Sodium percarbonate or sodium carbonate peroxide is a chemical substance with empirical formula Na2H3CO6. It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate) whose formula is more properly written as 2 Na2CO3 · 3 H2O2. It is a colorless, crystalline, hygroscopic and water-soluble solid.[3] It is sometimes abbreviated as SPC. It contains 32.5% by weight of hydrogen peroxide.
At room temperature, solid sodium percarbonate has the orthorhombiccrystal structure, with the Cmca crystallographic space group. The structure changes to Pbca as the crystals are cooled below about −30 °C.[1]
Chemistry
Dissolved in water, sodium percarbonate yields a mixture of hydrogen peroxide (which eventually decomposes to water and oxygen), sodiumcations (Na+ ), and carbonate (CO2− 3).[3][5]
2 Na2CO3 · 3 H2O2 → 3 H2O2 + 4 Na+ + 2 CO2−3
2 H2O2 → 2 H2O + O2
Production
Sodium percarbonate is produced industrially by crystallization of a solution of sodium carbonate and hydrogen peroxide, with proper control of the pH and concentrations.[6][1][7] This is also a convenient laboratory method.
Alternatively, dry sodium carbonate may be treated directly with concentrated hydrogen peroxide solution.[8]
It may also be formed from a process starting from sodium peroxide; when absolute ethyl alcohol reacts with sodium peroxide at 0°C, a perhydroxide is produced.[citation needed]
C2H5OH + Na2O2 → NaOOH + C2H5ONa
Carbon dioxide converts it into sodium hydrogen percarbonate.
World production capacity of this compound was estimated at several hundred thousand tons for 2004.[9]
Many commercial products mix a percentage of sodium percarbonate with sodium carbonate. The average "Oxy" product in the supermarket contains 35–40% sodium percarbonate with about 5% active oxygen when titrated.
Sodium percarbonate is also used as a cleaning agent in homebrewing.[10]
Sodium percarbonate can be used in organic synthesis as a convenient source of anhydrous H2O2, in particular in solvents that cannot dissolve the carbonate but can leach the H2O2 out of it.[11] A method for generating trifluoroperacetic acidin situ for use in Baeyer–Villiger oxidations from sodium percarbonate and trifluoroacetic anhydride has been reported; it provides a convenient and cheap approach to this reagent without the need to obtain highly concentrated hydrogen peroxide.[12][13]
^J. M. Adams and R. G. Pritchard (1977): "The crystal structure of sodium percarbonate: an unusual layered solid". Acta Crystallographica Section B, volume B33, issue 12, pages 3650–3653. doi:10.1107/S0567740877011790