**二氰乙炔**(Dicyanoacetylene)，又称为**低氮化碳**或**2-丁炔二腈**（IUPAC命名法），是一种氮元素与碳元素形成的化合物，化学式为C4N2。这种分子的空间构型为直线形：N≡C−C≡C−C≡N（通常可以简写成NC4N），叁键与单键交替连接形成共轭体系。它可以看做乙炔中的两个氢原子被两个氰基所取代的产物。

在室温下，二氰乙炔是一种澄清的液体。由于它的标准摩尔生成焓正值很大，是一种吸热化合物，它可以爆炸并生成碳粉和氮气。二氰乙炔在常壓氧气中燃烧产生蓝白色的火焰，温度高达5261K (4990°C，9010°F)，在臭氧中燃燒溫度更可達5516K (5243°C，9469°F)，该火焰的温度比任何已知物质都要高。

制备
--

将氮气通过加热到2673至3000K的石墨可以制得二氰乙炔：

{\rm {\ 4C+N\_{2}{\xrightarrow {2673-3000K}}C\_{4}N\_{2}}}

燃燒反應
----

{\displaystyle {\rm {(C\_{4}N\_{2})\_{g}+2O\_{2}\xrightarrow {\triangle } 4CO+N\_{2};\triangle H=+254.6kcal/mol}}}
{\displaystyle {\rm {(C\_{4}N\_{2})\_{g}+{\dfrac {4}{3}}O\_{3}\xrightarrow {\triangle } 4CO+N\_{2};\triangle H=+299.9kcal/mol}}}

有机化学试剂
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二氰乙炔是一种强亲双烯体，因为氰基具有强的吸电子诱导效应和吸电子共轭效应，因此它在Diels-Alder反应中可用于与不活泼的双烯体反应。它甚至能与芳香性的化合物均四甲苯（1,2,4,5-四甲基苯）发生加成反应得到双环辛三烯（bicyclooctatriene）衍生物。只有最活泼的亲双烯体可以进攻这些稳定的芳香化合物。

外层空间
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红外光谱证实，土卫六的大气层中存在固态的二氰乙炔。伴随着土卫六的季节变化，这种化合物周期性的凝固和熔化，这使得地球上的科学家研究土卫六的天气成为可能。

截止2006年，在星际介质中检测二氰乙炔是不可能的，因为它的对称性导致没有转动光谱信号。然而，结构类似却不对称的分子（例如氰基乙炔）已经被发现，因此科学家猜测这种环境中也存在二氰乙炔。

参见
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* 氰，N≡C−C≡N
* 丁二炔，H−C≡C−C≡C−H
* 氰基多炔烃（Cyanopolyyne）

参考资料
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1. ↑  Kirshenbaum, A. D.; Grosse, A. V.. Journal of the American Chemical Society. 1956, **78** (9): 2020. doi:10.1021/ja01590a075.
2. ↑  Ciganek, Engelbert; Krespan, Carl G.. The Journal of Organic Chemistry. 1968-02-01, **33** (2): 541–544. doi:10.1021/jo01266a014.  引文使用过时参数`coauthors` (帮助)
3. ↑  Weis, C. D.. Journal of Organic Chemistry. January 1963, **28** (1): 74–78. doi:10.1021/jo01036a015.
4. ↑  Samuelson, R. E.; L. A. Mayo, M. A. Knuckles, and R. J. Khanna.. Planetary and Space Science. August 1977, **45** (8): 941–948. Bibcode:1997P&SS...45..941S. doi:10.1016/S0032-0633(97)00088-3.  引文使用过时参数`coauthors` (帮助)
5. ↑  Kołos, Robert.. Journal of Chemical Physics. August 2002, **117** (5): 2063–2067. doi:10.1063/1.1489992.

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* 论
* 编
**氰化物** |
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| --- | --- | --- | --- | --- |
| HCN |  |  |  | He |
| LiCN | Be(CN)2 | B(CN)3 | C2(CN)2C(CN)4 | NH4CNN3CN | O | CNF | Ne |
| NaCN | Mg(CN)2 | Al(CN)3 | Si | P(CN)3 | (SCN)2 | CNCl | Ar |
| KCN | Ca(CN)2 | Sc(CN)3 | Ti(CN)4 | V | Cr(CN)3 | Mn(CN)2 | Fe(CN)2 | Co(CN)2 | Ni(CN)2 | CuCN | Zn(CN)2 | Ga(CN)3 | Ge | As(CN)3 | (SeCN)2 | CNBr | Kr |
| RbCN | Sr(CN)2 | Y | Zr(CN)4 | Nb | Mo | Tc | Ru | Rh | Pd(CN)2 | AgCN | Cd(CN)2 | In(CN)3 | Sn(CN)2Sn(CN)4 | Sb(CN)3 | Te | CNI | Xe |
| CsCN | Ba(CN)2 | 镧系 | Hf | Ta | W | Re | Os | Ir | Pt | AuCNAu(CN)3 | Hg(CN)2 | TlCN | Pb(CN)2 | Bi(CN)3 | Po | At | Rn |
| Fr | Ra(CN)2 | 锕系 | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
|  |  | ↓ |  |  |
| 镧系 | La(CN)3 | Ce(CN)3 | Pr(CN)3 | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb(CN)3 | Lu |
| 锕系 | Ac(CN)3 | Th(CN)4 | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |

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