See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Concept: The carbylamine reaction (isocyanide test) is a characteristic reaction of primary amines. When a primary amine is heated with chloroform (CHCl3) and alcoholic KOH, it undergoes the carbylamine reaction to form an isocyanide (also called isonitrile or carbylamine). Step 1: Identify the reactant. Ethylamine (C2H5NH2) is a primary amine. Step 2: Write the reaction. C2H5NH2 + CHCl3 + 3KOH(alc.) → C2H5NC + 3KCl + 3H2O. The product is ethyl isocyanide (C2H5NC). Step 3: Identify the product type. Ethyl isocyanide (C2H5-N≡C:) is an isocyanide. Isocyanides are notorious for their extremely offensive, foul smell, which is the defining feature mentioned in the question. Step 4: Why other options fail. - (a) A secondary amine: No nitrogen-nitrogen bond formation occurs here; the product is an isocyanide, not a secondary amine. - (c) A cyanide: A cyanide would have the structure R-C≡N, whereas the product here is R-N≡C (isocyanide). These are isomers but different compounds. - (d) An acid: No acidic product is formed in this reaction; KOH acts as a base, not a reactant forming an acid product. The carbylamine reaction is used as a test for primary amines and always yields an isocyanide with a characteristic offensive odor. Therefore, the correct answer is A.