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Manganese(IV) oxide

 
Manganese(IV) Oxide

 
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Manganese(IV) oxide
 
 
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Manganese(IV) oxide is the chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 MnO2, commonly called manganese dioxide. This blackish or brown solid occurs naturally as the mineral pyrolusite
Pyrolusite

Pyrolusite is a mineral consisting essentially of manganese dioxide and is important as an ore of manganese. It is a soft, black, amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts....
, which is the main ore of manganese
Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a Oxidation state in nature , and in many minerals....
. It is also present in manganese nodule
Manganese nodule

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....
s. The principal use for MnO2 is for dry-cell batteries
Battery (electricity)

In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity....
, such as the alkaline battery
Alkaline battery

Alkaline batteries and alkaline cells are a type of disposable battery or Rechargeable alkaline battery battery dependent upon the reaction between zinc and manganese oxide ....
 and the zinc-carbon battery
Zinc-carbon battery

A zinc-carbon dry cell or battery is packaged in a zinc can that serves as both a container and anode. It was developed from the wet Leclanch? cell ....
. In 1976 this application accounted for 500,000 tonne
Tonne

A tonne or metric ton , also referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms, or 2204.6226 pounds....
s of pyrolusite.[1] MnO2 is also used for production of MnO4–
Potassium permanganate

Potassium permanganate is the inorganic chemical compound potassiummanganeseoxygen4, a water soluble salt consisting of equal Mole amounts of potassium and permanganate ions....
.






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Manganese(IV) oxide is the chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 MnO2, commonly called manganese dioxide. This blackish or brown solid occurs naturally as the mineral pyrolusite
Pyrolusite

Pyrolusite is a mineral consisting essentially of manganese dioxide and is important as an ore of manganese. It is a soft, black, amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts....
, which is the main ore of manganese
Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a Oxidation state in nature , and in many minerals....
. It is also present in manganese nodule
Manganese nodule

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....
s. The principal use for MnO2 is for dry-cell batteries
Battery (electricity)

In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity....
, such as the alkaline battery
Alkaline battery

Alkaline batteries and alkaline cells are a type of disposable battery or Rechargeable alkaline battery battery dependent upon the reaction between zinc and manganese oxide ....
 and the zinc-carbon battery
Zinc-carbon battery

A zinc-carbon dry cell or battery is packaged in a zinc can that serves as both a container and anode. It was developed from the wet Leclanch? cell ....
. In 1976 this application accounted for 500,000 tonne
Tonne

A tonne or metric ton , also referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms, or 2204.6226 pounds....
s of pyrolusite.[1] MnO2 is also used for production of MnO4–
Potassium permanganate

Potassium permanganate is the inorganic chemical compound potassiummanganeseoxygen4, a water soluble salt consisting of equal Mole amounts of potassium and permanganate ions....
. It is used extensively as an oxidising agent
Redox

Redox describes all chemical reactions in which atoms have their oxidation number changed.This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
 in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
, for example, for the oxidation of allylic alcohol
Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
s.

Structure

A number of polymorphs
Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements....
 of MnO2 have been identified. The most common is ß-MnO2,(pyrolusite
Pyrolusite

Pyrolusite is a mineral consisting essentially of manganese dioxide and is important as an ore of manganese. It is a soft, black, amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts....
) which has the TiO2
Titanium dioxide

Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula titaniumoxygen2....
, rutile structure. Others are a-MnO2, ?-MnO2, e-MnO2, and ?-MnO2. The structures of all of these forms are closely related and are built from linked MnO6 octahedra and "tunnels" capable of holding cations are formed in all except ß-MnO2. Interest in these polymorphs
Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements....
 is due to their use in lithium ion batteries.

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. 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(A catalyst is used to speed up a chemical reaction) in the classical laboratory preparation of oxygen
    Oxygen

    Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
     from potassium chlorate
    Potassium chlorate

    Potassium chlorate is a compound containing potassium, chlorine and oxygen, with the chemical formula KClO3. In pure form, it is a white crystalline substance....
    . 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
    Hydrogen peroxide

    Hydrogen peroxide is a very pale blue liquid which appears colorless in a dilute solution, slightly more viscous than water. It is a weak acid....
     to oxygen and water
    Water

    Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
    :
2 H2O2(aq) ? O2(g
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
) + 2 H2O(l
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
)
  • Eighteenth-century British chemists referred to MnO2 simply as manganese. Elemental manganese was known as regulus of manganese.
  • Ancient cave painters
    Cave painting

    Cave paintings are paintings on cave walls and ceilings, and the term is used especially for those dating to prehistoric times. The earliest known European cave paintings date to 32,000 years ago....
     used MnO2 as a black or brown pigment.
  • MnO2 was used for production of chlorine
    Chlorine

    Chlorine...
     in the eighteenth century, before being displaced by electrolytic methods. The manganese dioxide was subsequently recovered by the Weldon process
    Weldon process

    The Weldon process is a process developed in 1870 by Walter Weldon for recovering manganese dioxide for re-use in chlorine manufacture.After reacting hydrochloric acid with manganese dioxide , the waste manganese chloride solution is treated with lime, steam and oxygen, producing calcium manganite :...
    .
  • 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


Other oxides of manganese

The green salt potassium manganate
Potassium manganate

Potassium manganate is the chemical compound with the chemical formula K2MnO4. This green salt is an intermediate in the industrial synthesis of potassium permanganate, a common chemical....
 is obtained in minutes when a solution of MnO2 in molten KOH or NaOH is treated with oxidizing agent
Oxidizing agent

An oxidizing agent can be defined as either:#a chemical compound that readily transfers oxygen atoms, or#a substance that gains electrons in a redox chemical reaction...
s such as potassium nitrate
Potassium nitrate

Potassium nitrate is a chemical compound with the chemical formula PotassiumNitrogenOxygen3. A naturally occurring mineral source of nitrogen, KNO3 constitutes a critical oxidation component of black powder/gunpowder....
 (K
Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
N
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
O3), potassium perchlorate
Potassium perchlorate

Potassium perchlorate is the inorganic salt with the chemical formula potassiumchlorineoxygen. Like other a perchlorates, this salt is a strong oxidizing agent....
 (KCl
Chlorine

Chlorine...
O4), or even oxygen gas:
2 MnO2 + 4 OH– + O2 ? 2 MnO4– + 2 H2O


Potassium manganate converts into purple potassium permanganate
Potassium permanganate

Potassium permanganate is the inorganic chemical compound potassiummanganeseoxygen4, a water soluble salt consisting of equal Mole amounts of potassium and permanganate ions....
 in aqueous acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
ic solution: 3 MnO42– + 4 H+ ? 2 MnO4– + MnO2(s) + 2 H2O

Sources


  • 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