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. ne 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 C=O (...) C=O are interpreted as evidence for nonbonded interactions of the dipole-dipole type. ne rather long (OH)-H-... distances indicate that the C(sp(3))-(HO)-O-... interactions are weak.