Epoxidation
Oxidation of olefins with peroxyacids leads to epoxides in a direct, easy and clean manner.
The most utilized peroxycarboxylic acids are:
The reaction is very selective:
The peroxyacid is attacked by the olefin bearing the highest electron density, i.e. by the most substituted one.
| Olefin | krel |
|---|---|
| ethylene | 1 |
| monosubstituted | 24 |
| disubstituted | 500 |
| trisubstituted | 6500 |
| tetrasubstituted | ≫ 6500 |
Olefin epoxidation, combined with the opening of the resulting epoxide with water in acidic medium, is an excellent method to obtain anti diols (glycols):
The trans stereochemistry of the starting olefin makes the reaction produce the meso form.
In turn, the cis olefin leads to a racemic mixture.