Types of peroxodisulphate oxidation mechanisms

The possible types of chain mechanisms for peroxodisulphate oxidation have been classified by Wilmarth and Haim according to the dominant initiation and termination steps, and the relative importance of sulphate radical-ions and hydroxyl radicals in the propagation steps. Some of the rate equations corresponding to the different types of mechanisms are the same, so the observation of a particular rate equation does not always permit a unique mechanism to be inferred. In certain cases the nature of the chain initiation step can be deduced from the effect of a free-radical scavenger on the reaction rate. Thus in the oxidation of 2-propanol, the addition of allyl acetate reduces the rate to that observed for the spontaneous decomposition of peroxodisulphate, indicating that the chain initiation step is the same as the rate-determining step of the spontaneous decomposition, viz. the fission of peroxodisulphate into sulphate radical-ions. 

As noted above, many peroxodisulphate oxidations are catalysed by silver 

In the following sections the peroxodisulphate oxidations of organic compounds are classified according to the nature of the substrate. Unless otherwise stated the solvent is water. 

---