Answer the question on the basis of passage given below:
There are three kinds of amines which are primary, secondary and tertiary amines. These amines may have alkyl group or aryl group or both alkyl and aryl groups. These amines can be distinguished from one another by various chemical tests.
An amine \(A\) on treatment with benzene sulphonyl chloride gives a compound \(B\) which easily dissolves in an alkali; then \(A\) is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Primary amine
Benzenesulphonyl chloride, \( \ce{C6H5SO2Cl} \) (Hinsberg’s reagent), distinguishes the three classes of amines. A primary amine gives an N-alkylbenzenesulphonamide that still has a hydrogen on nitrogen; the strongly electron-withdrawing sulphonyl group makes this H acidic, so the product dissolves in alkali.
\( \ce{C6H5SO2Cl + H2N-C2H5 -> C6H5SO2NHC2H5 + HCl} \)
\( \ce{C6H5SO2NHC2H5 + KOH -> C6H5SO2N^{-}C2H5 K+ + H2O} \) (soluble)
So A is a primary amine.
Why the other options are incorrect
Option (2) Secondary amine — Incorrect. It gives an N,N-dialkylbenzenesulphonamide, \( \ce{C6H5SO2NR2} \), with no H on nitrogen; it is not acidic and is insoluble in alkali.
Option (3) Tertiary amine — Incorrect. It has no H on nitrogen and does not react with benzenesulphonyl chloride.
Option (4) Tetra alkyl ammonium salt — Incorrect. The nitrogen has no lone pair and no hydrogen, so it cannot react with the reagent.
NCERT (2026-27 edition):
Chemical Reactions – …
