Cis/Trans Hydrogenation of Alkynes
Cis Hydrogenation of Alkynes
Alkynes are hydrogenated like alkenes with elemental hydrogen in the presence of a catalyst. Several different catalysts can be used for this purpose. Under typical alkene hydrogenation conditions, the hydrogenation of an alkyne does not stop at the stage of an alkene but an alkane is formed by complete hydrogenation of the alkyne.
Special, partially poisoned catalysts were developed for the selective hydrogenation of alkynes to alkenes. The generally-known Lindlar catalyst, for example, is made up of palladium on a calcium carbonate carrier which is partially poisoned with lead acetate in the presence of amines (e.g. quinoline). The hydrogenation with Lindlar catalyst is a stereospecific cis hydrogenation.