Biuret
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| Names | |
|---|---|
| Preferred IUPAC name
2-Imidodicarbonic diamide[1] | |
Other names
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| Identifiers | |
3D model (JSmol)
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| 1703510 | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.003.236 |
| EC Number |
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| 49702 | |
| KEGG | |
| MeSH | Biuret |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| HN(CONH2)2 | |
| Molar mass | 103.081 g·mol−1 |
| Appearance | White crystals |
| Odor | Odourless |
| Density | 1.467 g/cm3 |
| Melting point | 190 °C (decomposes) |
| Thermochemistry | |
Heat capacity (C)
|
131.3 J/(mol·K) |
Std molar
entropy (S⦵298) |
146.1 J/(mol·K) |
Std enthalpy of
formation (ΔfH⦵298) |
(−565.8) – (−561.6) kJ/mol |
Std enthalpy of
combustion (ΔcH⦵298) |
(−940.1) – (−935.9) kJ/mol |
| Hazards | |
| GHS labelling: | |
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| Warning | |
| H315, H319, H335 | |
| P261, P305+P351+P338 | |
| Related compounds | |
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Biuret (/ˈbjurɛt/ BYUR-ret) is a chemical compound with the chemical formula HN(CONH2)2. It is a white solid that is soluble in hot water. A variety of organic derivatives are known. The term "biuret" also describes a family of organic compounds with the chemical formula R1R2N−C(=O)−N(R3)−C(=O)−NR4R5, where R1, R2, R3, R4 and R5 are hydrogen, organyl or other groups. Also known as carbamylurea, it results from the condensation of two equivalents of urea. It is a common undesirable impurity in urea-based fertilizers, as biuret is toxic to plants.
Preparation and structure
[edit]The parent compound can be prepared by heating urea at 150 °C for ~6 hours until it gets slightly cloudy, then recrystallizing from water. After that, it can be recrystallized repeatedly from 2% sodium hydroxide solution and water to finally get base-free crystalline needles of the monohydrate which are free of cyanuric acid. While heating, a lot of ammonia is expelled:[3]
- 2 CO(NH2)2 → HN(CONH2)2 + NH3
Under related conditions, pyrolysis of urea affords triuret O=C(−N(H)−C(=O)−NH2)2.[3] In general, organic biurets (those with alkyl or aryl groups in place of one or more H atoms) are prepared by trimerization of isocyanates. For example, the trimer of 1,6-hexamethylene diisocyanate is also known as HDI-biuret.
In the anhydrous form, the molecule is planar and unsymmetrical in the solid state owing to intramolecular hydrogen bonding. The terminal C–N distances of 1.327 and 1.334 Å are shorter than the internal C–N distances of 1.379 and 1.391 Å. The C=O bond distances 1.247 and 1.237 Å. It crystallizes from water as the monohydrate.[4]
Applications
[edit]Biuret is also used as a non-protein nitrogen source in ruminant feed,[5] where it is converted into protein by gut microorganisms.[6] It is less favored than urea, due to its higher cost and lower digestibility[7] but the latter characteristic also slows down its digestion and so decreases the risk of ammonia toxicity.[7][8]
Biuret test
[edit]The biuret test is a chemical test for proteins and polypeptides. It is based on the biuret reagent, a blue solution that turns violet upon contact with proteins, or any substance with peptide bonds. The test and reagent do not actually contain biuret; they are so named because both biuret and proteins have the same response to the test.
History
[edit]Biuret was first prepared and studied by Gustav Heinrich Wiedemann (1826–1899) for his doctoral dissertation, which was submitted in 1847. His findings were reported in several articles.[9][10][11][12]
Related compounds
[edit]- Cyanuric acid
- Allophanic acid, the carboxylic acid derivative of biuret
References
[edit]- ^ a b Favre, Henri A.; Powell, Warren H. (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. p. 866. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
- ^ a b c d e Scifinder, version 2007.1; Chemical Abstracts Service: Columbus, OH; RN 108-19-0 (accessed June 15, 2012)
- ^ a b Meessen, J. H.; Petersen, H. "Urea". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_333. ISBN 978-3527306732.
- ^ E. W. Hughes; H. Yakel; H. C. Freeman (1961). "The Crystal Structure of Biuret Hydrate". Acta Crystallogr. 14 (4): 345–352. doi:10.1107/S0365110X61001194.
- ^ Beef cattle feed, Encyclopædia Britannica Online
- ^ Kunkle, B.; Fletcher, J.; Mayo, D. (2013). "Florida Cow-Calf Management, 2nd Edition - Feeding the Cow Herd". IFAS Extension, University of Florida. Publication #AN117. Archived from the original on 2019-05-13. Retrieved 2008-01-15.
- ^ a b Oltjen, R. R.; Williams, E. E.; Slyter, L. L.; Richardson, G. V. (1969). "Urea versus biuret in a roughage diet for steers". Journal of Animal Science. 29 (5): 816–822. doi:10.2527/jas1969.295816x. PMID 5391979. Archived from the original on 2021-01-12. Retrieved 2013-10-22.
- ^ Fonnesbeck, Paul V.; Kearl, Leonard C.; Harris, Lorin E. (1975). "Feed Grade Biuret as a Protein Replacement for Ruminants. A Review". Journal of Animal Science. 40 (6). Oxford University Press (OUP): 1150–1184. doi:10.2527/jas1975.4061150x. ISSN 0021-8812.
- ^ Wiedemann, G. (1848). "Ueber ein neues Zersetzungsproduct des Harnstoffs" [On a new decomposition product of urea]. Annalen der Physik. 150 (5): 67–84. Bibcode:1848AnP...150...67W. doi:10.1002/andp.18491500508.
- ^ Wiedemann, G. (1847). "Neues Zersetzungsproduct des Harnstoffs" [New decomposition product of urea]. Journal für Praktische Chemie. 42 (3–4): 255–256. doi:10.1002/prac.18470420134. This notice reports that biuret reacts with alkaline copper sulfate to produce a red solution – the so-called "Biuret test"
- ^ Wiedemann, G. (1848). "Ueber eine neue, aus dem Harnstoff entstehende Verbindung" [On a new compound arising from urea]. Journal für Praktische Chemie. 43 (5): 271–280. doi:10.1002/prac.18480430133.
- ^ Wiedemann, G. (1848). "Biuret. Zersetzungsprodukt des Harnstoffs" [Biuret: decomposition product of urea]. Justus Liebig's Annalen der Chemie. 68 (3): 323–326. doi:10.1002/jlac.18480680318.