Crystal structure of 1-chloroadamantane, C10H15Cl, in its plastic phase

Single crystal X-ray diffraction data were collected and interpreted for the plastic phase of 1-chloroadamantane, C10H15Cl, at 293 K. The unit cell is face centred cubic with a = 9·974 (7) Å, space group Fm3m, Z = 4. On the assumption of a rigid molecular skeleton, several types of orientational disorder were investigated: hindered reorientations between equally weighted orientations; free uniaxial rotation of the molecules about the C-Cl axis; and decomposition of the atomic orientational average density on symmetry adapted functions. With these three models agreement between observed and calculated structure factors is found, in which the C-Cl axis has six possible orientations along the fourfold axes of the crystal. The molecule performs quasi-free uniaxial rotation around the six equilibrium positions of the C-Cl axis.