Potassium permanganate 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
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
KMnO
4. It is a purplish-black crystalline salt, which dissolves in water as
K+ and
ions to give an intensely pink to purple solution.
Potassium permanganate is widely used in the
chemical industry
The chemical industry comprises the companies and other organizations that develop and produce industrial, specialty and other chemicals. Central to the modern world economy, the chemical industry converts raw materials ( oil, natural gas, air, ...
and
laboratories
A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which science, scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as s ...
as a strong
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...
, and also
as a medication for
dermatitis
Dermatitis is a term used for different types of skin inflammation, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened ...
, for cleaning
wound
A wound is any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma (mechanical, thermal, chemical), or can develop slowly over time due to underlying diseas ...
s, and general
disinfection
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
. It is commonly used as a
biocide
A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US Environmental Protection Agency (EPA) uses a sli ...
for
water treatment
Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, ...
purposes. It is on the
World Health Organization's List of Essential Medicines.
In 2000, worldwide production was estimated at 30,000 tons.
Properties
Potassium permanganate is the potassium salt of the tetrahedral
transition metal oxo complex permanganate
A permanganate () is a chemical compound with the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom has a +7 oxidation state, the permanganate(VII) ion is a strong oxidising agent. The ion is a transition ...
, in which four ligands are bound to a
manganese(VII) center.
Structure
forms
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
crystals with constants: ''a'' = 910.5
pm, ''b'' = 572.0 pm, ''c'' = 742.5 pm. The overall motif is similar to that for
barium sulfate
Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Ba SO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs in nature as the mineral barite, which is the main commercial source of ...
, with which it forms
solid solution
A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...
s. In the solid (as in solution), each centre is tetrahedral. The Mn–O distances are 1.62 Å.
Color
The purplish-black color of solid potassium permanganate, and the intensely pink to purple color of its solutions, is caused by its permanganate anion, which gets its color from a strong
charge-transfer absorption band caused by excitation of electrons from oxo ligand orbitals to empty orbitals of the manganese(VII) center.
Medical uses
Mechanism of action
Potassium permanganate functions as a strong
oxidising agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...
.
Through this mechanism it results in
disinfection
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
,
astringent effects, and decreased smell.
Clinical use
Potassium permanganate is used for a number of
skin condition
A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this ...
s.
This includes
fungal infections of the foot,
impetigo,
pemphigus
Pemphigus ( or ) is a rare group of blistering autoimmune diseases that affect the skin and mucous membranes.
The name is derived from the Greek root ''pemphix'', meaning "blister".
In pemphigus, autoantibody, autoantibodies form against de ...
, superficial wounds,
dermatitis
Dermatitis is a term used for different types of skin inflammation, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened ...
, and topical ulcers.
Radioactive contamination
Radioactive contamination, also called radiological pollution, is the deposition of, or presence of Radioactive decay, radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is uni ...
of the skin can be cleaned with potassium permanganate and vigorous scrubbing. For topical ulcers it is used together with
procaine benzylpenicillin.
Typically it is used in skin conditions that produce a lot of liquid.
It can be applied as a soaked dressing or a bath.
It can be used in children and adults.
Petroleum jelly may be used on the nails before soaking to prevent their discoloration.
For treating eczema, it is recommended using for only a few days at a time due to the possibility of it irritating the skin.
The
U.S. Food and Drug Administration does not recommend its use in the crystal or tablet form. It should only be used in a diluted liquid form.
Historical use
Potassium permanganate was first made in the 1600s and came into common medical use at least as early as the 1800s.
During
World War I
World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
Canadian soldiers were given potassium permanganate (to be applied mixed with an ointment) in an effort to prevent
sexually transmitted infections
A sexually transmitted infection (STI), also referred to as a sexually transmitted disease (STD) and the older term venereal disease (VD), is an infection that is spread by sexual activity, especially vaginal intercourse, anal sex, or ...
. Some have attempted to bring about an
abortion
Abortion is the early termination of a pregnancy by removal or expulsion of an embryo or fetus. Abortions that occur without intervention are known as miscarriages or "spontaneous abortions", and occur in roughly 30–40% of all pregnan ...
by putting it in the vagina, though this is not effective.
Other historical uses have included an effort to wash out the stomach in those with
strychnine
Strychnine (, , American English, US chiefly ) is a highly toxicity, toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, ...
or
picrotoxin poisoning.
Side effects
Side effects from
topical use may include irritation of the skin and discoloration of clothing.
A harsh burn on a child from an undissolved tablet has been reported.
Higher concentration solutions can result in
chemical burn
A chemical burn occurs when living tissue is exposed to a corrosive substance (such as a strong acid, base or oxidizer) or a cytotoxic agent (such as mustard gas, lewisite or arsine). Chemical burns follow standard burn classification and m ...
s. Therefore, the
British National Formulary
The ''British National Formulary'' (BNF) is a United Kingdom (UK) pharmaceutical reference book that contains a wide spectrum of information and advice on prescribing and pharmacology, along with specific facts and details about many medicin ...
recommends 100 mg be dissolved in a liter of water before use to form a 1:10,000 (0.01%) solution.
Wrapping the dressings soaked with potassium permanganate is not recommended.
Potassium permanganate is toxic if taken by mouth. Side effects may include nausea, vomiting, and shortness of breath may occur.
If a sufficiently large amount (about 10 grams) is eaten death may occur.
Concentrated solutions when drunk have resulted in
acute respiratory distress syndrome
Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin co ...
or swelling of the airway.
Recommended measures for those who have ingested potassium permanganate include
gastroscopy.
Activated charcoal
"Activated" is a song by English singer Cher Lloyd. It was released on 22 July 2016 through Vixen Records. The song was made available to stream exclusively on ''Rolling Stone'' a day before to release (on 21 July 2016).
Background
In an inter ...
or medications to cause vomiting are not recommended. While medications like
ranitidine
Ranitidine, previously sold under the brand name Zantac among others, is a medication used to decrease stomach acid production. It was commonly used in treatment of peptic ulcer disease, gastroesophageal reflux disease, and Zollinger–Ellis ...
and
acetylcysteine may be used in toxicity, evidence for this use is poor.
Pharmaceuticals
In the United States the FDA requires tablets of the medication to be sold by
prescription.
Potassium permanganate, however, does not have FDA approved uses and therefore non medical grade potassium permanganate is sometimes used for medical purposes.
It is available under a number of
brand names including Permasol, Koi Med Tricho-Ex, and Kalii permanganas RFF. It is occasionally called "Condy's crystals".
Veterinary medicine
Potassium permanganate may be used to prevent the spread of
glanders among horses.
Industrial and other uses
Almost all applications of potassium permanganate exploit its
oxidizing properties.
As a strong oxidant that does not generate toxic byproducts, KMnO
4 has many niche uses.
Water treatment
Potassium permanganate is used extensively in the water treatment industry. It is used as a regeneration chemical to remove
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
(rotten egg smell) from
well
A well is an excavation or structure created on the earth by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The ...
water via a "manganese greensand" filter. "Pot-Perm" is also obtainable at
pool
Pool may refer to:
Bodies of water
* Swimming pool, usually an artificial structure containing a large body of water intended for swimming
* Reflecting pool, a shallow pool designed to reflect a structure and its surroundings
* Tide pool, a roc ...
supply stores and is used additionally to treat wastewater. Historically it was used to disinfect drinking water and can turn the water pink. Modern hiking and survivalist guides advise against using potassium permanganate in the field because it is difficult to dose correctly. It currently finds application in the control of nuisance organisms such as
zebra mussel
The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel, an Aquatic animal, aquatic bivalve mollusk in the family Dreissenidae. The species originates from the lakes of southern Russia and Ukraine, but has been accidentally Intro ...
s in fresh water collection and treatment systems.
Synthesis of organic compounds

A major application of KMnO
4 is as a reagent for the synthesis of organic compounds. Significant amounts are required for the synthesis of
ascorbic acid
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent.
Asco ...
,
chloramphenicol,
saccharin,
isonicotinic acid, and
pyrazinoic acid.
KMnO
4 is used in
qualitative organic analysis to test for the presence of
unsaturation. It is sometimes referred to as Baeyer's reagent after the German organic chemist
Adolf von Baeyer
Johann Friedrich Wilhelm Adolf von Baeyer (; 31 October 1835 – 20 August 1917) was a German chemist who synthesised indigo dye, indigo and developed a Von Baeyer nomenclature, nomenclature for cyclic compounds (that was subsequently extended a ...
. The reagent is an alkaline solution of potassium permanganate. Reaction with double or triple bonds ( or ) causes the color to fade from purplish-pink to brown.
Aldehyde
In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...
s and
formic acid
Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid. It has the chemical formula HCOOH and structure . This acid is an important intermediate in chemical synthesis and occurs naturally, most notably in some an ...
(and
formates) also give a positive test. The test is antiquated.
KMnO
4 solution is a common
thin layer chromatography (TLC) stain for the detection of oxidizable functional groups, such as alcohols, aldehydes, alkenes, and ketones. Such compounds result in a white to orange spot on TLC plates.
Analytical use
Potassium permanganate can be used to quantitatively determine the total oxidizable organic material in an aqueous sample. The value determined is known as the ''permanganate value.'' In
analytical chemistry
Analytical skill, Analytical chemistry studies and uses instruments and methods to Separation process, separate, identify, and Quantification (science), quantify matter. In practice, separation, identification or quantification may constitute t ...
, a standardized
aqueous
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in wat ...
solution of KMnO
4 is sometimes used as an oxidizing
titrant for
redox titration
A redox titration is a type of titration based on a redox reaction between the analyte and titrant. It may involve the use of a redox indicator and/or a potentiometer. A common example of a redox titration is the treatment of a solution of iodine ...
s (
permanganometry). As potassium permanganate is titrated, the solution becomes a light shade of purple, which darkens as excess of the titrant is added to the solution. In a related way, it is used as a
reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
to determine the
Kappa number of wood pulp. For the standardization of KMnO
4 solutions, reduction by
oxalic acid
Oxalic acid is an organic acid with the systematic name ethanedioic acid and chemical formula , also written as or or . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name i ...
is often used. In agricultural chemistry, it is used for estimation of active
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
in soil.
Aqueous, acidic solutions of KMnO
4 are used to collect gaseous
mercury in flue gas during stationary source emissions testing.
In
histology
Histology,
also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...
, potassium permanganate was used as a bleaching agent.
Fruit preservation
Ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
absorbents extend storage time of
banana
A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...
s even at high temperatures. This effect can be exploited by packing bananas in
polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...
together with potassium permanganate. By removing ethylene by oxidation, the permanganate delays the ripening, increasing the fruit's shelf life up to 4 weeks without the need for refrigeration.
The chemical reaction, in which
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
(C
2H
4) is oxidised by potassium permanganate (KMnO
4) to
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
(CO
2),
manganese oxide (MnO
2) and
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 ...
(KOH), in the presence of water, is presented as follows:
3 C
2H
4 + 12 KMnO
4 + 2 H
2O → 6 CO
2 + 2 H
2O + 12 MnO
2 + 12 KOH
Survival kits
Potassium permanganate is sometimes included in survival kits: as a
hypergolic fire starter (when mixed with
glycerol
Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...
antifreeze from a car radiator);
as a water sterilizer; and for creating distress signals on snow.
Fire service
Potassium permanganate is added to "plastic sphere dispensers" to create backfires, burnouts, and
controlled burns. Polymer spheres resembling
ping-pong balls containing small amounts of permanganate are injected with
ethylene glycol and projected towards the area where ignition is desired, where they spontaneously ignite seconds later.
Both handheld helicopter- unmanned aircraft systems (UAS) or boat-mounted plastic sphere dispensers are used.
Other uses
Potassium permanganate is one of the principal chemicals used in the film and television industries to "age" props and set dressings. Its ready conversion to brown
MnO2 creates "hundred-year-old" or "ancient" looks on
hessian cloth (burlap), ropes, timber and glass.
Potassium permanganate can be used to oxidize
cocaine paste to purify it and increase its stability. This led to the
Drug Enforcement Administration
The Drug Enforcement Administration (DEA) is a Federal law enforcement in the United States, United States federal law enforcement agency under the U.S. Department of Justice tasked with combating illicit Illegal drug trade, drug trafficking a ...
launching Operation Purple in 2000, with the goal of monitoring the world supply of potassium permanganate; however, potassium permanganate derivatives and substitutes were soon used thereafter to avoid the operation.
Potassium permanganate is used as an
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...
in the synthesis of
cocaine
Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
and
methcathinone.
Potassium permanganate is one of a number of possible treatments for ''
Ichthyophthirius multifiliis'' (commonly known as "ich"), a parasite that infects and usually kills freshwater aquarium fish.
History
In 1659,
Johann Rudolf Glauber fused a mixture of the mineral
pyrolusite (manganese dioxide, MnO
2) and
potassium carbonate to obtain a material that, when dissolved in water, gave a green solution (
potassium manganate) which slowly shifted to violet and then finally red. The reaction that produced the color changes that Glauber observed in his solution of potassium permanganate and potassium manganate (K
2MnO
4) is now known as the "
chemical chameleon". This report represents the first description of the production of potassium permanganate. Just under 200 years later, London chemist
Henry Bollmann Condy had an interest in disinfectants; he found that fusing pyrolusite with
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly corrosive base (chemistry), ...
(NaOH) and dissolving it in water produced a solution with disinfectant properties. He patented this solution, and marketed it as 'Condy's Fluid'. Although effective, the solution was not very stable. This was overcome by using
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 ...
(KOH) rather than NaOH. This was more stable, and had the advantage of easy conversion to the equally effective potassium permanganate crystals. This crystalline material was known as 'Condy's crystals' or 'Condy's powder'. Potassium permanganate was comparatively easy to manufacture, so Condy was subsequently forced to spend considerable time in litigation to stop competitors from marketing similar products. According to
Varlam Shalamov, potassium permanganate solution was used as a catch-all treatment for dysentery, frostbite and ulcers in the Gulag camps of Kolyma.
Early photographers used it as a component of
flash powder. It is now replaced with other oxidizers, due to the instability of permanganate mixtures.
Preparation
Potassium permanganate is produced industrially from
manganese dioxide
Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cel ...
, which also occurs as the mineral
pyrolusite. In 2000, worldwide production was estimated at 30,000 tonnes.
The MnO
2 is fused with
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 ...
and heated in
air
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
or with another source of oxygen, like
potassium nitrate
Potassium nitrate is a chemical compound with a sharp, salty, bitter taste and the chemical formula . It is a potassium salt of nitric acid. This salt consists of potassium cations and nitrate anions , and is therefore an alkali metal nit ...
or
potassium chlorate.
This process gives
potassium manganate:
:
With sodium hydroxide, the end product is not
sodium manganate but a Mn(V) compound, which is one reason why the potassium permanganate is more commonly used than
sodium permanganate
Sodium permanganate is the inorganic compound with the formula sodium, NaPermanganate, MnO4. It is closely related to the more commonly encountered potassium permanganate, but it is generally less desirable, because it is more expensive to produce ...
. Furthermore, the potassium salt crystallizes better.
The potassium manganate is then converted into permanganate by
electrolytic oxidation in alkaline media:
:
Other methods
Although of no commercial importance, potassium manganate can be oxidized by
chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
or by
disproportionation under acidic conditions. The chlorine oxidation reaction is
:
and the acid-induced disproportionation reaction may be written as
:
A weak acid such as
carbonic acid
Carbonic acid is a chemical compound with the chemical formula . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion ...
is sufficient for this reaction:
:
Permanganate salts may also be generated by treating a solution of Mn
2+ ions with strong oxidants such as
lead dioxide (PbO
2),
sodium bismuthate (NaBiO
3), or
peroxydisulfate.
Tests
Test(s), testing, or TEST may refer to:
* Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities
Arts and entertainment
* ''Test'' (2013 film), an American film
* ''Test'' (2014 film) ...
for the presence of manganese exploit the vivid violet color of permanganate produced by these reagents.
Reactions
Organic chemistry
Dilute solutions of KMnO
4 convert
alkene
In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins.
The Internationa ...
s into
diols. This behaviour is also used as a
qualitative test for the presence of double or triple bonds in a molecule, since the reaction decolorizes the initially purple
permanganate
A permanganate () is a chemical compound with the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom has a +7 oxidation state, the permanganate(VII) ion is a strong oxidising agent. The ion is a transition ...
solution and generates a brown precipitate (MnO
2). In this context, it is sometimes called ''Baeyer's reagent''. However,
bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
serves better in measuring unsaturation (double or triple bonds) quantitatively, since KMnO
4, being a very strong
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...
, can react with a variety of groups.
Under acidic conditions, the alkene double bond is cleaved to give the appropriate
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
:
:
Potassium permanganate oxidizes aldehydes to carboxylic acids, illustrated by the conversion of ''n''-
heptanal to heptanoic acid:
:
Even an alkyl group (with a benzylic hydrogen) on an
aromatic ring is oxidized, e.g.
toluene
Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water
Water is an inorganic compound with the c ...
to
benzoic acid
Benzoic acid () is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. The benzoyl group is often abbreviated "Bz" (not to be confused with "Bn," which ...
.
:
Glycols and
polyol
In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, th ...
s are highly reactive toward KMnO
4. For example, addition of potassium permanganate to an aqueous solution of
sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...
and
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly corrosive base (chemistry), ...
produces the
chemical chameleon reaction, which involves dramatic color changes associated with the various oxidation states of
manganese
Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...
. A related vigorous reaction is exploited as a fire starter in survival kits. For example, a mixture of potassium permanganate and
glycerol
Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...
or pulverized
glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
ignites readily.
Its sterilizing properties are another reason for inclusion of KMnO
4 in a survival kit.
Ion exchange
Treating a mixture of aqueous potassium permanganate with a
quaternary ammonium salt
In organic chemistry, quaternary ammonium cations, also known as quats, are positively-charged polyatomic ions of the structure , where R is an alkyl group, an aryl group or organyl group. Unlike the ammonium ion () and the primary, secondary, ...
results in ion exchange, precipitating the quat salt of permanganate. Solutions of these salts are sometimes soluble in organic solvents:
:
Similarly, addition of a
crown ether also gives a lipophilic salt.
Reaction with acids and bases
Permanganate reacts with concentrated
hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
to give
chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
and manganese(II):
:
In
neutral solution, permanganate slowly reduces to
manganese dioxide
Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cel ...
(MnO
2). This is the material that stains one's skin when handling KMnO
4.
KMnO
4 reduces in
alkaline
In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...
solution to give green
K2MnO4:
:
This reaction illustrates the relatively rare role of hydroxide as a reducing agent.
Addition of concentrated sulfuric acid to potassium permanganate gives
Mn2O7. Although no reaction may be apparent, the vapor over the mixture will ignite paper impregnated with alcohol. Potassium permanganate and sulfuric acid react to produce some
ozone
Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...
, which has a high oxidizing power and rapidly oxidizes the alcohol, causing it to combust. As the reaction also produces explosive Mn
2O
7, this should only be attempted with great caution.
Thermal decomposition
Solid potassium
permanganate
A permanganate () is a chemical compound with the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom has a +7 oxidation state, the permanganate(VII) ion is a strong oxidising agent. The ion is a transition ...
decomposes when heated:
:
It is a redox reaction.
Safety and handling
Potassium permanganate poses risks as an
oxidizer.
Contact with skin can cause skin irritation and in some cases severe allergic reaction. It can also result in discoloration and clothing stains.
References
Further reading
"The reaction between manganese dioxide and potassium permanganate"(1893) by A. J. Hopkins
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