نتایج جستجو برای: free silica
تعداد نتایج: 549038 فیلتر نتایج به سال:
Multiwalled Carbon Nanotube (MWCNT) reinforced silica aerogel was synthesized in a very simple and cost effective sol - gel method. The process was followed by ambient pressure drying, and then the aerogel material was characterized by XRD, BET, SEM, EDX and FT-IR. 2.3 x 10-3 wt% MWCNTs were successfully incorporated in sodium silicate based silica aerogel. This metal-free nanocomposite catalyz...
The development of a silica-promoted highly selective synthesis of 1,2 or 1,3-dithioethers via solvent-free one-pot tandem reactions of an allyl bromide with excess thiol at room temperature is described. The choice of silica gel, either pre-calcined or moistened with water, exhibited notable regioselectivity in the formation of dithioethers. Plausible mechanistic routes were explored and postu...
The 2-hydroxy fatty acids tend to yield streaks in thin-layer chromatography on silica gel plates. If potassium oxalate is included with binder-free silica gel, good spots are obtained. Similar difficulties are found in paper chromatography of the fatty acid derivatives of coenzyme A, especially with long-chain acids. The same thin-layer system gives good spots with these compounds.
The utilization of perfluoro-tagged palladium nanoparticles immobilized on fluorous silica gel through fluorous-fluorous interactions (Pd(np)-/FSG) or linked to silica gel by covalent bonds (Pd(np)-) in the alkynylation of terminal alkynes with aryl halides under aerobic, copper- and phosphine-free conditions in water, and their recovery and re-utilization, is described.
Sol–gel chemistry is an efficient tool to control the morphology and reactivity of solids. Drying is the crucial step due to the capillary forces exerted during the classic ambient drying process, which induces the collapse of the wet gel porosity. The use of N, N-dimethylformamide (DMF), a newly found DCCA were found to be effective in the sol–gel synthesis of crack-free silica gel monolith fr...
The silica aerogel was prepared by the acid–base sol–gel polymerization of tetraethylorthosilicate precursor followed by ambient pressure drying. The prepared silica aerogels were characterized by Fourier transform infrared )FT-IR(, Thermo-gravimetric and differential thermal analysis )TG/DTA(, X-ray diffractometer )XRD(, Energy dispersive X-ray microanalysis )EDX(, Brunauer–Emmitt–Teller (BET)...
Silica-bonded N-propyldiethylenetriamine sulfamic acid (SPDTSA) is employed as a recyclable heterogeneous solid acid catalyst for the synthesis of benzopyrano[2,3-d]pyrimidines through one-pot condensation reaction of salicylaldehydes, malononitrile and secondary amines at room temperature under solvent-free conditions. SPDTSA showed much the same efficiency when used in con...
trimethylsilylation of a variety of alcohols and phenols, in the presence of silica chloride, using hexamethyldisilazane (hmds) in solution and under solvent-free conditions is reported. trimethylsilyl ethers were formed in excellent yields both for aliphatic alcohols and phenols without having an electron-withdrawing group. in addition, sio2-cl can be recovered and reused after drying.
1,8-dioxo-decahydroacridines have been synthesized by the three-component reaction of aromatic aldehydes, aromatic amines (or ammonium acetate), and dimedone in the presence of sulfonic acid functionalized nanoporous silica (sba-pr-so3h) under solvent-free conditions. excellent yields, short reaction times, mild reaction conditions, and easy work-up procedures are advantages of this green method.
nano-silica supported boron trifluoride (bf3.sio2) is an efficient, reusable and eco-friendly catalyst for chemoselective thioacetalization of aldehydes and ketones. so, this catalyst was applied for transthioacetalization of acetals and acylals into their corresponding 1,3-dithiolanes or 1,3-dithianes in good to excellent yields. the reactions were carried out at room temperature under solven...
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