Disproportionation

2 Sn²⁺ ? Sn + Sn⁴⁺

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• A chemical reaction of the type: 2A ? A' + A" where A, A' and A" are different chemical species. While the most common type is a redox
  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...
   reaction, other types are possible. For example: 2H₂O ? H₃O⁺ + OH^- is a disproportionation but is not a redox reaction.

• A chemical reaction (reversible or irreversible) in which a species is simultaneously reduced and oxidized so as to form two different products.

History

2 Sn²⁺ ? Sn + Sn⁴⁺

Examples

• The disproportionation 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....
   into water and oxygen catalysed by the enzyme
  Enzyme
  
  Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
   catalase
  Catalase
  
  Catalase is a common enzyme found in nearly all living organisms which are exposed to oxygen, where it functions to catalyst the decomposition of hydrogen peroxide to water and oxygen....
  :

2H₂O₂ ? 2H₂O + O₂

• In the HiPco method for producing carbon nanotubes
  Carbon nanotube
  
  Carbon nanotubes are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio of up to 28,000,000:1, which is significantly larger than any other material....
  , high pressure carbon monoxide
  Carbon monoxide
  
  Carbon monoxide, with the chemical formula CO, is a colorless and odorless, tasteless, yet highly toxic gas. Its molecules consist of one carbon atom covalent bond to one oxygen atom....
   disproportionates when catalysed on the surface of an iron particle:

2CO ? C + CO₂

• Chlorine
  Chlorine
  
  Chlorine...
   gas reacts with sodium hydroxide
  Sodium hydroxide
  
  Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
   to form sodium chloride
  Sodium chloride
  
  Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the chemical formula SodiumChlorine....
  , sodium chlorate
  Sodium chlorate
  
  Sodium chlorate is a chemical compound with the chemical formula . When pure, it is a white crystalline powder that is readily soluble in water....
   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....
  . The ionic equation for this reaction is as follows :

3Cl₂ + 6OH^- ? 5Cl^- + ClO₃^- + 3H₂O

As a reactant, the oxidation number of the elemental chlorine is 0. In some of the product, Cl^- has an oxidation number of -1, having been reduced; whereas the oxidation number of chlorine in the chlorate

Chlorate

The chlorate anion has the formula ClO3-. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; Chlorate#Compounds are the salt s of chloric acid....
 ion is +5, indicating that it has been oxidized.

• The dismutation of superoxide
  Superoxide
  
  Superoxide is the anion O2−. It is important as the product of the one-electron reduction of dioxygen, which occurs widely in nature....
   free radical to 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....
   and 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]]...
  , catalysed in living systems by superoxide dismutase
  Superoxide dismutase
  
  The enzyme superoxide dismutase , catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. As such, it is an important antioxidant defense in nearly all cells exposed to oxygen....
  :

2O₂^- + 2H⁺ ? H₂O₂ + O₂

The O₂ "species" has an oxidation state of -1 in the superoxide free radical anion, -2 in hydrogen peroxide and zero in dioxygen.

• In the Cannizzaro reaction
  Cannizzaro reaction
  
  The Cannizzaro reaction, named after its discoverer Stanislao Cannizzaro, is a chemical reaction that involves the base -induced disproportionation of an aldehyde lacking a hydrogen atom in the alpha position....
  , an aldehyde
  Aldehyde
  
  An aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom bonded to a hydrogen atom and double bond to an oxygen atom , is called the aldehyde group....
   is converted into an 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....
   and a carboxylic acid
  Carboxylic acid
  
  Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
  . In the related Tishchenko reaction
  Tishchenko reaction
  
  The Tishchenko reaction is a chemical reaction that involves disproportionation of an aldehyde lacking a hydrogen atom in the alpha position in the presence of an alkoxide....
  , the organic redox reaction
  Organic redox reaction
  
  Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. In organic chemistry oxidations and reductions are different from ordinary redox reactions because many reactions carry the name but do not actually involve electron transfer in the electrochemistry sense...
   product is the corresponding ester
  Ester
  
  An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
  . In the Kornblum–DeLaMare rearrangement
  Kornblum–DeLaMare rearrangement
  
  The Kornblum?DeLaMare rearrangement is a rearrangement reaction in organic chemistry in which a primary or secondary organic peroxide is converted to the corresponding ketone and alcohol under base catalysis....
  , a peroxide is converted to a ketone
  Ketone
  
  In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
   and an alcohol.

See also

• Dismutase
  Dismutase
  
  A dismutase is an enzyme that catalysis a dismutation reaction....