On the stability of large [4n]annulenes.
[reaction: see text] The stabilization energies (B3LYP/6-31G) of planar [4n]annulenes, evaluated by a new indene-isoindene isomerization method (see Abstract graphic), reveal that all 4n pi-electron rings larger than the energetically unfavorable cyclobutadiene are only slightly destabilized by the pi-electron interactions. Cyclooctatetraene prefers the "tub" conformation because of strain effects. Generally, the antiaromatic character of the larger systems with 4n pi-electrons is revealed best by their magnetic properties rather than by their energies.
Wannere
Chaitanya S
CS
[reaction: see text] Computational Chemistry Annex, Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
Moran
Damian
D
Allinger
Norman L
NL
Hess
B Andes
BA
Schaad
Lawrence J
LJ
Schleyer
Paul von Ragué
Pv