Crystal Structure of 3,4,5,6‐Tetrahydrophthalic Anhydride at 150 K

The crystal structure of 3,4,5,6-tetrahydrophthalic anhydride, (=4,5,6,7-tetrahydroisobenzofuran-1,3-dione; 1; C8H8O3) was determined and refined by an analysis of three-dimensional X-ray-diffraction data at 150 K. This bicyclic compound crystallizes in space group Pbca with two symmetry-independent molecules I and II per asymmetric unit. The cyclohexene ring in both molecules adopts a half-chair conformation. The obtained conformational descriptions of the six-membered rings in the crystal phase are consistent with conformational data derived from molecular-orbital calculations. The structure analysis evidences considerable distorsion of the partially hydrogenated six-membered ring; the furan ring is flattened in molecule I and slightly deviated from planarity in molecule II. The short intermolecular distances found for CO⋅⋅⋅CO are interpreted as evidence for nonbonded interactions of the dipole–dipole type. The rather long O⋅⋅⋅H distances indicate that the C(sp3)-H⋅⋅⋅O interactions are weak.