See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Step 1: Analyze Pair I - Benzene vs. the tricyclic compound (bicyclo[1.1.0] or [3]radialene-type structure shown as a rectangle divided into three parts, which represents bicyclo[2.2.0] or more likely the structure is 'bicyclo[2.2.0]hex-2-ene' or Dewar benzene or similar C6H6 isomer). Both benzene and the rectangular structure (Dewar benzene or [3]cumulene) have molecular formula C6H6. They have the same molecular formula but different connectivity (different bonding arrangement), so they are constitutional isomers. Therefore I -> A (Constitutional). Step 2: Analyze Pair II - 2-cyclohexen-1-one vs. cyclohexadiene oxide (1,2-epoxide of cyclohexadiene). Both have molecular formula C6H6O. They have the same molecular formula but different connectivity (a ketone vs. an epoxide), so they are constitutional isomers. Therefore II -> A (Constitutional). Step 3: Analyze Pair III - (Z)-1,2-dibromoethene vs. (E)-1,2-dibromoethene. Both have molecular formula C2H2Br2 and the same connectivity (both are 1,2-dibromoethene), but they differ in the spatial arrangement of groups around the double bond. This is a geometric (cis/trans) isomerism, which is a type of configurational isomerism. Therefore III -> B (Configurational). Step 4: Analyze Pair IV - D-glyceraldehyde vs. L-glyceraldehyde. These are mirror images of each other (enantiomers) that are non-superimposable. Enantiomers are a type of optical isomers. Therefore IV -> D (Optical). Summary: I-A, II-A, III-B, IV-D, which matches option (b). Why other options fail: - Option (a): assigns II-B (configurational) to pair II, but pair II differs in connectivity (constitutional isomers), not configuration. - Option (c): assigns I-B (configurational) to pair I, but pair I has different connectivity, making them constitutional isomers. - Option (d): assigns I-B, II-B, III-A, IV-B, which misidentifies nearly all relationships. Therefore, the correct answer is B.