Allophanic acid

Allophanic acid
Names
	Preferred IUPAC name Carbamoylcarbamic acid
Identifiers
CAS Number	625-78-5;
3D model (JSmol)	Interactive image;
Beilstein Reference	1756623
ChEBI	CHEBI:9889;
ChemSpider	132943;
KEGG	C01010;
PubChem CID	150833;
UNII	0W5I7B2C2H;
CompTox Dashboard (EPA)	DTXSID20211550 ;
	InChI InChI=1S/C2H4N2O3/c3-1(5)4-2(6)7/h(H,6,7)(H3,3,4,5) Key: AVWRKZWQTYIKIY-UHFFFAOYSA-N;
	SMILES C(=O)(N)NC(=O)O;
Properties
Chemical formula	C2H4N2O3
Molar mass	104.065 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Allophanic acid is the organic compound with the formula H₂NC(O)NHCO₂H. It is a carbamic acid, the carboxylated derivative of urea. Biuret can be viewed as the amide of allophanic acid.

Treating urea with sodium bicarbonate is claimed to give allophanic acid:^[1]

H₂NC(O)NH₂ + NaHCO₃ → H₂NC(O)NHCO₂H + NaOH

Although allophanic acid per se may not have been purified, its conjugate base, H₂NC(O)NHCO₂⁻, allophanate is well known. Salts of this anion have been characterized by X-ray crystallography.^[2]^[3] The allophanate anion is the substrate for the enzyme allophanate hydrolase.

Allophanate esters arise from the condensation of carbamates.

References

↑ Karachinskii, S. V.; Dragalov, V. V.; Chimishkyan, A. L.; Tsvetkov, V. Yu. (1987). "Reaction of urea with alkali metal carbonates". Zhurnal Organicheskoi Khimii. 23: 93–6.
↑ Mak, Thomas C. W.; Yip, Wai Hing; Li, Qi (1995). "Novel Hydrogen-Bonded Host Lattices Built of Urea and the Elusive Allophanate Ion". Journal of the American Chemical Society. 117 (48): 11995–11996. doi:10.1021/ja00153a022.
↑ Li, Qi; Mak, Thomas C. W. (1996). "A Novel Inclusion Compound Consolidated by Host-host and Host-guest Hydrogen Bonding: (2-hydro-xyethyl)trimethylammonium Ions Included in a Channel Host Lattice Built of Urea Molecules and Allophanate Ions". Supramolecular Chemistry. 8: 73–80. doi:10.1080/10610279608233970.

[1] Karachinskii, S. V.; Dragalov, V. V.; Chimishkyan, A. L.; Tsvetkov, V. Yu. (1987). "Reaction of urea with alkali metal carbonates". Zhurnal Organicheskoi Khimii. 23: 93–6.

[2] Mak, Thomas C. W.; Yip, Wai Hing; Li, Qi (1995). "Novel Hydrogen-Bonded Host Lattices Built of Urea and the Elusive Allophanate Ion". Journal of the American Chemical Society. 117 (48): 11995–11996. doi:10.1021/ja00153a022.

[3] Li, Qi; Mak, Thomas C. W. (1996). "A Novel Inclusion Compound Consolidated by Host-host and Host-guest Hydrogen Bonding: (2-hydro-xyethyl)trimethylammonium Ions Included in a Channel Host Lattice Built of Urea Molecules and Allophanate Ions". Supramolecular Chemistry. 8: 73–80. doi:10.1080/10610279608233970.

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