NIR FT Raman Spectroscopy–a Rapid Analytical Tool for Detecting the Transformation of Cellulose Polymorphs

This is a report of the combined use of NIR FT Raman spectroscopy and X-ray diffraction measurements (WAXS) to investigate the polymorphic transformation of cellulose I into cellulose II. For this reason samples of cellulose I were swelled in different concentrations of NaOH and dissolved in different molten inorganic salts hydrates (LiCl·2ZnCl₂·6H₂O, LiClO₄·3H₂O, LiSCN·2,5H₂O and ZnCl₂·4H₂O). NIR FT Raman spectra of the alkali treated samples were recorded. They characterize the pure modifications cellulose I and II as well as mixtures of the two polymorphic phases. The results of the Raman measurements were confirmed by X-ray scattering. The paper demonstrates that FT Raman vibrational spectroscopy is a powerful, rapid analytical method which may be used to follow the polymorphic transformation of cellulose I into cellulose II.     

Eco-friendly synthesis of imines by ultrasound irradiation

A series of imines was synthesized by an ultrasound-assisted reaction of aldehydes and primary amines using silica as the promoter. Products were obtained in high yields even in large scale synthesis.     

Biocatalytic Reduction of 2‐Monosubstituted 3‐Thiazolines Using Imine Reductases

The application of a straightforward biocatalytic technology for the reduction of racemic 2‐monosubstituted 3‐thiazolines, which are easily prepared via Asinger‐multicomponent reaction, is reported. The biocatalytic reduction yields racemic 2‐monosubstituted 3‐thiazolidines, which are difficult to be prepared by means of classic chemical routes, in moderate to high yields. Moreover, our study clarifies the stereochemical reaction course of the biocatalytic reduction. Furthermore, the efficiency of this biocatalytic technology is demonstrated in an experiment at an elevated substrate concentration of 60 mM leading to 96% conversion.     

Applications of FT Raman Spectroscopy and Micro Spectroscopy Characterizing Cellulose and Cellulosic Biomaterials

FT Raman spectroscopy and micro spectroscopy were used for the investigation of cellulose, cellulose derivatives and cellulosic plant fibres. Lattice structures of cellulose, polymorphic modifications I and II, as well as amorphous structure, were clearly identified by means of FT Raman vibrational spectra. Chemometric models were developed utilizing univariate calibration as well as methods of multivariate data analyses of FT Raman spectral data for the fast prediction of cellulose properties. Cellulose properties like the degree of crystallinity Xc_Raman, the degree of substitution DS_CMC, DS_AC and cellulose reactivity were determined. In situ/ in vivo FT Raman micro spectroscopy was used for the characterization of cellulose structures of flax and hemp fibres. Orientational and stress dependent FT Raman experiments were carried out.     

Properties of polythiophene and related conjugated polymers: a density-functional study

Using a parameter-free, density-functional method that has been developed explicitly for the theoretical treatment of infinite, periodic, isolated, helical polymers we study various polymers related to polythiophene. In particular we discuss how the electronic properties of polythiophene are changed when replacing some of the H atoms by CH3 group, by incorporating vinylene bridges into the backbone, or when replacing some or all the CH units of the backbone by N atoms. We observe the weakest effects for the methyl-substitution and the strongest for the N-incorporation. The latter leads to an overall downward shift of all bands, but in contrast to the case for polyacetylene, the unrelaxed compound with N atoms does not have N lone-pair orbitals as the highest occupied ones. Instead these occur at somewhat deeper energies. When comparing the aromatic and quinoid forms we found for the pure compound as well as for the methyl-containing one that the gap closes when passing from the one to the other form which was not found for any of the other materials of the present study. Moreover, the energy of the HOMO was found to depend stronger on the bond-length alternation than the energy of the LUMO, ultimately giving that polarons will induce two asymmetrically placed gap states with the energetically lower one appearing deeper in the gap than the other one.     

Über das Verhalten unterstöchiometrischer Übergangsmetallcarbide als Katalysatoren in Dehydrierungsprozessen

Zusammenfassung Messungen an unterstöchiometrischen Übergangsmetallcarbiden (Gruppe IV, V) im Hinblick auf deren Eignung als Katalysatoren für den Dehydrierungsprozeß Aethylbenzol Styrol zeigen eine Abhängigkeit der Dehydrierungsrate von der Konzentration des Kohlenstoffs im Metallgitter und von der Struktur der Carbidphase. Einige technische Anwendungsmöglichkeiten werden angeführt.

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The catalytic behaviour of substoichiometric transition metal carbides on dehydrogenation processes

The catalytic activities of substoichiometric carbides of transition metals (group IV, V) on the dehydrogenation process of ethylbenzene to styrene are described. The results show the dependence of the dehydrogenation rate versus the concentration of carbon in the metal lattice and of the structure of the used carbides. Some technical applications are mentioned.

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Mit 4 Abbildungen

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Herrn Prof. Dr.H. Nowotny gewidmet.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

Crystal structures of a pair of diastereomeric 3-(N,N-dimethylammonium)-1,1-diphenyl-1-butanol O,O′-di-p-toloyl hydrogen tartrates

The crystal structures of a pair of diastereomeric salts of (–)-(2R, 3R)-O, O-di-p-toloyl tartaric acid and (–)- and ( + )-3-N,N-dimethylamino-1,1-diphenyl-1-butanol have been determined. Crystal data: 3: (-)-(R)-C₁₈HC₂₄NO⁺(-)-(2R,3R)-C₂₀H₁₇O^- ₈ orthorhombic, P2₁2₁2₁, a = 7.873(2), b = 15.343(3), c = 28.76(1) Å, V = 3474(2) ų, Z = 4, and D _calc = 1.254 g cm^–3. 4: (+)- (S)-C₁₈H₂₄NO⁺, (-)-(2R,3R)-C₂₀H₁₇O^- ₈orthorhombic, P2₁2₁2₁, a = 7.504(1), b = 17.215(2), c = 26.490(4) Å, V = 3422.0(8) ų,Z = 4, and D _calc = 1.273 g cm^–3. The geometries and the conformational energies of the solid state conformations of the cations have been compared with global and local energy minimum conformations determined by molecular mechanics calculations. In the solid state, one conformation with and one without an intramolecular hydrogen bond are observed. The calculated global energy minimum conformation in aqueous solution contains the intramolecular hydrogen bond.