Carbon subnitride
Encyclopedia
Dicyanoacetylene, also called carbon subnitride or but-2-ynedinitrile (IUPAC), is a compound of carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 with chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C4N2. It has a linear molecular structure, N≡C−C≡C−C≡N (often abbreviated as NC4N), with alternating triple and single covalent bond
Covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....

s. It can be viewed as acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...

 with the two hydrogen atoms replaced by cyanide
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

 groups.

At room temperature, dicyanoacetylene is a clear liquid. Because of its high endothermic heat of formation, it can explode to carbon powder and nitrogen gas, and it burns in oxygen with a bright blue-white flame at a temperature of 5260 K (4990 °C, 9010 °F), which is the hottest flame of any chemical. This high flame temperature is also the result of the absence of hydrogen, and, therefore, water as a combustion product. Because of its high specific heat, water vapor as a combustion product tends to lower the flame temperature of hydrogen containing compounds. The endothermic dissociation of water at high temperatures above 2000 °C also prevents flame temperatures to rise above 3000 to 4000 °C.

Synthesis

Dicyanoacetylene can be prepared by passing nitrogen gas over a sample of graphite heated to temperatures between 2673 to 3000 K.

As a reagent in organic chemistry

Dicyanoacetylene is a powerful dienophile because the cyanide groups are electron-withdrawing, so it is a useful reagent for Diels-Alder reaction
Diels-Alder reaction
The Diels–Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system. The reaction can proceed even if some of the atoms in the newly formed ring are not carbon...

s with unreactive dienes. It even adds to the aromatic
Aromaticity
In organic chemistry, Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August...

 compound durene
Durene
Durene, or 1,2,4,5-tetramethylbenzene, is an aromatic hydrocarbon used as a solvent. It is also an intermediate in the manufacture of pyromellitic acid, which is used for manufacturing curing agents, adhesives and coating materials...

 (1,2,4,5-tetramethylbenzene) to form a substituted bicyclooctatriene. Only the most reactive of dienophiles can attack such aromatic compounds.

In outer space

Solid dicyanoacetylene has been detected in Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....

's atmosphere by infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...

. As the seasons change on Titan, the compound condenses and evaporates in a cycle, which allows scientists on Earth to study Titanian meteorology.

, the detection of dicyanoacetylene in the interstellar medium
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...

 has been impossible, because its symmetry means it has no rotational microwave spectrum
Rotational spectroscopy
Rotational spectroscopy or microwave spectroscopy studies the absorption and emission of electromagnetic radiation by molecules associated with a corresponding change in the rotational quantum number of the molecule...

. However, similar asymmetric molecules like cyanoacetylene
Cyanoacetylene
Cyanoacetylene is an organic compound with formula or H-C≡C-C≡N. It is the simplest cyanopolyyne. Cyanoacetylene has been detected by spectroscopic methods in interstellar clouds, in the coma of comet Hale–Bopp and in the atmosphere of Saturn's moon Titan....

have been observed, and its presence in those environments is therefore suspected.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK