The ring current in cyclopropane

by Fowler, P. W.; Baker, J.; Lillington, M.

Mapping of induced current density using the coupled Hartree-Fock "ipsocentric" (CTOCD-DZ/ 6-31G**//RHF/6-31G**) method shows a ring current arising in the sigma framework of cyclopropane that is intense, diatropic and annular, and hence is consistent with the numerous literature attributions of sigma-aromaticity to this molecule. Localised orbital analysis shows that this current can be attributed to the set of three carbon-carbon bonds. In a similar analysis, the four carbon-carbon bonds of (planar constrained) cyclobutane are found to give rise to a central paratropic current. The maps are consistent with the view that cyclopropane is strongly sigma-aromatic, cyclobutane is weakly sigma-anti-aromatic, and the larger cycloalkane systems are essentially sigma-non-aromatic.

Journal
Theoretical Chemistry Accounts
Volume
118
Issue
1
Year
2007
Start Page
123-127
URL
https://dx.doi.org/10.1007/s00214-007-0253-2
ISBN/ISSN
1432-2234; 1432-881X
DOI
10.1007/s00214-007-0253-2