lb from lc. The result leave open the possibility that lc
exists in the gas phase.
NEUTRAL HOMOAROMATIClTY: ALMOST BUT NOT QUITE. Dick van der Helm & M. Bilayet Hossain, Department of Chemistry & Biochemistry, University of Oklahoma, Norman, OK 73019 and Richard V. Williams,Vijay R.Gadgil & Kamlesh Chauhan, Department of Chemistry, University of Idaho, Moscow, ID 83844, and Lloyd M. Jackman & Errol Fernandes, Department of Chemistry, Pennsylvania State University, University Park, PA 16802.
The semibullvalenes have been recognized as the system most closely
approaching neutral homoaromaticity. Theoretical calculations indicate the
homoaromatic lc to be the ground state. However X-ray structure
determinations at 293K, 243K, 163K, 148K and 123K show an equal mixture of
la & lb at the higher temperatures and unequal mixtures of
1a & lb at the lower temperatures. The existence of both
la & lb is confirmed by solution NMR. The solid state NMR is
not able to distinguish la
lb from lc. The result leave open the possibility that lc
exists in the gas phase.
