Sand als Rohstoff

Pure sand and gravel qualities are becoming to be rare resources and technical goods of increasing strategic importance for various industrial branches worldwide. Quartz sand as a crystalline raw material is chemically transformed into intermediates for the final production of synthetic amorphous silicon dioxides (SAS). Precipitated SAS are produced by chemical reaction of sodium silicates. Chlorosilanes are produced by reaction of silicon and ferrosilicon with HCl. They are used to produce pyrogenic SAS. High‐resolution transmission electron microscopy is needed to reveal the fine structure of these amorphous materials. Pyrogenic and precipitated SAS show a similar nanostructure as silica‐gels and ‐aerogels. Differences in amorphicity and short range order in finely divided, alkaline‐free, amorphous SAS on the one hand and in alkaline‐containing amorphous SiO₂‐networks such as solid sodium silicates on the other still are not completely clarified.     

Linear and nonlinear optical properties of some organoxenon derivatives

We employ a series of state-of-the-art computational techniques to study the effect of inserting one or more Xe atoms in HC2H and HC4H, on the linear and nonlinear optical (L&NLO) properties of the resulting compounds. It has been found that the inserted Xe has a great effect on the L&NLO properties of the organoxenon derivatives. We analyze the bonding in HXeC2H, and the change of the electronic structure, which is induced by inserting Xe, in order to rationalize the observed extraordinary L&NLO properties. The derivatives, which are of interest in this work, have been synthesized in a Xe matrix. Thus the effect of the local field (LF), due to the Xe environment, on the properties of HXeC2H, has also been computed. It has been found that the LF effect on some properties is significant. The calculations have been performed by employing a hierarchy of basis sets and the techniques MP2 and CCSD(T) for taking into account correlation. For the interpretation of the results we have employed the complete active space valence bond and CASSCF/CASPT2 methods.     

The Temperature‐Composition Phase Equilibria in the Hg0.8Cd0.2Te‐HgI2 Pseudobinary System

The temperature‐composition phase equilibria of the Hg_0.8Cd_0.2Te‐HgI₂ system were investigated between about 100 and 800 °C using Debye‐Scherrer powder X‐ray diffraction techniques, differential thermal analysis, differential scanning calorimetry, and thermochemical and structural calculations. This system is a pseudobinary temperature‐ composition plane in the HgTe‐CdTe‐HgI₂ pseudoternary phase diagram. Measurable solid solutions of HgI₂ in Hg_0.8Cd_0.2Te with the cubic zinc blende‐type structure exist between about 290 and 700 °C, with a maximum solubility of 4.9 ± 0.3 mole‐% HgI₂ at 363 ± 3 °C. Further addition of HgI₂ to HgI₂‐saturated Hg_0.8Cd_0.2Te yields the formation of CdI₂, which reduces the mole fraction (x) of CdTe in the Hg_1—xCd_xTe host lattice. After sufficient HgI₂ is added, the host lattice is depleted in CdTe and forms Hg₃Te₂I₂ in addition to CdI₂. Phase fields containing the ternary compound Hg₃TeI₄, which we first observed in the HgTe‐HgI₂ system, also exist in the present system. Quaternary analogs of the known ternary compounds Hg₃Te₂I₂ and Hg₃TeI₄, i.e., Hg_3—yCd_yTe₂I₂ and Hg_3—yCd_yTeI₄, were not observed under present experimental conditions.     

Die Brüder Otto und Robert Margulies

It is difficult to understand that nearly no information can be found in encyclopedias and books about the history of the chemical industry about the Margulies family (father Benedikt and sons Otto and Robert), pioneers in industrial chemistry. The Margulies brothers realized the importance of catalysis and electrochemistry as a basis for industrial chemical processes. They initiated the fixation of N₂ from the air which resulted in the synthesis of Ammonia by Haber and Bosch and they also developed the first industrial process for the production of Hydrogen Peroxide and built the first industrial production unit in Austria. There is no monument to honor the pioneers, no price is named after them and they had very little benefit from what they initiated or made available on an industrial scale. This article is dedicated to their memories.     

The impact of structural biology on alkaloid biosynthesis research

Covering: 1997 to 2012In the recent past, macromolecular crystallography has gone through substantial methodological and technological development. The purpose of this review is to provide a general overview of structural biology and its impact on enzyme structure/function analysis and illustrate how it is modifying the focus of research relevant to alkaloid biosynthesis.     

Dielectric spectroscopy on aqueous solutions of some zwitterionic amino acids

The complex (electric) permittivity of aqueous solutions of dipolar solutes has been measured as a function of frequency between 1 MHz and 40 GHz. Solutes are the isomers DL-2-aminobutyric acid, DL-3-aminobutyric acid, and 4-aminobutyric acid, and also 6-aminohexanoic acid. The measured dielectric spectra show two dispersion/dielectric loss regions, one due to the orientational diffusion of the solute molecules the other one due to the dielectric relaxation of the solvent water. A relaxation spectral function based on a model of the solutions has been fitted to the measured frequency dependence of the complex permittivity. The values for the electric dipole moment and reorientation time of the zwitterionic part of the solute particles derived by this analysis from the measurements fairly agree with theoretical predictions. Quite remarkably, the dipole moment in solution of 4-aminobutyric acid and 6-aminohexanoic acid up to remarkably high solute concentrations is nearly constant. A noteworthy result for the hydration water of the amino acids is, that its relaxation time is almost independent of the solute dipole moment.     

Methanol – die Basischemikalie

Today methanol is produced from synthesis gas derived from coal and natural gas. However carbon dioxide and hydrogen obtained from water electrolysis with renewable energy have the potential to play a leading role as fuel, energy raw material and chemical feedstock. As a liquid energy storage system it can be used to easily transport electric power conserved in chemical bonds with unparalleled efficiency. Homologisation making use of the Mobil zeolite processes (MTG, MTO, MTA) for instance, or via the methanol derived platform chemicals methyl formate and dimethyl ether, the majority of organic chemicals established in chemical industry is available. Through its diverse of applications methanol has the potential to substitute crude oil and natural gas as the leading feedstock for organic chemicals.