TY - JOUR
T1 - Carbon Tunneling in the Automerization of Cyclo[18]carbon
AU - Nandi, Ashim
AU - Solel, Ephrath
AU - Kozuch, Sebastian
N1 - Funding Information:
This research was funded by the Israeli Science Foundation (grant no. 841/19). A.N acknowledges the Kreitman Graduate School for the Negev-Tsin scholarship.
Publisher Copyright:
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2020/1/13
Y1 - 2020/1/13
N2 - 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.
AB - 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.
KW - cyclocarbons
KW - energy splitting
KW - kinetic isotope effect
KW - quantum mechanical tunneling
KW - reactivity
UR - http://www.scopus.com/inward/record.url?scp=85076564565&partnerID=8YFLogxK
U2 - 10.1002/chem.201904929
DO - 10.1002/chem.201904929
M3 - Article
C2 - 31670421
AN - SCOPUS:85076564565
SN - 0947-6539
VL - 26
SP - 625
EP - 628
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 3
ER -