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排序方式: 共有254条查询结果,搜索用时 46 毫秒
91.
Mohammad Kazem Rofouei Mehdi Taghdiri Mojtaba Shamsipur 《Journal of inclusion phenomena and macrocyclic chemistry》2008,62(3-4):231-237
The complexation reactions between dicyclohexano-24-crown-8 (DC24C8) and K+, Rb+, Cs+ and Tl+ ions were studied conductometrically in the different acetonitrile-nitromethane mixtures at various temperatures. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance-mole ratio data at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in order of Tl+ > K+ > Rb+ ~ Cs+. The enthalpy and entropy changes of the complexation reactions were evaluated by the temperature dependence of formation constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent mixture. 相似文献
92.
Kazem D. Safa Akbar Hassanpour Shahin Tofangdarzadeh 《Journal of organometallic chemistry》2008,693(24):3622-3626
Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional and reactive groups in a convenient one-pot operation via the Peterson protocol. Then poly(styrene) and poly(α-methylstyrene) (?&II) random homopolymers were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. The aldehyde group is introduced by direct electrophilic substitution of polymers ? and II. This formylation reaction was conducted in two different solvents: dichloromethane (CH2Cl2) and nitrobenzene (PhNO2). The results indicate that PhNO2 appeared to be a more suitable solvent for such an aldehyde functionalization of the polymers. The formylated polymers (ICHO, IICHO) were then converted to Si-H functionalized polymers (ISi-H, IISi-H) via reaction with tris(dimethylsilyl)methyllithium, (HMe2Si)3CLi. 相似文献
93.
Mardia T. El‐Sayed Kazem Mahmoud Andreas Hilgeroth Issa M. I. Fakhr 《Journal of heterocyclic chemistry》2016,53(1):188-196
In the present work, we succeeded to synthesize the novel indolo‐spirocyclic compounds ( 4 , 5 , 6 , 7 and 11 ) via electrophilic condensation reactions of indoles with carbonyl compounds including different types of ketones, for example, heteroacetyl ketones (3‐acetylindole and 3‐acetylpyridine), cyclohexanone, isatin, cyclohexane‐1,4‐dione, whereas an attempt to prepare the spirocyclic 9 failed. This new idea will open a high prospective for continuous investigations related to the synthesis of novel indolo‐spirocyclic compounds. 相似文献
94.
Vahideh Raeisdasteh Hokmabad Hassan Abbasi Kazem D. Safa 《Journal of the Iranian Chemical Society》2017,14(3):665-670
A three-component efficient procedure is described for the synthesis of novel α-acyloxycarboxamides containing bis(trimethylsilyl)ethenyl group from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde, aromatic carboxylic acids and isocyanides, via the Passerini reaction. This reaction proceeds smoothly and cleanly under mild conditions in H2O and [bmim]BF4 at room temperature and led to products in good yields. The silylated aldehyde was obtained via Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium in THF at 0 °C. 相似文献
95.
A thin polydimethylsiloxane (PDMS) layer on polyethersulfone (PES) support was synthesized and pure and mixed gas permeation of C3H8, CH4, and H2 through it was measured. At first, a macroporous PES support was prepared by using the phase inversion method and characterized. Then, a thin layer of PDMS was coated over the support. Finally, permeation behavior of the synthesized composite membrane was investigated by pure and mixed gas experiments under various operating conditions. The synthesized PDMS/PES membrane showed much better gas permeation performance than others reported in the literature. Pure gas experiments showed that increase in the transmembrane pressure increases the permeability coefficient of heavier gases, C3H8, while decreases those of lighter ones, CH4 and H2. Exactly opposite behavior was observed in mixed gas experiments due to the competitive sorption and diffusion in the plasticized polymer matrix. Temperature was realized to induce similar effects on the permeability of pure and mixed gases. As expected, in rubbery membranes such as PDMS, permeability values of more condensable gases decrease with increasing temperature, whereas those of permanent gases increase. In the case of mixed gas experiments, increase in the C3H8 concentration in feed led to increase in the permeabilities of all the components due to the C3H8‐induced swelling of the PDMS film. High C3H8/H2 and C3H8/CH4 ideal selectivities of 22.1 and 14.7, respectively, at a transmembrane pressure of 7 atm as well as reasonable C3H8 separation factor (SF) values for all mixed gas experiments (in the range of 8.1–16.8) demonstrated the ability of the synthesized PDMS/PES membrane for the separation of organic vapors from permanent gases. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
96.
Kazem?KaramiEmail author Corrado?Rizzoli Naser?Rahimi 《Transition Metal Chemistry》2011,36(8):841-846
Reaction of the dinuclear complex [Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}Cl]2 (1) with ligands (L = 4-picoline, sym-collidine) gave the six-membered palladacycles [Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}Cl(L)] (2). The complex 1 reacted with AgX (X = CF3SO3, BF4) and bidentate ligands [L–L = phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), bipy(2,2′-bipyridine) and dppp
(bis(diphenylphosphino)propane)] giving the mononuclear orthopalladated complexes [Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}(L–L)] (3) [L–L = phen, dppe, bipy and dppp]. These compounds were characterized by physico-chemical methods, and the structure of
[Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}Cl(L)] (L = sym-collidine) was determined by single-crystal X-ray analysis. 相似文献
97.
In this article, a general formulation for the fractional-order Legendre functions (FLFs) is constructed to obtain the solution of the fractional-order differential equations. Fractional calculus has been used to model physical and engineering processes that are found to be best described by fractional differential equations. Therefore, an efficient and reliable technique for the solution of them is too important. For the concept of fractional derivative we will adopt Caputo’s definition by using Riemann–Liouville fractional integral operator. Our main aim is to generalize the new orthogonal functions based on Legendre polynomials to the fractional calculus. Also a general formulation for FLFs fractional derivatives and product operational matrices is driven. These matrices together with the Tau method are then utilized to reduce the solution of this problem to the solution of a system of algebraic equations. The method is applied to solve linear and nonlinear fractional differential equations. Illustrative examples are included to demonstrate the validity and applicability of the presented technique. 相似文献
98.
Kazem Shiroodi R Dudnik AS Gevorgyan V 《Journal of the American Chemical Society》2012,134(16):6928-6931
A double migratory cascade reaction of α-halogen-substituted propargylic phosphates to produce highly functionalized 1,3-dienes has been developed. This transformation features 1,3-phosphatyloxy group migration followed by 1,3-shifts of bromine and chlorine as well as the unprecedented 1,3-migration of iodine. The reaction is stereodivergent: (Z)-1,3-dienes are formed in the presence of a copper catalyst, whereas gold-catalyzed reactions exhibit inverted stereoselectivity, producing the corresponding E products. 相似文献
99.
Parisa Nekooi Rezgar Ahmadi Mohammad Kazem Amini 《Journal of the Iranian Chemical Society》2012,9(5):715-722
Highly methanol-tolerant CoSe nanoparticles supported on different carbon substrates were synthesized by microwave heating of glycerol solutions of cobalt(II) acetate and sodium selenite at different Se/Co mole ratios in the presence of different concentrations of acetic acid and ammonia. The resulting CoSe catalysts were used for the electrochemical oxygen reduction reaction (ORR) in acidic solution in the presence of methanol. The ORR activity of the catalyst was increased by increasing its Se content up to 50?mol%. The presence of acetic acid or ammonia in the synthesis solution significantly affects the electrocatalytic performance of the CoSe catalyst; highest activity was observed when the catalyst was synthesized at NH3/Co(II) mole ratio of 6. Among the catalysts prepared on different supports including carbon black (Vulcan XC-72R), and nanoporous carbons synthesized from resorcinol-formaldehyde and phloroglucinol-formaldehyde resins, the one supported on the carbon prepared from the last resin exhibited highest electrocatalytic activity for ORR. 相似文献
100.
In this paper, the nonlinear response in BK7 glass sample is investigated under irradiation of 200 fs laser pulses at 800 nm
wavelength by using of transmission measurement method. Nonlinear transmission is observed for incident pulse energies above
37μJ. A theoretical model based on simultaneously absorption of one, two and three-photon absorption is presented. The contribution
of free-carriers absorption is also included on the model. The differential equation is solved analytically. The experimental
results and predictions of theoretical model are in good agreement. The values of three-photon absorption coefficient and
free-carriers absorption cross-section are reported. 相似文献