Violuric acid

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
CAS Number	87-39-8;
3D model (JSmol)	Interactive image;
ChemSpider	4911386;
ECHA InfoCard	100.001.584
EC Number	201-741-4;
PubChem CID	66599;
UNII	05RFR8AC84;
CompTox Dashboard (EPA)	DTXSID8058954 ;
	InChI 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;
	SMILES C1(=C(NC(=O)NC1=O)O)N=O;
Properties
Chemical formula	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
Solubility in water	0.704 g/100 mL (20 °C)
Solubility	Soluble in alcohols
Vapor pressure	~0 mmHg
Acidity (pKa)	4.7
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Irritant
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	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). Infobox references

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]

Reactions

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

Preparation

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

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

^ "Registration Dossier - ECHA".
^ 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. doi:10.1107/S010827010701743X. PMID 17551193.
^ 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. doi:10.1107/S0108270107044241. PMID 17917236.
^ ^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.
^ Baeyer, Adolf (1863). "Untersuchungen über die Harnsäuregruppe". Annalen der Chemie und Pharmacie. 127 (2): 199–236. doi:10.1002/jlac.18631270214.
^ 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.
^ 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.
^ 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.
^ 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.
^ 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.
^ Muraca, R.F. (1955). "Photometric determination of sodium in blood serum with violuric acid". Chemist Analyst. 44: 38–42 – via CAB Direct.

[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. 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. doi:10.1107/S0108270107044241. PMID 17917236.

[Liebing-4] 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.

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