See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

**Step-by-step solution:** **Step 1: Analyze the target product** 3-Chloro-3-ethylpentane has the structure: $$CH_3CH_2-C(Cl)(C_2H_5)-CH_2CH_3$$ This is a saturated alkane with no double or triple bonds. **Step 2: Work backward from the product** - After photochemical chlorination, we get a saturated chloroalkane - Before chlorination, the intermediate must be an alkene (one $C=C$ double bond) - The alkene is: $CH_3CH_2-C(=CH_2)-CH_2CH_3$ (3-ethyl-1-butene or similar structure) **Step 3: Identify the starting alkyne** - Catalytic hydrogenation converts alkyne → alkene - For one hydrogenation step to produce one alkene, we need **one alkyne** (one $C \equiv C$ triple bond) - The alkyne would be: $CH_3CH_2-C(\equiv CH)-CH_2CH_3$ (3-ethylpent-1-yne or similar) **Step 4: Verify the reaction sequence** 1. Alkyne + $H_2$ (catalyst) → Alkene ✓ 2. Alkene + $Cl_2$ (photochemical) → Chloroalkane ✓ 3. Product matches 3-chloro-3-ethylpentane ✓ **Answer: (A) 1** Only **one alkyne** is needed to produce the target product through catalytic hydrogenation followed by photochemical chlorination.