Homogeneous Catalysts

In this section we look at how a homogeneous catalyst works and at some examples of homogeneous catalysis.

How a homogeneous catalyst works

In homogeneous catalysis the reactants, products and catalyst are all in the same phase. Often the reactants, products and catalyst are all dissolved in the same solvent. Due to environmental considerations this solvent is often water. In these situations the catalyst may be a transition metal ion catalysing a redox reaction.

Transition metals

The transition metal ion catalyses the original reaction by providing an alternative route between reactants and products that has a lower activation enthalpy. It can do this because transition metals can form stable compounds in more than one oxidation state and the transition metal ions can therefore readily move between oxidation states. During the catalysed reaction the transition metal ion is oxidised by one reactant to a higher oxidation state. This is then reduced back to the original form by reaction with the other reactant. The reactants are therefore converted to the same products as are formed without the catalyst. The only difference is that the reactants are converted into products more quickly.

reactant 1 + 

transition metal ion in low oxidation state

product + 

transition metal ion in high oxidation state

 

 

 

 

 

reactant 2 + 

transition metal ion in high oxidation state

product + 

transition metal ion in low oxidation state