To convert but-2-yne to trans-but-2-ene, we need to reduce the triple bond in but-2-yne (an alkyne) to a double bond in trans-but-2-ene (an alkene). This requires a specific reagent that induces partial hydrogenation and selectively gives the trans isomer.
The reagent used to achieve this transformation is sodium in liquid ammonia (Na/liquid NH₃). This reagent reduces alkynes to trans-alkenes via an anti-addition mechanism.
- H₂/Pd/C: Reduces the alkyne to cis-but-2-ene (syn addition), not the trans isomer.
- NaBH₄: A mild reducing agent, not suitable for reducing alkynes to alkenes.
- Sn/HCl: Typically used for reducing nitro groups, not alkynes.
- Na/liquid NH₃: Selectively reduces alkynes to trans-alkenes.
Correct Answer:
Correct Answer: (A) Na/liquid NH₃