In chemistry, an acetylide is a compound that can be viewed as the result of replacing one or both hydrogen atoms of acetylene (ethyne) HC≡CH by metallic or other cations. The term is also used, more loosely, for any compound obtained in the same way from an acetylene derivative RC≡CH, where R is some organic side chain.[1]
An acetylide may be a salt (ionic compound) containing the anion C≡C2+, HC≡C+, or RC≡C+, as in sodium acetylide [Na+]2C≡C2− or cobalt acetylide Co2+C≡C2−.[2] Other acetylides have the metal bound to the carbon atom(s) by covalent bonds, being therefore coordination or organometallic compounds.
When both hydrogens of acetylene are replaced by metals, the compound is a special case of carbide, and may be commonly called such, as in calcium carbide Ca2+C≡C2−. When only one hydrogen atom is replaced, the anion may be called hydrogen acetylide or the prefix mono- may be attached to the metal, as in monosodium acetylide Na+HC≡C−.
Calcium carbide is an important industrial compound, which has long been used to produce acetylene for welding and illumination. Other acetylides are reagents in organic synthesis.