See image — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Concept: To identify which test cannot differentiate ethylamine (primary amine) from diethylamine (secondary amine), we analyze each test. Step 1: Hinsberg test - Ethylamine (1° amine) reacts with benzenesulfonyl chloride to give a sulfonamide soluble in NaOH; diethylamine (2° amine) gives a sulfonamide insoluble in NaOH. These give different, distinguishable results. So Hinsberg test CAN differentiate them. Step 2: Carbylamine test - Only primary amines give the foul-smelling isocyanide (carbylamine) on reaction with CHCl3 and KOH. Ethylamine (1°) gives a positive test; diethylamine (2°) gives a negative test. So carbylamine test CAN differentiate them. Step 3: Iodoform test - The iodoform test is used to detect methyl ketones, acetaldehyde, or ethanol (compounds with CH3CO- group or ethanol). Neither ethylamine nor diethylamine contains the required structural feature (CH3-CH(OH)- or CH3CO-) for the iodoform test. Both amines give a negative iodoform test. Therefore, the iodoform test CANNOT differentiate between ethylamine and diethylamine. Step 4: Evaluating option (d) - Since the iodoform test alone (option c) already cannot differentiate them, and both Hinsberg and carbylamine tests can differentiate them, option (d) is incorrect. Therefore, the correct answer is C.