Crystal and molecular structure of 7-oxabicyclo[2,2,1]hept-5-ene-2,3-exo-dicarboxylic anhydride

Abstract

The crystal and molecular structure of the title compound (I) has been determined by three-dimensional X-ray analysis from 750 non-zero reflexions measured photographically. The compound crystallizes in the orthorhombic system, space group P2₁2₁2₁ with a= 7·00 ± 0·02, b= 18·93 ± 0·03, and c= 5·38 ± 0·01 Å, Z= 4. The crystal structure has been solved by the symbolic addition procedure applied to non-centrosymmetric crystals, and refined by least-squares calculations to R 0·087. The compound has the exo-conformation. The introduction of an oxygen atom in position 7 of the norbornene skeleton produces interesting modifications in some bond distances and angles.