On the conformational structure of cyclohexadecane,the corresponding ketone,the 1,9-dione and the corresponding ketals

The title compounds have been prepared, and their structures have been studied using molecular mechanics calculations, together with dipole moment measurements, and thermodynamic and spectroscopic data reported in the literature. It is concluded that the parent hydrocarbon exists to a very large extent in a “square” diamondoid conformation (D_2d symmetry). Other conformations (rectangular, nearly D₂, and puckered, (D_2d) are considerably higher in energy. The ketone consists of a mixture of both square and rectangular conformations with the CO group in several different positions. The monoethylene ketal exists primarily in a conformation which is square, with the ketal group on a corner. The diketone, diketal, and monoketal of the dione are considered in the light of the above, and conclusions are drawn regarding their conformations. The dipole moments of the difunctional compounds are in agreement with the conformational conclusions reached by the calculations.