Sodium superoxide
{{chembox
| Watchedfields = changed
| verifiedrevid = 430303174
| Name = Sodium superoxide
| ImageSize = 300px
| ImageName = Oxidised sodium after improper storage under contaminated hexane showing an orange crust of sodium superoxide.
| ImageFile = Oxidised sodium after being stored under contaminated hexane.jpg
| IUPACName = sodium superoxide
| OtherNames = sodium superoxide
sodium dioxide
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 1313-60-6
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 3GSN3JCJ5K
| ChemSpiderID = 8305406
| PubChem = 61542
| RTECS = WE2860010
| UNNumber = 2547
| StdInChI=1S/Na.HO2/c;1-2/h;1H/q+1;/p-1
| StdInChIKey = TZACNHSIZFFYEH-UHFFFAOYSA-M
| SMILES = [O-][O].[Na+]
}}
| Section2 = {{Chembox Properties
| Formula = NaO2
| MolarMass = 54.9886 g/mol
| Appearance = Yellow to orange crystalline solid
| Density = 2.2 g/cm3
| Solubility = Decomposes
| MeltingPtC = 551.7
| BoilingPt = Decomposes
| pKb = N/A
}}
| Section3 = {{Chembox Structure
| Coordination =
| CrystalStruct = cubic
| Dipole =
}}
| Section4 =
| Section5 = {{Chembox Thermochemistry
| DeltaHf = −260.2 kJ/mol
| DeltaGf = −218.4 kJ/mol
| Entropy = 115.9 J/mol K
| HeatCapacity = 72.1 J/mol K
}}
| Section6 =
| Section7 = {{Chembox Hazards
| ExternalSDS =
| GHS_ref=
| GHSPictograms = {{GHS03}}{{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|H271|H314}}
| PPhrases = {{P-phrases|P210|P220|P260|P280|P303+P361+P353|P305+P351+P338}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 1
| NFPA-S = OX
| FlashPt = Non flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = sodium oxide
sodium peroxide
| OtherCations = Lithium superoxide
Potassium superoxide
Rubidium superoxide
Caesium superoxide
}}
}}
Sodium superoxide is the inorganic compound with the formula NaO2.{{cite journal | last1=Hayyan | first1=Maan | last2=Hashim | first2=Mohd Ali | last3=AlNashef | first3=Inas M. | title=Superoxide Ion: Generation and Chemical Implications | journal=Chemical Reviews | publisher=American Chemical Society (ACS) | volume=116 | issue=5 | date=2016-02-15 | issn=0009-2665 | doi=10.1021/acs.chemrev.5b00407 | pages=3029–3085| pmid=26875845 | doi-access=free }} 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:Stephen E. Stephanou, Edgar J. Seyb Jr., Jacob Kleinberg "Sodium Superoxide" Inorganic Syntheses 1953; Vol. 4, 82-85.
: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.{{Cite journal |last=Schechter |first=William H. |last2=Sisler |first2=Harry H. |last3=Kleinberg |first3=Jacob |date=January 1948 |title=The Absorption of Oxygen by Sodium in Liquid Ammonia: Evidence for the Existence of Sodium Superoxide |url=https://pubs.acs.org/doi/abs/10.1021/ja01181a083 |journal=Journal of the American Chemical Society |language=en |volume=70 |issue=1 |pages=267–269 |doi=10.1021/ja01181a083 |issn=0002-7863|url-access=subscription }}
Properties
The product is paramagnetic, as expected for a salt of the {{chem|O|2|-}} anion. It hydrolyses readily to give a mixture of sodium hydroxide, oxygen and hydrogen peroxide.Sasol Encyclopaedia of Science and Technology , G.C. Gerrans, P. Hartmann-Petersen , p.243 "sodium oxides" , [https://books.google.com/books?id=1wS3aWR5SO4C&dq=sodium+superoxide&pg=PA243 google books link] It crystallizes in the NaCl motif.
References
{{Sodium compounds}}
{{oxygen compounds}}
Category:Photographic chemicals
{{inorganic-compound-stub}}