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ChemicalBook CAS DataBase List Barbituric acid
67-52-7

Barbituric acid synthesis

13synthesis methods
Barbituric acid is derived By the reaction of diethyl malonate and urea. First put Urea in a reaction tank containing methanol ,heat , reflux , dissolve, then add the dried diethyl malonate and sodium methoxide, the reaction is refluxed at 66-68°C for 4-5h, after distillation to recover methanol, cooling to 40-50°C, add dilute hydrochloric acid to adjust to pH 1-2.Cool to room temperature, throw to obtain crude, wash with distilled water once, dry to get crude , and then purify with water and activated carbon, dry to obtain products. Industrial barbituric acid is white or pink crystalline powder, strongly acidic, more than 98% content, melting point ≥245°C. Material consumption fixed: diethyl malonate 1098kg/t, urea 476kg/t, hydrochloric acid (reagent grade III) 681kg/t, sodium methanol (28%) 369kg/t, methanol 1025kg/t.
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Yield:67-52-7 70%

Reaction Conditions:

sodium methylate in ethylene glycol at 110; for 6 h;Conversion of starting material;

Steps:

15

Barbituric acid Starting Materials Diethyl malonate 0.5 mol Barbituric acid Starting Materials Diethyl malonate 0.5 mol Urea 0.55 mol Sodium methoxide (catalyst) 0.5 mol Ethylene Glycol 223 g. Operating Conditions Pressure Atmospheric Temperature/time regime 110° C./6 h. Reaction Progress Monitored by TLC using Merck's silica gel plates, benzene- methanol (1:1) Work-up The reaction mixture was cooled to 60° C., diluted with 500 mL water at 50° C., made acidic (to a blue color with congo red indicator) by addition of 55.8 g. concentrated aqueous hydrochloric acid, refri- gerated overnight and filtered. The filter cake was washed with 50 mL cold (10° C.) water and dried at 90° C. during 4 h. 44.6 g, of white crystals, m.p. 245° C. (dec.) were obtained (literature 248° C. “with some decomposition”) Yield 70%

References:

US2005/27120,2005,A1 Location in patent:Page/Page column 8

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