Silica ethylene glycol solution

Cyclohexanone (0.52 g, 5.3 mmol) is added, under a nitrogen atmosphere, to a mixture of dry ethylene glycol (3 mb, 54 mmol) and dry methanol (20 mb). Tri-methylchlorosilane 14 (1.4 mb, 11 mmol) is added and the mixture stirred for 16 h at room temperature. The mixture is neutralized to pH 6 by addition of a 5% solution of sodium methoxide in methanol and the solvent is removed under reduced pressure. The residue is dissolved in 20 mb ether and filtered through 5 g silica gel, which is then washed with 2x10 mb ether. The combined ether eluates are evaporated and the crude residue submitted to flash chromatography on silica gel with ethyl acetate-hexane (1 10) to give 0.63 g (83%) cyclohexanoneethylene ketal 392 [28] (Scheme 5.87). 

The ethylene glycol-containing silica precursor has been combined, as mentioned above, with most commercially important polysaccharides and two proteins listed in Table 3.1. In spite of the wide variety of their nature, structure and properties, the jellification processes on addition of THEOS to solutions of all of these biopolymers (Scheme 3.2) had a common feature, that is the formation of monolithic nanocomposite materials, proceeding without phase separation and precipitation. The syner-esis mentioned in a number of cases in Table 3.1 was not more than 10 vol.%. It is worthwhile to compare it with common sol-gel processes. For example, the volume shrinkage of gels fabricated with the help of TEOS and diglyceryl silane was 70 and 53 %, respectively [138,141]. 

Polyfluorobenzene or perfluoronaphthalene (30 mmol) was mixed with pyridine (20 mL) and the mixture refluxed. After about 10 min a solution of the alkanethiol (10 mmol) and the appropriate amount of NaOH in ethylene glycol (10 mL) was slowly added to the pyridine solution which was refluxed for an additional 15 min. Then the mixture was poured into ice water, acidified with HC1 and extracted with Et20 (3 x 25 mL). The organic phase was dried (MgS04), the Et20 evaporated, and the crude product purified by distillation and by chromatography (silica gel, toluene/cyclohexane 3 2). 

Killmann and Eckart65) were the first to determine adsorption enthalpies by calorimetry. They measured the enthalpies for poly(ethylene glycol) adsorbed from carbon tetrachloride, benzene, water, and methanol solutions onto finely grained silica. The obtained values increased linearly with adsorbance in the order methanol, water, benzene, and carbon tetrachloride. 

Integral adsorption enthalpies AH for the adsorption of poly(vinyl acetate), poly(n-butyl methacrylate), and polycaprolactone from carbon tetrachloride solutions on Aerosil 200 silica were measured by Korn and Killmann98), who used IR spectroscopy for the determination of p. The values obtained for the three polymers exhibited the same characteristic dependence on adsorbance as that observed for poly(ethylene glycol). If the enthalpy of polymer-solvent and polymer-polymer interactions is neglected, the net binding adsorption enthalpy AHp A can be calculated from... 

A solution of 0.11 g of sodium in 3.0 ml of ethylene glycol and equivalent of 4-t-butyl-N-[6-chloro-5-(2-methoxyphenoxy)-2-(pyrimidin-2-yl)-pyrimidin-4-yl]benzenesulphonamide were heated to 100°C, cooled for a further 4 hours, poured on to ice and adjusted to pH 3 with 1 M tartaric acid. The suspension obtained was extracted with ethyl acetate, the organic extracts were combined, washed with water, dried with sodium sulfate and concentrated under reduced pressure. The residue was chromatographed on silica gel with CH2CI2-ethyl acetate 9 1 and yielded 4-t-butyl-N-[6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-(pyrimidin-2-yl)-pyrimidin-4-yl]benzenesulphonamide as a solid. Sodium salt melted at 195°-198°C. 

We determined that vicinal dihydroxy organic reagents stabilize the soluble forms of silica. The stability of monosilicic acid solution is determined by the structure of the stabilizer ethylene glycol and humic acids do not stabilize soluble forms of silica enough, but glycerin and catechol stabilize the silica solution when they are added at 5 - 7% to the solution. This fact is connected with the formation of hydrogen bonds and stable penta- and hexacoordinated compounds, preventing the processes of polycondensation of silica in solution. 

To act as an SDA, a molecule must fulfil certain other prerequisites besides stability [5-7]. A critical factor is its solubility in the solvent used (usually water). The potential SDA must possess at least a limited solubility to take part in the reaction. However, if the solubility is too high or if the SDA forms strong hydrogen bonds with water, then its tendency to co-crystallize with the silica will be low and it will prefer to stay in solution. For this reason, alcohols are only weak SDAs, for instance. The fact that ethylene glycol and ethanolamine are grouped with other SDAs for the synthesis of silica sodalite in Fig. Id seems to contradict this conclusion. However, these molecules act as SDAs only in solvothermal synthesis, in which the SDA simultaneously acts as the solvent. 

Figure 1.13 GC analysis of organic acid methyl esters in a) standard solution, b) Chardonnay wine, c) Asti sparkling wine. 1. methyl lactate, 2. dimethyl succinate, 3. dimethyl maleate (i.s.), 4. dimethyl malate, 5. dimethyl tartrate, 6. trimethyl citrate. Chromatographic conditions poly(ethylene) glycol fused silica capillary column (30m x 0,25mm 0.25 xm), injector and detector temperature 250°C, flame ionization detector. Oven program 2min at 50 °C, from 50 to 200 °C at rate 4°C/min, 200°C isotherm for lOmin (Di Stefano and Bruno, 1983)...

Sample preparation and derivatization methods for GC analysis of BAs have been also proposed. In a method developed by Daudt and Ough (1980), amines are distilled from the alkalized grape juice or wine sample and trapped in an acidified solution. After concentration under vacuum, methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, isobutylamine, a-amylamine, isoamylamine, pyrrolidine, and 2-phenethylamine in their salt form are derivatized with triflu-oroacetic (TFA) anhydride. TFA derivatives are extracted with ethyl ether and analyzed by GC-MS with a capillary fused silica poly( ethylene) glycol (PEG) column and the following oven temperature program 8 min at 70 °C, l°C/min to 160 °C, isotherm for 90 min. 

Mixed solutions of cationic surfactants and nonionic poly(ethylene glycol) or block copolymers were employed for the synthesis of monolithic trimodal porous silica.[176] Lyotropic mixtures of block copolymers of different lengths with hydrophilic linear PEO chains were also applied to their nanocasting into bimodal micro-mesoporous silica to formulate the dependence of the mesopore sizes and the microporosity on the lengths or sizes of the hydrophobic and the hydrophilic blocks, but the mesostructures were worm-type in morphology and several hundred nanometers or more in size. 

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