The reaction is the partial reduction of propyne (a terminal alkyne) to propene (an alkene). - Lindlar catalyst is a poisoned palladium catalyst (typically Pd on calcium carbonate with lead acetate and quinoline) used for the catalytic hydrogenation of alkynes specifically to cis alkenes. For terminal alkynes like propyne, it reduces the triple bond to a double bond, forming the corresponding alkene. - H₂/Pd (Palladium catalyst): Catalytic hydrogenation with a non-poisoned palladium catalyst would fully reduce the alkyne to an alkane (propane). CH₃C ≡ CH + 2H₂/Pd → CH₃CH₂CH₃. - NaBH₄ (Sodium borohydride) and LiAlH₄ (Lithium aluminum hydride) are reducing agents primarily used for carbonyl compounds (aldehydes, ketones, esters, etc.) and other functional groups like nitriles and halides, respectively. They are generally not used to reduce alkynes to alkenes. Therefore, Lindlar catalyst is the specific reagent used for the partial hydrogenation of alkynes to alkenes.