See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Concept: The carbylamine reaction (isocyanide test) is a named reaction in organic chemistry where a primary amine reacts with chloroform (CHCl3) in the presence of ethanolic KOH to form an isocyanide (carbylamine). Step 1: Identify the reagents. The reactants are a primary amine (R-NH2), chloroform (CHCl3), and ethanolic KOH (base). Step 2: Understand the mechanism. Ethanolic KOH dehydrohalogenates chloroform to generate dichlorocarbene (:CCl2), a highly reactive intermediate. The dichlorocarbene reacts with the primary amine, and after successive loss of HCl (aided by KOH), an isocyanide (R-NC) is formed. Step 3: The overall reaction is: R-NH2 + CHCl3 + 3KOH → R-NC + 3KCl + 3H2O. The product R-NC is an isocyanide (carbylamine), characterized by its extremely foul smell. Step 4: Why other options fail: - (b) an aldehyde: Aldehydes are not formed in this reaction; no oxidation or hydration of a triple bond occurs here. - (c) a cyanide: A cyanide would be R-CN (nitrile), where carbon is bonded to nitrogen at the terminal end. In isocyanides, nitrogen is the connecting atom to R (R-N≡C), making them structural isomers of nitriles. The product here is specifically an isocyanide, not a cyanide. - (d) an alcohol: No alcohol is produced; KOH acts as a base, not a nucleophile introducing -OH into the amine carbon chain in this context. This reaction is also used as a qualitative test for primary amines, as the isocyanide produced has a very offensive odor. Therefore, the correct answer is A.