Dicyanoacetylene, also called carbon subnitride or but-2-ynedinitrile (
IUPAC
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
), is a compound of
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
and
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
with
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
. At room temperature, dicyanoacetylene is a colorless volatile liquid. It has a
linear molecular structure, (often abbreviated as ), with alternating triple and single
covalent bond
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...
s. It can be viewed as
acetylene
Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is u ...
with the two hydrogen atoms replaced by
cyanide groups.
Because of its high
endothermic heat of formation, dicyanoacetylene can explode to carbon powder and nitrogen gas,
:
and it burns in
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
with a bright blue-white flame at a temperature of , the
hottest flame in oxygen; burned in
ozone
Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...
at high pressure the flame temperature exceeds . Dicyanoacetylene polymerizes at room temperature into a dark solid.
Synthesis
Dicyanoacetylene can be prepared by passing
nitrogen gas over a sample of
graphite
Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...
heated to temperatures between . It may also be synthesized via a reaction between a dihaloacetylene and a
cyanide salt:
:
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 reactions with unreactive
diene
In organic chemistry, a diene ( ); also diolefin, ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nome ...
s. It even adds to the
aromatic compound
durene (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 the
atmosphere of Titan by
infrared spectroscopy. As the seasons change on Titan, the compound condenses and evaporates in a cycle, which allows scientists on
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
to study Titanian meteorology.
, the detection of dicyanoacetylene in the
interstellar medium
The interstellar medium (ISM) is the matter and radiation that exists in the outer space, space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as cosmic dust, dust and cosmic rays. It f ...
has been impossible, because its symmetry means it has no
rotational microwave spectrum. However, similar asymmetric molecules like
cyanoacetylene have been observed, and its presence in those environments is therefore suspected.
See also
*
Cyanogen, N≡C−C≡N
*
Diacetylene, H−C≡C−C≡C−H
*
Cyanopolyynes
References
{{reflist
Conjugated nitriles
Alkyne derivatives