Biuret

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Not to be confused with burette. ‹See Tfd›
Biuret
Skeletal formula of biuret
Ball-and-stick model of biuret
Spacefill model of biuret
Identifiers
CAS number 108-19-0 YesY
PubChem 7913
ChemSpider 7625 YesY
EC number 203-559-0
KEGG C06555 YesY
MeSH Biuret
ChEBI CHEBI:18138 YesY
Beilstein Reference 1703510
Gmelin Reference 49702
3DMet B00969
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C2H5N3O2
Molar mass 103.08 g mol−1
Appearance White crystals
Odor Odourless
Thermochemistry
Specific
heat capacity
C
131.3 J K−1 mol−1
Std molar
entropy
So298
146.1 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
−565.8–−561.6 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−940.1–−935.9 kJ mol−1
Hazards
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word WARNING
GHS hazard statements H315, H319, H335
GHS precautionary statements P261, P305+351+338
EU classification Irritant Xi
R-phrases R36/37/38
S-phrases S26, S36
Related compounds
Related compounds urea, triuret, cyanuric acid
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Biuret is a chemical compound with the chemical formula H2NC(O)NHC(O)NH2. It is the result of condensation of two molecules of urea and is a problematic impurity in urea-based fertilizers. This white solid is soluble in hot water. 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.[2][3][4][5]

The term "biuret" also describes a family of organic compounds with the functional group -(HN-CO-)2N-. Thus dimethyl biuret is CH3HN-CO-NR'-CO-NHCH3. A variety of organic derivatives are possible.

Preparation[edit]

The parent compound can be prepared by heating urea above the melting point at which temperature ammonia is expelled:[6]

2 CO(NH2)2 → H2N-CO-NH-CO-NH2 + NH3

In general, organic biurets are prepared by trimerization of isocyanates. For example the trimer of 1,6-hexamethylene diisocyanate is also known as HDI-biuret.

Applications[edit]

Biuret is also used as a non-protein nitrogen source in ruminant feed,[7] where it is converted into protein by gut microorganisms.[8] It is less favored than urea, due to its higher cost and lower digestibility[9] but this characteristic also slows down its digestion and so decreases the risk of ammonia toxicity.[9][10]

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.

Related compounds[edit]

References[edit]

  1. ^ a b c d e Scifinder, version 2007.1; Chemical Abstracts Service: Columbus, OH; RN 108-19-0 (accessed June 15, 2012)
  2. ^ Wiedemann, G. (1848). "Ueber ein neues Zersetzungsproduct des Harnstoffs" [On a new decomposition product of urea]. Annalen der Physik 150 (5): 67–84. doi:10.1002/andp.18491500508. 
  3. ^ Wiedemann, G. (1847). "Neues Zersetzungsproduct des Harnstoffs" [New decomposition product of urea]. Journal für praktische Chemie 42 (3–4): 255–256.  This notice reports that biuret reacts with alkaline copper sulfate to produce a red solution -- the so-called "Biuret test"
  4. ^ 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. 
  5. ^ 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. 
  6. ^ Meessen, J. H.; Petersen, H. (2005), "Urea", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a27_333 
  7. ^ Beef cattle feed, Encyclopædia Britannica Online
  8. ^ Kunkle, B.; Fletcher, J.; Mayo, D. (2013). "Florida Cow-Calf Management, 2nd Edition - Feeding the Cow Herd". IFAS Extension, University of Florida. Publication #AN117. 
  9. ^ 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. PMID 5391979. 
  10. ^ Fonnesbeck, P. V.; Kearl, L. C.; Harris, L. E. (1975). "Feed Grade Biuret as a Protein Replacement for Ruminants. A Review". Journal of Animal Science 40 (6): 1150–1184.