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| Names | |
|---|---|
| Preferred IUPAC name But-2-ynedinitrile | |
Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| Properties | |
| C4N2 | |
| Molar mass | 76.058 g·mol−1 |
| Appearance | Colorless volatile liquid |
| Odor | Strong |
| Density | 0.907 g/cm3 |
| Melting point | 20.5 °C (68.9 °F; 293.6 K) |
| Boiling point | 76.5 °C (169.7 °F; 349.6 K) |
| Solubility | Soluble in organic solvents |
| Thermochemistry | |
| 77.6017 J/(mol·K) | |
Std enthalpy of formation(ΔfH⦵298) | +500.4 kJ/mol |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Very flammable. Explosive. |
| Related compounds | |
Related compounds | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Dicyanoacetylene, also calledcarbon subnitride orbut-2-ynedinitrile (IUPAC), is a compound ofcarbon andnitrogen withchemical formulaC4N2. At room temperature, dicyanoacetylene is a colorless volatile liquid. It has alinear molecular structure,N≡C−C≡C−C≡N (often abbreviated asNC4N), with alternating triple and singlecovalent bonds. It can be viewed asacetylene with the two hydrogen atoms replaced bycyanide groups.
Because of its highendothermicheat of formation, dicyanoacetylene can explode to carbon powder and nitrogen gas, and it burns inoxygen with a bright blue-white flame at a temperature of 5,260 K (4,990 °C; 9,010 °F), thehottest flame in oxygen; burned inozone at high pressure the flame temperature exceeds 6,000 K (5,730 °C; 10,340 °F).[1] Dicyanoacetylene polymerizes at room temperature into a dark solid.[2]
Dicyanoacetylene can be prepared by passingnitrogen gas over a sample ofgraphite heated to temperatures between 2,673 and 3,000 K (2,400 and 2,727 °C; 4,352 and 4,940 °F).[3] It may also be synthesized via a reaction between a dihaloacetylene and acyanide salt:[citation needed]
Dicyanoacetylene is a powerfuldienophile because the cyanide groups areelectron-withdrawing, so it is a useful reagent forDiels–Alder reactions with unreactivedienes. It even adds to thearomatic compounddurene (1,2,4,5-tetramethylbenzene) to form a substituted bicyclooctatriene.[4] Only the most reactive of dienophiles can attack such aromatic compounds.
Solid dicyanoacetylene has been detected in theatmosphere of Titan byinfrared spectroscopy.[5] As the seasons change on Titan, the compound condenses and evaporates in a cycle, which allows scientists onEarth to study Titanian meteorology.
As of 2006[update], the detection of dicyanoacetylene in theinterstellar medium has been impossible, because its symmetry means it has norotational microwave spectrum. However, similar asymmetric molecules likecyanoacetylene have been observed, and its presence in those environments is therefore suspected.[6]
