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MCM‐41‐SO3H, an ordered mesoporous silica material in which MCM‐41 with covalently anchored sulfonic acid groups was used as an acidic catalyst for the rapid and ‘green’ synthesis of pyrano[3,2‐c]pyridine derivatives under solvent‐free conditions. Reusability of the catalyst, high yields, short reaction times, simplicity and easy workup are advantages of this novel synthetic procedure compared to the conventional methods reported in the literature. 相似文献
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Hossein Hazrati Mohammad Rostamizadeh Mohammad R. Omidkhah Zahra Sadeghian 《Comptes Rendus Chimie》2018,21(1):19-26
The present study deals with the synthesis of nanostructured silicalite-1 membranes on porous α-Al2O3 supports by a hydrothermal method. Different parameters including the synthesis conditions (temperature and alkalinity) and operating conditions (temperature and pressure) were investigated. The membranes were characterized by X-ray diffraction and scanning electron microscopy techniques. The optimum synthesis temperature and alkalinity were determined to be 160 °C and pH = 11, respectively. The permeability of CO2 and CH4 through the optimized membrane was determined by the pressure drop method. The results revealed that the main effective separation mechanism was adsorption. The permeation of CO2 and CH4 declined with increasing temperature, whereas high feed pressures enhanced the single gas flux. The CO2 and CH4 permeability values at 30 °C and 2 bar were 1.62 × 10?7 and 2.07 × 10?7 mol m?2 s?1 Pa?1, respectively. Furthermore, the response surface methodology analysis confirmed the significance of all the variables and the proposed model. Excellent correlation between the experimental and predicted data (R2 = 0.99) was obtained, confirming that response surface methodology is a powerful tool for modeling nanostructured silicalite-1 membrane processes. 相似文献
23.
Symmetrical 1,3-disubstituted ureas and cyclic ureas have been synthesized from corresponding isocyanates and diisocyanates by a new versatile, simple and quick method in the presence of tertiary amines at room temperature. The method under investigation has several advantages over the existing techniques, as it is simple to carry out; does not require complicated equipment; work-up is simple, as it does not use expensive chemicals. Moreover, the yields are almost quantitative. It has a potential for commercial applications in pharmaceutical chemistry. 相似文献
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Mohammad Sarwar Shahnaz Parveen Hamdani Iftikhar Ahmad R. J. Thibert 《Mikrochimica acta》1971,59(4):573-576
Summary A rapid, convenient and accurate method for the determination of xanthates has been developed. N-bromosuccinimide has been used to displace iodine from potassium iodide which in turn oxidizes xanthate to dixanthogen. The pH 4 is optimum for the determination. The maximum relative standard deviation is 6% in the case of ethyl potassium xanthate when a 0.5 mg sample was taken.
Zusammenfassung Ein genaues Verfahren zur raschen Bestimmung von Xanthat wurde entwickelt. N-Bromsuccinimid dient zur Freisetzung von Jod aus KJ; Jod oxydiert Xanthat zu Dixanthogen. Das optimale pH für die Bestimmung ist 4. Die größte relative Standardabweichung ist 6% bei einer Einwaage von 0,5 mg Kaliumäthylxanthat.相似文献
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Shahnaz Kouser Muhammad Nouman Sarwar Qureshi Khalid Hussain Shah Hassan Amir Shah 《等离子体物理论文集》2020,60(10):e202000058
In this paper, we have studied the propagation of non-linear ion-acoustic waves in a plasma comprising of (r, q) -distributed electrons and kappa-distributed positrons. We have investigated the effect of complete electron distribution profile on the propagation of small, as well as arbitrary, amplitude solitons (via pseudopotential technique) by using generalized (r, q) distribution, which exhibits a spiky and flat top nature at low energies and a super-thermal tail at high energies. Interestingly, for negative values of r , solitons are formed with both polarities, positive (compressive) and negative (rarefactive), separately within a small amplitude limit and exist simultaneously in an arbitrary amplitude limit. We also found that the propagation of solitons has been affected by the change in parameters r , q , positron concentration, and electron to positron temperature ratio. The results presented in this study add to the fundamental understanding of the complete profile of the electron distribution function, high- and low-energy parts, and in the formation of compressive and rarefactive small and finite amplitude solitons in both space and astrophysical plasmas. 相似文献
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A series of new symmetrical tetrazole-based carbazole derivatives starting from the initially generated 3,6-diformyl-N-alkylcarbazoles were successfully synthesized through a one-pot Ugi-azide reaction in moderate to high yields. Simplicity, easily accessible chemicals, mild reaction conditions, and fast separation of the products with the formation of bistetrazole-based carbazole derivatives in one step are some advantages of this method. The structure of the products was characterized and confirmed by using spectroscopic techniques such as 1H NMR, 13C NMR, FT-IR, and MS spectroscopy. 相似文献
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Shahnaz Rostamizadeh Hamid Estiri Mohammad Azad 《Journal of the Iranian Chemical Society》2016,13(7):1367-1374
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Seraj Faiza Kanwal Khan Khalid Mohammed Khan Ajmal Ali Muhammad Khalil Ruqaiya Ul-Haq Zaheer Hameed Shehryar Taha Muhammad Salar Uzma Perveen Shahnaz 《Molecular diversity》2021,25(1):143-157
Molecular Diversity - Novel ibuprofen derivatives 1–19 including ibuprofen hydrazide 1, and substituted thiourea derivatives 2–19 were synthesized and characterized by EI-MS, FAB-MS,... 相似文献