NationMaster - Encyclopedia: Manganese dioxide

Manganese(IV) oxide

IUPAC name	Manganese dioxide Manganese(IV) oxide
Other names	Pyrolusite
Identifiers
CAS number	[1313-13-9]
EINECS number	215-202-6
Properties
Molecular formula	MnO₂
Molar mass	86.9368 g/mol (varies)
Appearance	black solid
Density	5.026 g/cm³, solid
Melting point	535 °C decomp. 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 is a mineral consisting essentially of manganese dioxide (MnO2) and is important as an ore of manganese. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The EINECS number (for European Inventory of Existing Chemical Substances) is a registry number given to each chemical substance commercially available in the European Union between 1 January 1971 and 18 September 1981. ... A chemical formula is an easy 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. ... For other uses, see Density (disambiguation). ... The melting point of a solid is the temperature range at which it changes state from solid to liquid. ...
Solubility in water	Insoluble
Thermochemistry
Std enthalpy of formation Δ_fH^o₂₉₈	−520.9 kJ/mol
Standard molar entropy S^o₂₉₈	53.1 J.K⁻¹.mol⁻¹
Hazards
EU classification	Harmful (Xn)
NFPA 704	0 2 1 OX
R-phrases	R20/22
S-phrases	S2, S25
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, commonly 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 used for production of MnO₄^–. It is used extensively as an oxidising agent in organic synthesis, for example, for the oxidation of allylic alcohols. Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... 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 European Union law concerning chemical safety. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links NFPA_704. ... 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. ... This article is about the electrically charged particle. ... This article is about the electrically charged particle. ... Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. ... Manganese(VII) oxide is Mn2O7. ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... Look up chemical compound in Wiktionary, the free dictionary. ... Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO2) and is important as an ore of manganese. ... General Name, symbol, number manganese, Mn, 25 Chemical series transition metals Group, period, block 7, 4, d Appearance silvery metallic Standard atomic weight 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. ... For other uses, see Battery. ... Alkaline batteries A Duracell AA alkaline battery 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. ... This article is about the metric tonne. ... Potassium permanganate is the chemical compound KMnO4. ... ed|other uses|reduction}} Illustration of a redox reaction Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions 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. ... This article does not cite any references or sources. ...

1 MnO₂ in organic synthesis
2 Example of Use
3 Other oxides of manganese
4 References
5 Sources
6 Further reading
7 External links

MnO₂ in organic synthesis

Manganese dioxide is used as an oxidant in organic synthesis. 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.^[1] The mineral pyrolusite makes a poor reagent. 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 predominant application of MnO₂ is for the oxidation of allylic alcohols to the corresponding aldehydes:

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

The configuration of the double bond is conserved in the reaction. 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.

Example of Use

Some examples of the use of MnO₂ are given below:

MnO₂ is used as a catalyst in the classical laboratory preparation of oxygen from potassium chlorate. A mixture of potassium chlorate and manganese dioxide is heated in a hard glass container and the oxygen gas collected over water.
MnO₂ is used in combination with anthracite, sand, and gravel in industrial water treatment plants.
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 regulus of manganese.
Ancient cave painters used MnO₂ as a black or brown pigment.
MnO₂ was used for production of chlorine in the eighteenth century, before being displaced by electrolytic methods. The manganese dioxide was subsequently recovered by the Weldon process.
Earliest glassmakers used MnO₂ to remove the natural bluish-green tint of glass, or to add a pinkish or purplish color.
It is also used in batteries

It has been suggested that this article or section be merged into Catalysis. ... This article is about the chemical element and its most stable form, or dioxygen. ... Potassium chlorate is a compound containing potassium, chlorine and oxygen, with the chemical formula KClO3. ... Anthracite coal Anthracite (Greek Î‘Î½Î¸ÏÎ±ÎºÎ¯Ï„Î·Ï‚, literally a form of coal, from Anthrax [Î†Î½Î¸ÏÎ±Î¾], coal) is a hard, compact variety of mineral coal that has a high luster. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colorless in a dilute solution, slightly more viscous than water. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Drinking water This article focuses on water as we experience it every day. ... For other uses, see Gas (disambiguation). ... For other uses, see Liquid (disambiguation). ... Cave or Rock Paintings are paintings on cave or rock walls and ceilings, usually dating to prehistoric times. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... The Weldon process is a process for recovering manganese dioxide in chlorine manufacturing. ...

Other oxides of manganese

The green salt potassium manganate is obtained in minutes when a solution of MnO₂ in molten KOH or NaOH is treated with oxidizing agents such as potassium nitrate (K NO₃), potassium perchlorate (KClO₄), or even oxygen gas: 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 oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ... R-phrases S-phrases Supplementary data page Structure and properties n, Îµr, etc. ... General Name, symbol, number potassium, K, 19 Chemical series alkali metals Group, period, block 1, 4, s Appearance silvery white Standard atomic weight 39. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Potassium perchlorate, a perchlorate salt with the chemical formula KClO4, is a strong oxidizer. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

2 MnO₂ + 4 OH^– + O₂ → 2 MnO₄^2– + 2 H₂O

Potassium manganate converts into purple potassium permanganate in aqueous acidic solution: 3 MnO₄^2– + 4 H⁺ → 2 MnO₄^– + MnO₂(s) + 2 H₂O Potassium permanganate is the chemical compound KMnO4. ... Drinking water This article focuses on water as we experience it every day. ... For other uses, see acid (disambiguation). ...

References

^ Attenburrow, J.; Cameron, A. F. B.; Chapman, J. H.; Evans, R. M.; Hems, B. A.; Jansen, A. B. A.; Walker, T. J. Chem. Soc. 1952, 1094.

Sources

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

External links

Index of Organic Synthesis procedures utilizing MnO₂
Example Reactions with Mn(IV) oxide
National Pollutant Inventory - Manganese and compounds Fact Sheet
PubChem summary of MnO₂
International Chemical Safety Card 0175

Categories: Manganese compounds | Oxides | Oxidizing agents

Results from FactBites:

Manganese Dioxide (1042 words)
	Ingestion : The absorption of manganese by the stomach or intestine is limited in comparison with that from inhalation; it is very unlikely, therefore, that a sufficient quantity of material could be ingested to give rise to symptoms which require first aid.
	Manganese dioxide may enter the body via the lungs or digestive tract, the pulmonary route is the most common and presents the greatest danger.
	Absorbed manganese accumulates in the blood until a certain threshold value is exceeded after which further absorption leads to deposition in the majority of the bodys organs and chronic manganese poisoning results.

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