Hexatriynyl radical

The hexatriynyl radical, C6H, is an organic radical molecule consisting of a linear chain of six carbon atoms terminated by a hydrogen (H\sC\tC\sC\tC\sC\tC•). 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 buta-1,3-diene in a mole ratio of 1500:1
 * Argon gas and acetylene 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, using the Green Bank Telescope. 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 C2H2. The reaction takes place within a DC discharge at reduced pressure in a mixture with 15% argon. The product is observed by millimeter-wave spectroscopy.

Analogous species
The two species C4H− and C8H− have also been detected.