Why doesn't carbon form bonds with itself to form a molecule? Carbon shows the property of catenation, so why doesn't it form a cyclic molecule such as:

 C = C 
 ‖   ‖ 
 C = C 
  • 9
    $\begingroup$ graphene, diamond, fullerenes ... $\endgroup$
    – gilleain
    Nov 15, 2018 at 9:23
  • 1
    $\begingroup$ also relevant : chemistry.stackexchange.com/questions/43887/… $\endgroup$
    – gilleain
    Nov 15, 2018 at 11:58
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    $\begingroup$ buckyball also... $\endgroup$
    – MaxW
    Nov 15, 2018 at 20:55
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    $\begingroup$ Diamond and graphene if not engineered down do not qualify as molecules. Buckyballs is a nik for Buckminsterfullerenes. See Oscar Lanzi below for an answer $\endgroup$
    – Alchimista
    Nov 17, 2018 at 17:43
  • $\begingroup$ That specific molecule would be monstrously unstable due to ring strain. But plenty of other molecules with just carbon would not be and many exist. $\endgroup$
    – matt_black
    Dec 18, 2023 at 12:38

1 Answer 1


They do form. Besides fullerenes, there are carbon molecules with varying numbers of atoms around some stars[1]. Vaporized graphite in such envirinments produce chains of 3 to 30 carbobs and larger spheroidal clusters of 40 to as many as 100 carbins. These may combine with hydrogen and nitrogen to form circumstellar polyynes. Such molecular forms are, of course, less stable than the macromolecular structures we more commonly see under ambient conditions.


  1. H. W. Kroto, J. R. Heatth, S. C. O'Brien, R. F. Curl. R. E. Smalley (1987). "Long Carbon Chain Molecules in Circumstellar Shells". The Astrophysical Journal 314, 352-355.

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