Crystal and molecular structure of bicyclo[2,2,1]hept-5-ene-2,3-endo-dicarboxylic acid

Abstract

The crystal and molecular structure of bicyclo[2,2,1]hept-5-ene-2,3-endo-dicarboxylic acid, C₉H₁₀O₄, has been determined by single-crystal X-ray diffraction techniques. The crystals are monoclinic:P2₁/c,a = 11·009(5),b = 7·394(5),c = 10·479(5) Å, β = 98 ° 22′(3) andZ = 4. The least-squares refinement of 1826 diffractometer reflexions resulted in a conventionalR of 0·074. Bond distances and angles of the bicyclo [2,2, 1]hept-5-ene ring system agree well with other recently published structures of this type, including similar asymmetry of bond distances. Hydrogen bonding of the acid groups occurs between the molecules so as to form infinite chains in the direction of thea-axis. Large anisotropic thermal motions of the oxygen atoms of one carboxylic acid group are, presumably, the result of differences in hydrogen-bonding geometry.