question_answer 16)

Write short notes on the following : (i) Carbylamine reaction (ii) Diazotization (iii) Hofmann's bromamide reaction (iv) Coupling reaction (v) Ammonolysis (vi) Acetyiation (vii) Gabriel phthalimide synthesis.  

Answer:

(i) Carbylamine reactionWhen aliphatic and aromatic primary amines are heated with chloroform, and ethanolicpotassium hydroxide, carbylamines or isocyanides are formed.These substances produced have foul smell, Secondary and tertiary amines do not give this reaction. This reaction is used todetect primary amines. (ii) Diazotization Aromatic amines react with nitrous acid at lowtemperatures (273-278K) to form diazonium salts. This reaction iscalled diazotization reaction. Note When primary aliphatic amines react with nitrous acid, aliphaticdiazonium salts are formed (Unstable), which liberate nitrogen gas and alcohols. (iii) Hofmann's bromamide reactionThis is a method used forconverting primary amide into primary amine. An amide is treated with bromine in an aqueous or ethanolicsolution of sodium hydroxide. The amine so formed contains onecarbon less than that present in the amide. e.g., (iv) Coupling reaction When diazonium salts react with phenols oraromatic amines they form azo compounds of general formula,. This reaction is called coupling reaction. Thereaction takes place in alkaline medium (pH 9 to 10) e.g. e.g., (a) (b) (v) Ammonolysis The process of cleavage of C?X bond by ammonia molecule is known as ammonolysis.   (vi) AcetylationThe process in which acetyl group isintroduced in a molecule, is called acetylation, Reagents used forthis purpose are acetyl chloride or acetic anhydride.   (vii) Gabriel phthalimide synthesisThis method is used for thepreparation of aliphatic primary amines. Phthalimide on reactionwith ethanolic potassium hydroxide forms potassium salt ofphthalimide. This potassium salt on heating with alkyl halidefollowed by alkaline hydrolysis produces primary amine.