See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Concept: The reaction of a vicinal diol (1,2-diol) with H2SO4 involves a pinacol-pinacolone type rearrangement. Under acidic conditions, one OH is protonated and leaves as water, generating a carbocation, which is then stabilized by a 1,2-shift (migration of an aryl or alkyl group from the adjacent carbon bearing the other OH), followed by loss of a proton to give a ketone. Step 1 - Analyze Compound (A): Ph-C(Ph)(OH)-C(CH3)(OH)-CH3 The diol has C1 bearing two Ph groups and OH, and C2 bearing two CH3 groups and OH. Under H2SO4, the OH on C2 is protonated (leaving group), forming a carbocation at C2. This carbocation is then stabilized by migration of one phenyl group from C1 (which already bears the OH that becomes the carbonyl). The product is Ph-C(Ph)(CH3)-C(=O)-CH3, which is product (p). Alternatively, the OH on C1 is protonated and leaves, but C1 already has two Ph groups stabilizing it. Migration of CH3 from C2 to C1 gives Ph-C(Ph)(CH3)-C(=O)-CH3, still product (p). In either pathway for compound (A), the only product is (p) because both groups on C2 are CH3, so migration of either gives the same product. Step 2 - Analyze Compound (B): Ph-C(Ph)(OH)-C(Et)(OH)-Et The diol has C1 bearing two Ph groups and OH, and C2 bearing two Et groups and OH. Under H2SO4, similar mechanism applies. Migration of Ph from C1 to C2 carbocation gives Ph-C(Ph)(Et)-C(=O)-Et, which is product (q). Alternatively, migration of Et from C2 to C1 carbocation gives Ph-C(Ph)(Et)-C(=O)-Et, still product (q). Since both groups on C2 are Et, only one product (q) is formed. Step 3 - Why not (r) and (s)? Product (r) would be Ph-C(Ph)(Et)-C(=O)-CH3, which would require mixing of groups from both (A) and (B) - this is not possible in a pinacol rearrangement since each diol reacts independently. Product (s) would be Ph-C(Ph)(CH3)-C(=O)-Et, similarly requiring cross-migration between molecules of (A) and (B). Since (A) and (B) are separate molecules reacting independently with H2SO4, no cross-products (r) or (s) are formed. Each diol gives only its own rearrangement product: (A) gives (p) and (B) gives (q). Step 4 - Conclusion: Only products (p) and (q) are obtained, corresponding to answer (b). Therefore, the correct answer is B.