Tetracyanoethylene
Encyclopedia
Tetracyanoethylene is a clear colored organic compound
consisting of ethylene
with the four hydrogen atom replaced with cyano groups. It is an important member of the cyanocarbon
s.
in the presence of potassium bromide
to give the KBr-complex, and dehalogenating with copper
.
Oxidation of TCNE with hydrogen peroxide
gives the corresponding epoxide, which has unusual properties.
salts gives the radical anion:
Because of its planarity and its ability to accept electrons, TCNE has been used to prepare numerous organic superconductors, usually by serving as a single electron oxidant of an organic electron donor. Such charge-transfer salts are sometimes called Bechgaard salt
.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
consisting of ethylene
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
with the four hydrogen atom replaced with cyano groups. It is an important member of the cyanocarbon
Cyanocarbon
Cyanocarbons are a chemical compounds that contain several cyanide groups. Such substances generally are classified as organic compounds, since they are formally derived from hydrocarbons by replacing one or more hydrogen atoms with a cyanide. The parent member is C4. Organic chemists often...
s.
Synthesis and reactions
TCNE is prepared by brominating malononitrileMalononitrile
Malononitrile, also propanedinitrile, is a nitrile, with formula CH22. Malononitrile is relatively acidic, with an pKa of 11 in water...
in the presence of potassium bromide
Potassium bromide
Potassium bromide is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the United States. Its action is due to the bromide ion...
to give the KBr-complex, and dehalogenating with copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
.
Oxidation of TCNE with hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
gives the corresponding epoxide, which has unusual properties.
Redox chemistry
TCNE is often used as an electron acceptor. Cyano groups have low energy π* orbitals, and the presence of four such groups, with their π systems linked (conjugated) to the central C=C double bond, gives rise to an excellent acceptor. Thus, treatment of TCNE with iodideIodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...
salts gives the radical anion:
- C2(CN)4 + I- → [C2(CN)4]- + 0.5 I2
Because of its planarity and its ability to accept electrons, TCNE has been used to prepare numerous organic superconductors, usually by serving as a single electron oxidant of an organic electron donor. Such charge-transfer salts are sometimes called Bechgaard salt
Bechgaard salt
A Bechgaard salt is any one of a number of organic charge-transfer complexes that exhibit superconductivity at low temperatures . They are named for chemist Klaus Bechgaard, who was one of the first scientists to synthesize them and demonstrate their superconductivity with the help of physicist...
.