See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1: Identify the product. The product shown is bicyclopentyl — specifically a cyclohexane ring connected to a cyclobutane ring (cyclohexylcyclobutane). This is a fully saturated compound with two rings, so its degree of unsaturation (DBE) = 2. Step 2: Determine the molecular formula of the product. Cyclohexylcyclobutane has the formula C10H18. DBE of product = (2×10 + 2 - 18)/2 = (22 - 18)/2 = 4/2 = 2. This confirms 2 rings, 0 double bonds in the product. Step 3: Determine compound (A). Since 1 mole of H2 is added to (A) to give the product, compound (A) has one more degree of unsaturation than the product (one double bond was hydrogenated). The product has DBE = 2, so (A) has DBE = 2 + 1 = 3. Step 4: Verify. (A) contains two rings (contributing DBE = 2) and one carbon-carbon double bond (contributing DBE = 1), giving total DBE = 3. Upon hydrogenation with 1 mole H2/Pt, the double bond is reduced, leaving only the two ring systems in the product. Step 5: Why other options fail: - (a) 1: Would mean (A) has only one ring or one double bond, inconsistent with the bicyclic saturated product. - (b) 2: Would mean (A) has the same DBE as the product, implying no double bond was reduced, contradicting the use of H2. - (d) 4: Would require two double bonds or an extra ring, but only 1 mole H2 is consumed. Therefore, the correct answer is C.