Mechanism of the hydrogenation of acetylenic hydrocarbons over raney nickel

Summary

• 1. A study was made of the mechanism of the addition of hydrogen at a triple bond by the method of hydrogenating binary mixtures of acetylenic and ethylenic hydrocarbons (C₅ and C₆).

• 2. β-Acetylenic hydrocarbons are hydrogenated largely selectively and stereospecifically; the process proceeds in the main through the stage of the formation of the cis olefin. The saturated hydrocarbon and products of cis-trans isomerization and of double-bond migration are formed in the first stage of the hydrogenation only in small amounts and only by the scheme (2).

• 3. In the first stage of the process anα-acetylenic hydrocarbon is partially hydrogenated to the saturated hydrocarbon, whereas theα-olefin component of the mixture is hydrogenated to a very small extent and is not isomerized. Anα-acetylenic hydrocarbon is therefore hydrogenated by two mechanisms simultaneously: with intermediate formation of the olefin and without formation of an olefin that desorbs into the bulk phase.