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

  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.
Allikas: https://en.wikipedia.org/wiki/Allophanate
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