Hydrogenation of alkynes catalysts

Alkenes and alkanes are among the most common structural features found in industrially relevant small molecules. Alkynes can be readily hydrogenated to alkenes or alkanes under mild conditions using a supported catalyst. The catalytic hydrogenation of alkynes is generally more facile than any other functional group. Terminal acetylenes are the most easily reduced alkynes. 

The selective catalytic hydrogenation of alkynes to an alkene without further hydrogenation to the corresponding alkane can be carried out with a palladium catalyst. The best known and most commonly used catalyst is the alkyne Lindlar catalyst; a palladium catalyst on a calcium carbonate support modified by the addition of lead acetate. Selectivity to the alkene can also be improved by limiting the hydrogen availability. In the absence of isomerisation, the selective hydrogenation of a disubstituted alkyne will produce the cis alkene.