PEC) by a hexacyanoferrate(III) ion at a constant ionic strength of 0.1 mol dm−3 has been investigated spectrophotometrically. The oxidation rates were found to increase with increasing the alkali concentration, indicating that the nature of reaction was base catalyzed. The agreement of [pectin] dependence of the rate constants to the Michaelis-Menten kinetics proves the formation of 1:1 intermediate complex prior to the rate-determining step. The deviation of the pseudo–first-order curves from linearity after 65-70% of reaction completion indicates the interference of some oxidation products during the reaction progression. The oxidation process was proceeding via a free-radical intervention mechanism. The activation parameters have been evaluated, and a suitable reaction mechanism is suggested and discussed. 相似文献
64.
Samia M. Rida Farid S. G. Soliman El-Sayed A. M. Badawey E. El-Ghazzawi O. Kader Thomas Kappe 《Journal of heterocyclic chemistry》1988,25(4):1087-1093
The synthesis of some substituted 3-hydroxy-1-oxo-1H,5H-pyrido[1,2-a]benzimidazole-4-carbonitriles and 4-ethyl carboxylates 3 and their 0- and N-dialkyl derivatives 5,6 is described. 3-Ethoxy-5-ethyl-2-phenyl-1H,5H-pyrido[1,2-a]benzimidazol-1-one 7 was obtained during the course of ethylating the parent ester 3t with triethyl phosphate. Chlorination of 3 with phosphorus oxychloride afforded the corresponding 1,3-dichloropyrido[1,2-a]benzimidazoles 8 which were converted to a variety of azido, amino, morpholino and methoxy derivatives of the system. The synthesis of the indolopyridobenzimidazole 15 is also described. Two compounds exhibited in vitro antibacterial activity. Many compounds were screened for antileukemic, antimicrobial, herbicidal and plant antifungal potencies but were inactive. 相似文献
65.
Manal F. Abou Taleb Samia E. Abdel-Aal Nabil A. El-Kelesh El-Sayed A. Hegazy 《European Polymer Journal》2007,43(2):468-477
Adsorption and controlled release of Chlortetracycline HCl to and from multifunctional polymeric materials (HEMA/MAA) hydrogels were investigated. P(HEMA/MAA) hydrogels were synthesized by gamma radiation-induced copolymerization of 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA) in aqueous solution. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion into the glassy polymer were discussed. Drug, Chlortetracycline HCl containing hydrogels, with different drug concentration to polymer ratios, was loaded by direct adsorption method. The influence of MAA content in the gel on the adsorption capacities of hydrogel was studied. Chlortetracycline HCl adsorption capacity of hydrogels was found to increase from 8 to 138 mg Chlortetracycline HCl per gram dry gel with increasing amount of MAA in the gel system and drug concentration. The effect of pH on the releasing behavior of Chlortetracycline HCl from gel matrix was investigated. In vitro drug release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and MAA content of hydrogel. 相似文献
66.
Samia M. Rida Farid S. G. Soliman El-Sayed A. M. Badawey Thomas Kappe 《Journal of heterocyclic chemistry》1988,25(6):1725-1728
The synthesis of some 3-substituted and 2,3-disubstituted-1-oxo-1H,5H-pyrido[1,2-a]benzimidazole-4-carbo-nitriles 5,6 by fusing 1H-benzimidazole-2-acetonitrile 1 with some β-keto esters 2,4 in the presence of ammonium acetate or with ethyl β-aminocrotonate 3 is described. The tricyclic compounds were converted to their N-5 methyl of N-5 ethyl derivatives 8,9. Vilsmeir-Haack formylation of 3-methyl-1-oxo-1H,5H-pyrido[1,2-a]-benzimidazole-4-carbonitrile 5a afforded its 2-formyl derivative 10. Chlorination of 5 and 6 with phosphorus oxychloride yielded the respective 1-chloropyrido[1,2-a]benzimidazole-4-carbonitriles 11,12 which were utilized to prepare the 1-azido, 1-amino, 1-piperidino and 1-methoxy derivatives of the ring system. Compound 11a exhibited strong in vitro activity against S. aureus. Four compounds were screened against P-388 lymphocytic leukemia in mice but were inactive. 相似文献
67.
Maurice Medebielle Samia Ait-Mohand William R. Dolbier Jr. Anne-Marie Aubertin 《Journal of fluorine chemistry》2005,126(4):533-540
In an effort to prepare new fluorine-containing compounds, which are active against HIV, several chemical modifications of a series of benzoxazole and 1,2,4-oxadiazole-CF2CHOHAr derivatives were carried out. The products (9-30) which all have one or two CF2 groups were tested for activity against HIV-1; they were devoid of significant activity, one of them being cytotoxic. 相似文献
68.
69.
This work illustrates the modification of polypropylene (PP) films through its grafting with glycidylmethacrelate monomer (GMA). Further chemical treatment of PP-g-GMA to convert epoxy groups into amine groups is discussed. Different factors affecting the grafting percent such as solvents, monomer concentrations, irradiation dose have been studied. Fourier transform infrared (FTIR) and thermogravimetric (TGA) analysis confirm the grafting of PP. Morphological changes of PP, PP-g-GMA and treated PP-g-GMA are confirmed by scanning electron microscopy (SEM). The X-ray diffraction (XRD) pattern shows changes in the crystallinity on grafting. Adsorption and kinetic studies of mercury onto the prepared PP grafted and chemically treated films in sorption of Hg+ 2 metal ions from aqueous solutions have been studied. The experimental data fit favorably to the Langmuir isotherm with a high correlation coefficient. Moreover, the pseudo first and second order kinetics is also indicated. The results suggest that the pseudo-second-order kinetic model better represent the adsorption kinetics, suggesting that the adsorption process may be chemisorptions. It is more likely to predict that the adsorption behavior may involve valence forces through the sharing of electrons between Hg2 + and adsorbent. On the basis of these investigations, the applicability of the prepared membranes is discussed. Also the confirmation of metal ions adsorbed was confirmed using EDS spectrometric techniques. 相似文献
70.