Experimental charge density study of 7-dispiro[2.0.2.1]heptane carboxylic acid

The experimental charge density distribution in 7-dispiro[2.0.2.1]heptane carboxylic acid has been determined using single-crystal X-ray diffraction data measured at 100 K. Multipole refinement converged at R = 0.023 for 5539 reflections with I ≥ 3σ(I) and sin θ/λ ≤ 1.08 Å⁻¹. Inclusion of hexadecapole functions for C atoms in the refinement is shown to be necessary. Experimental maps of the deformation density and of the Laplacian of ρ are in good agreement with those from ab initio calculations and also have some features specific for polyspirocyclopropanes. Analysis of the bond critical-point properties reveals that the effect of the π-acceptor hydroxycarbonyl substituent is more pronounced on the endo-side of the molecule, which can be related to the chemical behaviour of the compound. The influence of small conformational changes on the bond length distribution in the skeleton is also discussed.

-1