UREIDES. 



In the same way as ammonia forms amides with acids so also 

 does urea form ureides. Ureides are therefore derivatives of urea with 

 acid radicles. 



A. UREIDES OF MONOBASIC ACIDS, e.g. acetyl urea. 



These are obtained by the action of acid chlorides, or acid anhydrides, 

 upon urea : 



CH 3 . CO . C1 + H a N . CO . NH 2 = HC1 + CH 3 . CO NH . CO . NH 2 . 



They are solid compounds. Acetyl urea forms long silky needles which 

 melt at 214 and which are not easily soluble in cold water or alcohol. 

 They are neutral in reaction and do not form salts with acids. 



Like amides they are easily decomposed by hydrolysis, especially by 

 alkalies and are converted into their constituents : 



CH 3 . CO NH . CO . NH 2 + H 2 O = CH 3 . COOH + H 2 N . CO . NH 2 . 



The urea may be decomposed into ammonia and carbon dioxide. 

 Diacetyl urea, CH 3 . CO NH . CO . NH CO . CH 3 , is formed by the 

 action of carbonyl chloride upon acetamide. 



B. UREIDES OF HYDROXY AND ALDEHYDE ACIDS. 



Two classes of ureides are formed with these acids, an open chain 

 compound such as hydantoic acid, and a closed chain compound (a 

 cyclic ureide) such as hydantoin. Both these compounds are ureides 

 of glycollic acid : 



CH a HN CH 2 HN 



\ I X 



CO /CO 



CO HN 

 COOH NH 2 



Hydantoic acid or Hydantoin. 



glycoluric acid. 



Hydantoic Acid. 



Hydantoic acid is obtained from hydantoin by boiling it with baryta 

 water. It may be synthesised from glycine sulphate and potassium cyanate, 

 a reaction analogous to the synthesis of urea : 

 CH 2 .NH 2 .HOCN CH 2 .NH 



CO 



COOH COOH NH 2 . 



Hydantoic acid is a white solid easily soluble in water and alcohol. It 

 is converted into glycine, carbon dioxide and ammonia on heating with 

 hydriodic acid. 



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