Q.The correct structure of the product 'A' formed in the reaction: cyclohex-2-en-1-one (a six-membered ring carrying a ketone at C1 conjugated with a ring C2=C3 double bond), treated with H2 gas (1 atm) over Pd/C in ethanol -- A is (NEET): a) an isomer of cyclohexenol (the ring C=O reduced to -OH, the ring C=C retained, drawn with OH and the double bond on nearly opposite sides of the ring) b) cyclohexanone (the ring C=O retained intact, the ring C=C fully hydrogenated so the ring is otherwise saturated) c) a second cyclohexenol isomer (OH retained together with the C=C, but the double bond drawn immediately adjacent to the OH-bearing carbon, an allylic arrangement) d) cyclohexanol (both the ring C=O and the ring C=C fully reduced, giving a fully saturated ring bearing only -OH)

Step 1. The substrate is cyclohex-2-en-1-one -- a six-membered ring bearing a ketone at C1, conjugated with a ring C2=C3 double bond.

Step 2. Catalytic hydrogenation over Pd/C at MILD conditions (1 atm H2, ethanol) is well known to reduce an isolated or conjugated carbon-carbon double bond much faster than it reduces a carbonyl group -- a ketone typically needs a stronger hydride reagent (LiAlH4/NaBH4) or more forcing catalytic conditions to be reduced at all.

Step 3. So under these specific mild conditions, only the ring's C2=C3 double bond is hydrogenated; the ketone at C1 is left completely intact.

Step 4. The product is therefore the fully saturated ring bearing only the original ketone -- cyclohexanone -- with no -OH formed and no double bond remaining.

Recognise that H2/Pd-C at 1 atmosphere is a mild, alkene-selective hydrogenation, not a carbonyl-reducing one -- contrast this with LiAlH4, which does the exact opposite (reduces C=O, leaves C=C untouched) for the same class of alpha,beta-unsaturated carbonyl substrate.

• Assuming ANY catalytic hydrogenation reduces both the alkene and the ketone together, giving cyclohexanol -- that would need a much stronger/prolonged hydrogenation than the mild 1 atm conditions stated here.