130 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Acetamide. 



Preparation. 



Acetamide is usually prepared by distilling ammonium acetate. About 

 50 gm. are melted in a basin and poured into a distilling flask attached to a 

 wide air condenser. Water, acetic acid and ammonia first pass over on heating, 

 but at about 180 acetamide commences to distil. It solidifies in the receiver. 

 A better yield is obtained if, previous to the distillation, the ammonium 

 acetate be heated in a sealed tube to 200 for 5 hours. 



Acetamide is more easily prepared by mixing together 5 c.c. of 

 ethyl acetate and 5 c.c. of strong ammonia (sp. gr. -880) in a small 

 flask, closing the flask and allowing it to stand in a warm place for 

 some time. The two layers gradually form a single homogeneous 

 solution. The liquid is' fractionally distilled : ammonia, alcohol and 

 water pass over first and subsequently acetamide, which solidifies. 



Properties and Reactions. 



Acetamide is a white crystalline solid which melts at 82 and boils 

 at 222. It is easily soluble in water, alcohol and ether. It forms a 

 salt with hydrochloric acid when the gas is passed into its solution in 

 ether ; the salt is decomposed by water. 



(1) On boiling a solution of acetamide (about 50 c.c.) with an 

 excess of caustic soda, ammonia is evolved, recognisable by its smell 

 and action on red litmus paper. The boiling is continued until 

 ammonia is no longer produced, and the solution is tested for acetic 

 acid by carefully neutralising and adding ferric chloride (p. 97). 



(2) Acetamide is also hydrolysed by heating with acid in the same 

 way; the ammonia may be detected by adding excess of magnesium 

 oxide and boiling ; the acid by neutralising and testing with ferric 

 chloride : 



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



(3) On adding dilute hydrochloric acid and a few drops of sodium 

 nitrite solution to a solution of acetamide, an effervescence of nitrogen 



occurs : 



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



Acetic acid is formed and may be detected in the usual manner. 

 This reaction is typical of all organic compounds containing the 

 NH 2 group (compare primary amines and amino acids). 



Oxamide. 



Preparation. 



Oxamide is precipitated on adding excess of ammonia to ethyl oxal- 

 ate (i c.c). The precipitate is filtered off, washed with water and dried. 



Properties and Reactions. 



Oxamide is a white solid almost insoluble in water. 



On boiling it for some time with caustic soda, it gradually dissolves 

 forming sodium oxalate and at the same time ammonia is evolved. 



