Question

Which of the following compounds will dissolve in an alkali solution after it has undergone reaction with Hinsberg reagent?

• A.
  $(C_6{H}_5{)}_{2}NH$
• B.
  $(C{H}_3{)}_{3}N$
• C.
  $C{H}_{3}N{H}_2$
• D.
  $C_6{H}_{5}NHC{H}_3$

Answer 1

The correct option is C

$C{H}_{3}N{H}_2$
Primary and secondary amines react with Hinsberg reagent. Further, only sulphonamide formed by primary amines then react with alkali because of presence of one acidic hydrogen on the nitrogen atom.

Primary amine reacts with benzene sulphonyl chloride forming N-alkyl benzenesulphonamide. It is simple acid-base type of reaction. Amine has lone pairs of electron on N so it acts as a base and attacks the electrophilic centre of reagent. Attack of $N{H}_2$ helps in removal of $Cl$ and product is sulphonamide. The primary amine sulphonamide is soluble in alkali.

Secondary amine reacts with benzenesulphonyl chloride forming N, N-dialkyl benzenesulphonyl chloride forming N, N-dialkyl benzenesulphonamide, which is insoluble in alkali.

So, (c) is the correct answer because it is a primary amine.