Beitrag zur mikroskopischen Identifizierung organischer Stoffe nach Kofler. 1. Mitt.

Zusammenfassung Für eine Reihe organischer Verbindungen wurden die vier zur Identifizierung nachKofler vorgesehenen physikalischen Konstanten (Schmelzpunkt, zwei eutektische Temperaturen, Lichtbrechung der Schmelze) in einer Tabelle zusammengestellt. Zusätzlich wurden mikrochemische Reaktionen, vor allem solche, die zur Bildung von Derivaten führen, angegeben. Die Derivate, teils durch Fällung aus Lösungen, teils im Kontaktpräparat hergestellt, wurden durch ihr Verhalten am Heiztisch näher charakterisiert.

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Contribution to the microscopical identification of organic compounds according to Kofler

Summary A table has been constructed containing for a number of organic compounds the four physical constants thatKofler suggested for identification (melting point, two eutectic temperatures, light refraction of the fusion). In addition, microchemical reactions are included, especially those that lead to the formation of derivatives. The derivatives, some prepared by precipitation form solutions, others by contact preparation, are more closely characterized by their behavior on the heating table.

     

Beitrag zur mikroskopischen Identifizierung organischer Stoffe nach Kofler. II

Zusammenfassung Für eine weitere Reihe organischer und organisch-anorganischer Verbindungen werden die nachKofler zur Identifizierung vorgesehenen physikalischen Konstanten in einer Tabelle zusammengestellt und außerdem verschiedene mikrochemische Reaktionen angegeben. Auf das Verhalten einiger Hydrate beim Erwärmen in Luft, in Paraffin oder in Siliconöl wird besonders hingewiesen.

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Contribution to the microscopic identification of organic materials after Kofler. II

Summary The physical constants provided for byKofler for identification purposes have been assembled in a table for an additional series of organic and organic-inorganic compounds, and in addition the various microchemical reactions are stated. Special notice is given of the behavior of a number of hydrates when warmed in the air, in paraffin or in silicone oil.

     

Studies on structures of lipid A-monophosphate clusters

Single crystalline clusters of lipid A-monophosphate were grown from organic dispersions containing 5-15% (v/v) water at various volume fractions, φ, and temperatures. The morphology of the single lipid A-monophosphate crystals was either rhombohedral or hexagonal. The hexagonal crystals were needlelike or cylindrical in shape, with the long dimension parallel to the c axis of the unit cell. The crystalline clusters were studied using electron microscopy and x-ray powder diffraction. Employing molecular location methods following a Rietveld refinement and whole-pattern refinement revealed two monoclinic crystal structures in the space groups P2(1) and C2, both converged with R(F) = 0.179. The two monoclinic crystal structures were packing (hydrocarbon chains) and conformational (sugar) polymorphs. Neither of these two structures had been encountered previously. Only intramolecular hydrogen bonding was observed for the polymorphs, which were located between the amide and the carboxyl groups. Another crystalline structure was found in the volume-fraction range 2.00 × 10(-3) ≤ φ ≤ 2.50 × 10(-3), which displayed hexagonal symmetry. The hexagonal symmetry of the self-assembled lipid A-monophosphate crystalline phase might be reconciled with the monoclinic symmetry found at low-volume-fractions. Therefore, lowering the symmetry from cubic, i.e., Ia 3d, to rhombohedral R 3 m, and finally to the monoclinic space group C2 was acceptable if the lipid A-monophosphate anion was completely orientationally ordered.     

Structure of blue phase III of cholesteric liquid crystals

We report large scale simulations of the blue phases of cholesteric liquid crystals. Our results suggest a structure for blue phase III, the blue fog, which has been the subject of a long debate in liquid crystal physics. We propose that blue phase III is an amorphous network of disclination lines, which is thermodynamically and kinetically stabilized over crystalline blue phases at intermediate chiralities. This amorphous network becomes ordered under an applied electric field, as seen in experiments.     

Synthesis and characterization of polystyrene chains on the surface of silica nanoparticles: comparison of SANS, SAXS, and DLS results

An extensive characterization of well-defined polystyrene (PS)-grafted silica nanoparticles is reported. Bare SiO₂ particles (diameter 50 nm) were functionalized with a suitable initiator for the surface-initiated anionic polymerization of styrene. Both grafted and free PS chains were characterized and compared by size-exclusion chromatography (SEC). PS-grafted particles were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), small-angle x-ray scattering (SAXS), small-angle neutron scattering (SANS), and dynamic light scattering (DLS). The thickness of the grafted PS chains was obtained by SANS and DLS and scaled with $M_{\mathrm {w}}^{0.6}$ displaying similar behavior with free PS chains in the same solvent used, tetrahydrofuran (THF). Grafting densities obtained from SANS data and TGA were found to be small, and the thickness of the grafted PS chains determined by SANS was found to be similar to $2R_{\mathrm {g}}$ of free PS chains in THF. Both results are consistent with a “coil-like” conformation of the grafted PS chains.     

Synthesis of Deuterated and Protiated Triacylglycerides by Using 1,1’-Carbonyldiimidazole Activated Fatty Acids

Synthetic model triacylglyceride oils are important compounds for applications in pharmaceutical and food chemistry. Herein, a practical and highly efficient methodology for the synthesis of saturated and unsaturated triacylglycerides utilizing saturated and unsaturated fatty acids activated by 1,1’-carbonyldiimidazole (CDI) has been developed and applied in the synthesis of deuterated medium chain triglyceride (MCT) oil for studies of plant-based and diary food emulsions. The deuterium labelled compounds were used to gain new insight into the mechanism of the reaction, which was confirmed by density-functional theory (DFT) calculations.