Potassium superoxide is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula . It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the

superoxide In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of t ...

anion. It is used as a scrubber, dehumidifier, and generator in rebreathers,

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

submarines A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or info ...

, and

spacesuit A space suit (or spacesuit) is an environmental suit used for protection from the harsh Space environment, environment of outer space, mainly from its Vacuum (outer space), vacuum as a highly specialized pressure suit, but also its temperatu ...

Production and reactions

Potassium superoxide is produced by burning molten potassium in an atmosphere of excess

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

. : The salt consists of and ions, linked by ionic bonding. The O–O distance is 1.28 Å.

Reactivity

Potassium superoxide is a source of superoxide, which is an oxidant and a nucleophile, depending on its reaction partner. Upon contact with water, it undergoes disproportionation to

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...

, oxygen, and hydrogen peroxide: : : It reacts with carbon dioxide, releasing oxygen: : : Theoretically, 1 kg of absorbs 0.310 kg of while releasing 0.338 kg of . One mole of absorbs 0.5 moles of and releases 0.75 moles of oxygen. Potassium superoxide finds only niche uses as a laboratory reagent. Because it reacts with water, is often studied in organic solvents. Since the salt is poorly soluble in nonpolar solvents, crown ethers are typically used. The

tetraethylammonium Tetraethylammonium (TEA) is a quaternary ammonium cation with the chemical formula , consisting of four ethyl groups (, denoted Et) attached to a central nitrogen atom. It is a counterion used in the research laboratory to prepare lipophilic salt ...

salt is also known. Representative reactions of these salts involve using superoxide as a

nucleophile In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

, e.g., in converting alkyl bromides to alcohols and acyl chlorides to diacyl peroxides. Ion exchange with tetramethylammonium hydroxide gives tetramethylammonium superoxide, a yellow solid.

Applications

The

Russian Space Agency The State Corporation for Space Activities "Roscosmos", commonly known simply as Roscosmos (), is a state corporation of the Russian Federation responsible for space flights, cosmonautics programs, and aerospace research. Originating from ...

has successfully used potassium superoxide in chemical oxygen generators for its spacesuits and Soyuz spacecraft. Potassium superoxide was also used in a rudimentary life support system for five mice as part of the Biological Cosmic Ray Experiment on Apollo 17. has also been used in canisters for rebreathers for

firefighting Firefighting is a profession aimed at controlling and extinguishing fire. A person who engages in firefighting is known as a firefighter or fireman. Firefighters typically undergo a high degree of technical training. This involves structural fir ...

and mine rescue, and in cartridges for chemical oxygen generators on submarines. A flash fire caused by dropping such a cartridge into seawater contributed to the ''Kursk'' disaster. This highly

exothermic reaction In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change Δ''H''⚬ is negative." Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC define ...

with water is also the reason why potassium superoxide has had only limited use in scuba rebreathers.

References

{{Oxygen compounds Oxidizing agents Potassium compounds Rebreather components Superoxides