{{Distinguish|Burette|Beirut}} {{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 455517063 | Name = | ImageFile = Biuret.jpg | ImageFile_Ref = {{chemboximage|correct|??}} | ImageSize = 160 | ImageAlt = Freshly recrystallised biuret | ImageFile1 = Biuret struct.svg | ImageFile1_Ref = {{chemboximage|correct|??}} | ImageSize1 = 160 | ImageAlt1 = Skeletal formula of biuret | ImageFile2_Ref = {{chemboximage|correct|??}} | ImageSize2 = 160 | ImageAlt2 = Space-filling model of the biuret molecule | PIN = 2-Imidodicarbonic diamide<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = The Royal Society of Chemistry | date = 2014 | location = Cambridge | page = 866 | doi = 10.1039/9781849733069 | isbn = 978-0-85404-182-4 | last1 = Favre | first1 = Henri A. | last2 = Powell | first2 = Warren H. }}</ref> | SystematicName = | OtherNames = {{ubl|Biuret<ref name=iupac2013/>|Allophanamide<ref name=SciFinder>Scifinder, version 2007.1; Chemical Abstracts Service: Columbus, OH; RN 108-19-0 (accessed June 15, 2012)</ref>|Carbamylurea<ref name=SciFinder/>|Allophanic acid amide<ref name=SciFinder/>|Allophanimidic acid<ref name=SciFinder/>|''N''-carbamoylaminomethanamide{{citation needed|date=June 2012}}|Ureidoformamide<ref name=SciFinder/>|Imidodicarbonic diamide{{citation needed|date=May 2012}}|Diurea{{citation needed|date=January 2016}}}} | IUPACName = | Section1 = {{Chembox Identifiers | CASNo = 108-19-0 | CASNo_Ref = {{cascite|correct|CAS}} | UNII_Ref = {{fdacite|changed|FDA}} | UNII = 89LJ369D1H | PubChem = 7913 | ChemSpiderID = 7625 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | EINECS = 203-559-0 | KEGG = C06555 | KEGG_Ref = {{keggcite|correct|kegg}} | MeSHName = Biuret | ChEBI = 18138 | ChEBI_Ref = {{ebicite|correct|EBI}} | Beilstein = 1703510 | Gmelin = 49702 | 3DMet = B00969 | SMILES = NC(=O)NC(N)=O | StdInChI = 1S/C2H5N3O2/c3-1(6)5-2(4)7/h(H5,3,4,5,6,7) | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = OHJMTUPIZMNBFR-UHFFFAOYSA-N | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} }} | Section2 = {{Chembox Properties | Formula = {{chem2|HN(CONH2)2}} | C=2|H=5|N=3|O=2 | Appearance = White crystals | Odor = Odourless | Density = 1.467 g/cm<sup>3</sup> | MeltingPt = 190 °C (decomposes) }} | Section3 = {{Chembox Thermochemistry | DeltaHf = (−565.8) – (−561.6) kJ/mol | DeltaHc = (−940.1) – (−935.9) kJ/mol | Entropy = 146.1 J/(mol·K) | HeatCapacity = 131.3 J/(mol·K) }} | Section4 = {{Chembox Hazards | GHSPictograms = {{gHS exclamation mark}} | GHSSignalWord = '''WARNING''' | HPhrases = {{h-phrases|315|319|335}} | PPhrases = {{p-phrases|261|305+351+338}} }} | Section5 = {{Chembox Related | OtherCompounds = {{ubl|urea|triuret|cyanuric acid}} }} | Section6 = }} '''Biuret''' ({{IPAc-en|ˈ|b|j|u|r|ɛ|t|}} {{respell|BYUR|ret}}) is a chemical compound with the chemical formula {{chem2|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 {{chem2|R^{1}R^{2}N\sC(\dO)\sN(R^{3})\sC(\dO)\sNR^{4}R^{5}|}}, where {{chem2|R^{1}, R^{2}, R^{3}, R^{4} and R^{5}|}} 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== 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:<ref name=Ullmann>{{ Ullmann | author = Meessen, J. H. | author2 = Petersen, H. | title = Urea | doi = 10.1002/14356007.a27_333 }}</ref> :{{chem2|2 CO(NH2)2 → HN(CONH2)2 + NH3}} Under related conditions, pyrolysis of urea affords triuret {{chem2|O\dC(\sN(H)\sC(\dO)\sNH2)2}}.<ref name=Ullmann/> 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.<ref>{{cite journal|journal=Acta Crystallogr.|year=1961|volume=14|issue=4|pages=345–352|doi=10.1107/S0365110X61001194 |title=The Crystal Structure of Biuret Hydrate |author=E. W. Hughes |author2=H. Yakel |author3=H. C. Freeman|doi-access=free}}</ref> 220 px|thumb|left|Structure of biuret in the solid state (blue = N, red = O, gray = C, cyan = H).
==Use as feed== Biuret is used as a non-protein nitrogen source in ruminant feed,<ref>[http://www.britannica.com/eb/article-67947/livestock-farming Beef cattle feed], ''Encyclopædia Britannica'' Online</ref> where it is converted into protein by gut microorganisms.<ref>{{cite web | url = http://edis.ifas.ufl.edu/AN117 | author1 = Kunkle, B. | author2 = Fletcher, J. | author3 = Mayo, D. | year = 2013 | title = Florida Cow-Calf Management, 2nd Edition - Feeding the Cow Herd | publisher = IFAS Extension, University of Florida | id = Publication #AN117 | access-date = 2008-01-15 | archive-date = 2019-05-13 | archive-url = https://web.archive.org/web/20190513085424/http://edis.ifas.ufl.edu/an117 | url-status = dead }}</ref> It is less favored than urea, due to its higher cost and lower digestibility<ref name="oltjen">{{cite journal | author1 = Oltjen, R. R. | author2 = Williams, E. E. | author3 = Slyter, L. L. | author4 = Richardson, G. V. | title = Urea versus biuret in a roughage diet for steers | journal = Journal of Animal Science | year = 1969 | volume = 29 | issue = 5 | pages = 816–822 | pmid = 5391979 | url = http://www.journalofanimalscience.org/content/29/5/816 | doi = 10.2527/jas1969.295816x | access-date = 2013-10-22 | archive-date = 2021-01-12 | archive-url = https://web.archive.org/web/20210112220628/https://www.asas.org/publications/jas/content/29/5/816 | url-status = dead | url-access = subscription }}</ref> but the latter characteristic also slows down its digestion and so decreases the risk of ammonia toxicity.<ref name="oltjen"/><ref>{{cite journal | last1=Fonnesbeck | first1=Paul V. | last2=Kearl | first2=Leonard C. | last3=Harris | first3=Lorin E. | title=Feed Grade Biuret as a Protein Replacement for Ruminants. A Review | journal=Journal of Animal Science | publisher=Oxford University Press (OUP) | volume=40 | issue=6 | date=1975 | issn=0021-8812 | doi=10.2527/jas1975.4061150x | pages=1150–1184 | url=https://academic.oup.com/jas/article-abstract/40/6/1150/4699012| url-access=subscription }}</ref>
==Biuret test== 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== 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.<ref>{{ cite journal | author = Wiedemann, G. | title = Ueber ein neues Zersetzungsproduct des Harnstoffs |trans-title=On a new decomposition product of urea | journal = Annalen der Physik | volume = 150 | issue = 5 | pages = 67–84 | year = 1848 | doi = 10.1002/andp.18491500508 | bibcode = 1848AnP...150...67W | url = https://zenodo.org/record/1423618 }}</ref><ref>{{ cite journal | author = Wiedemann, G. | title = Neues Zersetzungsproduct des Harnstoffs |trans-title=New decomposition product of urea | journal = Journal für Praktische Chemie | year = 1847 | volume = 42 | issue = 3–4 | pages = 255–256 | url = https://books.google.com/books?id=WNQPAAAAQAAJ&pg=PA255 | doi = 10.1002/prac.18470420134 | url-access = subscription }} This notice reports that biuret reacts with alkaline copper sulfate to produce a red solution – the so-called "Biuret test"</ref><ref>{{ cite journal | author = Wiedemann, G. | title = Ueber eine neue, aus dem Harnstoff entstehende Verbindung |trans-title=On a new compound arising from urea | journal = Journal für Praktische Chemie | year = 1848 | volume = 43 | issue = 5 | pages = 271–280 | doi = 10.1002/prac.18480430133 | url = https://books.google.com/books?id=hgYwAAAAIAAJ&pg=PA271 }}</ref><ref>{{ cite journal | author = Wiedemann, G. | year = 1848 | title = Biuret. Zersetzungsprodukt des Harnstoffs |trans-title=Biuret: decomposition product of urea | journal = Justus Liebig's Annalen der Chemie | volume = 68 | issue = 3 | pages = 323–326 | doi = 10.1002/jlac.18480680318 }}</ref>
==Related compounds== * Cyanuric acid * Allophanic acid, the carboxylic acid derivative of biuret
==References== {{reflist}}
Category:Ureas Category:Functional groups