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排序方式: 共有173条查询结果,搜索用时 31 毫秒
1.
Yasmen M. Moghazy Magda F. Fathalla Nagwa M. M. Hamada Yasser R. Elmarassi Ezzat A. Hamed 《国际化学动力学杂志》2020,52(5):341-355
Reactions of aniline derivatives in dimethyl sulfoxide with phenyl 1-(2,4-dinitronaphthyl) ether yield aryl 1-(2,4-dinitronaphthyl) amine, which results in substitution of the phenoxy groups at the naphthyl ipso carbon atom. Rate constants were measured spectrophotometrically, and reaction proton transfer was rate limiting. The values of the rate coefficients indicate a rate-limiting proton transfer mechanism with significant substituent effects. The calculated activation parameters were of regular variation with substituents in 4- and 3-position in the aniline nucleophile, and the reaction proceeded through a common mechanism. Hammett's reaction constant showed that the reaction rate constants depend on the electron density of the nitrogen atom of aniline derivative, whereas the coefficient value obtained from the Brönsted relation indicated that the reaction was significantly associative and quite zwitterion like. Computational studies of the substitution were carried out based on density functional theory, and theoretical to the experimental agreement was achieved. 相似文献
2.
Ezzat Hany G. Bayoumi Ashraf H. Sherbiny Farag F. El-Morsy Ahmed M. Ghiaty Adel Alswah Mohamed Abulkhair Hamada S. 《Molecular diversity》2021,25(1):291-306
Molecular Diversity - Many shreds of evidence have recently correlated A2B receptor antagonism with anticancer activity. Hence, the search for an efficient A2B antagonist may help in the... 相似文献
3.
Eman M. Moaaz Amr M. Mahmoud Ahmed S. Fayed Mamdouh R. Rezk Ezzat M. Abdel-Moety 《Electroanalysis》2021,33(8):1895-1901
Antibiotics determination plays a major role in minimizing antimicrobial resistance starting from quality control of pharmaceutical formulations to therapeutic drug monitoring. Green modified glassy carbon electrode has been developed for determination of tedizolid phosphate; new antibiotic prodrug; in presence of its active metabolite. The graphene transducer interlayer, dispersed with PVC, improved the electrode stability and standard potential reproducibility. Graphene hydrophobicity prevented the water layer formation between the sensing layers that decreased the potential drift down to 267 μV h−1. Electrochemical impedance showed a low resistance value for graphene containing sensor due to its high electron transfer ability. 相似文献
4.
Nurul Hidayah Abdullah Kamyar Shameli Ezzat Chan Abdullah Luqman Chuah Abdullah 《中国化学快报》2017,28(7):1590-1596
A facile and green synthetic approach for fabrication of starch-stabilized magnetite nanoparticles was implemented at moderate temperature. This synthesis involved the use of iron salts, potato starch,sodium hydroxide and deionized water as iron precursors, stabilizer, reducing agent and solvent respectively. The nanoparticles(NPs) were characterized by UV-vis, PXRD, HR-TEM, FESEM, EDX, VSM and FT-IR spectroscopy. The ultrasonic assisted co-precipitation technique provides well formation of highly distributed starch/Fe_3O_4-NPs. Based on UV–vis analysis, the sample showed the characteristic of surface plasmon resonance in the presence of Fe_3O_4-NPs. The PXRD pattern depicted the characteristic of the cubic lattice structure of Fe_3O_4-NPs. HR-TEM analysis showed the good dispersion of NPs with a mean diameter and standard deviation of 10.68 4.207 nm. The d spacing measured from the lattice images were found to be around 0.30 nm and 0.52 nm attributed to the Fe3O4 and starch, respectively. FESEM analysis confirmed the formation of spherical starch/Fe_3O_4-NPs with the emission of elements of C, O and Fe by EDX analysis. The magnetic properties illustrated by VSM analysis indicated that the as synthesized sample has a saturation magnetization and coercivity of 5.30 emu/g and 22.898 G respectively.Additionally, the FTIR analysis confirmed the binding of starch with Fe_3O_4-NPs. This method was cost effective, facile and eco-friendly alternative for preparation of NPs. 相似文献
5.
Hany H. Sherief Magdy A. Ezzat 《International Journal of Solids and Structures》1996,33(30):4449-4459
The one-dimensional problem of distribution of thermal stresses and temperature is considered in a generalized thermoelastic electrically conducting half-space permeated by a primary uniform magnetic field when the bounding plane is suddenly heated to a constant temperature.The Laplace transform technique is used to solve the problem. Inverse transforms are obtained in an approximate manner using asymptotic expansions valid for small values of time.Nurnerical computations for two particular cases are carried out. 相似文献
6.
Ahmed Ezzat 《Experimental Mechanics》1961,1(7):10-15
Tanks and pipes vibrating in flexure and filled with various materials have been a problem in power plants, factories, airplanes and tankers. The present experimental investigation was carried out on a pipe vibrating in flexure and filled with various materials, both liquid and solid. The tests showed that, in general, filling a pipe in flexure with any material, liquid or solid, increases its damping characteristics. An increase in the kinematic viscosity of the filling liquid, or a decrease in the size of the particles of the filling solid, will result in a corresponding increase in the equivalent damping factor of the system. 相似文献
7.
Ezzat M. Abdel-moety 《光谱学快报》2013,46(5):669-677
A direct derivative, D1 i.e. dA/dλ, spectrophotometric procedure for simultaneous determination of diethylamine salicylate and methyl nicotinate in their binary mixtures and in ointments has been investigated. Good percent mean recoveries, 99.68 ± 0.58 & 99.71 ± 0.27 and 100.85 ± 0.21, could be obtained for diethylamine salicylate at 303 nm & 236 nm and methyl nicotinate at 224 nm, in order, added to ointment. The band overlapping in the first order due to the coexisting parabens, main additive, and the water-washable ointment base occurs sufficient away from those wavelengths chosen for the direct D1-measurement of both drug substances. 相似文献
8.
The new inorganic–organic hybrids based on SO3H‐functionalized ionic liquids (ILs) and Keggin‐type heteropoly acids (H3PW12O40, H3PMo12O40, and H4SiW12O40; HPAs) are prepared and characterized by FT‐IR, NMR, XRD, CV, SEM/EDX, ICP‐OES, BJH and UV. Different molecular structures according to the different inorganic part were also proved. Potentiometric titration showed a good relationship between catalytic activity and acidity of the catalysts. Electrochemical aspects showed electron transfer ability of the compounds. For understanding catalytic activities of the HPA‐IL hybrids in N‐formylation reaction, effect of catalyst composition, substrate, and reaction conditions were studied. The best SO3H‐functionalized ionic liquid catalyst was readily recovered and reused for four runs. Easy preparation of the catalyst, simple and easy work‐up, mild reaction conditions, low cost, excellent yields and short reaction times are the key features of this work. 相似文献
9.
Synthesis of 1‐silacyclopent‐2‐ene derivatives using 1,2‐hydroboration, 1,1‐organoboration and protodeborylation 下载免费PDF全文
The reaction of di(alkyn‐1‐yl)vinylsilanes R1(H2C═CH)Si(C≡C―R)2 (R1 = Me ( 1 ), Ph ( 2 ); R = Bu (a), Ph (b), Me2HSi (c)) at 25°C with 1 equiv. of 9‐borabicyclo[3.3.1]nonane (9‐BBN) affords 1‐silacyclopent‐2‐ene derivatives ( 3a , 3b , 3c , 4a , 4b ), bearing one Si―C≡C―R function readily available for further transformations. These compounds are formed by consecutive 1,2‐hydroboration followed by intramolecular 1,1‐carboboration. Treated with a further equivalent of 9‐BBN in benzene they are converted at relatively high temperature (80–100°C) into 1‐alkenyl‐1‐silacyclopent‐2‐ene derivatives ( 5a , 5b 6a , 6b ) as a result of 1,2‐hydroboration of the Si―C≡C―R function. Protodeborylation of the 9‐BBN‐substituted 1‐silacyclopent‐2‐ene derivatives 3 , 4 , 5 , 6 , using acetic acid in excess, proceeds smoothly to give the novel 1‐silacyclopent‐2‐ene ( 7 , 8 , 9 , 10 ). The solution‐state structural assignment of all new compounds, i.e. di(alkyn‐1‐yl)vinylsilanes and 1‐silacyclopent‐2‐ene derivatives, was carried out using multinuclear magnetic resonance techniques (1H, 13C, 11B, 29Si NMR). The gas phase structures of some examples were calculated and optimized by density functional theory methods (B3LYP/6‐311+G/(d,p) level of theory), and 29Si NMR parameters were calculated (chemical shifts δ29Si and coupling constants nJ(29Si,13C)). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
In this work we introduce a model of the boundary layer equations for a perfect conducting micropolar fluid with stretch, bounded by an infinite vertical flat plane surface of a constant temperature. This model is applied to study the effects of free convection currents on the flow of the fluid in the presence of a constant magnetic field. The state space technique is adopted for the solution of a one‐dimensional problem for any set of boundary conditions. The resulting formulation together with the Laplace transform techniques are applied to a thermal shock problem. The inversion of the Laplace transforms is carried out using a numerical approach. Numerical results are given and illustrated graphically for the problem. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献