Oxidative coupling in

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

is a

coupling reaction A coupling reaction in organic chemistry is a general term for a variety of reactions where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = ...

of two molecular entities through an oxidative process. Usually oxidative couplings are catalysed by a

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...

complex like in classical

cross-coupling In organic chemistry, a cross-coupling reaction is a reaction where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M = ...

reactions, although the underlying mechanism is different due to the oxidation process that requires an external (or internal) oxidant. Many such couplings utilize dioxygen as the stoichiometric

oxidant An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

but proceed by

electron transfer Electron transfer (ET) occurs when an electron relocates from an atom or molecule to another such chemical entity. ET is a mechanistic description of certain kinds of redox reactions involving transfer of electrons. Electrochemical processes ar ...

C-C Couplings

Many oxidative couplings generate new C-C bonds. Early examples involve coupling of terminal alkynes: :2 RC≡CH + 2 Cu(I) → RC≡C-C≡CR + 2 Cu + 2 H⁺

Coupling of methane

Coupling reactions involving methane are highly sought, related to C1 chemistry because C₂ derivatives are far more valuable than methane. The oxidative coupling of methane gives ethylene: : 2 + → + 2

Aromatic coupling

In oxidative aromatic coupling the reactants are

electron-rich In chemistry, electron-rich is jargon that is used in multiple related meanings with either or both kinetic and thermodynamic implications: *with regards to electron-transfer, electron-rich species have low ionization energy and/or are reducing a ...

aromatic compound Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...

s. Typical substrates are phenols and typical catalysts are copper and iron compounds and enzymes. The first reported synthetic application dates back to 1868 with Julius Löwe and the synthesis of

ellagic acid Ellagic acid is a polyphenol found in numerous fruits and vegetables. It is the dilactone of hexahydroxydiphenic acid. Name The name comes from the French term ''acide ellagique'', from the word ''galle'' spelled backwards because it can be ...

by heating

gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants ...

with

arsenic acid Arsenic acid or trihydrogen arsenate is the chemical compound with the formula . More descriptively written as , this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as su ...

or silver oxide. Another reaction is the synthesis of 1,1'-Bi-2-naphthol from 2-naphthol by

iron chloride Iron chloride may refer to: * Iron(II) chloride (ferrous chloride, iron dichloride), FeCl2 * Iron(III) chloride Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the + ...

, discovered in 1873 by Alexander Dianin (''S'')-BINOL can be prepared directly from an asymmetric oxidative coupling of 2-naphthol with

copper(II) chloride Copper(II) chloride is the chemical compound with the chemical formula CuCl2. The anhydrous form is yellowish brown but slowly absorbs moisture to form a blue-green dihydrate. Both the anhydrous and the dihydrate forms occur naturally as the ve ...

Other oxidative couplings

The

oxygen evolution Oxygen evolution is the process of generating molecular oxygen (O2) by a chemical reaction, usually from water. Oxygen evolution from water is effected by oxygenic photosynthesis, electrolysis of water, and thermal decomposition of various oxides ...

reaction entails, in effect, the oxidative coupling of water molecules to give O₂. Electrolysis of Water

References

{{Reflist Chemical reactions