Manganese dioxide is the

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 In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

. This blackish or brown solid occurs naturally as the mineral

pyrolusite Pyrolusite is a mineral consisting essentially of manganese dioxide ( Mn O2) and is important as an ore of manganese.. It is a black, amorphous appearing mineral, often with a granular, fibrous, or columnar structure, sometimes forming reniform ...

, which is the main ore 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 ...

and a component of

manganese nodule Polymetallic nodules, also called manganese nodules, are mineral concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. As nodules can be found in vast quantities, and contain valuable metals, ...

s. The principal use for is for dry-cell batteries, such as the

alkaline battery An alkaline battery (IEC code: L) is a type of primary battery where the electrolyte (most commonly potassium hydroxide) has a pH value above 7. Typically, these batteries derive energy from the reaction between zinc metal and manganese diox ...

and the

zinc–carbon battery A zinc–carbon battery (or carbon zinc battery in U.S. English) is the generic “heavy duty” disposable battery. It has been overtaken in recent times by the longer-lasting alkaline battery. A zinc–carbon battery is a dry cell that provi ...

, although it is also used for other battery chemistries such as

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 ...

zinc-ion batteries.. is also used as a

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

and as a precursor to other manganese compounds, such as . 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 ...

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

, for example, for the oxidation of

allylic In organic chemistry, an allyl group is a substituent with the structural formula . It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, . In 1844, Theodor Wertheim isolat ...

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

s. has an α- polymorph that can incorporate a variety of atoms (as well as water molecules) in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in as a possible cathode for

lithium-ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. Li-ion batteries are characterized by higher specific energy, energy ...

Structure

Several polymorphs of are claimed, as well as a hydrated form. Like many other dioxides, crystallizes in the

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at vis ...

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

(this polymorph is called

or ), with three-coordinate oxide anions and octahedral metal centres. is characteristically nonstoichiometric, being deficient in oxygen. The complicated

solid-state chemistry Solid-state chemistry, also sometimes referred as materials chemistry, is the study of the Chemical synthesis, synthesis, structure, and properties of solid phase materials. It therefore has a strong overlap with solid-state physics, mineralogy, cr ...

of this material is relevant to the lore of "freshly prepared" in

. The α-polymorph of has a very open structure with "channels", which can accommodate metal ions such as silver or barium. is often called

hollandite Hollandite (chemical formula: Ba(Mn4+6Mn3+2)O16) is a manganese oxide mineral. Its structure consists of double chains of MnO6 octahedra delimiting 2 × 2 tunnels. The electrostatic charge created by the Mn3+ for Mn4+ substitution is balanced by ...

, after a closely related mineral. Two other polymorphs, Todorokite and Romanechite , have a similar structure to but with larger channels. exhibits a layered structure more akin to that of

graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

Production

Naturally occurring manganese dioxide contains impurities and a considerable amount of

manganese(III) oxide Manganese(III) oxide is a chemical compound with the formula Mn2O3. It occurs in nature as the mineral bixbyite (recently changed to bixbyite-(Mn)IMA 21-H: Redefinition of bixbyite and definition of bixbyite-(Fe) and bixbyite-(Mn). CNMNC Newslett ...

. Production of batteries and ferrite (two of the primary uses of manganese dioxide) requires high purity manganese dioxide. Batteries require "electrolytic manganese dioxide" while ferrites require "chemical manganese dioxide"..

Chemical manganese dioxide

One method starts with natural manganese dioxide and converts it using

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

and water to a

manganese(II) nitrate Manganese(II) nitrate refers to the inorganic compounds with formula Mn( NO3)2·(H2O)n. These compounds are nitrate salts containing varying amounts of water. A common derivative is the tetrahydrate, Mn(NO3)2·4H2O, but mono- and hexahydrates are ...

solution. Evaporation of the water leaves the crystalline nitrate salt. At temperatures of 400 °C, the salt decomposes, releasing and leaving a residue of purified manganese dioxide. These two steps can be summarized as: : + In another process, manganese dioxide is carbothermically reduced to

manganese(II) oxide Manganese(II) oxide is an inorganic compound with chemical formula MnO.Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. It forms green crystals. The compound is produced on a large s ...

which is dissolved in

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

. The filtered solution is treated with

ammonium carbonate Ammonium carbonate is a chemical compound with the chemical formula . It is an ammonium salt of carbonic acid. It is composed of ammonium cations and carbonate anions . Since ammonium carbonate readily degrades to gaseous ammonia and carbon diox ...

to precipitate . The carbonate is

calcined Calcination is thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), generally fo ...

in air to give a mixture of manganese(II) and manganese(IV) oxides. To complete the process, a suspension of this material in sulfuric acid is treated with

sodium chlorate Sodium chlorate is an inorganic compound with the chemical formula Na ClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leaves sodium chloride. Sever ...

Chloric acid Chloric acid, H Cl O3, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid ( p''K''a ≈ −2.7) and an oxidizing agent. Properties Chloric acid is thermodynamically unstable with respect to disproportio ...

, which forms in situ, converts any Mn(III) and Mn(II) oxides to the dioxide, releasing chlorine as a by-product. Lastly, the action of

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. 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 us ...

over manganese sulfate crystals produces the desired oxide. :2 + 3 + 2 → 5 + + 2

Electrolytic manganese dioxide

Electrolytic manganese dioxide (EMD) is used in zinc–carbon batteries together with

zinc chloride Zinc chloride is an Inorganic chemistry, inorganic chemical compound with the chemical formula, formula ZnCl2·''n''H2O, with ''n'' ranging from 0 to 4.5, forming water of hydration, hydrates. Zinc chloride, anhydrous and its hydrates, are colo ...

and

ammonium chloride Ammonium chloride is an inorganic chemical compound with the chemical formula , also written as . It is an ammonium salt of hydrogen chloride. It consists of ammonium cations and chloride anions . It is a white crystalline salt (chemistry), sal ...

. EMD is commonly used in zinc manganese dioxide rechargeable alkaline (Zn RAM) cells also. For these applications, purity is extremely important. EMD is produced in a similar fashion as electrolytic tough pitch (ETP) copper: The manganese dioxide is dissolved in

(sometimes mixed with manganese sulfate) and subjected to a current between two electrodes. The MnO₂ dissolves, enters solution as the sulfate, and is deposited on the

anode An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the devic ...

Reactions

The important reactions of are associated with its

redox Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is t ...

, both oxidation and reduction.

Reduction

is the principal precursor to

ferromanganese Ferromanganese is an alloy of iron and manganese, with other elements such as silicon, carbon, sulfur, nitrogen and phosphorus. The primary use of ferromanganese is as a type of processed manganese source to add to different types of steel, such ...

and related alloys, which are widely used in the steel industry. The conversions involve

carbothermal reduction Carbothermic reactions involve the reduction of substances, often metal oxides (O2-), using carbon (C) as the reducing agent. The reduction is usually conducted in the electric arc furnace or reverberatory furnace, depending on the metal ore. Thes ...

using coke: : + 2 C → Mn + 2 CO The key redox reactions of in batteries is the one-electron reduction: : + e⁻ + → MnO(OH) catalyses several reactions that form . In a classical laboratory demonstration, heating a mixture of

potassium chlorate Potassium chlorate is the inorganic compound with the molecular formula KClO3. In its pure form, it is a white solid. After sodium chlorate, it is the second most common chlorate in industrial use. It is a strong oxidizing agent and its most impor ...

and manganese dioxide produces oxygen gas. Manganese dioxide also catalyses the decomposition of

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

to oxygen and

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

: :2 → 2 + Manganese dioxide decomposes above about 530 °C to

and oxygen. At temperatures close to 1000 °C, the

mixed-valence compound Mixed valence complexes contain an element which is present in more than one oxidation state. Well-known mixed valence compounds include the Creutz–Taube complex, Prussian blue, and molybdenum blue. Many solids are mixed-valency including ...

forms. Higher temperatures give MnO, which is reduced only with difficulty. Hot concentrated

reduces to

manganese(II) sulfate Manganese(II) sulfate usually refers to the inorganic compound with the Chemical formula, formula MnSO4·H2O. This pale pink deliquescent solid is a commercially significant manganese(II) salt. Approximately 260,000 tonnes of manganese(II) sulfate ...

: :2 + 2 → 2 + + 2 The reaction of

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

with was used by

Carl Wilhelm Scheele Carl Wilhelm Scheele (, ; 9 December 1742 – 21 May 1786) was a Swedish Pomerania, German-Swedish pharmaceutical chemist. Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified the elements molybd ...

in the original isolation of

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 ...

gas in 1774: : + 4 HCl → + + 2 As a source of hydrogen chloride, Scheele treated

sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...

with concentrated sulfuric acid. ::''E''^o ((s) + 4 + 2 e⁻ Mn²⁺ + 2 ) = +1.23 V ::''E''^o ((g) + 2 e⁻ 2 Cl⁻) = +1.36 V The reaction would not be expected to proceed, based on the

standard electrode potential In electrochemistry, standard electrode potential E^\ominus, or E^\ominus_, is the electrode potential (a measure of the reducing power of any element or compound) which the IUPAC "Gold Book" defines as ''"the value of the standard emf ( electrom ...

s, but is favoured by the extremely high

acidity An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen cation, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid. The first category of acids are the ...

and the evolution (and removal) of gaseous chlorine. This reaction is also a convenient way to remove the manganese dioxide

precipitate In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemic ...

from the

ground glass joint Ground glass joints are used in laboratories to quickly and easily fit leak-tight apparatus together from interchangeable commonly available parts. For example, a round bottom flask, Liebig condenser, and oil bubbler with ground glass joints may ...

s after running a reaction (for example, an oxidation with

Oxidation

Heating a mixture of KOH and in air gives green potassium manganate: :2 + 4 KOH + → 2 + 2 Potassium manganate is the precursor to

, a common oxidant.

Occurrence and applications

Prehistory

Excavations at the Pech-de-l'Azé cave site in southwestern France have yielded blocks of manganese dioxide writing tools, which date back 50,000 years and have been attributed to

Neanderthals Neanderthals ( ; ''Homo neanderthalensis'' or sometimes ''H. sapiens neanderthalensis'') are an extinction, extinct group of archaic humans who inhabited Europe and Western and Central Asia during the Middle Pleistocene, Middle to Late Plei ...

. Scientists have conjectured that Neanderthals used this mineral for body decoration, but there are many other readily available minerals that are more suitable for that purpose. Heyes et al. (in 2016) determined that the manganese dioxide lowers the combustion temperatures for wood from above 350°C (662°F) to 250°C (482°F), making fire making much easier and this is likely to be the purpose of the blocks.

Batteries

The predominant application of is as a component of

dry cell An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its nega ...

batteries: alkaline batteries and so called

Leclanché cell The Leclanché cell is a battery invented and patented by the French scientist Georges Leclanché in 1866. The battery contained a conducting solution (electrolyte) of ammonium chloride, a cathode (positive terminal) of carbon, a depolarizer of ...

, or zinc–carbon batteries. Approximately 500,000

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...

s are consumed for this application annually. δ- has also been researched as the primary cathode material for aqueous zinc-ion battery systems. Such cathodes often contain additives to address structural, kinetic, and conductivity-based issues. These carbon additives can include reduced graphene oxide (rGO) and

carbon nanotubes A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized: * ''Single-walled carbon nanotubes'' (''SWC ...

, among others.

Organic synthesis

A specialized use of manganese dioxide is as oxidant in

.. The effectiveness of the reagent depends on the method of preparation, a problem that is typical for other heterogeneous reagents where surface area, among other variables, is a significant factor. The mineral

makes a poor reagent. Usually, however, the reagent is generated in situ by treatment of an aqueous solution with a Mn(II) salt, typically the sulfate. oxidizes

alcohols to the corresponding

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 or

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

s: ::cis-RCH= + → cis-RCH=CHCHO +

MnO Manganese(II) oxide is an inorganic compound with chemical formula MnO.Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. It forms green crystals. The compound is produced on a large s ...

+ The configuration of the

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

is conserved in the reaction. The corresponding

acetylenic In organic chemistry, the term acetylenic designates *A doubly unsaturated position (''sp''-hybridized) on a molecular framework, for instance in an alkyne such as acetylene Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemi ...

alcohols are also suitable substrates, although the resulting

propargylic In organic chemistry, the propargyl group is a functional group of 2- propynyl with the structure . It is an alkyl group derived from propyne (). The term propargylic refers to a saturated position ( ''sp''3-hybridized) on a molecular framewor ...

aldehydes can be quite reactive. Benzylic and even unactivated alcohols are also good substrates. 1,2-

Diol A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol may also be called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. They are used as protecting gro ...

s are cleaved by to

dialdehyde 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 or diketones. Otherwise, the applications of are numerous, being applicable to many kinds of reactions including

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

oxidation, aromatization, oxidative coupling, and

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

oxidation.

Other potential applications

In '' Geobacteraceae'' sp., MnO₂ functions as an electron acceptor coupled to the oxidation of organic compounds. This theme has possible implications for

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi in mycoremediation, and plants in phytoremediation), living or dead, is employed for removing environmental pollutants from air, wate ...

within the field of microbiology. is used as an inorganic

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

s and in

glassmaking Glass production involves two main methods – the float glass process that produces sheet glass, and glassblowing that produces bottles and other containers. It has been done in a variety of ways during the history of glass. Glass container ...

References

Cited sources

External links

Index of Organic Synthesis procedures utilizing

Example Reactions with Mn(IV) oxide

* ttps://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=14801 PubChem summary of
International Chemical Safety Card 0175

*
The reaction between manganese dioxide and potassium permanganate
' (1893) by A. J. Hopkins {{DEFAULTSORT:Manganese Dioxide Manganese(IV) compounds Inorganic pigments Transition metal oxides Glass dyes