AMIDES. 



The amides are derivatives of fatty acids, dibasic acids, etc., in 

 which the hydroxyl of the carboxyl group or groups has been replaced 

 by an amino (NH 2 ) group. They may also be regarded as derived 

 from ammonia by the replacement of one of the hydrogen atoms by 

 an acid radicle, e.g. : 



/ NH 2 COOH CO . NH 2 



H.CO.NH 2 CO | | 



\NH 2 CO.NH 2 CO.NH 2 



Formamide. Carbamide Oxamic Oxamide. 



or acid, 

 urea. 



Amides are found in nature both in animals and plants : in plants 

 asparagine, the monamide of aspartic acid (p. 138), is perhaps the 

 most common, in animals urea. Urea is formed by the liver (and 

 other organs) from ammonia and carbon dioxide. It circulates in 

 the blood and is excreted by the kidney. Urine contains about 

 2 per cent, or 30 gm. per day. 



The amides resemble the primary amines in containing an amino 

 (NH 2 ) group, but differ from them in other respects. 



Preparation. 



Amides are prepared by several methods : 



(I) by the distillation of the ammonium salt of an acid : 



CH 3 . COONH 4 = H 2 + CH 3 . CO . NH 2 



(2] by the action of ammonia upon an acid chloride : 



^/Cl ^NH, 



CO + aNH 3 = CO + 2HC1. 

 ^Cl ^NH 2 



(3) by the action of ammonia upon an acid anhydride : 



CH 3 .CO 



>O + aNH 3 = CH 3 . CO . NH 2 + CH 3 . COONH 4 

 CH 3 . CO/ 



(4) by the action of ammonia upon an ester : 



COOC 2 H 5 CO . NH 2 



+ 2 NH 3 = | + 2 C 2 H 5 OH. 



COOC 2 H 5 CO . NH 2 



Properties. 



The amides, except formamide which is liquid, are white crystalline 

 solids generally easily soluble in water and alcohol. The substitution 

 of a hydrogen atom in ammonia by acid radicles decreases its basic 

 character ; the amides are consequently neutral in reaction, but {Jiey 

 are weak bases and form salts only with strong acids. They are un- 

 stable compounds and are readily decomposed into their constituent 

 acid and ammonia by boiling with acid or alkali. 



129 5 



