ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
A study has been made of the crystal structure and electron density distribution of (CD32(OH)C-C≡C-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 θ/2θ step-scan technique, (sin θ)/λ ≤ 1.0 Å-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{\bar 1}, a = 8.483 (3), b = 9.933 (3), c = 8.801 (3) Å, α = 95.63 (3), β = 85.57 (3), γ = 119.63 (3)° 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 θ)/λ 〉 0.70 Å-1. The [Fo - Fc(HO)] map was calculated with the reflexions having (sin θ)/λ 〈 0.65 Å-1. Deformation density maxima of 0.58 and 0.36 e Å-3, σ = 0.025 e Å-3, were observed for the triple and single C-C bonds respectively. At C-O the maximum is much lower, 0.09 e Å-3. The integrated electron contents of the maxima are 0.28 for C≡C 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S056773947700117X
Permalink
