ethynylene
Ethynylene is the divalent fragment derived from acetylene by removing both terminal hydrogens, giving the linear -C≡C- unit that can link two organic groups. In practice, ethynylene refers to the fragment R−C≡C−R′, where two substituents occupy the ends of a carbon–carbon triple bond. The unit is strictly linear at the C≡C axis and the two carbons are sp-hybridized; the triple bond provides a short, rigid linkage that can contribute to conjugation in π systems.
Ethynylene groups are widely used as linking units in conjugated materials, notably polyphenylene ethynylene polymers, which
Reactivity: terminal ethynyl groups (−C≡C−H) participate in various cycloadditions and coupling processes; the internal ethynylene unit
See also: ethynyl, acetylene, polyphenylene ethynylene, Sonogashira coupling.