Silica, reaction with

SODIUM VAPOR, VITREOUS SILICA REACTION WITH... 

Sodium vapor, vitreous silica reaction with, 22 418... 

The chemical interaction of metal ions precipitating from a homogeneous solution with silica at higher temperatures has been confirmed extensively. With finely divided silica, reaction with synthetic clay minerals... 

Carbodi-imide-mediated reaction with epichlorohydrin-activated agarose previously treated with glycine Reaction with a syw-trichlorotriazine-activated polystyrene anion exchanger reaction with 1,4-benzoqumone-activated aminopropyl silica reaction with an N-hydroxysuccinimide ester derivative of 3-succinimidopropyl silica Carbodi-imide- or 2,4-toluenedi-isocyanate-mediated reaction with amino-or carboxy-aerosU... 

Toxicology ACGIH TLV/TWA 5 ppm LC50 (inh., rat, 4 h) 9600 ppm may cause thermal bums inh. hazard inh. may cause headache, nausea reaction prod, with air is silica reaction with air may produce irritation or thermal bums to skin, eyes, mucous membranes TSCA listed Precaution Flamm. gas pyrophoric (autoigniting in air) may form mixts.with air that do not autoignite, but are flamm. or explosive violently reactive with oxidizers, halogens excessive pressure may develop in gas cylinders exposed to fire, which may result in explosion avoid ignition sources, exposure to air... 

Silica reaction with TESPT Silanated silica... 

The o,p-dinitrostyrene (1 mmol) and ammonium formate (10 mmol) W ere dissolved in methanol and 10% Pd/ C (5% by wt) was added. The mixture was refluxed under nitrogen for 1 h. Formic acid (0.44 ml) w as added and reflux was continued for 0.5-1 h until the completion of the reaction (tic). The solution was filtered through Celite, evaporated in vacuo and eluted through silica gel with CH2CI2. 

Silica and Alumina. The manufacture of Pordand cement is predicated on the reaction of lime with siUca and alumina to form tricalcium sihcate [12168-85-3] and aluminate. However, under certain ambient conditions of compaction with sustained optimum moisture content, lime reacts very slowly to form complex mono- and dicalcium siUcates, ie, cementitious compounds (9,10). If such a moist, compact mixture of lime and siUca is subjected to steam and pressure in an autoclave, the lime—silica reaction is greatiy accelerated, and when sand and aggregate is added, materials of concrete-like hardness are produced. Limestone does not react with siUca and alumina under any circumstances, unless it is first calcined to lime, as in the case of hydrauhc lime or cement manufacture. 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

With 2537 k-Light. 1 g (140) in 140 ml anhydrous dioxane is irradiated for 20 hr at room temperature with a Hanau NK 6/20 low-pressure mercury lamp placed in a central water-cooled quartz finger. 0.19 g of (141) crystallize from the crude reaction mixture as described above. Chromatography of the residual material on silica gel with benzene-ethyl acetate (4 1) gives 0.29 g of B-nortestosterone acetate [(142) 28.5 %] and starting material (140). 

The Zincke reaction has also been adapted for the solid phase. Dupas et al. prepared NADH-model precursors 58, immobilized on silica, by reaction of bound amino functions 57 with Zincke salt 8 (Scheme 8.4.19) for subsequent reduction to the 1,4-dihydropyridines with sodium dithionite. Earlier, Ise and co-workers utilized the Zincke reaction to prepare catalytic polyelectrolytes, starting from poly(4-vinylpyridine). Formation of Zincke salts at pyridine positions within the polymer was achieved by reaction with 2,4-dinitrochlorobenzene, and these sites were then functionalized with various amines. The resulting polymers showed catalytic activity in ester hydrolysis. ... 

Quinoxaline 1,4-dioxides have also been prepared by condensation reactions carried out on the surface of solid catalysts such as silica gel, " molecular sieves, " or alumina. " As a representative example, " BFO 1 and the P-dicarbonyl compound 16 were combined with silica gel in methanol. The excess methanol was removed by evaporation and the silica gel with adsorbed reagents was allowed to stand for two weeks without drying. The quinoxaline 1,4-dioxide 17 was obtained in 90% yield after elution from a silica gel column. 

The moist cells were suspended in 750 parts of volume of ethanol and extracted by warming at 60°C for 1 hour. A total of 3 extractions were carried out in a similar manner and the extracts were pooled, diluted with water and further extracted three times with 1,000 parts of volume portions of n-hexane. The n-hexane layer was concentrated to dryness under reduced pressure to recover 4.12 parts of a yellow oil. This oily residue was dissolved in 6 parts by volume of benzene and passed through a column (500 parts by volume capacity) packed with Floridil (100 to 200 meshes). Elution was carried out using benzene and the eluate was collected in 10 parts by volume fractions. Each fraction was analyzed by thin-layer chromatography and color reaction and the fractions rich in ubiquinone-10 were pooled and concentrated under reduced pressure. By this procedure was obtained 0.562 part of a yellow oil. This product was dissolved in 5 parts by volume of chloroform, coated onto a thin layer plate of silica gel GF254 (silica gel with calcium sulfate) and developed with benzene. The fractions corresponding to ubiquinone-10 were extracted, whereby 0.054 part of a yellow oil was obtained. This oil was dissolved in 10 parts by volume of ethanol and allowed to cool, whereupon 0.029 part of yellow crystals of ubiquinone-10 were obtained, its melting point 4B°to 50°C. 

The product distribution in the reaction of benzene with dodecene was determined for a number of catalysts (Table 5.1-4). As can be seen, the reaction with the zeolite H-Beta gave predominantly the 2-phenyldodecane, whereas the reaction in the pure ionic liquid gave a mixture of isomers, with selectivity similar to that of aluminium chloride. The two supported ionic liquid reactions (H-Beta / IL and T 350 / IL) again gave product distributions similar to aluminium(III) chloride (T350 is a silica support made by Degussa). 

This process is to ensure that the silica is in the correct form for reaction with ammonium molybdate. If the solution is too hot, the red colour may not develop. 

Oxidation of the methyl substituent in compounds 4 to the corresponding aldehydes and subsequent reaction with ephedrine leads to (V.O-acetals, which can be separated by crystallization into the two diastereomers. Treatment with silica gel then gives the enantiomerically pure aldehydes.17... 

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