Carbon Tunneling in the Automerization of Cyclo[18]carbon

Ashim Nandi, Ephrath Solel, Sebastian Kozuch

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Cyclo[18]carbon (C18), a recently synthesized carbon allotrope, was found to have a polyynic ground-state structure with D9h symmetry and formally alternating single and triple bonds. Yet, under less influencing experimental conditions this molecule might undergo an automerization reaction between its two degenerate geometries through a cumulenic (non-alternating, adjacent double bonds) D18h transition state. Herein, we discuss the role of quantum mechanical tunneling (QMT) in this degenerate reaction. Our computations predict that at the experimental temperature (5 K) the reaction in the gas phase is completely driven by an extremely rapid heavy atom tunneling (k=2.1×108 s−1). Even when approaching room temperature, the QMT rate is still an order of magnitude faster than the semi-classical one. We propose an experimental test to support our prediction, by measuring a characteristic tunneling energy splitting within the radio wave region. Additionally, we examine the role of QMT in other hypothetical C4n+2 carbon clusters.

Original languageEnglish
Pages (from-to)625-628
Number of pages4
JournalChemistry - A European Journal
Issue number3
StatePublished - 13 Jan 2020


  • cyclocarbons
  • energy splitting
  • kinetic isotope effect
  • quantum mechanical tunneling
  • reactivity

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry


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