Ethanol, absolute, preparation extraction

Absolute Preparation obtained by extracting a concrete with ethanol and... 

Ammonium cyanate, because of its instability in solution, is usually prepared (NHJaSO, + 2KCNO 2NH4CNO + KjSO by mixing aqueous solutions of ammonium sulphate and potassium cyanate. Complete evaporation then gives a mixture of potassium sulphate and urea, from which the urea may be extracted w ith hot absolute ethanol, in which potassium sulphate is insoluble. 

Hydrolysis of the ester is achieved by refluxing in aqueous N or 2N NaOH solution until the insoluble ester dissolves. The solution is then cooled, and the alcohol is extracted into a suitable solvent, e.g. ether, toluene or alcohol-free chloroform. The extract is dried (CaS04, MgS04) and distilled, then fractionally distilled if liquid or recrystallised if solid. (The p-nitrobenzoic acid can be recovered by acidification of the aqueous layer.) In most cases where the alcohol to be purified can be readily extracted fi-om ethanol, the hydrolysis of the ester is best achieved with N or 2N ethanolic NaOH or 85% aqueous ethanolic N NaOH. The former is prepared by dissolving the necessary alkali in a minimum volume of water and diluting with absolute alcohol. The ethanolic solution is refluxed for one to two hours and hydrolysis is complete when an aliquot gives a clear solution on dilution with four or five times its volume of water. The bulk of the ethanol is distilled off and the residue is... 

C) Preparation of Doxapram Hydrochloride [3,3-Diphenyl-1-Ethyl-4-(2-Morpholino-Ethylj-2-Pyrrolidinone Hydrochloride Monohydrate] A solution of 25 grams (0.076 mol) of 4-(2-chloroethyl)-3,3-diphenyl-1-ethyl-2-pyrrolidinone and 13.3 grams (0.153 mol) of morpholine in 500 ml of absolute ethanol was heated at 95°-120°C for 21 hours in a closed system and concentrated in vacuo. The residue was dissolved in 3(X) ml of two normal hydrochloric acid and extracted with 150 ml of ethyl acetate. A solid crystallized (13 g) during the extraction and was removed by filtration. MP 217°-219°C. The acid extracts were made basic with sodium hydroxide and extracted with ether, and the ether solution was concentrated in vacuo and the residue was suspended in six normal hydrochloric acid. Additional crystalline product formed and was recrystallized from two normal hydrochloric acid. Yield, 10 grams MP 217°-219°C. Total yield, 23 grams (70%). 

Preparation of 1-Methyl-5-Allyl-5-( 1-Methyl-2-Pentynyl) Barbituric Acid A solution of 23.8 g of sodium in 360 ml of absolute alcohol was prepared and thereto were added 38.3 g of methyl urea and 96.8 g of diethyl allyl (1-methyl-2-pentynyl) malonate. The mixture was refluxed for about 20 hours, cooled, and the ethanol was removed by distillation in vacuo. The residue was dissolved in about 300 ml of water and the aqueous solution was washed with ether, and the washings were discarded. The aqueous solution was then acidified with acetic acid, and extracted with three 150 ml of portions of ether. 

The requisite intermediate, ethyl 4-dimethylaminocyclohexylcarboxylate is prepared as follows 33 g of ethyl p-aminobenzoate dissolved in 300 cc of absolute ethanol containing 16.B cc of concentrated hydrochloric acid is hydrogenated at 50 pounds hydrogen pressure in the presence of 2 g of platinum oxide. The theoretical quantity of hydrogen is absorbed in several hours, the catalyst removed by filtration and the filtrate concentrated to dryness in vacuo. The residue Is dissolved in water, made alkaline with ammonium hydroxide and extracted with chloroform. After removal of the solvent, the residual oil is distilled to yield ethyl 4-aminocyclohexylcarboxylate, boiling point 114°C to 117°C/10 mm. 

The same general method has been used by the submitters to prepare diethyl acetylenedicarboxylate. In this case absolute ethanol was used, and the ether extract was dried over anhydrous magnesium sulfate. The yield of diethyl ester from 100 g. of the acid potassium salt of acetylenedicarboxylic acid was 57-59 g. (51-53%) b.p. 96-98°/8 mm. n 1.4397. 

A solution of 0.8 g of diethyl N-[l-methyl-3-(2-nitro-3-chlorophenyl)-3-oxopropylidene]aminomalonate in 4 ml of absolute tetrahydrofuran was added dropwise with stirring to a solution prepared with 8 ml of absolute ethanol and 100 mg of metallic sodium. After the reaction mixture was refluxed for 4.5 hours, the solvents were distilled off under reduced pressure. The residue was added with an ice-water and the solution was extracted with ether. The extract was washed with water, dried over anhydrous magnesium sulfate, after which ether was distilled off. The residue was recrystallized from benzene to obtain ethyl 3-(2-nitro-3-chlorophenyl)-5-methylpyrrole-2-carboxylate as colorless needles having MP 220°-223°C. 

According to the British Pharmacopoeia 2002 [2] and Indian Pharmacopoeia [6], mefenamic acid in capsule and tablet preparations are identified by examination using infrared absorption spectrophotometry as the following procedure. Extract a quantity of the capsule contents (or powdered tablets) containing 0.25 g of mefenamic acid with two 30 mL quantities of ether. Wash the combined extracts with water, evaporate to dryness on a water bath, and dry the residue at 105°C. Dissolve a sufficient quantity in the minimum volume of absolute ethanol, and evaporate to dryness on a water bath. The infrared absorption spectrum is concordant with the reference spectrum of mefenamic acid. 

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