Die Kristallstruktur der 1, 6‐Methano‐cyclodecapentaen‐2‐carbonsäure

The crystal structure of 1, 6‐methano‐cyclodecapentaene‐2‐carboxylic acid has been determined by X‐ray analysis of three‐dimensional diffractometer intensity data. The crystals are monoclinic, a = 7.59, b = 8.75, c = 15.02 Å, γ = 108° 5′, Z = 4, space group P 2 1 / b . The structure was established by direct methods and refined by full‐matrix least‐squares analysis, using anisotropic temperature factors. The perimeter is non‐planar, with bond lengths in the range 1.38–1.42 Å, but showing small, systematic variations. The methylene bridge has CC = 1.477 Å, ∢ CCC = 99.6°; these values are discussed in terms of a simple strain energy scheme. Hydrogen bonds (2.62 Å) between pairs of carboxyl groups lead to the formation of dimers in the crystal. The arrangement of CO and COH bonds appears to be disordered.