See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is 1,2-bis(methoxycarbonyl)cyclohex-1-ene, a cyclohexene ring with a double bond between C1 and C2, each carbon bearing a -CO2CH3 (ester) group. Step 2 - Reaction with H2 (1 mole) / Pt: Catalytic hydrogenation with one mole of H2 over platinum reduces the C1=C2 double bond. Both H atoms are delivered to the same face of the double bond (syn addition). Step 3 - Determine the stereocenters formed: After hydrogenation, C1 and C2 each bear: a -CO2CH3 group, an H (newly added), and two ring carbons. Both C1 and C2 become stereocenters. Step 4 - Analyze the stereochemistry of syn addition: Syn (cis) addition of H2 delivers both hydrogens to the same face. Because the molecule has a plane of symmetry (the two substituents at C1 and C2 are identical - both are -CO2CH3), syn addition from either face gives the same compound: the one where both -CO2CH3 groups end up on the same side (cis relationship). Step 5 - Identify the product: The product has C1 and C2 both bearing -CO2CH3 groups in a cis configuration on the cyclohexane ring. Because C1 and C2 carry identical substituents (-CO2CH3, -H, and the ring), the molecule possesses an internal plane of symmetry making it a meso compound. The two stereocenters are of opposite configuration (R and S) but are mirror images of each other within the same molecule, resulting in no net optical activity. Step 6 - Why other options fail: - (b) Racemic mixture: A racemic mixture would result from anti addition or a non-stereospecific process giving equal R,R and S,S enantiomers. Syn addition to this symmetric substrate gives only the meso form, not a racemic mixture. - (c) Diastereomers: A single product (meso) is formed, not a mixture of diastereomers. - (d) Optically active: The meso compound has an internal plane of symmetry and is optically inactive. Therefore, the correct answer is A.