Annulation should tilt the benzene/Dewar-benzene equilibrium toward benzenes the largest effective annulating ring being six-membered; MP2(fc)/6-31G*//RHF/6-31G* methods are needed to reproduce experimental isomerization energies, but 6-31G calculations suffice to show trends for molecular design. (matrix prensented) Smaller "n" should favor isomerization; effective rings will have n ≤ 6.
Bibliographical noteFunding Information:
We are indebted to Professor J. Clayton Baum for many helpful discussions; we thank I. Beros and J.P.M. Fessenden for preliminary calculations, and a referee for several useful suggestions. This study was supported in part by the donors of the Petroleum Research Fund, administered by the American Chemical Society; purchase of computers was assisted by the National Science Foundation.
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- Valence isomerism