AROMATIC COMPOUNDS 247 



About I c.c. of aniline is placed in about 10 c.c. of dilute hydro- 

 chloric acid. On shaking the aniline dissolves. On making alkaline 

 with about 10 c.c. of caustic soda the aniline separates in oily drops. 



The salt of the aniline is obtained by evaporating its solution in 

 the corresponding amount of acid until it crystallises. 



Reactions. 



(1) Aniline is readily brominated : 



A solution of aniline in water is prepared as above and bromine 

 water is added ; a pinkish precipitate, which becomes grey-green, of 

 tribromaniline is formed : 



C 8 H 5 NH 2 + 3 Br 2 = C 6 H 2 Br 3 . NH 2 + 3HBr. 



(2) In aqueous solution (above) it is readily oxidised by bleaching 

 powder, giving a violet coloration. 



(3) It turns black when it is oxidised with potassium bichromate 

 and dilute sulphuric acid. 



(4) A blue colour is formed if a drop of aniline be mixed with 

 2 or 3 drops of strong sulphuric acid and the paste so formed stirred 

 with a few drops of potassium bichromate solution. 



(5) It gives the carbylamine reaction with chloroform and alcoholic 

 potash (p. 61). 



Acetanilide. C 6 H 5 . NH . OC . CH 3 . 



Aniline is acylated by treatment with acetyl chloride, glacial acetic 

 acid or acetic anhydride : 



C 6 H 6 . NH 2 + HOOC . CH 3 = H 2 O + C 6 H 5 . NH OC . CH 3 . 



Preparation. 



2 c.c. of aniline are boiled under a reflux air condenser with 4 c.c. of 

 glacial acetic acid for an hour. The mixture is poured into water. 

 Acetanilide is precipitated and is recrystallised from boiling water. 



Properties. 



Acetanilide is a white crystalline solid which melts at 114 and is 

 used in medicine under the name of antifebrin. It is readily decomposed 

 by boiling with acids or alkalies : 



C 6 H B NH OC . CH 3 + H 2 O = C 6 H 5 . NH 2 + HOOC . CH 3 . 



Thus, on boiling about 2 gm. of acetanilide with about 5 c.c. of 

 concentrated hydrochloric acid for a few minutes and pouring the solu- 

 tion into water, a clear solution is obtained. On adding excess of caustic 

 soda, the aniline is precipitated and may be extracted with ether and 

 tested for as above. 



