Sodium superoxide

Sodium superoxide

Names
IUPAC name sodium(I) superoxide
Other names sodium superoxide
Identifiers
CAS Number	12034-12-7
Jmol interactive 3D	Image
PubChem	61542
RTECS number	WE2860010
InChI InChI=1S/Na.O2/c;1-2/q+1;
SMILES O=O.[Na+]
Properties
Chemical formula	NaO2
Molar mass	54.9886 g/mol
Appearance	Yellow to orange crystalline solid
Density	2.2 g/cm^3
Melting point	551.7 °C (1,025.1 °F; 824.9 K)
Boiling point	Decomposes
Solubility in water	Decomposes
Basicity (pKb)	N/A
Structure
Crystal structure	cubic
Thermochemistry
Specific heat capacity (C)	72.1 J/mol K
Std molar entropy (S^o298)	115.9 J/mol K
Std enthalpy of formation (ΔfH^o298)	-260.2 kJ/mol
Gibbs free energy (ΔfG˚)	-218.4 kJ/mol
Hazards
EU classification (DSD)	Corrosive
R-phrases	R35
S-phrases	S1/2, S26, S37/39, S45
NFPA 704	0 3 1 OX
Flash point	Non flammable
Related compounds
Other anions	sodium oxide sodium peroxide
Other cations	potassium superoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium superoxide is the inorganic compound with the formula NaO₂. This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen.

Preparation

NaO₂ is prepared by treating sodium peroxide with oxygen at high pressures:^[1]

Na₂O₂ + O₂ → 2 NaO₂

It can also be prepared by careful oxygenation of a solution of sodium in ammonia:

Na(in NH₃) + O₂ → NaO₂

Properties

The product is paramagnetic, as expected for a salt of the O−
2 anion. It hydrolyses readily to give a mixture of sodium hydroxide, oxygen and hydrogen peroxide.^[2] It crystallizes in the NaCl motif.

References

1. Stephen E. Stephanou, Edgar J. Seyb Jr., Jacob Kleinberg "Sodium Superoxide" Inorganic Syntheses 1953; Vol. 4, 82-85.
2. Sasol Encyclopaedia of Science and Technology , G.C. Gerrans, P. Hartmann-Petersen , p.243 "sodium oxides" , google books link