See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Cyclic Isomers of $C_5H_{10}$ **Step 1: Determine degree of unsaturation** $$\text{DBE} = \frac{2(5) + 2 - 10}{2} = \frac{2}{2} = 1$$ One degree of unsaturation means **one ring** (no double bonds in cyclic structures). **Step 2: Identify all possible cyclic structures** For monocyclic alkanes with formula $C_5H_{10}$, we need a 5-carbon ring with no additional unsaturation. **The 5 cyclic isomers are:** 1. **Cyclopentane** — regular 5-membered ring 2. **Methylcyclobutane** — 4-membered ring + methyl substituent 3. **1,1-Dimethylcyclopropane** — 3-membered ring + two methyl groups on same carbon 4. **1,2-Dimethylcyclopropane** — 3-membered ring + two methyl groups on adjacent carbons 5. **Ethylcyclopropane** — 3-membered ring + ethyl substituent **Step 3: Verify each is distinct** - Different ring sizes (5, 4, or 3 membered) - Different substitution patterns and positions - No stereoisomers counted (as specified in the problem) **Answer: (B) 5**