Possible reaction mechanism

The chemical formula for urea is CO(NH₂)₂. Here two –NH₂ groups are directly attached to carbonyl group i.e. C=O. Actually it looks that urea should be a base due to presence of lone pair of electron on nitrogen atom. But due to electronegative nature of carbonyl group, it becomes a neutral compound. However, when urea gets reacted in presence of enzyme urease or at high temperature then there is conversion of urea into ammonia by hydrolysis as shown in Fig. 1.

Conversion of urea to ammonia by hydrolysis.

In first step of reaction, there is break down of Urea into Ammonia and isocyanate ions as byproduct. This reaction is reversible at pH less than 5 and greater than 12. In second reaction, Isocyanate get hydrolyze to produce Ammonia and carbon dioxide is evolved as a byproduct. Urea hydrolysis is higher at temperature 35 °C than at 15 °C. The effect of pH is only observed between the pH 6 and pH 8³².