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.March Jerry; (1985). Advanced Organic Chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. Instead the relevant criterion for organic oxidation is gain of oxygen and/or loss of hydrogen, respectively.''Organic Redox Systems: Synthesis, Properties, and Applications'', Tohru Nishinaga 2016 Simple functional groups can be arranged in order of increasing oxidation state. The

oxidation numbers In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

are only an approximation: When methane is oxidized to carbon dioxide its oxidation number changes from −4 to +4. Classical reductions include alkene reduction to

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

s and classical oxidations include oxidation of alcohols to aldehydes. In oxidations electrons are removed and the electron density of a molecule is reduced. In reductions electron density increases when electrons are added to the molecule. This terminology is always centered on the organic compound. For example, it is usual to refer to the reduction of a

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

lithium aluminium hydride Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li Al H4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic ...

, but not to the oxidation of lithium aluminium hydride by a ketone. Many oxidations involve removal of hydrogen atoms from the organic molecule, and reduction adds hydrogens to an organic molecule. Many reactions classified as reductions also appear in other classes. For instance, conversion of the ketone to an alcohol by lithium aluminium hydride can be considered a reduction but the hydride is also a good

nucleophile In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

in nucleophilic substitution. Many redox reactions in organic chemistry have coupling reaction

reaction mechanism In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of ...

involving free radical intermediates. True organic redox chemistry can be found in electrochemical organic synthesis or electrosynthesis. Examples of organic reactions that can take place in an electrochemical cell are the Kolbe electrolysis.http://www.electrosynthesis.co
Link
In disproportionation reactions the reactant is both oxidised and reduced in the same chemical reaction forming two separate compounds.

Asymmetric catalytic reduction Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from othe ...

s and

asymmetric catalytic oxidation Asymmetric catalytic oxidation is a technique of oxidizing various substrates to give an enantio-enriched product using a catalyst. Typically, but not necessarily, asymmetry is induced by the chirality of the catalyst. Typically, but again not ne ...

s are important in

asymmetric synthesis Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecul ...

Organic oxidations

Most oxidations are conducted with air or oxygen. These oxidation include routes to chemical compounds, remediation of pollutants, and combustion. Several reaction mechanisms exist for organic oxidations: * Single electron transfer * Oxidations through ester intermediates with chromic acid or

manganese dioxide Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cell ...

* Hydrogen atom transfer as in free radical halogenation * Oxidation involving ozone in ozonolysis or peroxides (e.g.

peroxy acid A peroxy acid (often spelled as one word, peroxyacid, and sometimes called peracid) is an acid which contains an acidic –OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the peroxy ...

s) * Oxidations involving an elimination reaction mechanism such as the Swern oxidation, the

Kornblum oxidation The Kornblum oxidation, named after Nathan Kornblum, is an organic oxidation reaction that converts alkyl halides and tosylates into carbonyl compounds. Mechanism Similar to sulfonium-based oxidation of alcohols to aldehydes reactions, the ...

and with reagents such as

IBX acid 2-Iodoxybenzoic acid (IBX) is an organic compound used in organic synthesis as an oxidizing agent. This periodinane is especially suited to oxidize alcohols to aldehydes. IBX is prepared from 2-iodobenzoic acid, potassium bromate, and sulfuric ...

and Dess-Martin periodinane. * Oxidation by nitroxide

radicals Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...

Fremy's salt or TEMPO

Organic reductions

Several reaction mechanisms exist for organic reductions: * Direct electron transfers (e.g. Birch reduction). * Hydride transfer in reductions with for example

or a hydride shift as in the Meerwein-Ponndorf-Verley reduction * Hydrogenations using a variety of catalysts (e.g. Raney nickel or

platinum dioxide Adams' catalyst, also known as platinum dioxide, is usually represented as platinum(IV) oxide hydrate, PtO2•H2O. It is a catalyst for hydrogenation and hydrogenolysis in organic synthesis. This dark brown powder is commercially available. The ...

) or specific reductions (e.g. named reactions such as

Rosenmund reduction The Rosenmund reduction is a hydrogenation process in which an acyl chloride is selectively reduced to an aldehyde. The reaction was named after Karl Wilhelm Rosenmund, who first reported it in 1918. The reaction, a hydrogenolysis, is catalyse ...

). * Disproportionation reaction such as the Cannizzaro reaction Reductions that do not fit in any reduction reaction mechanism and in which just the change in oxidation state is reflected include the Wolff-Kishner reaction.

References

{{Organic reactions Redox

Organic oxidations

Organic reductions

See also

Functional group oxidations

Functional group reductions

References