Peroxycarbonates (also known as peroxocarbonates) play an important role in the synthesis of plastics, for example in the production of PVC or PE. Many heavy-duty detergents contain percarbonates as bleaching substances.
Peroxy(di)carbonates contain bound peroxides
The underlying peroxycarboxylic acid H2CO4 is not stable and rather hypothetical, but there are the anions HCO4– and CO42-, which are present in sodium peroxycarbonate.
There are also sodium peroxydicarbonates with the anion C2O62-.
Peroxydicarboantes can be formed by the electrolysis of carbonates:
2 CO32- —> C2O62- + 2 e– (Anode)
When in contact with water, peroxy(di)carbonate anions easily convert to normal carbonate CO32- ions. In this process hydrogen peroxide is split off.
HCO4– + H2O —> HCO3– + H2O2
CO42- + H2O —> CO32- + H2O2
C2O62- + 2 H2O —> 2 HCO3– + H2O2
During the synthesis of plastics, sodium peroxydicarbonate breaks down into two radicals as the peroxo bridge is split homolytically.
C2O62- —> 2 CO3–•
These radicals start the polymerization of monomer molecules in the synthesis of plastics.
Sodium percarbonates are peroxohydrates
However, these are only hydrate-like H2O2 adducts, like 2 Na2CO3 • 3 H2O2. The exact name for the group is sodium carbonate peroxohydrate.
They disintegrate in water with the formation of carbonate as well as oxygen and hydroxyl radicals. These have a bleaching effect, which is why percarbonates are added to detergents instead of peroxoborates. Unlike perborates, sodium percarbonate does not have a harmful effect on the environment.