Barbituric acid

Barbituric acid
Barbituric acid
CAS number 67-52-7 YesY
PubChem 6211
ChemSpider 5976 YesY
UNII WQ92Y2793G YesY
EC number 200-658-0
KEGG C00813 YesY
ChEBI CHEBI:16294 YesY
Jmol-3D images Image 1
Molecular formula C4H4N2O3
Molar mass 128.09 g mol−1
Appearance White crystals
Melting point

245 °C

Boiling point

260 °C

Solubility in water 142 g/l (20 °C)
MSDS External MSDS
R-phrases R36/38, R43
S-phrases S22, S26, S28
NFPA 704
NFPA 704.svg
 YesY acid (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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. 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the compound its namesake), by combining urea and malonic acid in a condensation reaction.[1] Malonic acid has since been replaced by diethyl malonate,[2] as using the ester avoids the problem of having to deal with the acidity of the carboxylic acid and its unreactive carboxylate.

The synthesis of barbituric acid from malonic acid and urea

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 stabilisation of the carbanion. Using the Knoevenagel condensation reaction, barbituric acid can form a large variety of barbiturate drugs that behave as central nervous system depressants.

Barbituric acid is used in synthesis of riboflavin[citation needed].

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, phenobarbitone a.k.a. phenobarbital was first marketed in 1912.

See also


  1. ^ Baeyer, Adolf (1864). "Untersuchungen über die Harnsäuregruppe". Annalen der Chemie und Pharmacie 131 (3): 291. doi:10.1002/jlac.18641310306. 
  2. ^ J. B. Dickey & A. R. Gray (1943), "Barbituric acid", Org. Synth., ; Coll. Vol. 2: 60 

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Look at other dictionaries:

  • barbituric acid — [bär΄bə tyoor′ik, bär΄bətoor′ik] n. [< Ger barbitursäure (< ModL Usnea barbata, lit., bearded moss + ursäure, a ureide of acid character < urea, urea + säure, acid) + IC] a white, odorless, crystalline acid, C4H4O3N2, used in the… …   English World dictionary

  • Barbituric acid — Bar bi*tu ric ac id (Chem.) A white, crystalline substance, {CH2(CO.NH)2.CO}, derived from alloxantin, also from malonic acid and urea, and regarded as a substituted urea. [1913 Webster] …   The Collaborative International Dictionary of English

  • barbituric acid — bar′bitu′ric ac′id [[t]ˈbɑr bɪˈtʊər ɪk, ˈtyʊər , ˌbɑr [/t]] n. chem. pha a white, crystalline, slightly water soluble powder, C4H4N2O3, used chiefly in the synthesis of barbiturates • Etymology: 1865–70; < F barbiturique < G Barbitur(sӓure) …   From formal English to slang

  • barbituric acid — barbitūro rūgštis statusas T sritis chemija atitikmenys: angl. barbituric acid rus. барбитуровая кислота ryšiai: sinonimas – 2,4,6(1H,3H,5H) pirimidintrionas …   Chemijos terminų aiškinamasis žodynas

  • barbituric acid — A crystalline dibasic acid from which barbital and other barbiturates are derived; has no sedative action. SYN: malonylurea. * * * bar·bi·tu·ric acid .bär bə .t(y)u̇r ik n a synthetic crystalline acid C4H4N2O3 that is a derivative of pyrimidine …   Medical dictionary

  • barbituric acid — noun Etymology: part translation of German Barbitursäure, irregular from the name Barbara + International Scientific Vocabulary uric + German Säure acid Date: 1866 a synthetic crystalline acid C4H4N2O3 derived from pyrimidine …   New Collegiate Dictionary

  • barbituric acid — n. Chem. an organic acid from which various sedatives and sleep inducing drugs are derived. Etymology: F barbiturique f. G Barbitursaumlure (Saumlure acid) f. the name Barbara …   Useful english dictionary

  • barbituric acid — synthetic crystalline acid, substance from which several sedative drugs are derived …   English contemporary dictionary

  • barbituric acid — [ˌbα:bɪ tjʊərɪk, tʃʊərɪk] noun Chemistry a synthetic organic compound from which the barbiturates are derived. Origin C19: from Fr. barbiturique, from Ger. Barbitursäure, from the given name Barbara + Säure acid …   English new terms dictionary

  • barbituric acid — /babəˌtjʊərɪk ˈæsəd/ (say bahbuh.tyoouhrik asuhd) noun a heterocyclic compound, C4H4N2O3.2H2O, from which several hypnotic and sedative drugs are derived; malonyl urea. {German Barbitursäure, perhaps from the name Barbara + ur(ic) + Säure acid} …  

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