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Is the tetrakis[2.1.1]bicyclohexano‐cycloocta‐1,3,5,7‐tetraene a good model for the D 4 h‐1,3,5,7‐cyclooctatetraene?
Author(s) -
Stanger Am
Publication year - 2019
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3908
Subject(s) - cyclooctatetraene , cyclobutadiene , aromaticity , chemistry , antiaromaticity , ring (chemistry) , benzene , computational chemistry , excited state , ground state , molecule , organic chemistry , atomic physics , physics
Recently, it was claimed that D 4 h‐1,3,5,7‐cyclooctatetraene ( 2 ) is nonaromatic, according to a definition of aromaticity, which relies of the behavior of excited states. This conclusion is based mainly on MCD studies of tetrakis[2.1.1]bicyclohexano‐1,3,5,7‐cyclooctatetraene ( 1 ) and computational work on 2 at different symmetries. In this work, the aromaticity of 2 is studied by ground state criteria—aromatic stabilization energy (ASE) and magnetic properties. The ASE of 2 is studied and compared with those of benzene and cyclobutadiene. NICS(1) π,zz studies of 1 and 2 and comparison with tris‐bicyclo[2.1.1]hexanobenzene and benzene suggests a dramatic reduction of ring currents in the annulated systems. The reason was found to be mixing of the p orbitals of the bridgehead carbon atoms into the central rings π systems. It is unclear whether 2 should be considered antiaromatic, nonaromatic, or aromatic, but it is clear that 1 is not a good model for 2 for aromaticity studies purposes according to ground‐state properties (energy and magnetic).