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Sodium superoxide

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Sodium superoxide
Oxidised sodium after improper storage under contaminated hexane showing an orange crust of sodium superoxide.
Names
IUPAC name sodium superoxide
Other names sodium superoxide
sodium dioxide
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
PubChem CID
RTECS number
  • WE2860010
UNII
UN number 2547
CompTox Dashboard (EPA)
InChI
  • InChI=1S/Na.HO2/c;1-2/h;1H/q+1;/p-1Key: TZACNHSIZFFYEH-UHFFFAOYSA-M
SMILES
  • .
Properties
Chemical formula NaO2
Molar mass 54.9886 g/mol
Appearance Yellow to orange crystalline solid
Density 2.2 g/cm
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
Heat capacity (C) 72.1 J/mol K
Std molar
entropy (S298) 		115.9 J/mol K
Std enthalpy of
formation (ΔfH298) 		-260.2 kJ/mol
Gibbs free energy (ΔfG) -218.4 kJ/mol
Hazards
GHS labelling:
Pictograms GHS03: OxidizingGHS05: Corrosive
Signal word Danger
Hazard statements H271, H314
Precautionary statements P210, P220, P260, P280, P303+P361+P353, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3 0 1OX
Flash point Non flammable
Related compounds
Other anions sodium oxide
sodium peroxide
Other cations Lithium superoxide
Potassium superoxide
Rubidium superoxide
Caesium superoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

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:

Na2O2 + O2 → 2 NaO2

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

Na(in NH3) + O2 → NaO2

Although the existence of a sodium oxide higher than peroxide was speculated since 19th century, it was not until 1948 when American chemists were able to definitely synthesize it by the latter method.

It is also produced, along with sodium peroxide, when sodium is stored under inappropriate conditions (e.g. in dirty or partially halogenated solvents).

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. It crystallizes in the NaCl motif.

References

  1. Hayyan, Maan; Hashim, Mohd Ali; AlNashef, Inas M. (2016-02-15). "Superoxide Ion: Generation and Chemical Implications". Chemical Reviews. 116 (5). American Chemical Society (ACS): 3029–3085. doi:10.1021/acs.chemrev.5b00407. ISSN 0009-2665. PMID 26875845.
  2. Stephen E. Stephanou, Edgar J. Seyb Jr., Jacob Kleinberg "Sodium Superoxide" Inorganic Syntheses 1953; Vol. 4, 82-85.
  3. Schechter, William H.; Sisler, Harry H.; Kleinberg, Jacob (January 1948). "The Absorption of Oxygen by Sodium in Liquid Ammonia: Evidence for the Existence of Sodium Superoxide". Journal of the American Chemical Society. 70 (1): 267–269. doi:10.1021/ja01181a083. ISSN 0002-7863.
  4. Sasol Encyclopaedia of Science and Technology , G.C. Gerrans, P. Hartmann-Petersen , p.243 "sodium oxides" , google books link
Sodium compounds
Inorganic
Halides
Chalcogenides
Pnictogenides
Oxyhalides
Oxychalcogenides
Oxypnictogenides
Others
Organic
Oxygen compounds
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