Working With Hazardous Chemicals: A Publication of Reliable Methods For The Preparation of Organic Compounds
Working With Hazardous Chemicals: A Publication of Reliable Methods For The Preparation of Organic Compounds
Working With Hazardous Chemicals: A Publication of Reliable Methods For The Preparation of Organic Compounds
of Reliable Methods
for the Preparation
of Organic Compounds
The procedures in Organic Syntheses are intended for use only by persons with proper
training in experimental organic chemistry. All hazardous materials should be handled
using the standard procedures for work with chemicals described in references such as
"Prudent Practices in the Laboratory" (The National Academies Press, Washington, D.C.,
2011; the full text can be accessed free of charge at
http://www.nap.edu/catalog.php?record_id=12654). All chemical waste should be
disposed of in accordance with local regulations. For general guidelines for the
management of chemical waste, see Chapter 8 of Prudent Practices.
The procedures described in Organic Syntheses are provided as published and are
conducted at one's own risk. Organic Syntheses, Inc., its Editors, and its Board of
Directors do not warrant or guarantee the safety of individuals using these procedures and
hereby disclaim any liability for any injuries or damages claimed to have resulted from or
related in any way to the procedures herein.
These paragraphs were added in September 2014. The statements above do not supersede any specific
hazard caution notes and safety instructions included in the procedure.
DOI:10.15227/orgsyn.018.0008
Organic Syntheses, Coll. Vol. 2, p.60 (1943); Vol. 18, p.8 (1938).
BARBITURIC ACID
1. Procedure
In a 2-l. round-bottomed flask fitted with a reflux condenser protected by a calcium chloride tube,
11.5 g. (0.5 gram atom) of finely cut sodium is dissolved in 250 cc. of absolute alcohol. To this solution
is added 80 g. (0.5 mole) of ethyl malonate followed by 30 g. (0.5 mole) of dry urea dissolved in 250 cc.
of hot (70) absolute alcohol. After being well shaken the mixture is refluxed for seven hours on an oil
bath heated to 110. A white solid separates rapidly. After the reaction is completed, 500 cc. of hot (50)
water is added and then enough hydrochloric acid (sp. gr. 1.18) to make the solution acidic (about 45
cc.). The resulting clear solution is filtered and cooled in an ice bath overnight. The white product is
collected on a Bchner funnel, washed with 50 cc. of cold water, and then dried in an oven at 105110
for three to four hours. The yield of barbituric acid is 4650 g. (7278 per cent of the theoretical
amount).
3. Discussion
Barbituric acid has been prepared by the action of phosphorus oxychloride on malonic acid and
urea;1 by treating an acetic acid solution of urea and malonic acid with acetic anhydride;2 from ethyl
malonate and urea using sodium ethoxide as a condensing agent;3 and from ethyl malonate and the
sodium derivative of urea prepared from urea and sodium in liquid ammonia.4
The procedure described is an adaption of that of Michael.3
This preparation is referenced from:
1. Grimaux, Compt. rend. 87, 752 (1878); Conrad and Guthzeit, Ber. 14, 1643 (1881); Grimaux,
Bull. soc. chim. (2) 31, 146 (1879); Matignon, Ann. chim. phys. (6) 28, 289 (1893).
2. Biltz and Wittek, Ber. 54, 1035 (1921).
3. Michael, J. prakt. Chem. (2) 35, 456 (1887); Tafel and Weinschenk, Ber. 33, 3383 (1900);
Gabriel and Colman, ibid. 37, 3657 (1904).
4. Jacobson, U. S. pat. 2,090,594 [C. A. 31, 7068 (1937)].
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
alcohol (64-17-5)
ammonia (7664-41-7)
sodium (13966-32-0)
urea (57-13-6)