For the transformation shown, select the most appropriate reagent(s) to effect the change.

Question

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The starting material is an alkyne and the desired product is an alkene with cis stereochemistry. This is indicative of a reduction reaction that specifically stops at the alkene stage. Lindlar's catalyst (a palladium-carbon catalyst poisoned with lead) is specific for this type of reduction to give cis-alkenes. Therefore, the best choice is E, H₂, Lindlar's catalyst. The other options include reagents that are not specific for this type of transformation (A, C), a strong reducing agent that would reduce the product further to an alkane (D), or a reagent that would not give the desired cis stereochemistry (B).

For the Transformation Shown, Select the Most Appropriate Reagent(s) to Effect