Which of the following is known as Hinsberg's reagent?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Benzenesulphonyl chloride
Hinsberg’s reagent is benzenesulphonyl chloride, \( \ce{C6H5SO2Cl} \). It is used to distinguish primary, secondary and tertiary amines:
Primary amine: gives an N-alkylbenzenesulphonamide, which still has an acidic N–H and so dissolves in alkali.
\( \displaystyle \ce{C6H5SO2Cl + H2N-R -> C6H5SO2NHR + HCl} \)
Secondary amine: gives an N,N-dialkylbenzenesulphonamide with no N–H, which is insoluble in alkali.
\( \displaystyle \ce{C6H5SO2Cl + HNR2 -> C6H5SO2NR2 + HCl} \)
Tertiary amine: has no N–H and does not react.
NCERT (2026-27 edition):
Reaction with Arylsulphonyl Chloride – “Benzenesulphonyl chloride (C6H5SO2Cl), which is also known as Hinsberg’s reagent, reacts with primary and secondary amines to form sulphonamides.”
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | 21-05 S1 | 19-07 S1 | – | – |