A permanganate () is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

containing the manganate(VII)

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

, , the

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

permanganic acid Permanganic acid (or manganic(VII) acid) is the inorganic compound with the formula H MnO4. This strong oxoacid has been isolated as its dihydrate. It is the conjugate acid of permanganate salts. It is the subject of few publications and its c ...

. Because the

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

atom is in the +7

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

, the permanganate(VII) ion is 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 ). In other words, an oxi ...

. The ion is a transition metal oxo complex with tetrahedral geometry. Permanganate solutions are purple in color and are stable in

neutral Neutral or neutrality may refer to: Mathematics and natural science Biology * Neutral organisms, in ecology, those that obey the unified neutral theory of biodiversity Chemistry and physics * Neutralization (chemistry), a chemical reaction in ...

or slightly alkaline media. The exact chemical reaction is dependent upon the organic contaminants present and the oxidant utilized. For example, trichloroethane (C₂H₃Cl₃) is oxidized by permanganate ions to form carbon dioxide (CO₂), manganese dioxide (MnO₂), hydrogen ions (H⁺), and chloride ions (Cl⁻). :8 + 3 → 6 + 8 + + 4 + 9 In an acidic solution, permanganate(VII) is reduced to the pale pink +2 oxidation state of the manganese(II) (Mn²⁺) ion. :8 + + 5 e⁻ → Mn²⁺ + 4 H₂O In a strongly basic solution, permanganate(VII) is reduced to the green +6 oxidation state of the manganate ion, . : + e⁻ → In a neutral medium, however, it gets reduced to the brown +4 oxidation state of manganese dioxide MnO₂. :2 H₂O + + 3 e⁻ → MnO₂ + 4 OH⁻

Production

Permanganates can be produced by oxidation of manganese compounds such as

manganese chloride Manganese(II) chloride is the dichloride salt of manganese, MnCl2. This inorganic chemical exists in the anhydrous form, as well as the diWater of crystallization, hydrate (MnCl2·2H2O) and tetrahydrate (MnCl2·4H2O), with the tetrahydrate being t ...

or manganese sulfate by strong oxidizing agents, for instance,

sodium hypochlorite Sodium hypochlorite (commonly known in a dilute solution as bleach) is an inorganic chemical compound with the formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may also be viewed as the sodium s ...

or lead dioxide: :2 MnCl₂ + 5 NaClO + 6 NaOH → 2 NaMnO₄ + 9 NaCl + 3 H₂O :2 MnSO₄ + 5 PbO₂ + 3 H₂SO₄ → 2 HMnO₄ + 5 PbSO₄ + 2 H₂O It may also be produced by the disproportionation of manganates, with manganese dioxide as a side-product: :3 Na₂MnO₄ + 2 H₂O → 2 NaMnO₄ + MnO₂ + 4 NaOH They are produced commercially by electrolysis or air oxidation of alkaline solutions of manganate salts (). Potassium permanganate solutions 2

Properties

Permanganates(VII) are

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

s of permanganic acid. They have a deep purple colour, due to a charge transfer transition from oxo ligand ''p'' orbitals to empty orbitals derived from manganese(VII) ''d'' orbitals. Permanganate(VII) is a strong

oxidizer 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 ). In other words, an oxid ...

, and similar to perchlorate. It is therefore in common use in qualitative analysis that involves redox reactions (

permanganometry Permanganometry is one of the techniques used in chemical quantitative analysis. It is a redox titration that involves the use of permanganates to measure the amount of analyte present in unknown chemical samples. It involves two steps, namely the t ...

). According to theory, permanganate is strong enough to oxidize water, but this does not actually happen to any extent. Besides this, it is stable. It is a useful reagent, but it is not very selective with organic compounds.

Potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

is used as a disinfectant and water treatment additive in aquaculture. Manganates(VII) are not very stable thermally. For instance,

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

decomposes at 230 °C to

potassium manganate Potassium manganate is the inorganic compound with the formula . This green-colored salt is an intermediate in the industrial synthesis of potassium permanganate (), a common chemical. Occasionally, potassium manganate and potassium ''per''manga ...

and manganese dioxide, releasing

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 ...

gas: :2 KMnO₄ → K₂MnO₄ + MnO₂ + O₂ A permanganate can oxidize an

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

to a

nitro compound In organic chemistry, nitro compounds are organic compounds that contain one or more nitro functional groups (). The nitro group is one of the most common explosophores (functional group that makes a compound explosive) used globally. The nitr ...

, an alcohol to a ketone, an

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

to a carboxylic acid, a terminal

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

to a carboxylic acid, oxalic acid to

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

, and an

to a diol. This list is not exhaustive. In alkene oxidations one intermediate is a cyclic Mn(V) species:. : PermanganateMechanismOxidation

Compounds

* Ammonium permanganate, NH₄MnO₄ * Barium permanganate, Ba(MnO₄)₂ *

Calcium permanganate Calcium permanganate is an oxidizing agent and chemical compound with the chemical formula Ca(MnO4)2. This salt consists of the metal calcium and two permanganate ions. Preparation The salt is prepared from the reaction of potassium permanganat ...

, Ca(MnO₄)₂ *

, KMnO₄ *

Sodium permanganate Sodium permanganate is the inorganic compound with the formula Na 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. It is mainly avai ...

, NaMnO₄ * Silver permanganate, AgMnO₄

References

{{Reflist, 30em Oxometallates

Production

Properties

Compounds

See also

References