Tetracyanoethylene

Tetracyanoethylene (TCNE) is organic compound with the formula C2(CN)4. It is a colorless solid. It is an important member of the cyanocarbons.

Tetracyanoethylene
tetracyanoethylene
Names
IUPAC name
Ethenetetracarbonitrile
Other names
TCNE
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.010.527
UNII
Properties
C6N4
Molar mass 128.094 g·mol−1
Density 1.35 g/cm3
Melting point 199 °C (390 °F; 472 K)
Boiling point 130 to 140 °C (266 to 284 °F; 403 to 413 K) 0.1 mmHg (sublimes)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis and reactions

TCNE is prepared by brominating malononitrile in the presence of potassium bromide to give the KBr-complex, and dehalogenating with copper.[1]

Oxidation of TCNE with hydrogen peroxide gives the corresponding epoxide, which has unusual properties.[2]

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 (conjugated) to the central C=C double bond, gives rise to an electrophilic alkene. TCNE is reduced by iodide to give the radical anion:

C2(CN)4 + I− → [C2(CN)4]− + ​1⁄2 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 salts.

Safety

TCNE hydrolyzes in moist air to give hydrogen cyanide and should be handled accordingly.[1]

References
  1. Carboni, R. A. (1963). "Tetracyanoethylene". Organic Syntheses.; Collective Volume, 4, p. 877
  2. Linn, W. J. (1973). "Tetracyanoethylene Oxide". Organic Syntheses.; Collective Volume, 5, p. 1007
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