Manganese(IV) oxide
General
Systematic name	Manganese dioxide Manganese(IV) oxide
Other names	Pyrolusite
Molecular formula	MnO2
Molar mass	86.94 g/mol (varies)
Appearance	black solid
CAS number	[1313-13-9]
Properties
Density and phase	5.026 g/cm3, solid
Solubility in water	Insoluble
Melting point	535 °C decomp.
Thermodynamic data
Standard enthalpy of formation ΔfH°solid	−520.9 kJ/mol
Standard molar entropy S°solid	53.1 J.K−1.mol−1
Hazards
EU classification	Harmful (Xn)
R-phrases	R20/22
S-phrases	S2, S25
NFPA 704
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Regulatory data	Flash point, RTECS number, etc.
Related compounds
Other anions	Manganese disulfide
Other cations	Technetium dioxide Rhenium dioxide
Related compounds	Manganese(II) oxide Hausmannite Manganese(III) oxide Manganese trioxide Manganese heptoxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Manganese(IV) oxide is the chemical compound MnO₂, more usually called manganese dioxide. This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese. It is also present in manganese nodules. The principal use for MnO₂ is for dry-cell batteries, such as the alkaline battery and the zinc-carbon battery. In 1976 this application accounted for 500,000 tonnes of pyrolusite.^[1] MnO₂ is also be used for production of MnO₄^-. It is used extensively as an oxidising agent in organic synthesis, for example, for the oxidation of allylic alcohols. Image File history File links Manganese(IV)_oxide. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... Pyrolusite This article incorporates text from the public domain 1911 Encyclopædia Britannica. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... It has been suggested that this article or section be merged with Solution. ... Water has the chemical formula H2O, meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 atmosphere... In chemistry, the standard molar entropy is the entropy content of one mole of substance, under conditions of standard temperature and pressure. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main source of European Union law concerning chemical safety. ... R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The dielectric constant εr (represented as or K in some cases) is defined as the ratio: where εs is the static permittivity of the material in question, and ε0 is the vacuum permittivity. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... IR spectrum of a thin film of liquid ethanol. ... Nuclear Magnetic Resonance Spectroscopy most commonly known as NMR Spectroscopy is the name given to the technique which exploits the magnetic properties of nuclei. ... Basic schematic of mass spectrometry Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. ... The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture with air. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... // An ion is an atom or a group of atoms (a chemical substance), or subatomic particle, with a net electric charge. ... // An ion is an atom or a group of atoms (a chemical substance), or subatomic particle, with a net electric charge. ... Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. ... Pyrolusite This article incorporates text from the public domain 1911 Encyclopædia Britannica. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Atomic mass 54. ... Polymetallic nodules, also called manganese nodules, are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. ... This article or section is missing references or citation of sources. ... 2 Duracell-Brand AAA Alkaline batteries Alkaline batteries are a type of power cell dependent upon the reaction between zinc and manganese dioxide (Zn/MnO2). ... Zinc-carbon batteries of different sizes. ... A tonne (symbol t), sometimes referred to as a metric tonne, is a measurement of weight. ... Potassium permanganate (KMnO4) is an inorganic chemical compound composed of potassium (K+) and permanganate (MnO4−) ions. ... Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... Organic synthesis is the construction of organic molecules via chemical processes. ... An allyl group is an alkene hydrocarbon group with the formula H2C=CH-CH2-. It is made up of a vinyl group, CH2=CH-, attached to a methylene -CH2. ... In chemistry, an alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group. ...

Other oxides of manganese (see Manganate)

The green salt potassium manganate is obtained after about 10 minutes when a solution of MnO₂ in molten KOH or NaOH is treated with oxidizing agents such as saltpeter (potassium nitrate KNO₃) or potassium perchlorate (KClO₄). Definition The manganate ion is MnO42-. A manganate is a compound that contains this group. ... Potassium permanganate (KMnO4) is an inorganic chemical compound composed of potassium (K+) and permanganate (MnO4-) ions. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidising agents An oxidizing agent is a compound that oxidizes another substance in electrochemistry or redox chemical reactions. ... Saltpeter is variously: potassium nitrate (niter); or sodium nitrate (soda niter) Uses: manufacture of gunpowder, the manufacture of sulfuric and nitric acids, glassmaking, an oxidant and flux in metallurgical operations, curing of meat when mixed with salt and sugar, the preparation of fluxing and denoting powders, manure, used in many... R-phrases   S-phrases   Supplementary data page Structure and properties n, εr, etc. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Potassium perchlorate, chemical formula KClO4, is a strong oxidizer. ... General Name, Symbol, Number potassium, K, 19 Series alkali metals Group, Period, Block 1(IA), 4 , s Density, Hardness 856 kg/m3, 0. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...

2MnO₂ + 4OH^- + O₂ → 2MnO₄^2- + 2H₂O

Potassium manganate converts into purple potassium permanganate in aqueous acidic solution: 3MnO₄^2- + 4H⁺ → 2 MnO₄^- + MnO₂(s) + 2H₂O Potassium permanganate (KMnO4) is an inorganic chemical compound composed of potassium (K+) and permanganate (MnO4−) ions. ... Drinking water This article focuses on water as we experience it every day. ... For other uses, see Acid (disambiguation). ...

MnO₂ in organic synthesis

Manganese dioxide is widely used as an oxidant in organic synthesis. Forms of MnO₂ useful as an oxidizing reagent is not a straightforwardly stoichiometric reagent, far from it. The method of reagent preparation, sample history, and solvents are serious considerations. These problems are typical for many heterogeneous reagents where surface area, among other variables, is a significant variable. Compounding this problem, MnO₂ exists in various crystalline forms and is not stoichiometric, being better described as MnO_2-x(H₂O)_n where 0<x<0.5 and n can be nonzero. The mineral pyrolusite makes a poor reagent. A variety of recipes exist for "MnO₂." Usually, however, the reagent is generated by treatment of an aqueous solution KMnO₄ with a Mn(II) salt, typically the sulfate at various pH’s. The brown precipitate of “manganese dioxide” is dried and activated thermally. It is used in anywhere from 5-50x excess relative to the substrate. Typical solvents are aromatic hydrocarbons, chlorocarbons, diethyl ether, THF, acetone, and ethyl acetate.

The predominant application of MnO₂ is for the oxidation of allylic alcohols to the corresponding aldehydes. The configuration of the double bond is conserved:

cis-RCH=CHCH₂OH + MnO₂ → cis-RCH=CHCHO + H₂O + “MnO”

The corresponding acetylenic alcohols are also suitable substrates, although the resulting propargylic aldehydes can be quite reactive. Benzylic and even unactivated alcohols are also good substrates. 1,2-Diols are cleaved by MnO₂ to dialdehydes or diketones. Otherwise, the applications of MnO₂ are numerous, being applicable to many kinds of reactions including amine oxidation, aromatization, oxidative coupling, and thiol oxidation.

Miscellaneous lore

MnO₂ has found many applications and investigations inside and beyond the laboratory. The examples below illustrate some:

• MnO₂is used as a catalyst in the laboratory preparation of oxygen from potassium chlorate, a classical experiments of elementary chemistry classes. The procedure consists of merely heating potassium chlorate and manganese dioxide together in a hard glass container and collecting the gas over water. See oxygen, manganese and potassium chlorate for precautions. Manganese dioxide also catalyses the decomposition of hydrogen peroxide to oxygen and water.

2 H₂O₂(aq) → O₂(g) + 2 H₂O(l)

• Eighteenth-century British chemists referred to MnO₂ simply as manganese. Elemental manganese was known as reglus of manganese.
• Ancient cave painters sometimes used MnO₂ as black paint.
• The MnO₂ was used for production of chlorine in the eighteenth century, before being displaced by eletrolytic methods. The Mn recovery process used in connection with such production is called the Weldon process.

A catalyst (Greek: καταλύτης, catalytēs) is a substance that accelerates the rate (speed) or ease of a chemical reaction (see also catalysis) without itself being changed at the end of the chemical reaction . ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... R-phrases R9, R22, R51/53 S-phrases S2, S13, S17, S46, S61 Flash point none Supplementary data page Structure and properties n, εr, etc. ... Chemistry (derived from alchemy) is the science of matter at or near the atomic scale. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Atomic mass 54. ... R-phrases R9, R22, R51/53 S-phrases S2, S13, S17, S46, S61 Flash point none Supplementary data page Structure and properties n, εr, etc. ... Flash point Non-flammable. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Water (from the Old English waeter; c. ... Flash point Non-flammable. ... Drinking water This article focuses on water as we experience it every day. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... Water has the chemical formula H2O, meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom. ... A liquid will assume the shape of its container. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ... The Weldon process is a process for recovering manganese dioxide in chlorine manufacturing. ...

References

1. Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.). Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4.
2. Oosterhoeks Encyclopedie (Dutch)

Further reading

• Cahiez, G.; Alami, M.; Taylor, R. J. K.; Reid, M.; Foot, J. S. "Manganese Dioxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.

External links

• Index of Organic Synthesis procedures utilizing MnO₂
• National Pollutant Inventory - Manganese and compounds Fact Sheet
• PubChem summary of MnO₂
• International Chemical Safety Card 0175