Which of the following amines forms a sulfonamide precipitate with Hinsberg's reagent (benzenesulpho — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Hinsberg's reagent reacts with primary ($1^\circ$) and secondary ($2^\circ$) amines to form sulfonamides. Primary amines form N-alkylbenzenesulphonamides which have an acidic hydrogen and are soluble in aqueous $NaOH$. Secondary amines (like N-methylaniline) form N,N-dialkylbenzenesulphonamides which lack an acidic hydrogen and are thus insoluble in alkali. Tertiary amines do not react.