See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Free radical chlorination of cyclopentane with excess Cl2/hv can introduce two chlorine atoms at various positions. We must count all structurally distinct dichlorocyclopentane products including stereoisomers (cis/trans pairs). Step 1: Identify the unique monochlorination site. Cyclopentane has only one type of carbon (all equivalent), so monochlorination gives only chlorocyclopentane. Step 2: For dichlorination, we place the second Cl on chlorocyclopentane. Number the ring carbons 1-5, with Cl already at C1. The unique positions for the second Cl are C1, C2 (=C5 by symmetry), and C3 (=C4 by symmetry). Step 3: Enumerate products: - 1,1-dichlorocyclopentane: both Cl on same carbon. No stereocenters. 1 product. - 1,2-dichlorocyclopentane: C1 and C2 both have Cl and H. This gives cis and trans isomers. The trans isomer has two stereocenters and is chiral (exists as R,S enantiomers = 2 enantiomers), and the cis isomer also has two stereocenters (1R,2S and 1S,2R) but the ring makes them... actually for cyclopentane with substituents at 1,2: cis-1,2 gives a pair of enantiomers (1R,2S and 1S,2R), trans-1,2 gives a pair of enantiomers (1R,2R and 1S,2S). So 4 stereoisomers total for 1,2-dichloro. - 1,3-dichlorocyclopentane: C1 and C3. Similarly, cis-1,3 gives enantiomers (2 stereoisomers) and trans-1,3 gives enantiomers (2 stereoisomers). So 4 stereoisomers total for 1,3-dichloro. Step 4: Total count = 1 (1,1-) + 4 (1,2-) + ... wait, let me recount carefully. - 1,1-dichlorocyclopentane: 1 compound - 1,2-dichlorocyclopentane: cis (meso? No - cyclopentane 1,2 substitution: cis-1,2 has a plane of symmetry? C1 and C2 both bearing Cl and H with same substituents - cis means both Cl on same face. The molecule has a plane of symmetry through C1-C2 bond midpoint perpendicular... actually cis-1,2-dichlorocyclopentane is a meso compound (has internal plane of symmetry), so 1 compound. Trans-1,2-dichlorocyclopentane has no plane of symmetry, exists as a pair of enantiomers = 2 compounds. Total: 3 compounds for 1,2. - 1,3-dichlorocyclopentane: cis-1,3: C1 and C3 with Cl on same face - plane of symmetry through C2 and midpoint of C4-C5, so meso = 1 compound. Trans-1,3: no plane of symmetry, pair of enantiomers = 2 compounds. Total: 3 compounds for 1,3. Step 5: Grand total = 1 + 3 + 3 = 7 products. This matches option (c) 7. The other options fail because: (a) 5 undercounts stereoisomers, (b) 6 misses one isomer, (d) 9 overcounts. Therefore, the correct answer is C.