Molecular-mechanical analysis of the structure of stressed organic molecules. 4. Spiro hydrocarbons

Three-Membered-Ring-Based Molecular Architectures

“…X-ray crystal structure analyses established the conformations of 730 and 732 in the solids. , In solution, however, [6]rotane 732 is especially intriguing as an example of a completely substituted cyclohexane, the conformations and dynamic behavior of which are dominated by strong nonbonding interactions. As a consequence, an unusual accumulation of anomalies was observed for such compounds . Thus, while cyclohexanes normally adopt a chair conformation, and the free energy of activation for the chair-to-chair interconversion seldom exceeds 11.9 kcal/mol, [6]rotane 732 was the first per(cyclo)alkylated cyclohexane for which the chair-to-chair interconversion was frozen at room temperature in solution.…”