See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Determine degree of unsaturation from hydrogenation: Alkene (A) reacts with 3 moles of H2 to give 1-isopropyl-4-methylcyclohexane. This means alkene (A) has 3 degrees of unsaturation (3 C=C double bonds). The product is a cyclohexane with an isopropyl group at C1 and a methyl group at C4, so the carbon skeleton of A must be the same as 1-isopropyl-4-methylcyclohexane but with 3 double bonds. Step 2 - Identify ozonolysis products: Ozonolysis (reductive workup) cleaves each C=C double bond to give carbonyl compounds. The three products obtained are: - HCHO (formaldehyde): comes from a =CH2 terminal group - OHC-CH2-CO-CO-CH3: a 1,2-diketone/dialdehyde fragment suggesting cleavage of two adjacent double bonds on a chain - CH3-CO-CH2-CHO: a keto-aldehyde fragment Step 3 - Reconstruct the structure: The presence of formaldehyde indicates a =CH2 (isopropenyl-type) terminal double bond. The carbon skeleton must contain a cyclohexane ring with two additional double bonds in the ring (making it a cyclohexadiene) plus one exocyclic double bond (=CH2 on the isopropyl-derived carbon), totaling 3 double bonds. Option (b) shows a non-aromatic cyclohexadiene ring (1,3-cyclohexadiene system) bearing an isopropenyl group (=CH2) and a methyl group at the para position. This structure has: one exocyclic C=C (the =CH2, giving HCHO on ozonolysis) and two endocyclic C=C bonds in the 1,3-diene system of the ring. Step 4 - Verify ozonolysis of option (b): With the 1,3-cyclohexadiene bearing isopropenyl at C1 and methyl at C4, ozonolysis of all three double bonds would fragment the ring and side chain. The =CH2 gives HCHO. The ring diene portion, when cleaved at both double bonds, gives a linear fragment OHC-CH2-CO-CO-CH3 (from one end) and CH3-CO-CH2-CHO (from the other end), consistent with the products shown. Step 5 - Eliminate other options: (a) is aromatic (benzene ring), which would require more than 3 moles H2 for full reduction and aromatic rings resist ozonolysis under standard conditions; also the product would be different. (c) has an isopropylidene (=CMe2) exocyclic double bond, which would give acetone not formaldehyde. (d) has only one ring double bond plus one exocyclic, totaling only 2 double bonds, inconsistent with 3 moles H2 consumption. Therefore, the correct answer is B.