In organic chemistry, a cycloalkyne is the cyclic analog of an alkyne. A cycloalkyne consists of a closed ring of carbon atoms containing one or more triple bonds. Cycloalkynes have a general formula Cn H2n-4 Because of the linear nature of the C-CΞC-C alkyne unit, cycloalkynes are usually highly strained and can only exist when the number of carbon atoms in the ring is great enough to provide the flexibility necessary to accommodate this geometry. Consequently, cyclooctyne (C8H12) is the smallest cycloalkyne capable of being isolated and stored as a stable compound. Despite this, smaller cycloalkynes can be produced and trapped by a suitable reagent.
^An experimental and theoretical evaluation of the intramolecular reactions of cyclohexyne John Tseng, Michael L. McKee, and Philip B. Shevlin J. Am. Chem. Soc.; 1987; 109(18) pp 5474 - 5477; doi:10.1021/ja00252a028