Abstract

A study has been made of the crystal structure and electron density distribution of (CD32(OH)C-CC-C(OH) (CD3)2 by X-ray diffraction at 90 K. The intensities were measured with monochromatized Mo radiation (graphite monochromator) on a CAD4 diffractometer with the /2 step-scan technique, (sin )/ 1.0 A-1. Care was taken to obtain a homogeneous X-ray beam and to avoid multiple diffraction. Profile analysis was used to determine the integrated peak intensities. The compound is triclinic, P, a = 8.483 (3), b = 9.933 (3), c = 8.801 (3) A, = 95.63 (3), = 85.57 (3), = 119.63 (3)Degrees at 90 K, Z = 3. A least-squares refinement with all reflexions gave R = 0.045. For the study of the deformation density the atomic parameters were determined by a least-squares refinement based on reflexions with (sin )/ > 0.70 A-1. The Fo - Fc(HO) map was calculated with the reflexions having (sin )/ < 0.65 A-1. Deformation density maxima of 0.58 and 0.36 e A-3, = 0.025 e A-3, were observed for the triple and single C-C bonds respectively. At C-O the maximum is much lower, 0.09 e A-3. The integrated electron contents of the maxima are 0.28 for CC and 0.07 for C-C, in good agreement with the dynamical difference density calculated for a model compound by ab initio methods (6,3/3 GTO basis set). The lone-pair regions of the O atoms are positive with a tendency for the electrons to contract around the hydrogen bonds.