Potassium superoxide: Difference between revisions

| Verifiedfields = changed

| verifiedrevid = 449304270

| Name = Potassium superoxide

| ImageFile = Potassium-superoxide-unit-cell-3D-ionic.png

| ImageName = Unit cell of potassium superoxide

| ImageCaption = {{legend|rgb(160,0,224)|Potassium cations, {{chem2|K+}}}}{{legend|red|Superoxide anions, {{chem2|O2−}}}}

| ImageFile1 = Potassium superoxide powder.png

| IUPACName = Potassium superoxide

| OtherNames =

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|??}}

| CASNo = 12030-88-5

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 8329498

| EINECS = 234-746-5

| PubChem = 61541

| RTECS = TT6053000

| UNNumber = 2466

| InChI = 1/2K.O2/c;;1-2/q2*+1;-2

| InChIKey = XXQBEVHPUKOQEO-UHFFFAOYAV

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChI = 1S/2K.O2/c;;1-2/q2*+1;-2

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = XXQBEVHPUKOQEO-UHFFFAOYSA-N

| SMILES = [K+].[O-]=O

}}

|Section2={{Chembox Properties

| K=1|O=2

| Appearance = yellow solid

| Density = 2.14 g/cm³, solid

| MagSus = +3230·10⁻⁶ cm³/mol<ref>{{Cite web |url=https://hbcp.chemnetbase.com/faces/contents/ContentsSearch.xhtml |title=Handbook of Chemistry and Physics 102nd Edition |publisher=[[CRC Press]]}}</ref>

| Solubility = [[Hydrolysis]]

| MeltingPtC = 560

| MeltingPt_notes = (decomposes)

}}

|Section3={{Chembox Structure

| Coordination =

| CrystalStruct = Body-centered tetragonal<ref name= Abrahams/><ref>{{cite web |title=Information card for entry 2310803 |url=http://www.crystallography.net/cod/2310803.html |website=[[Crystallography Open Database]] |access-date=28 July 2022 |language=en}}</ref>

}}

|Section4={{Chembox Thermochemistry

| DeltaHf = −283&nbsp;kJ/mol<ref name=b1>{{cite book |last= Zumdahl |first=Steven S. |title =Chemical Principles |edition=6th | publisher = Houghton Mifflin |year=2009 | isbn = 978-0-618-94690-7 |page=A22}}</ref>

| Entropy = 117&nbsp;J/(mol·K)<ref name=b1/>

}}

|Section7={{Chembox Hazards

| ExternalSDS =

| MainHazards = Corrosive, oxidizer, reacts violently with water

| GHS_ref=<ref>{{cite web |title=Potassium superoxide |url=https://pubchem.ncbi.nlm.nih.gov/compound/61541#section=Safety-and-Hazards |website=pubchem.ncbi.nlm.nih.gov |access-date=14 December 2021 |language=en}}</ref>

| GHSPictograms = {{GHS03}}{{GHS05}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|271|314}}

| PPhrases = {{P-phrases|210|220|221|260|264|280|283|301+330+331|303+361+353|304+340|305+351+338|306+360|310|321|363|370+378|371+380+375|405|501}}

| NFPA-H = 3

| NFPA-F = 0

| NFPA-R = 3

| NFPA-S = W+OX

}}

|Section8={{Chembox Related

| OtherAnions =

| OtherCations = {{ubl|[[Lithium superoxide]]|[[Sodium superoxide]]|[[Rubidium superoxide]]|[[Caesium superoxide]]}}

| OtherFunction = {{ubl|[[Potassium oxide]]|[[Potassium peroxide]]|[[Potassium ozonide]]}}

| OtherFunction_label = [[potassium]] [[oxide]]s

}}

'''Potassium superoxide''' is an [[inorganic compound]] with the formula {{chem2|KO2|auto=1}}.<ref>{{cite journal|author1=Hayyan M. |author2=Hashim M. A. |author3=AlNashef I. M. |title=Superoxide Ion: Generation and Chemical Implications|journal=Chem. Rev.|year=2016|volume=116|issue=5|pages=3029–3085|doi=10.1021/acs.chemrev.5b00407|pmid=26875845|doi-access=free}}</ref> It is a yellow [[paramagnetic]] solid that decomposes in moist air. It is a rare example of a stable salt of the [[superoxide]] anion. It is used as a [[carbon dioxide|{{chem2|CO2}}]] scrubber, [[Water|{{chem2|H2O}}]] dehumidifier, and [[Oxygen|{{chem2|O2}}]] generator in [[rebreather]]s, [[spacecraft]], [[submarines]], and [[spacesuit]]s.

==Production and reactions==

Potassium superoxide is produced by burning molten potassium in an atmosphere of excess [[oxygen]].<ref name=Ullmann>{{cite book |first1=Harald |last1=Jakob |first2=Stefan |last2=Leininger |first3=Thomas |last3=Lehmann |first4=Sylvia |last4=Jacobi |first5=Sven |last5=Gutewort |chapter=Peroxo Compounds, Inorganic |title=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley-VCH |year=2007 |isbn= 978-3527306732|doi=10.1002/14356007.a19_177.pub2}}</ref>

:{{chem2|K + O2 → KO2}}

The salt consists of {{chem2|K+}} and {{chem2|O2−}} ions, linked by ionic bonding. The O–O distance is 1.28 Å.<ref name= Abrahams>{{cite journal | last1 = Abrahams | first1 = S. C. | last2 = Kalnajs | first2 = J. | year = 1955 | title = The Crystal Structure of α-Potassium Superoxide | journal = Acta Crystallographica | volume = 8 | issue = 8 | pages = 503–6 | doi = 10.1107/S0365110X55001540 | doi-access = free}}</ref>

==Reactivity==

Potassium superoxide is a source of superoxide, which is an oxidant and a nucleophile, depending on its reaction partner.<ref>{{cite book |doi=10.1002/047084289X.rp250.pub2 |chapter=Potassium Superoxide |title=Encyclopedia of Reagents for Organic Synthesis |year=2007 |last1=Johnson |first1=Roy A. |last2=Adrio |first2=Javier |last3=Ribagorda |first3=María |isbn=978-0471936237}}</ref>

Upon contact with water, it undergoes [[disproportionation]] to [[potassium hydroxide]], oxygen, and hydrogen peroxide:

:{{chem2|4 KO2 + 2 H2O → 4 KOH + 3 O2}}

:{{chem2|2 KO2 + 2 H2O → 2 KOH + H2O2 + O2}}<ref>{{Cite book|title=A Text Book of Inorganic Chemistry|last=Kumar De|first=Anil|publisher=New Age International|year=2007|isbn=978-8122413847|pages=247}}</ref>

It reacts with carbon dioxide, releasing oxygen:

:{{chem2|4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2}}

:{{chem2|4 KO2 + 4 CO2 + 2 H2O → 4 KHCO3 + 3 O2}}

Potassium superoxide finds only niche uses as a laboratory reagent. Because it reacts with water, {{chem2|KO2}} is often studied in organic solvents. Since the salt is poorly soluble in nonpolar solvents, [[crown ether]]s are typically used. The [[tetraethylammonium]] salt is also known. Representative reactions of these salts involve using superoxide as a [[nucleophile]], e.g., in converting alkyl bromides to alcohols and acyl chlorides to [[diacyl peroxide]]s.<ref>{{cite book |first1=Roy A. |last1=Johnson |first2=Javier |last2=Adrio |first3=María |last3=Ribagorda |chapter=Potassium Superoxide |title=e-EROS Encyclopedia of Reagents for Organic Synthesis |publisher=Wiley |year=2001 |isbn= 0471936235|doi=10.1002/047084289X.rp250.pub2}}</ref>

Ion exchange with [[tetramethylammonium hydroxide]] gives tetramethylammonium superoxide, a yellow solid.<ref>{{cite book |doi=10.1002/0471653683.ch1|title=Tetramethylammonium Salts of Superoxide and Peroxynitrite |series=Inorganic Syntheses |year=2004 |last1=Bohle |first1=D. Scott |last2=Sagan |first2=Elisabeth S.|pages=36}}</ref>

==Applications==

The [[Russian Space Agency]] has had success using potassium superoxide in [[chemical oxygen generator]]s for its spacesuits and [[Soyuz spacecraft]]. {{chem2|KO2}} has also been used in canisters for rebreathers for [[fire fighting]] and [[mine rescue]] work, but had limited use in [[Scuba set|scuba]] rebreathers because of its highly exothermic reaction with water. Potassium superoxide was used in a rudimentary life support system for five mice as part of the Biological Cosmic Ray Experiment on Apollo 17.<ref>{{Cite journal |last=Haymaker |first=Webb |last2=Look |first2=Bonne C. |last3=Benton |first3=Eugene V. |last4=Richard C. Simmonds |date=1975-01-01 |title=The Apollo 17 pocket mouse experiment (Biocore) |url=https://ntrs.nasa.gov/citations/19760005599 |journal=Biomedical Results of Apollo |language=en |volume=NASA-SP-368}}</ref>

Theoretically, 1&nbsp;kg of {{chem2|KO2}} absorbs 0.310&nbsp;kg of {{CO2}} while releasing 0.338&nbsp;kg of {{chem2|O2}}. One mole of {{chem2|KO2}} absorbs 0.5 moles of {{CO2}} and releases 0.75 moles of oxygen.

{{oxygen compounds}}