Ab Initio and in-Crystal Geometry of trans-1,4-Dibromo1,4-dicarboxymethylcyclohexane

The structure of trans-1,4-dibromo-1,4-dicarboxymethylcyclohexane (I) has been determined by single crystal x-ray diffraction. The molecules, located on symmetry centers, are in the rigid chair conformation with the Br and COOCH₃ axial and equatorial, respectively. The molecular geometry observed in the crystal is similar to that calculated for the isolated molecule using ab initio calculations performed at the HF/6-31(d) level. A peculiar arrangement of the carboxymethyl substituents, along with short contacts involving the Br atoms, seem to play a role in the stabilization of the crystalline structure.