MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

The given reaction is the Hofmann elimination of a quaternary ammonium salt. Substrate A reacts with moist Ag _2 O to form a quaternary ammonium hydroxide, which on heating undergoes -elimination to yield an alkene, a tertiary amine, and water. The products obtained are CH _3 CH _2 N(CH _3)_2 (N,N-dimethylethylamine) and CH _2= CH _2 (ethene). The quaternary ammonium ion must contain the alkyl groups present in the tertiary amine along with the alkyl group that underwent elimination to form the alkene. Combining an ethyl group (from ethene) with N,N-dimethylethylamine gives the diethyldimethylammonium ion, [( CH _3 CH _2)_2 N ( CH _3)_2]^+. Since moist Ag _2 O is used in the first step to replace a halide ion with a hydroxide ion, substrate A must be a halide. Therefore, substrate A is diethyldimethylammonium halide. Answer: Diethyldimethylammonium halide