Hydrogenation

(see electrophilic addition)

Homogeneous Catalysis

The term ‘homogeneous catalysis’ refers to a catalyst that is present in the same medium as the reaction mixture – i.e. in solution. Most often used as catalysts for this are complexes of 2nd and 3rd row transition metals e.g. Rh, Ir, Pt etc. – a good example of such a complex is the much used Wilkinson’s Catalyst RhCl(PPh)3. The catalytic cycle goes as follows:
NB. the electron rich carbon-carbon double bond can donate to a metal centre as a ligand. (refer to the Inorganic Section for explanation of ligands)

With Alkali Metals in Liquid Ammonia

The interesting property of alkali metals when they dissolve in liquid ammonia is the solution contains solvated electrons from the metal;

The solution is therefore quite reducing, and can be used to selectively reduce alkenes that have Electron Withdrawing Groups, as long as there is a proton source e.g. an alcohol.

Mechanism;