Polyyne

In chemistry, a polyyne /ˈpɒlɪʌɪn/ is any organic compound with alternating single and triple bonds; that is, a series of consecutive alkynes, (−C≡C−)
n with n greater than 1. The simplest example is diacetylene or buta-1,3-diyne, H−C≡C−C≡C−H.

These compounds have also been called oligoynes, or carbinoids after "carbyne" (−C≡C−)
∞, the hypothetical allotrope of carbon that would be the ultimate member of the series. The synthesis of this substance has been claimed several times since the 1960s, but those reports have been disputed. Indeed, the substances identified as short chains of "carbyne" in many early organic synthesis attempts would be called polyynes today.