See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1: Nitration of benzene with HNO3/H2SO4 gives nitrobenzene (PhNO2). Step 2: Reduction with H2/Pd/C converts nitrobenzene to aniline (PhNH2). Step 3: Treatment of aniline with NaNO2/HCl at 0°C gives benzenediazonium chloride (PhN2+Cl-). Step 4: Sandmeyer reaction with CuCN replaces the diazonium group with a cyano group, giving benzonitrile (PhCN). Step 5: Reaction of benzonitrile with MeMgBr (methylmagnesium bromide, a Grignard reagent) adds to the nitrile carbon. The Grignard reagent attacks the electrophilic carbon of the C≡N group, forming an imine salt intermediate (Ph-C(=NMgBr)-CH3). Step 6: Aqueous acid workup (H3O+) hydrolyzes the imine intermediate. The imine (Ph-C(=NH)-CH3) is hydrolyzed under acidic aqueous conditions to give a ketone: Ph-CO-CH3, which is acetophenone. Why other options fail: - (a) Benzoic acid would result from hydrolysis of benzonitrile directly, not Grignard addition. - (c) Phenylacetic acid would require different chemistry (e.g., homologation). - (d) Phenol would result from diazonium hydrolysis, not CuCN/Grignard sequence. The reaction of a nitrile with a Grignard reagent followed by hydrolysis is a classic method for making ketones: RCN + R'MgBr → [RC(=NMgBr)R'] → H3O+ → RCOR'. Here PhCN + CH3MgBr → Ph-CO-CH3 (acetophenone). Therefore, the correct answer is B.