Bildung siliciumorganischer Verbindungen. 95. Die Kristallstruktur eines Hexadecamethyl-octasila-dispiro-[5.1.5.1]-tetradecans,Si8C22H65

Formation of Organosilicon Compounds. 95. Crystal Structure of a Hexadecamethyloctasila-dispiro [5.1.5.1]tetradecane, Si₈C₂₂H₅₆ 1,1,3,3,5,5,7,7,9,9,11,11,13,13,14,14-Hexadecamethyl-1,3,5,7,9,11,13,14-octasila-dispiro[5.1.5.1]tetradecane crystallizes monoclinically in the space group P2₁/n (No. 14) with a = 1352.4 pm, b = 1215.5 pm, c = 1001.2 pm, β = 92.11° and Z = 2 molecules per unit cell. The dispiro system is formed by a central disilacyclobutane and two C-spiro connected trisilacyclohexane rings. The symmetry of the molecule is 2/m, with flattened six membered rings in chair conformation. The Si? C bonds are enlarged (192 pm) at the strained spiro region whereas the Si? C bonds are distinctly shortened (186 pm) at the opposite Si atoms in the six membered rings.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXXVI [1]. Das Quecksilber(II)-bis-tri-tert-butoxysilanthiolat

Contributions to the Chemistry of Silicon-Sulfur Compounds. XXXVI. Mercury(II)-bis-tri-tert-butoxysilanethiolate Mercury(II)bis-tri-tert-butoxysilanethiolate was obtained in reaction of HgO with (t-C₄H₉O)₃SiSH. This compound forms colourless triclinic plates. The central S? Hg? S bond element is linear, with Hg? S bond distance of 231.6 pm. The Hg atom is coordinated by two oxygens of the two butoxy groups, with Hg? O distance of 287.8 pm. The mean bond angle at the two-bonded sulfur is 95.6°. (Space group P1 ; a = 930.8, b = 944.0, c = 1204.8 pm, α = 100.34, β = 97,64, γ = 116.50°; Z = 1; R = 0.035; 3390 reflections hkl).     

TiOBr; Darstellung,Eigenschaften und Struktur*

TiOBr was prepared by reaction of Ti with TiO₂ and Br₂. The compound forms fiat reddish-brown needles and shows a temperature independent weak paramagnetism. It crystallises in the orthorhombic system (Pmmn; a = 3.787, b = 3.487, c = 8.529 Å) with the FeOCl type of structure. The interatomic distances are Ti?O = 1.952; 2.245 Å (2X) and Ti?Br = 2.544 Å (2X).     

Analysis of corky off-flavour compounds at ultra trace level with multidimensional gas chromatography-electron capture detection

A robust method for routine quality control of corky off-flavour compounds in wine and cork soak matrices has been established. Based on an automated headspace solid phase microextraction (HS-SPME), the method needs only marginal sample preparation and achieves low (sub-ng L⁻¹) trace level detection limits (LODs) for the most relevant off-flavour compounds, such as 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA). Particularly for wine matrix, reliable trace level quantification had only been achieved after applying heart-cutting multidimensional gas chromatography (MDGC). Using a halogen-sensitive electron capture detector (ECD) and quantification with a stable isotope dilution assay (SIDA), LODs of 0.1 ng L⁻¹ for TCA, TeCA and TBA could be obtained. Since a SIDA based quantification method is used with a non-mass spectrometric detector, the necessary chromatographic resolution of internal standard and target analyte peaks resulted from the use of highly deuterated [²H₅]-isotopologues.     

Linear dichroism of perylene derivatives in a nematic liquid crystal

The polarized absorption spectra of derivatives of 3,4,9-perylenetricarboxylic acid and of 3,4,9,10-perylenetetracarboxylic acid dissolved in the nematic liquid crystal mixture ZLI 1695 have been recorded as a function of temperature. On the basis of these spectra, the directions of the absorption transition moments with respect to the principle axes of the order tensor, and the order parameters S * and D * for perylene derivatives have been determined assuming a C s or C 2 point symmetry group for the dyes molecules. From a generalized equation describing properties of anisotropic phases, the conditions necessary to determine a complete set of the order parameters and the pieces of possible information that can be obtained from the polarized optical spectroscopy are discussed.