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IUPAC name
Other names
Molar mass 76.06 g/mol
Appearance Colorless volatile liquid
Density 1.176 g/cm3
Melting point 20.5 °C (68.9 °F; 293.6 K)
Boiling point 76.5 °C (169.7 °F; 349.6 K)
Soluble in organic solvents
500.4 kJ/mol
Safety data sheet None
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Dicyanoacetylene, also known as carbon subnitride or but-2-ynedinitrile, is a chemical compound with the formula C4N2.



Dicyanoacetylene burns when mixed with oxygen giving a bright blue-white flame at a temperature of 4990 °C (5260 K, 9010 °F), which is the hottest flame of any known chemical reaction.

Dicyanoacetylene polymerizes at room temperature into a dark solid.[1]


Dicyanoacetylene is a flammable colorless liquid at standard conditions, with a strong odor. While stable at low temperatures, such as those obtained using dry ice (-78 °C), at room temperature it polymerizes, turning into a dark solid mass.


Dicyanoacetylene is hard to find, and there don't appear to be any sellers that would sell to individuals. This is because it's difficult to properly handle and expensive to produce.


There are several ways to produce dicyanoacetylene, neither methods being very easy.

A common industrial route involves passing dry nitrogen gas over a sample of graphite heated to temperatures between 2400 and 2700 °C.

Dehydration of acetylene dicarboxyamide with phosphorus pentoxide will give carbon subnitride. Maximum yield from this process is 40%.[2]

A dangerous route involves the reaction of cyanogen chloride or cyanogen bromide (which can be obtained by reacting chlorine or bromine with sodium cyanide) with a carbide, such as sodium or calcium carbide. The resulting dicyanoacetylene is purified from the resulting reaction products. Due to the high toxicity of the cyanogens, this reaction is not safe to perform without proper equipment.


  • Make the hottest flame known to man
  • Reagent for Diels-Alder reactions with unreactive dienes[3]



Dicyanoacetylene is extremely flammable. The pure compound and concentrated solutions pose an explosive risk. It is considered to be quite toxic, and due to its high vapor pressure, it poses a significant hazard.[4]


Dicyanoacetylene can only be kept at very low temperatures, in dry ice or liquid nitrogen, like a dewar, away from light and oxygen, as it may polymerize. Do not store it for long.

Diluted solutions of dicyanoacetylene are much more stable, and can be safely kept at standard conditions.


Dicyanoacetylene can be safely burned outside. Be careful, as the flame is very hot and the vapors are toxic.


  1. Syntheses of dicyanoacetylene, Engelbert Ciganek, and Carl G. Krespan, J. Org. Chem., 1968, 33 (2), pp 541–544
  2. Dunn, Peter J.; Rees, Charles W.; Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999); (1987); p. 1579 - 1584
  3. http://www.lookchem.com/Dicyanoacetylene/
  4. Syntheses of dicyanoacetylene, Engelbert Ciganek, and Carl G. Krespan, J. Org. Chem., 1968, 33 (2), pp 541–544

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