Organic Chemistry/Introduction to reactions/Hydrogenation

Steps in the process of catalytic hydrogenation: the attachment of an alkene and atomic hydrogens, the reaction of the two, and the formation of the alkane product.

A hydrogenation reaction is a type of addition reaction which results in the syn addition of hydrogens across the double bond of an alkene. The double bond is replaced with a single bond and the product is an alkane.

The catalyst, represented by M, can be one of either platinum oxide (${\ce {PtO2}}$), Raney nickel, or palladium on carbon (${\ce {Pd/C}}$).

The metal catalyst provides a catalytic surface on which the hydrogenation can take place. It first absorbs hydrogen atoms and the alkene; then, it facilitates the interaction by bringing the two into close proximity on its surface and allowing them to react. Since the hydrogens are secured to the catalyst's surface, they approach the alkene double bond from the same direction, resulting in a syn addition.