Rosenmund described a simple apparatus for performing the reduction. Audier, L. This forms an anion, which can be protonated by a hydrogen in an ammonia solvent. The Hydrogen H2 atoms get added in pairs to the alkenes where the triple bond of the alkynes gets reduced to a double bonded alkene. The catalytic addition of hydrogen to 2-butyne provides heat of reaction data that reflect the relative thermodynamic stabilities of these hydrocarbons, as shown above. In the case of catalytic hydrogenation, the usual Pt and Pd hydrogenation catalysts are so effective in promoting addition of hydrogen to both double and triple carbon-carbon bonds that the alkene intermediate formed by hydrogen addition to an alkyne cannot be isolated.
HCA , 9,
Lindlar's Catalyst: Hydrogenation of an Alkyne to a Trans-Alkene Alkynes can be reduced to trans-alkenes with the use of sodium dissolved in an ammonia solvent.
However, benzaldehydes subjected to the conditions of the amine-modified reduction are hydrogenated to the alcohols, but more slowly than in the absence of the amine and substantially slower on a catalyst which has been used previously in a hydrogenation of an acid chloride. Organic Chemistry: Structure and Function. Regioselective opening of a 1,2-disubstituted epoxide was observed with this catalyst eq However, the use of two other catalysts can be used to hydrogenate alkynes to alkanes.