Tetracyanoethylene
Organic compound with formula C2(CN)4
From Wikipedia, the free encyclopedia
Tetracyanoethylene (TCNE) is organic compound with the formula C2(CN)4. It is a colorless solid, although samples are often off-white. It is an important member of the cyanocarbons.
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| Names | |||
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| Preferred IUPAC name
Ethenetetracarbonitrile | |||
| Other names
TCNE | |||
| Identifiers | |||
3D model (JSmol) |
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| ChemSpider | |||
| ECHA InfoCard | 100.010.527 | ||
PubChem CID |
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| UNII | |||
CompTox Dashboard (EPA) |
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| Properties | |||
| C2(CN)4 | |||
| 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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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]
In the presence of base, TCNE reacts with malononitrile to give salts of pentacyanopropenide:[3]
- C2(CN)4 + CH2(CN)2 → [(NC)2C=C(CN)−C(CN)2]− + CN− + 2 H+
Redox chemistry
TCNE is 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 at −0.27 V vs ferrocene/ferrocenium:[4]
- C2(CN)4 + e− → [C2(CN)4]−
Because of its ability to accept an electron, TCNE has been used to prepare numerous charge-transfer salts[5] and magnetic molecular materials.
The central C=C distance in TCNE is 135 pm.[6] Upon reduction, this bond elongates to 141–145 pm, depending on the counterion.[7]
Safety
TCNE hydrolyzes in moist air to give hydrogen cyanide and should be handled accordingly.[1]