Esters distillation

Alternatively, the ester may be extracted with two SO ml. portions of ether. The ethereal solution is washed with concentrated sodium bicarbonate solution (handle the separatory funnel cautiously as carbon dioxide is evolved) until effervescence ceases, then with water, and dried over anhydrous magnesium sulphate. The ether is removed with the aid of the apparatus depicted in Fig. II, 13, 4, and the residual ester distilled. 

Ethyl Propane-a,a,y,y-tetracarboxylate.—To a mixture of 1600 g. (10 moles, 1510 cc.) of ethyl malonate (Note 1) and 400 g. of 40 per cent formalin (5.3 moles) in a 5-I. round-bottom flask, cooled to 50 by immersion in ice, is added 25 g. (35 cc.) of diethyl-amine. The mixture is then allowed to come to room temperature and remain for fifteen hours, after which the flask is heated under a reflux condenser on a boiling water bath for six hours. The aqueous layer is then separated, and the residue is distilled under reduced pressure (Note 2) from a 3-I. special Claisen flask (Org. Syn. 1,40). The ester distils at i9o-2oo°/i2 mm.(2io-2i5°/2o mm.) The yield (Note 3) is 1000 g. (61 per cent of the theoretical amount). 

After removal of the drying agent, the ester is fractionally distilled through an efficient fractionating column (Note 2). A fore-run of 21-37 g. is collected up to a temperature of 95°. The pure ester distils between 95° and 96° and amounts to 129-148 g. (53-60%) (Note 3). 

Some unchanged ester distils prior to the nitrobenzene its removal aids in the subsequent separation of the two layers. 

To 50 ml. of a well-cooled 6N sodium hydroxide solution is added, with stirring, 32 g. (0.15 mole) of the phosphite salt. The stirring is continued until all the solid has dissolved. The solution is transferred to a 125-ml. separatory funnel, extracted with three 20-ml. portions of ether, and the combined extracts dried over anhydrous sodium sulfate. The drying agent is removed by filtration, the solvent removed under reduced pressure, and the glycine f-butyl ester distilled, b.p. 65-67° (20 mm.), 1.4237,... 

Four hundred cubic centimeters of 25 per cent sulfuric acid is added, and the contents of the funnel are shaken continually until the copper derivative has disappeared (five to ten minutes). After separation of the ethereal layer, the aqueous layer is extracted twice with 100-cc. portions of ether, and the combined ethereal extracts are dried over calcium chloride. The ether is removed on the steam bath and the residual ester distilled under diminished pressure. A few drops come over up to 90°, but the bulk of the material distils at 92-98°/i2 mm. Redistillation yields pure ethyl diacetylacetate boiling at 95-970/12 mm. The yield is 80-90 g. (46-52 per cent of the theoretical amount). 

Cognate preparations. Butyl oleate. Proceed as for isopropyl lactate using 28 g (0.1 mol) of redistilled oleic acid, 37.0 g (46 ml, 0.5 mol) of butan-l-ol (the excess of the latter acts as the water carrier) and 8.0 g of Zerolit 225/H in a 250-ml flask. Reflux the mixture with magnetic stirring for 4 hours, allow to cool, separate the resin by suction filtration and wash it with three 5 ml portions of butan-l-ol. Remove the butanol from the combined filtrate and washings by distillation under reduced pressure (water pump) the residue consists of crude ester. Distil the residue under diminished pressure (oil pump) and collect the butyl oleate at 232 °C/9 mmHg. The yield is 27 g (85%). 

To H-Ala-OEt (5.73 g, 49 mmol) in CH2CI2 (10 mL), triflyl azide in CH2CI2 (ca. 1 M, 1 equiv) was added along with a catalytic amount (ca. 0.1 mmol) of methyltrioctylammonium chloride, and the soln was stirred at rt for 10-15 h. The mixture was washed with 0.25 M citric acid (2 x 30 mL), the CH2CI2 layer was dried (Na2S04) and concentrated and the azido ester distilled at reduced pressure yield 4.32 g (62%). 

In the DOD, phytosterols are present in both the free and esterified forms with fatty acids. Therefore, the first step in the extraction of phytosterols is conversion of phytosterol fatty esters into free phytosterols. This is achieved either by hydrolysis or trani-esterification. Hydrolysis could be carried out under strong basic conditions (saponification with further acidulation), under strong acidic conditions, or under chemical or enzyme (specific or nonspecific) catalyzation. Re-esterification of phytosterols occurs during methyl ester distillation as a result of the high temperatures involved therefore, a further trani-esterification step for free sterols is required. Esterification of phytosterols or trani-esterification of sterol fatty acid esters is the second step in this process. Methanol is the most commonly used alcohol, and it leads to methyl esters, which are characterized by a higher volatility, however, other Ci to C4 alcohols may also be used. Esterification and trans-esterification of fatty acids or phytosterols can be catalyzed by metal alcoholates, or hydroxide, by organic catalysts, or by enzymes (Table 7). 

Acid Color 1963 Gardtwr, Short-Path Methyl Ester Distillation High Pressure Liquid Chromatography ... 

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