Violuric acid

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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
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
Safety data sheet Sigma-Aldrich (monohydrate)
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 chemical compound, used to prepare various colored salts. It was discovered in 1863/64 by Adolf Baeyer.[2]

Properties

Chemical

Violuric acid reacts with metals to form brightly colored violurate salts. Even touching the free acid with a metal spatula may cause the formation of violurate salts.

Violuric acid tautomerizes in water from the isonitroso- form to the violet nitroso- form.

Physical

Violuric acid is a yellowish solid, poorly soluble in water.

Availability

Violuric acid is sold by chemical suppliers.

Preparation

Violuric acid can be prepared by acidifying sodium violurate with hydrochloric acid. Sodium violurate can be prepared by adding barbituric acid to a hot aq. solution of sodium nitrite and stir. The sodium salt can be precipitated out of the solution by adding NaCl.[3]

Can also be prepared from from hydroxylamine and alloxan.[4]

Projects

  • Make brightly colored salts

Handling

Safety

There is little data available for its toxicity and environmental effects.

Storage

In closed plastic or glass bottles.

Disposal

No special disposal is required.

References

  1. https://echa.europa.eu/registration-dossier/-/registered-dossier/26979/4/9
  2. Baeyer, A. (1863), Untersuchungen über die Harnsäuregruppe. Justus Liebigs Ann. Chem., 127: 199-236. https://doi.org/10.1002/jlac.18631270214
  3. German thread on violuric acid, https://illumina-chemie.de/viewtopic.php?f=69&t=5502
  4. Guinchard, J. (1899), Ueber die farbigen Salze aus Violursäure und anderen ringförmigen Oximidoketonen. Ber. Dtsch. Chem. Ges., 32: 1723-1741. https://doi.org/10.1002/cber.18990320260

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