Crystal structure and electron density distribution of deuterated 2,5-di­methyl-3-hexyn-2,5-diol, C8H2D12O2, at 90 K

R. B. Helmholdt, A. Vos

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A study has been made of the crystal structure and electron density distribution of (CD32(OH)C-C[equivalent to]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 [theta]/2[theta] step-scan technique, (sin [theta])/[lambda] [less-than or equal to] 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, [alpha] = 95.63 (3), [beta] = 85.57 (3), [gamma] = 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 [theta])/[lambda] > 0.70 Å-1. The [Fo - Fc(HO)] map was calculated with the reflexions having (sin [theta])/[lambda] < 0.65 Å-1. Deformation density maxima of 0.58 and 0.36 e Å-3, [sigma] = 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[equivalent to]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.
Original languageEnglish
Pages (from-to)456-465
Number of pages10
JournalActa Crystallographica Section A
Publication statusPublished - 1977

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