Identify the compound that will react with Hinsberg's reagent to give a solid which dissolves in alkali.
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Answer
(3) [figure]
Solution
Hinsberg's reagent is benzenesulphonyl chloride, C6H5SO2Cl.
(3) Ethanamine is a primary amine:
C6H5SO2Cl + H2N-C2H5 C6H5SO2NH-C2H5 + HCl
∵ the H atom on N of N-ethylbenzenesulphonamide is strongly acidic (strong electron-withdrawing sulphonyl group) ⇒ the solid dissolves in alkali.
(2) N-Methylethanamine, a secondary amine, gives N,N-dialkylbenzenesulphonamide, which has no H on N ⇒ insoluble in alkali.
(4) Tertiary amine has no H on N ⇒ does not react with Hinsberg's reagent.
(1) Nitroethane is not an amine ⇒ no sulphonamide is formed.
∴ the compound is CH3-CH2-NH2.
Answer: (3)