Violuric acid is an organic compound with the formula HON=C(CONH)2CO. It crystallizes as white or off-white monohydrate. The compound has attracted attention because its salts are deeply colored.[2]

Violuric acid
Names
IUPAC name
6-Hydroxy-5-nitroso-1H-pyrimidine-2,4-dione
Other names
2,4,5,6(1H,3H)-Pyrimidinetetrone 5-oxime
5-Hydroxyiminobarbituric acid
5-Isonitrosobarbituric acid
Alloxan 5-oxime
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.001.584 Edit this at Wikidata
EC Number
  • 201-741-4
UNII
  • InChI=1S/C4H3N3O4/c8-2-1(7-11)3(9)6-4(10)5-2/h(H3,5,6,8,9,10)
    Key: HRRVLSKRYVIEPR-UHFFFAOYSA-N
  • C1(=C(NC(=O)NC1=O)O)N=O
Properties
C4H3N3O4 (anhydrous)
C4H3N3O4·H2O (monohydrate)
Molar mass 157.08 g/mol (anhydrous)
175.10 g/mol (monohydrate)
Appearance Off-white yellow or yellow cream solid
Odor Odorless
Melting point 247 °C (477 °F; 520 K) (decomposes)
Boiling point Decomposes
0.704 g/100 mL (20 °C)[1]
Solubility Soluble in alcohols
Vapor pressure ~0 mmHg
Acidity (pKa) 4.7
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Irritant
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P305+P351+P338
Related compounds
Related compounds
Barbituric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Reactions

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It readily deprotonated to give salts of the anion [ON=C(CONH)2CO], which are often deeply colored.[3][4]

Preparation

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It was prepared by Adolf Baeyer by reaction of barbituric acid with nitrous acid.[5] It can also be produced by condensation of alloxan with hydroxylamine.[4][6] as typical for forming the oxime of other carbonyl compounds.

Analytical reagents

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Structure of the ferrous complex with three violurate ligands.[7]

Violuric acid and many of its derivatives, such as thiovioluric acid, 1,3-dimethylvioluric acid, and diphenylthiovioluric acid, have historically been used as analytical reagents for spectrophotometric determination and titration of various metals and metal-ions.[8] It was also used as a novel staining/spraying agent for inorganic paper chromatography to identify and separate metals based on color.[9] Most derivatives of violuric acid will also typically form brightly colored salts with most metals and nitrogen bases.[10]

Because of the characteristic and diverse colors that violuric acid forms with alkali metals, it has been used photometrically to determine the amount of sodium in blood serum.[11]

References

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  1. ^ "Registration Dossier - ECHA".
  2. ^ Guille, Kathy; Harrington, Ross W.; Clegg, William (2007). "Violuric acid monohydrate: A second polymorph with more extensive hydrogen bonding". Acta Crystallographica Section C Crystal Structure Communications. 63 (6): o327–o329. Bibcode:2007AcCrC..63O.327G. doi:10.1107/S010827010701743X. PMID 17551193.
  3. ^ Nichol, Gary S.; Clegg, William (2007). "Ammonium Violurate: A Compact Structure with Extensive Hydrogen Bonding in Three Dimensions". Acta Crystallographica Section C Crystal Structure Communications. 63 (10): o609–o612. Bibcode:2007AcCrC..63O.609N. doi:10.1107/S0108270107044241. PMID 17917236.
  4. ^ a b Liebing, Phil; Stein, Franziska; Hilfert, Liane; Lorenz, Volker; Oliynyk, Karyna; Edelmann, Frank T. (2019). "Synthesis and Structural Investigation of Brightly Colored Organoammonium Violurates". Zeitschrift für Anorganische und Allgemeine Chemie. 645: 36–43. doi:10.1002/zaac.201800439. S2CID 104376844.
  5. ^ Baeyer, Adolf (1863). "Untersuchungen über die Harnsäuregruppe". Annalen der Chemie und Pharmacie. 127 (2): 199–236. doi:10.1002/jlac.18631270214.
  6. ^ Guinchard, J. (1899). "Ueber die farbigen Salze aus Violursäure und anderen ringförmigen Oximidoketonen". Berichte der Deutschen Chemischen Gesellschaft. 32 (2): 1723–1741. doi:10.1002/cber.18990320260.
  7. ^ Raston, Colin L.; White, Allan H. (1976). "Salts of the Tris(violurato)ferrate(II) Ion: Crystal Structure of Ammonium Tris(violurato)ferrate(II) Hydrate". Journal of the Chemical Society, Dalton Transactions (19): 1915. doi:10.1039/DT9760001915.
  8. ^ Taylor, M. E.; Robinson, R. J. (1962-04-01). "The Use of 1,3-Dimethylvioluric Acid in Spectrophotometric Titrations of Alkali and Alkaline Earth Salts". Analytical Chemistry. 34 (4): 533–536. doi:10.1021/ac60184a026. ISSN 0003-2700.
  9. ^ Singh, A. K.; Katyal, Mohan; Singh, R. P. (1976). "Violuric Acids as Analytical Reagents". Current Science. 45 (11): 405–408. ISSN 0011-3891. JSTOR 24079761.
  10. ^ Lorenz, Volker; Liebing, Phil; Engelhardt, Felix; Stein, Franziska; Kühling, Marcel; Schröder, Lea; Edelmann, Frank T. (2019-01-02). "Review: the multicolored coordination chemistry of violurate anions". Journal of Coordination Chemistry. 72 (1): 1–34. doi:10.1080/00958972.2018.1560431. ISSN 0095-8972. S2CID 104419386.
  11. ^ Muraca, R.F. (1955). "Photometric determination of sodium in blood serum with violuric acid". Chemist Analyst. 44: 38–42 – via CAB Direct.