排序方式: 共有115条查询结果,搜索用时 15 毫秒
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Ziba Tavakoli Mojtaba Bagherneghad Khodabakhsh Niknam 《Journal of heterocyclic chemistry》2012,49(3):634-639
Sulfuric acid ([3‐(3‐silicapropyl)sulfanyl]propyl]ester (SASPSPE) is used as a recyclable catalyst for the synthesis of 1,2,4,5‐tetrasubstituted imidazoles. A range of various polysubstituted imidazoles was synthesized via four‐component condensation of benzil, aldehydes, amines, and ammonium acetate in the presence of SASPSPE under solvent‐free conditions at 140°C. The heterogeneous catalyst was recycled for five runs on the reaction of benzil, 4‐methylbenzaldehyde, benzyl amine, and ammonium acetate without losing its catalytic activity. 相似文献
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Mohammad Javad Jafari Mohsen Niknam Sharak Ali Khavanin Touraj Ebadzadeh Mahmood Fazlali Rohollah Fallah Madvari 《声与振动》2021,55(2):117-130
Fabricating of metal foams with desired morphological parameters including pore size, porosity and pore opening is possible now using sintering technology. Thus, if it is possible to determine the morphology of metal foam to absorb sound at a given frequency, and then fabricate it through sintering, it is expected to have optimized metal foams for the best sound absorption. Theoretical sound absorption models such as Lu model describe the relationship between morphological parameters and the sound absorption coefficient. In this study, the Lu model was used to optimize the morphological parameters of Aluminum metal foam for the best sound absorption coefficient. For this purpose, the Lu model was numerically solved using written codes in MATLAB software. After validating the proposed codes with benchmark data, the genetic algorithm (GA) was applied to optimize the affecting morphological parameters on the sound absorption coefficient. The optimization was carried out for the thicknesses of 5 mm to 40 mm at the sound frequency range of 250 Hz–8000 Hz. The optimized parameters ranged from 50% to 95% for porosity, 0.1 mm to 4.5 mm for pore size, and 0.07 mm to 0.6 mm for pore opening size. The result of this study was applied to fabricate the desired Aluminum metal foams for the best sound absorption. The novel approach applied in this study, is expected to be successfully applied in for best sound absorption in desired frequencies. 相似文献
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Khodabakhsh Niknam Abdollah DerisFatemeh Naeimi Fatemeh Majleci 《Tetrahedron letters》2011,52(36):4642-4645
A simple and efficient procedure for the preparation of silica-bonded propylpiperazine-N-sulfamic acid (SBPPSA) by the reaction of 3-piperazine-N-propylsilica (3-PNPS) and chlorosulfonic acid in chloroform is described. Silica-bonded propylpiperazine-N-sulfamic acid is employed as a recyclable catalyst for the synthesis of highly substituted imidazoles from the reaction of benzil, aromatic aldehydes, ammonium acetate and amines under solvent-free conditions. The heterogeneous catalyst was recycled for five runs upon the reaction of benzil, 4-methylbenzaldehyde, benzylamine, and ammonium acetate without losing its catalytic activity. 相似文献
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A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid(SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine(SBPTET) with chlorosulfonic acid in chloroform is described.Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative,an aromatic aldehyde,malononitrile,and ammonium acetate under solvent-free conditions at 100 °C.The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone,4-chloroenzaldehyde,malononitrile,and ammonium acetate without significant loses to its catalytic activity. 相似文献
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Loghavi Mohammad Mohsen Zarei-Jelyani Mohammad Babaiee Mohsen Niknam Zeinab Eqra Rahim 《Journal of Solid State Electrochemistry》2023,27(8):2237-2250
Journal of Solid State Electrochemistry - Electrocatalysts have a key role in the reactions of vanadium redox flow batteries (VRFB). A practical immersion-drying method is used to decorate graphene... 相似文献
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Mohammad Ali Zolfigol Gholamabbas Chehardoli Mina Dehghanian Khodabakhsh Niknam Farhad Shirini Ahmad Khoramabadi‐Zad 《中国化学会会志》2008,55(4):885-889
A mixture of ethyl formate and a catalytic amount of silica sulfuric acid or Al(HSO4)3 as suitable formylating systems can formylate various alcohols to their corresponding formate ester derivatives under mild, nearly neutral and heterogeneous conditions at room temperature with good to excellent yields. 相似文献
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Morteza Karimzadeh Neda Manouchehri Dariush Saberi Khodabakhsh Niknam 《Structural chemistry》2018,29(2):383-391
All available conformers of tisopurine as an important pharmaceutical molecule are optimized and frequency calculations calculated at M06-2X/6-311++G(2d,2p) level of theory. These conformers are classified in 22 different tautomers, tautomer Z showing the most stable tautomer in the gas phase. Effects of four different solvents on the most stable conformer of each tautomer is calculated. Solvents cause stabilization of all conformers and relative solvent stabilization is as follows: water > DMSO > acetone > toluene. Energy profile for such stabilization is illustrated and mechanism of proton transfer studied at the same level of theory. Solvent-assisted proton transfer performed when water and methanol used as solvents. Results indicate that explicit solvent effect has much more stabilization on tautomerization processes compared to implicit solvent effect. 相似文献
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M Shamsipur T Poursaberi S Rouhani K Niknam H Sharghi M R Ganjali 《Analytical sciences》2001,17(9):1049-1054
A PVC-membrane electrode based on a recently synthesized 18-membered macrocyclic diamide is presented. The electrode reveals a Nernstian potentiometric response for Co2+ over a wide concentration range (2.0 x 10(-6)-1.0 x 10(-2) M). The electrode has a response time of about 10 s and can be used for at least 2 months without any divergence. The proposed sensor revealed very good selectivities for Co2+ over a wide variety of other metal ions, and could be used over a wide pH range (3.0-8.0). The detection limit of the sensor is 6.0 x 10(-7) M. It was successfully applied to the direct determination and potentiometric titration of cobalt ion. 相似文献
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A sensitive and simple method for the simultaneous preconcentration of trace transition and heavy metal ions is reported. The method is based on the adsorption of Cu, Fe, Pb and Zn on N,N′‐Diacetyl‐4‐bromo‐2,6‐di(aminomethyl)anisole (DABDAMA) loaded on sodium dodecyl sulfate (SDS) coated alumina. The metal content on the complexes are eluted using 6 mL of 2 mol l−1 nitric acid. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95% with a low RSD. The method has been successfully applied for these metals content evaluation in samples including soil, blood and vegetable samples. 相似文献