Preparation and Properties of Urea

Urea is prepared industrially by heating ammonium carbamate under pressure at 130°. 

The historical S3mthesis of urea by heating potassium cyanate and ammonium sulfate is analogous to the synthesis of substituted ureas from amines and the cyanate  

Substituted urea may also be formed by heating urea with an amine salt. Urea in aqueous solutions is in equilibrium with a small amount of ammonium cyanate as shown in equation (2), which reacts with the amine salt in the same manner as potassium cyanate is shown to react in equation (3). 

Urea is a diamide, and as such it exhibits the general properties of its functional groups. Its acyl derivatives are called ureides. A number of synthetic drugs are cyclic ureides. Uric acid is a complex cyclic ureide. On oxidation with nitric acid it forms a molecule of urea and alloxan. The latter may be regarded as derived from 

2 ml of dilute nitric acid, and press to drain the mother liquor. 

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