How can I explain the stereochemistry of hydrogen addition?

1 Answer
Jan 3, 2015

The stereochemistry arises because both the hydrogen and the alkene must be adsorbed on the surface of a solid catalyst.

The catalytic hydrogenation of an alkene results in a syn addition.

Chemists believe that the hydrogen attaches to the surface of the catalysts and forms metal-hydrogen bonds.

Then the alkene is adsorbed onto the metal surface.

The H atoms add to the alkene while it is attached to the metal surface.

This means that they must add to the same face of the double bond. The reaction is therefore a syn addition.

Here's a video on the catalytic hydrogenation of alkenes.