THE STRUCTURE OF PERHYDRO[2.2]PARACYCLOPHANE - MOLECULAR STRAIN, MOLECULAR RIGIDITY AND CRYSTAL PACKING

The structure of the highly-strained title compound perhydroparacyclop hane, C16H28, has been studied at five temperatures from 128 to 295 K. The conformation and detailed geometry calculated from molecular mech anics by Boyd in 1969 are confirmed by the crystal study. The molecule is apparently quite rigid at temperatures up to 200 K. One of the two non-equivalent centrosymmetric molecules in the unit cell is disorder ed at room temperature. The disorder is absent at 145 K, appears when the same crystal is studied at room temperature, and disappears almost entirely when the crystal is cooled again. The different behavior of the two molecules at higher temperatures is attributed to differences in packing.