Ethanol-water media synthesis

Sn/V/Nb/Sb/0 catalysts were prepared with the co-precipitahon technique, developed for the synthesis of ratile Sn02-based systems claimed by Rhodia (8). The preparation involved the dissoluhon of SnCl45H20, VO(acac)2, SbCh and NbCls in absolute ethanol, and by dropping the soluhon into a buffered aqueous soluhon maintained at pH 7. The precipitate obtained was separated from the liquid by filtrahon. The solid was then dried at 120°C and calcined in air at 700°C for 3 hours. The V/Sb/0 catalyst was prepared by means of the slurry method that consists in a redox reachon between Sb203 and NH4VO3 in water medium, for 18h at 95°C. The... 

In addition to the abovementioned results consisting only the increasing yields (Scheme 6) [38], another example of effective microwave-assisted synthesis of azolopyrimidine carboxamides should be described. Tu et al. [47] reported eco-friendly three-component reaction of 2-aminobenzimidazole, aromatic aldehydes, and some p-dicarbonyl compounds under microwave irradiation (Scheme 8). It was shown that the treatment of the starting materials can be most efficiently carried out at 90°C (200 W MW power) in water medium instead of traditional organic solvents like ethanol, acetic acid, or DMF. 

Other Fission Processes - Considerable use is being made of radical reactions in organic synthesis. For example, Deng and Kutateladze have described a novel method for the synthesis of esters. This involves the irradiation of the ester (124) in the presence of terminal alkenes. Unfiltered light from a medium pressure mercury arc lamp results in the fission of the S-methylene bond and the formation of a radical which adds to the alkenes. The yields obtained are reasonable with acetonitrile as the solvent. Other solvents such as methanol or ethanol/water can also be used. Yields of the products obtained are shown in Scheme 7. 

Blasco et al. (12,13) developed a novel method for the synthesis of Al-free Ti-beta zeolite in a fluoride medium. The Ti-beta zeolite thus obtained (Ti-beta(F)) was free of connectivity defects and was hydrophobic. The typical unseeded synthesis of Al-free Ti-beta zeolite (Ti-beta(F)) involves hydrolysis of TEOS in aqueous solutions of TEAOH (35%) and H202, followed by hydrolysis of TEOT and evaporation of ethanol and water. The water lost in the evaporation and... 

As an example, thermosensitive PVME microgels can be used as template and stabilizer for the synthesis of composite polypyrrole (PPy) particles [32], The PVME microgels were obtained by electron beam irradiation above the phase transition temperature as described in Sect. 3.2.1 [3,4], Pyrrole (Py) was polymerized by oxidative polymerization with ferric chloride in the presence of the PVME microgels in water/ethanol mixtures as reaction medium. For comparison, the synthesis was also carried out in the presence of uncross-linked PVME. 

Solvothermal reactions in alcohols are sometimes called alcohothermal reactions this word is derived from alcoholysis based on the similarity between hydrothermal and hydrolysis. Alcohols are the most common solvents for sol-gel synthesis. Primary alcohols are fairly stable at higher temperatures (up to 360°C) and therefore are widely used for the solvothermal reactions." For example, amorphous gel derived by hydrolysis of metal alkoxides can be crystallized by solvothermal treatment in alcohols. Since lower alcohols (methanol, ethanol, and 1-propanol) are completely miscible with water, water molecules present in the precursor gel may be replaced with the solvent alcohols. Therefore the precursor gel is easily dispersed in the solvent, where crystallization takes place. Detailed mechanisms for the formation of crystals are not yet fully elucidated. Crystallization of metal oxides is usually reported to take place by dissolution-recrystallization mechanisms, but the mechanism seems to depend on the gel structure. Moreover, water molecules dissolved from the gel in the reaction medium may facilitate crystallization of the product. More discussion is given in Section III.D of this chapter. 

In this mode of synthesis of polymeric nanoparticles (e.g., of polybutylcycanoacrylates), monomeric materials (e.g., butylcyanoacrylate) are dispersed in a suitable solvent and emulsified. An initiator is generally added to the system and the monomers condense to form a polymeric matrix, although in the case of the alkyl cyanoacrylates no initiator is required as the aqueous medium acts as the initiator of polymerization. As one example (78) isobutylcyanoacrylate dissolved in ethanol can be mixed with an oil plus an oil-soluble drug to constitute one phase the second phase is an aqueous solution of 0.5% Pluronic F68 (poloxamer 118). The two phases are mixed and the polyisobutylcyanoa-crylate is formed at the interface between the oil and the water. The formation of alkylcyanoacrylate films at oil/water interfaces was investigated over 30 years ago (79). 

The synthesis of Sn-beta (68,151) with isolated single tin sites was accomphshed in a fluoride medium TEOS was hydrolyzed in a stirred aqueous solution of TEAOH. Then a solution of SnC 5H2O in water was added and the mixture stirred until the ethanol formed by hydrolysis of the TEOS had evaporated. HF was added to the resulting clear solution, and a thick paste formed. Then a suspension of nanocrystalline seeds (20 nm in diameter) of dealuminated zeolite beta in water was added. The crystallization was carried out in aTeflon-hned stainless-steel autoclave, which was heated to a temperature of 140 °C and continuously rotated for 20 days. After drying and calcining of the resultant sohd, XRD showed that a highly crystalline material with BEA structure was obtained, which contained 1.6 wt% Sn according to chemical analysis. Further characterization by XRD and UV, IR, and Sn MAS NMR spectroscopies verified the structure and the isomorphous substitution of siHcon by tin. 

The new version of solketal synthesis based on the use of ethanol, can raise the yield to a practically quantitative, because ethanol is more effectively involved in the azeotropic removal of water and it also alters the chemical nature of the reaction medium by semiketal formation in interaction with acetone. It is known that the interaction of nonhindered lower alcohols and ketones gives almost quantitative formation of semiketals. This is detected by the change of physical parameters UV-absorbtion,... 

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