See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: Grignard reagents react with nitriles to give ketones after hydrolysis. Step 1: Identify the transformation. PhCN (benzonitrile) must be converted to PhCOCH3 (acetophenone). This requires adding a methyl group and converting the CN to a C=O, net result being insertion of a CH3CO- group on the phenyl ring — equivalently, the nitrile carbon becomes the carbonyl carbon and a methyl group is added. Step 2: Reaction of PhCN with CH3MgBr. The Grignard reagent (CH3MgBr) acts as a nucleophile and adds to the electrophilic carbon of the nitrile group (C≡N). The nitrogen lone pair attacks magnesium, forming an imine-magnesium salt intermediate: Ph-C(=NMgBr)-CH3. Step 3: Hydrolysis. Upon aqueous workup (hydrolysis), the imine salt (Ph-C(=NH)-CH3) is hydrolyzed to give the ketone PhCOCH3 (acetophenone) and NH3. The C=NH is converted to C=O. Step 4: Why other options fail. - Option (b): I2/NaOH is a haloform reaction condition and CH3I is an alkylating agent; these do not convert a nitrile to a methyl ketone. - Option (c): Dil. H2SO4 hydrolyzes PhCN to PhCOOH (benzoic acid), not to PhCOCH3. Subsequent reaction with CH2N2 (diazomethane) would give the methyl ester PhCOOCH3, not the ketone PhCOCH3. - Option (d): LAH reduces PhCN to PhCH2NH2 (benzylamine), an amine, not a carbonyl compound. Subsequent CH3I would alkylate the amine nitrogen, not give the ketone. Therefore, the correct answer is A.