See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Cyclopentane Structures for $C_5H_{14}$ **Step 1: Identify the molecular formula.** $C_5H_{14}$ represents cyclopentane with all possible alkyl substitution patterns (no double bonds or rings other than the cyclopentane ring). **Step 2: Recognize that we need one cyclopentane ring.** A cyclopentane ring uses $C_5H_{10}$, leaving $H_4$ to account for — this means **4 additional hydrogens**, implying one degree of unsaturation is already satisfied by the ring. **Step 3: List all possible structural isomers.** Since we have a 5-membered ring with saturated substituents, the isomers are: 1. **Cyclopentane** (unsubstituted) 2. **Methylcyclobutane** (4-membered ring + $CH_3$) 3. **Ethylcyclopropane** (3-membered ring + $C_2H_5$) 4. **1,1-Dimethylcyclopropane** (3-membered ring + 2 × $CH_3$ at same carbon) 5. **1,2-Dimethylcyclopropane** (3-membered ring + 2 × $CH_3$ on adjacent carbons) 6. **Cyclopropylmethane** (equivalent to #3) 7. **Spiropentane** (two fused 3-membered rings sharing one carbon) 8. **Bicyclo[2.1.0]pentane** (bicyclic structure) **Step 4: Count distinct structures (excluding stereoisomers).** The total number of structural isomers is **8**. **The answer is (A) 8** because these represent all topologically distinct cyclopentane isomers with formula $C_5H_{14}$, excluding stereoisomers like cis/trans isomers.