Let's analyze the transformation step-by-step: ## Step 1: **Identify the Transformation** **Starting Material:** A six-carbon chain with a terminal alkyne (triple bond at the end). **Product:** A six-carbon chain with a terminal alkene (double bond at the end). This transformation is **reduction of an alkyne to an alkene**, specifically a **cis-alkene** (Z-alkene), as shown by the product structure. --- ## Step 2: **Recognize the Reagent for Cis-Alkene Formation** To convert an alkyne to a **cis-alkene**, the classic reagent is **Lindlar's catalyst**, which is a **partially deactivated palladium catalyst** (Pd/CaCO₃, Pb(OAc)₂, and quinoline). This selectively reduces alkynes to cis-alkenes. **In the choices:** - **A. (Lindlar's catalyst)**: "G, Lindlar (.5 eq)" - **B. "Na/NH₃"**: This is a dissolving metal reduction for *trans-alkene* (not the desired product). - **Others**: Not relevant for selective alkyne reduction to cis-alkene. --- ## Step 3: **Final Answer** The necessary reagent for this transformation is **G** (Lindlar's catalyst). ### **Answer:** ``` G ``` --- ## **Summary Table** | Step | Reagent Used | Product Type Produced | |-------------|-----------------------------|-----------------------| | Alkyne to alkene (cis) | Lindlar's catalyst (G) | Cis-alkene | | Alkyne to alkene (trans) | Na/NH₃ (B) | Trans-alkene | **So, the correct answer is:** **G**