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A cyclo[n]carbon is a chemical compound consisting solely of an n number of carbon atoms linked in a ring by double covalent bonds (a cyclic cumulene). Since the compound is composed only of carbon atoms, it is considered an exotic carbon allotrope. If n is even there is an alternative structure where the bonds alternate between single and triple bonds (a cyclic polyyne).[1][2][3] The (hypothetical) six-carbon member of this family (C6) is also called benzotriyne.

The smallest cyclo[n]carbon predicted to be thermodynamically stable is C18, with a computed strain energy of 72 kilocalories per mole.[1][3]


  1. ^ a b George A. Adamson; Charles W. Rees (1996). "Towards the total synthesis of cyclo[n]carbons and the generation of cyclo[6]carbon". J. Chem. Soc., Perkin Trans. 1 (13): 1535–1543. doi:10.1039/P19960001535. 
  2. ^ Yves Rubin; Carolyn B. Knobler; Francois Diederich (1990). "Precursors to the cyclo[n]carbons: from 3,4-dialkynyl-3-cyclobutene-1,2-diones and 3,4-dialkynyl-3-cyclobutene-1,2-diols to cyclobutenodehydroannulenes and higher oxides of carbon". J. Am. Chem. Soc. 112 (4): 1607–1617. doi:10.1021/ja00160a047. 
  3. ^ a b François Diederich; Yves Rubin; Carolyn B. Knobler; Robert L. Whetten; Kenneth E. Schriver; Kendall N. Houk; Yi Li (8 September 1989). "All-Carbon Molecules: Evidence for the Generation of Cyclo[18]carbon from a Stable Organic Precursor". Science. 245 (4922): 1088–1090. Bibcode:1989Sci...245.1088D. doi:10.1126/science.245.4922.1088. PMID 17838807.