Alkenes react with hydrogen in presence of a metal catalyst (platinum or palladium) to yield alkanes.

 

 

Catalytic hydrogenation is stereoespecific reation.  The two hydrogen atoms are added to the same face of the double bond (syn addition)

 

 

Catalytic hydrogenation take place at the less hindered side of alkene.  In this example the botom faces of double bond is more exposed, and both hydrogens are transferred to that faces. Top side of double bond are blocked by methyl groups.