Manganese dioxide

Jump to navigation Jump to search

Template:Chembox new

WikiDoc Resources for Manganese dioxide

Articles

Most recent articles on Manganese dioxide

Most cited articles on Manganese dioxide

Review articles on Manganese dioxide

Articles on Manganese dioxide in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Manganese dioxide

Images of Manganese dioxide

Photos of Manganese dioxide

Podcasts & MP3s on Manganese dioxide

Videos on Manganese dioxide

Evidence Based Medicine

Cochrane Collaboration on Manganese dioxide

Bandolier on Manganese dioxide

TRIP on Manganese dioxide

Clinical Trials

Ongoing Trials on Manganese dioxide at Clinical Trials.gov

Trial results on Manganese dioxide

Clinical Trials on Manganese dioxide at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Manganese dioxide

NICE Guidance on Manganese dioxide

NHS PRODIGY Guidance

FDA on Manganese dioxide

CDC on Manganese dioxide

Books

Books on Manganese dioxide

News

Manganese dioxide in the news

Be alerted to news on Manganese dioxide

News trends on Manganese dioxide

Commentary

Blogs on Manganese dioxide

Definitions

Definitions of Manganese dioxide

Patient Resources / Community

Patient resources on Manganese dioxide

Discussion groups on Manganese dioxide

Patient Handouts on Manganese dioxide

Directions to Hospitals Treating Manganese dioxide

Risk calculators and risk factors for Manganese dioxide

Healthcare Provider Resources

Symptoms of Manganese dioxide

Causes & Risk Factors for Manganese dioxide

Diagnostic studies for Manganese dioxide

Treatment of Manganese dioxide

Continuing Medical Education (CME)

CME Programs on Manganese dioxide

International

Manganese dioxide en Espanol

Manganese dioxide en Francais

Business

Manganese dioxide in the Marketplace

Patents on Manganese dioxide

Experimental / Informatics

List of terms related to Manganese dioxide


Overview

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.

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.[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.

Miscellaneous

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

  • MnO2 is used as a catalyst in the laboratory preparation of oxygen from potassium chlorate, a classical experiment of elementary chemistry classes. The procedure consists of heating a mixture potassium chlorate and manganese dioxide in a hard glass container and collecting the gas over water. 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.
  • The MnO2 was used for production of chlorine in the eighteenth century, before being displaced by eletrolytic methods. Manganese was recovered from such production by the so-called Weldon process.
  • Earliest glassmakers used manganese to remove the natural bluish-green tint of glass or to add a pinkish or purplish color.

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 KNO3), potassium perchlorate (KClO4), or even oxygen gas:

2 MnO2 + 4 OH + O2 → 2 MnO42– + 2 H2O

Potassium manganate converts into purple potassium permanganate in aqueous acidic solution: 3 MnO42– + 4 H+ → 2 MnO4 + MnO2(s) + 2 H2O

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

de:Mangandioxid it:Diossido di manganese nl:Mangaandioxide sl:Manganov oksid fi:Mangaanidioksidi sv:Mangandioxid

Template:Jb1

Template:WikiDoc Sources

  1. 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.