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Magnesium peroxide

Magnesium peroxide
FeS2structure.jpg
Names
IUPAC name
Magnesium peroxide
Other names
Magnesium dioxide, magnesium bioxide, UN 1476
Identifiers
3D model (Jmol)
ChemSpider
ECHA InfoCard 100.034.928
EC Number 238-438-1
PubChem CID
Properties
MgO2
Molar mass 56.3038 g/mol
Appearance White or off-white powder
Density 3 g/cm3
Melting point 223 °C (433 °F; 496 K)
Boiling point 350 °C (662 °F; 623 K) (decomposes)
insoluble
Structure
Cubic, cP12
Pa3, No. 205
Pharmacology
A02AA03 (WHO) A06AD03 (WHO)
Hazards
Main hazards Oxidizing (O)
R-phrases R8
S-phrases S17, S36
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Magnesium peroxide (MgO2) is an odorless fine powder peroxide with a white to off-white color. It is similar to calcium peroxide because magnesium peroxide also releases oxygen by breaking down at a controlled rate with water. Commercially, magnesium peroxide often exists as a compound of magnesium peroxide and magnesium hydroxide.

O2, similarly to N2, has the ability to bind either side-on or end-on. The structure of MgO2 has been calculated as a triangular shape with the O2 molecule binding side-on to the magnesium. This arrangement is a result of the Mg+ donating charge to the oxygen and creating a Mg2+O22−. The bond between to O2 and the magnesium atom has an approximate dissociation energy of 90 kJ mol−1.

In the solid state, MgO2 has a cubic pyrite-type crystal structure with 6-coordinate Mg2+ ions and O22− peroxide-groups, according to experimental data and evolutionary crystal structure prediction, the latter predicting a phase transition at the pressure of 53 GPa to a tetragonal structure with 8-coordinate Mg2+ ions. While at normal conditions MgO2 is a metastable compound (less stable than MgO+1/2O2), at pressures above 116 GPa it is predicted to become thermodynamically stable in the tetragonal phase. This theoretical prediction has been experimentally confirmed via synthesis in a laser-heated diamond anvil cell.

MgO2 can be produced by mixing MgO with hydrogen peroxide to create magnesium peroxide and water. This being an exothermic reaction should be cooled and kept around 30–40 degrees Celsius. It is also important to remove as much iron from the reaction environment as possible due to iron's ability to catalyze the degradation of the peroxide. The addition of oxygen stabilizers such as sodium silicate can also be used to help prevent the premature degradation of the peroxide. Regardless, a good yield from this reaction is only about 35%.

High yields are further complicated by the fact that MgO2 reacts with water to degrade the peroxide into magnesium hydroxide, also known as milk of magnesia.


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