(a) Acyl derivatives of urea are called ureides. They are of two types:
(i) Simple ureides : These are obtained by the reaction of acid halides and urea. Acetyl urea is the example of this class.
(ii) Cyclic ureides : These are obtained by the reaction of dicarboxylic acid or their derivatives and urea. Barbituric acid is the example of this class.
(b) Barbiturates are the derivatives of barbituric acid in which two hydrogen atom of `CH_(2)` group have been replaced by alkyl or aryl groups. Examples are :
These are used as sedatives.
(c ) Urea is estimated by hypobromite method. A known volume of urea solution is treated with sodium hypobromite solution containing NaOH. The evolved carbon dioxide is absorbed by NaOH and the volume of nitrogen evolved measured in the nitrometer. From the volume of nitrogen, the amount of urea in the sample can be determined.
