cis-1,2,3,6-tetrahydrophthalic anhydride

The crystal structure of cis-1,2,3,6-tetrahydrophthalic anhydride, C8H8O3, has been determined by X-ray diffraction, This bicyclic compound crystalliz es in space group P2(1)/a, with two independent molecules per asymmetric un it. The folded conformation found for the two molecules is in close agreeme nt with the results obtained for other cyclic anhydrides having a similar m olecular arrangement. The same feature is observed in the anhydride ring st ructure. The differences between the two independent molecules in the unit cell were interpreted as the result of packing effects, caused by intermole cular nucleophile-electrophile (Nu-El) interactions.