Barbituric acid

Barbituric acid

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Names
IUPAC name pyrimidine-2,4,6(1H,3H,5H)-trione
Other names 2,4,6(1H,3H,5H)-pyrimidinetrione 2,4,6-trioxohexahydropyrimidine 2,4,6-trihydroxypyrimidine 2,4,6-trioxypyrimidine 2,4,6-pyrimidinetriol 2,4,6-pyrimidinetrione pyrimidinetriol 2,4,6-trihydroxy-1,3-diazine N,N-malonylurea malonylurea 6-hydroxyuracil 6-hydroxy-hydrouracil N,N-(1,3-dioxo-1,3-propanediyl)urea
Identifiers
CAS Number	67-52-7 Y
ChEBI	CHEBI:16294 Y
ChEMBL	ChEMBL574699 Y
ChemSpider	5976 Y
EC Number	200-658-0
Jmol 3D model	Interactive image
KEGG	C00813 Y
PubChem	6211
UNII	WQ92Y2793G Y
InChI InChI=1S/C4H4N2O3/c7-2-1-3(8)6-4(9)5-2/h1H2,(H2,5,6,7,8,9) Y Key: HNYOPLTXPVRDBG-UHFFFAOYSA-N Y InChI=1/C4H4N2O3/c7-2-1-3(8)6-4(9)5-2/h1H2,(H2,5,6,7,8,9) Key: HNYOPLTXPVRDBG-UHFFFAOYAE
SMILES O=C1NC(=O)NC(=O)C1
Properties
Chemical formula	C4H4N2O3
Molar mass	128.09 g·mol−1
Appearance	White crystals
Melting point	245 °C (473 °F; 518 K)
Boiling point	260 °C (500 °F; 533 K)
Solubility in water	142 g/l (20 °C)
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Barbituric acid or malonylurea or 6-hydroxyuracil is an organic compound based on a pyrimidine heterocyclic skeleton. It is an odorless powder soluble in water. Barbituric acid is the parent compound of barbiturate drugs, although barbituric acid itself is not pharmacologically active.

Synthesis

The compound was discovered by the German chemist Adolf von Baeyer on December 4, 1864, the feast of Saint Barbara (who gave the compound its namesake), by combining urea and malonic acid in a condensation reaction. Malonic acid has since been replaced by diethyl malonate, as using the ester avoids the problem of having to deal with the acidity of the carboxylic acid and its unreactive carboxylate.

File:Barbituric acid synthesis.svg

The synthesis of barbituric acid from malonic acid and urea

Properties

The α-carbon has a reactive hydrogen atom and is quite acidic (pKa = 4.01) even for a diketone species (cf. dimedone with pKa 5.23 and acetylacetone with pKa 8.95) because of the additional aromatic stabilization of the carbanion.

Uses

Using the Knoevenagel condensation reaction, barbituric acid can form a large variety of barbiturate drugs that behave as central nervous system depressants. As of 2007, more than 2550 barbiturates and related compounds have been synthesised, with 50 to 55 in clinical use around the world at present. The first to be used in medicine was barbital (Veronal) starting in 1903, and the second, phenobarbital was first marketed in 1912.

Barbituric acid is one of four ingredients used to make riboflavin (vitamin B₂).

Health and safety

Overdose of barbituric acid can cause respiratory problems and death.

See also

• Barbiturase

References

Mahmudov K.T., Kopylovich M.N., Maharramov A.M., Kurbanova M.M., Gurbanov A.V., Pombeiro A.J.L. Barbituric acids as a useful tool for the construction of coordination and supramolecular compounds, Coordination Chemistry Reviews, 2014, 265, 1-37. DOI: 10.1016/j.ccr.2014.01.002 http://www.sciencedirect.com/science/article/pii/S0010854514000046

Mahmudov K.T., Kopylovich M.N., Maharramov A.M., Kurbanova M.M., Gurbanov A.V., Pombeiro A.J.L. Barbituric acids as a useful tool for the construction of coordination and supramolecular compounds, Coordination Chemistry Reviews, 2014, 265, 1-37. DOI: 10.1016/j.ccr.2014.01.002 http://www.sciencedirect.com/science/article/pii/S0010854514000046