Potassium superoxide is an
inorganic compound with the formula KO
2. It is a yellow
paramagnetic
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, ...
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
rebreather
A rebreather is a breathing apparatus that absorbs the carbon dioxide of a user's breathing, exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. ...
s,
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
,
submarines, and
spacesuits.
Production and reactions
Potassium superoxide is produced by burning molten potassium in an atmosphere of excess
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
.
:K + →
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 a reductant and a nucleophile, depending on its reaction partner.
Upon contact with water, it undergoes
disproportionation
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. More generally, the term can ...
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 exp ...
, oxygen, and hydrogen peroxide:
:2 + → 2 KOH +
: + → KOH + +
It reacts with carbon dioxide, releasing oxygen:
:2 + → K
2CO
3 +
:2 + 2 + H
2O → 2 KHCO
3 +
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 ether
In organic chemistry, crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups (). The most common crown ethers are cyclic oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., . Impo ...
s are typically used. The
tetraethylammonium
Tetraethylammonium (TEA), () or (Et4N+) is a quaternary ammonium cation consisting of four ethyl groups attached to a central nitrogen atom, and is positively charged. It is a counterion used in the research laboratory to prepare lipophilic salts ...
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 peroxides.
Ion exchange with
tetramethylammonium hydroxide gives tetramethylammonium superoxide, a yellow solid.
Applications
The
Russian Space Agency
The State Space Corporation "Roscosmos" (russian: Государственная корпорация по космической деятельности «Роскосмос»), commonly known simply as Roscosmos (russian: Роскосмос) ...
has had success using potassium superoxide in
chemical oxygen generator
A chemical oxygen generator is a device that releases oxygen via a chemical reaction. The oxygen source is usually an inorganic superoxide, chlorate, or perchlorate; ozonides are a promising group of oxygen sources. The generators are usually ig ...
s for its spacesuits and
Soyuz spacecraft. has also been used in canisters for rebreathers for
fire fighting
Firefighting is the act of extinguishing or preventing the spread of unwanted fires from threatening human lives and destroying property and the environment. A person who engages in firefighting is known as a firefighter.
Firefighters typicall ...
and
mine rescue
Mine rescue or mines rescue is the specialised job of rescuing miners and others who have become trapped or injured in underground mines because of mining accidents, roof falls or floods and disasters such as explosions.
Background
Mining ...
work, but had limited use in
scuba rebreathers because of its highly exothermic reaction with water.
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.
References
{{oxygen compounds
Potassium compounds
Superoxides
Oxidizing agents