Tetracyanoethylene (TCNE) is

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula . It is a colorless solid, although samples are often off-white. It is an important member of the cyanocarbons.

Synthesis and reactions

TCNE is prepared by brominating

malononitrile Malononitrile is an organic compound nitrile with the formula . It is a colorless or white solid, although aged samples appear yellow or even brown. It is a widely used building block in organic synthesis. Preparation and reactions It can be pre ...

in the presence of potassium bromide to give the KBr-complex, and dehalogenating with

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

. Oxidation of TCNE with

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

gives the corresponding epoxide, which has unusual properties. In the presence of base, TCNE reacts with

to give

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

s of pentacyanopropenide: :

Redox chemistry

TCNE is an

electron acceptor An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. Electron acceptors are oxidizing agents. The electron accepting power of an electron acceptor is measured by its redox potential. In the ...

. Cyano groups have low energy π* orbitals, and the presence of four such groups, with their π systems (conjugated) to the central

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

, gives rise to an electrophilic

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

. TCNE is reduced at −0.27 V vs ferrocene/ ferrocenium: : Because of its ability to accept an electron, TCNE has been used to prepare numerous charge-transfer salts and magnetic molecular materials. The central C=C distance in TCNE is 135 pm. Upon reduction, this bond elongates to 141–145 pm, depending on the counterion.

Safety

TCNE hydrolyzes in moist air to give

hydrogen cyanide Hydrogen cyanide (formerly known as prussic acid) is a chemical compound with the chemical formula, formula HCN and structural formula . It is a highly toxic and flammable liquid that boiling, boils slightly above room temperature, at . HCN is ...

and should be handled accordingly.

References

{{reflist Alkene derivatives Nitriles Superconductors