Hexatriynyl radical
Encyclopedia
The hexatriynyl radical, C6H, is an organic radical
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...

 molecule consisting of a chain of six carbon atoms terminated by a hydrogen.

The unpaired electron is located at the opposite end to the hydrogen atom, as indicated. Both experimental work and computer simulations on this species was done in the early 1990s.

Synthesis of the radical

The radical can be synthesized by photolysis. Two different examples involve
  • Argon gas and 1,3-butadiene
    1,3-Butadiene
    1,3-Butadiene is a simple conjugated diene with the formula C4H6. It is an important industrial chemical used as a monomer in the production of synthetic rubber. When the word butadiene is used, most of the time it refers to 1,3-butadiene....

     in a mole ratio of 1500:1
  • Argon gas and 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...

     in a mole ratio of 100:1

Hexatriyne anion

In 2006 the negatively charged hexatriyne anion of this molecule, C6H, was the first negatively charged ion to be discovered to exist 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...

, using the Green Bank Telescope
Green Bank Telescope
The Robert C. Byrd Green Bank Telescope is the world's largest fully steerable radio telescope and the world's largest land-based movable structure. It is part of the National Radio Astronomy Observatory site at Green Bank, West Virginia, USA. The telescope honors the name of the late Senator...

. Negative ions were thought to be unstable in this environment due to the prevalence of ultraviolet light, which dislodges extra electrons such as this.

Synthesis of the anion

The laboratory synthesis starts from 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...

 C2H2. The reaction takes place within a DC discharge at reduced pressure in a mixture with 15% argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

. The product is observed by millimeter-wave spectroscopy.

Analogous species

The two species C4H and C8H
Octatetraynyl radical
Octatetraynyl radical is an organic free radical with eight carbon atoms linked in a chain with alternating single bonds and triple bonds....

have also been detected.
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