Allophanic acid
# Allophanic acid

Allophanic acid is the organic compound with the formula $H_2NC(O)NHCO_2H.$ It is a carbamic acid, the carboxylated derivative of urea. Biuret can be viewed as the amide of allophanic acid. The compound can be prepared by treating urea with sodium bicarbonate:

    $H_2NC(O)NH_2$ + $NaHCO_3$ → $H_2NC(O)NHCO_2H$ + NaOH

The anionicconjugate base, $H_2NC(O)NHCO_2^−,$ is called allophanate. Salt of this anion have been characterized by X-ray crystallography. The anion allophonate is the substrate for the enzyme allophanate hydrolase.

Allophonate esters arise from the condensation of carbamates.

