The complete set of 86 isolated-pentagon-rule (IPR) isomers of C 92 has been described by the SAM1 quantum-chemical method, and their energetics checked by density functional theory at the B3LYP/6-31G* level. Although the lowest-energy cage is not identical in both approaches, it still exhibits D 2 symmetry in both cases. As energetics themselves cannot produce reliable relative stabilities at high temperatures, entropy terms are also computed and the relative-stability problem is treated entirely in terms of the Gibbs function. The lowest-energy structure is not the most populated isomer at higher temperatures -it is replaced by a D 3 structure. Further stability interchanges are possible at very high temperatures, when C 3 and C 1 structures are also important. There is a partial agreement of the computations with available observed data.

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Oxidative acetylation of tetramethyl bisphenol-F (2) using two different reagents is described. The reaction of (2) with NaIO 4 in acetic anhydride furnished a novel triacetate (3) and its reaction with lead tetraacetate (LTA) in dry benzene resulted in the formation of a novel bis-cyclohexadienone (4).