Diacetylene with the formula C₄H₂, is a highly unsaturated

Alkyne

Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the formula CnH2n-2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature...

 hydrocarbon

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 that contains three single bonds and two triple bond

Triple bond

A triple bond in chemistry is a chemical bond between two chemical elements involving six bonding electrons instead of the usual two in a covalent single bond. The most common triple bond, that between two carbon atoms, can be found in alkynes. Other functional groups containing a triple bond are...

s. It is the first in the series of polyyne

Polyyne

The polyynes are a group of organic compounds with alternating single and triple bonds. The simplest example is diacetylene or buta-1,3-diyne, HC≡C-C≡CH....

s.

Occurrence

Diacetylene has been identified in the atmosphere of 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....

 and in the protoplanetary nebula

Protoplanetary nebula

A protoplanetary nebula or preplanetary nebula is an astronomical object which is at the short-lived episode during a star's rapid stellar evolution between the late asymptotic giant branch phase and the subsequent planetary nebula phase. A PPN emits strongly in infrared radiation, and is a...

 CRL 618 by its characteristic vibrational modes. The molecule is most likely to have formed in Titan's atmosphere by a reaction between 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...

 and the ethynyl radical

Ethynyl radical

The ethynyl radical, with chemical formula C2H, is an abundant interstellar polyatomic molecule that does not occur naturally on Earth. It was first observed by electron spin resonance isolated in a solid argon matrix at liquid helium temperatures in 1963 by Cochran and coworkers at the Johns...

 C₂H, which is produced when acetylene undergoes photolysis. This radical can in turn attack the triple bond in acetylene and react efficiently even at cold temperatures. Diacetylene has also been found on the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

.

Preparation

This compound may be made by the dehydrohalogenation of 1,4-dichloro-2-butyne by potassium hydroxide at low temperature:

ClCH₂C≡CCH₂Cl → HC≡C-C≡CH

The bis(trimethylsilyl

Trimethylsilyl

A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule...

)-protected derivative may be prepared by the Hay coupling of (trimethylsilyl)acetylene:

2 (tms)C≡CH → (tms)C≡C-C≡CH