Allophanic acid is the

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula H₂NC(O)NHCO₂H. It is a

carbamic acid Carbamic acid, which might also be called aminoformic acid or aminocarboxylic acid, is the chemical compound with the formula . It can be obtained by the reaction of ammonia and carbon dioxide at very low temperatures, which also yields ammoni ...

, the carboxylated derivative of

urea Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...

Biuret Biuret ( ) is a chemical compound with the chemical formula . 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 , ...

can be viewed as the amide of allophanic acid. Treating urea with sodium bicarbonate is claimed to give allophanic acid: :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 X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

.{{cite journal , doi=10.1080/10610279608233970, title=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, year=1996, last1=Li, first1=Qi, last2=Mak, first2=Thomas C. W., journal=Supramolecular Chemistry, volume=8, pages=73–80 The allophanate anion is the substrate for the enzyme

allophanate hydrolase In enzymology, an allophanate hydrolase () is an enzyme that catalyzes the chemical reaction :allophanate + 3 H2O + H+ \rightleftharpoons 2 HCO3− + 2 NH4+ Thus, the two substrates of this enzyme are allophanate (urea-1-carboxylate or ''N''-ca ...

. Allophanate esters arise from the condensation of carbamates.

References

Ureas Functional groups Carbamates