Dilute sulfuric acid pretreatment of corn stover at high solids concentrations

Applied Biochemistry and Biotechnology - The enzymatic digestibility of a pretreated substrate is enhanced by increasing the severity of the pretreatment conditions, apparently because a greater...     

Zur Theorie der Chiralitätsfunktionen

The Algebraic Theory of Chirality Functions is derived by means of exclusively qualitative considerations. Hence, the significance of quantitative results is questionable. Moreover the construction of “Näherungsansätze” (”Approximation-Ansatz”), which may be interpreted as semiempirical methods, is achieved on the basis of plausibility and mathematical simplicity. Since physical arguments are not included, the consistency or inconsistency of “Näherungsansätze” with experimental results do not justify direct physical conclusions.     

X-ray diffraction/Calorimetry coupling

Polymorphism of trilaurin mixed with 4% of cholesterol was studied with a setup coupling calorimetry and phase characterisation by in-situ X-ray diffraction (Microcalix). Four polymorphic forms were identified. Monotropic and enantiotropic transitions were identified from the reconstruction of Gibbs free energy diagram which allows the control of trilaurin polymorphism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Darstellung und Kristallstruktur von HgPb2O(OH)Br3

Inhaltsübersicht. Die erstmals dargestellte Verbindung HgPb₂O(OH)Br₃ kristallisiert orthorhombisch in der Raumgruppe Aba2 (Nr. 41) mit den Gitterkonstanten a = 14,652(3) Å, b = 14,6491(8) Å, c = 7,782(2) Å und Z = 8. Die Bestimmung der Kristallstruktur mit Einkristallmethoden zeigte “isolierte”, verzerrt würfelförmige Baugruppen der Zusammensetzung [Hg₂Pb₄O₂(OH)₂]. Diese Einheiten werden von Bromidionen umhüllt. HgPb₂O(OH)Br₃ stellt damit hinsichtlich des strukturellen Aufbaus ein Bindeglied zwischen den Verbindungen [Pb₄(OH)₄](ClO₄)₄ · 2H₂O [1] und Pb₉O₄Br₁₀ [2] dar. Preparation and Crystal Structure of HgPb₂O(OH)Br₃ The new compound, HgPb₂O(OH)Br₃ was prepared and investigated by X-ray crystal structure analysis. Crystals of orthorhombic symmetry show space group Aba2 (No. 41) with lattice parameters a = 14.652(3) Å, b = 14.6491(8) Å, c = 7.782(2) Å, and Z = 8. Remarcable structural units with heterocubane skeleton were found. The [Hg₂Pb₄O₂(OH)₂] group forms a new member of the structural class between [Pb₄(OH)₄] and [Pb₈O₄] units with the relating compounds [Pb₄(OH)₄)](ClO₄)₄ · 2 H₂O [1] und Pb₉O₄Br₁₀ [2].     

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 64 Äußert sich die zwitterionische Natur des Triphenylphosphanoxid‐Liganden auch in seinen spektrochemischen Eigenschaften?

Electronic Structures of Organometallic Compounds of f Elements. 64 Does the Zwitterionic Nature of the Triphenylphosphine Oxide Ligand Manifest itself in its Spectrochemical Properties? The triphenylphosphine oxide mono adducts of the moiety tris(η⁵‐cyclopentadienyl)lanthanide(III) (Ln(Cp)₃; Ln = Pr ( 1 ), La ( 2 )) were synthesized and structurally characterized. The Ln–O distances of these compounds are noticeably shorter than those of the corresponding THF adducts. A crystal field (CF) analysis of the optical spectra of 1 leads to a low absolute value of the quadratic CF parameter which is comparable with those of [Pr(Cp)₃(L)]^? adducts with anionic bases but not with [Pr(Cp)₃(MeTHF)]. Reasons for the latter finding are presented.     

Synthese und Kristallstruktur von Blei(II)‐oxidhalogenid‐Alkoholaten mit unterschiedlichen Verknüpfungsvarianten von Pb4O4‐Heterokubaneinheiten

Synthesis and Crystal Structure Determination of Lead(II) Oxide Halide Alcoholates with Different Connectivity of Pb₄O₄ Heterocubane‐like Subunits The reaction of red lead(II) oxide (Litharge) and lead(II) halide (Cl^? and Br^?) with diethylene glycole at a temperature of 180 °C leads to the isotypic compounds [Pb₆(C₄H₈O₃)O₂Cl₆] (1) and [Pb₆(C₄H₈O₃)O₂Br₆] (2) . In a similar synthesis with PbI₂ as educt at temperature of 160 °C the two modifications β‐[Pb₆(C₄H₈O₃)O₂I₆] (3) and α‐[Pb₆(C₄H₈O₃)O₂I₆] (4) were found, whereas at a reaction temperature of 180 °C [Pb₉(C₂H₄O₂)(C₄H₈O₃)O₃I₈] (5) was surprisingly obtained as product. The X‐ray diffraction data show that at a temperature of 180 °C a splitting of the ether took place. The cited compounds show cubane like subunits built by lead and oxygen atoms. These fragments are connected by alkoholate molecules. In 5 additionally an I₆ octahedra centered by lead is observed.     

Synthese und Fluoreszenzeigenschaften von cyansubstituierten 2-Aminopyridinen

The synthesis of several 2-aminopyridines is described. The reaction of tetracyanoethylene with 3-imino-propane-carbonitrile gives 2-amino-3,4,5-tricyano-pyridines with alkyl and aryl-substituents, resp., in position 6. Nucleophilic substitution of 2-amino-6-chloro-3,5-dicyanopyridines and 2-amino-6-chloro-3,4,5-tricyano-pyridines with phenolates leads to a variety of pyridines. Spectroscopical data of absorption and fluorescence are presented and the influence of the cyano groups is discussed. The results are in good agreement with quantum chemical calculations (PPP).

Herrn Univ-Prof. Dr.A. Holasek zum 60. Geburtstag gewidmet.