Isolierung von (−)-Dunnion aus Calceolaria integrifolia MURR. (Scrophulariaceae)

Isolation of (?)-dunnione from the leaves of Calceolaria integrifolia, MURR . (fam. Scrophulariaceae) From the leaves of Calceolaria integrifolia, a plant often used in horticulture. partially racemic (?)-dunnione (1) has been isolated. This seems to be the first record of its occurrence outside the family Gesneriaceae, where it previously has been found in two species as the (+)-enantiomer.     

Dual-label autoradiographic analysis of human skin fibroblast and myoblast proteins by two-dimensional polyacrylamide gel electrophoresis using immobilised pH gradients in the first dimension

Horizontal two-dimensional polyacrylamide gel electrophoresis with immobilised pH gradients in the first dimension has been applied to the analysis of human skin fibroblast and muscle myoblast total cell proteins. Excellent two-dimensional separations of skin fibroblast proteins were obtained using pH 4-10 immobilised pH gradient gels with a long interelectrode distance (16 cm), but resolution was degraded, particularly of the more acidic proteins, by the use of shorter (10 cm) gels. Improved resolution of acidic and basic proteins was obtained using separate pH 4-7 and pH 7-10 immobilised pH gradient gels respectively in the first dimension. Two-dimensional protein maps of skin fibroblast proteins were visualised both by silver staining and by autoradiography of samples labelled synthetically with [35S]methionine. Horizontal two-dimensional electrophoresis, using pH 4-7 and pH 7-10 immobilised pH gradient gels in the first dimension, was applied to the analysis of protein samples from skin fibroblasts and muscle myoblasts dual-labelled synthetically with [35S]methionine and [75Se]selenomethionine in an attempt to identify sets of proteins specific to each cell type. In addition, two-dimensional maps or protein samples derived from normal individuals and patients with Duchenne muscular dystrophy were compared to search for protein changes associated with the disease state. Although sets of qualitative protein spot differences were observed by visual inspection of the two-dimensional gels, more rigorous qualitative and quantitative analysis of the patterns using a computerised analysis system will be required to obtain the maximum amount of information from these data.     

Low-Field NMR Relaxation Analysis of High-Pressure Ethane Adsorption in Mesoporous Silicas

Understanding the behaviour of short-chain hydrocarbons confined to porous solids informs the targeted extraction of natural resources from geological features, and underpins rational developments in separation, storage and catalytic conversion processes. Herein, we report the application of low-field (12.7 MHz) ¹H nuclear magnetic resonance (NMR) relaxation measurements to characterise ethane dynamics within mesoporous silica materials exhibiting mean pore diameters between 6 and 50 nm. Our measurements provide NMR-based adsorption isotherms within the range 25–50 bar and at ambient temperature, incorporating the ethane condensation point (40.7 bar at our experimental temperature of 23.6 °C). The quantitative nature of the acquired data is validated via a direct comparison of NMR-derived excess adsorption capacities with ex situ gravimetric ethane adsorption measurements, which are demonstrated to agree to within 0.2 mmol g⁻¹ of the observed ethane capacity. NMR relaxation time distributions are further demonstrated as a means to decouple interparticle and mesopore dominated adsorption phenomena, with unexpectedly rapid relaxation rates associated with interparticle ethane gas confirmed via a direct comparison with NMR self-diffusion analysis.     

Studium des gegenseitigen Einflusses der Bindungen in Thiocyanat-Kupfer(II)-Komplexen mit Methyl- und Dimethylpyridinen mittels Infrarotspektroskopie

The infrared spectra of thiocyanato-copper(II) complexes of the type Cu(NCS)₂ L ₂ with all isomeric picolines and lutidines (L) as well as those of the type Cu(NCS)₂ L ₃ withL=3- and 4-picoline, 3,4- and 3,5-lutidine were measured. The behaviour of the (CN) stretching vibrations of the Cu(NCS)₂ L ₂ complexes led to conclusions on the different kind of coordination of the NCS groups in dependence on the ligandL. The mutually conditioned strength of the Cu–NCS and Cu–N(L) bonds in the equatorial plane, especially in the presence of ligandsL with the steric effect, was determined from the frequency shift of the Cu–NCS and Cu–N(L) stretching vibrations with regard to the vibrations for Cu(NCS)₂(pyridine)₂.

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Mit 1 Abbildung     

Die Massenspektren der Pyrrolidide einiger aliphatisch-alicyclischer Carbonsäuren

The mass spectra of the pyrrolidides of some long-chain carboxylic acids with alicyclic residues attached to their ω-end are discussed and compared with the spectra of the corresponding esters. Fragmentation triggered by the pyrrolidide group generates a series of peaks, which clearly exhibits the size and the structure of the carbon chain.     

Hexacyanopalladium(IV)-säure und Hexacyanopalladate(IV)

The preparation and the properties of the hexacyanopalladium(IV) acid (H₃O)₂[Pd(CN)₆] and of a number of metal hexacyanopalladates(IV) are described. UV, IR and Raman spectra are reported, force constants have been calculated and the bonding properties are discussed. K₂[Pd(CN)₆] crystallizes in a hexagonal lattice; a = 7.42, c = 6.65 Å, Z = 1.     

Die spezifische Wärme des Polyvinylchlorids

Zusammenfassung Die spezifische Wärme verschiedener handelsüblicher Polyvinylchlorid-Sorten (Suspensions- und Emulsions-PVC, schlagfestes PVC und ein Vinylchlorid-Vinylacetat-Copolymerisat) wurde im Temperaturbereich 20 (bzw. –50) bis 140 °C mit einem adiabatischen Kalorimeter gemessen. Besondere Aufmerksamkeit wurde dem Einfluß der thermischen Vorgeschichte gewidmet. Messungen an getemperten Proben ergaben — in Übereinstimmung mit den Ergebnissen anderer Autoren —einfache Kurvenzüge mit einem Steilanstieg der spezifischen Wärme im Einfriergebiet. Untersuchungen an abgeschreckten Proben ließen zu Beginn des Einfrierbereiches Minima der spezifischen Wärme infolge Enthalpierelaxation erkennen. Oberhalb des Einfrierbereichs zeigten sich Kristallisationserscheinungen mit Wärmetönungen von etwa –1,3 cal/g (exotherm). Hieraus wurde der kristalline Anteil des Polyvinylchlorids zu rund 3% abgeschätzt. Der Schmelzpunkt der PVC-Kristallite wurde differentialthermoanalytisch zu 156 bzw. 170 °C gefunden. Das schlagfeste PVC ließ das Schmelzen einer Spur Polyäthylen zwischen 102 und 125 °C erkennen. Die kalorimetrisch bestimmten Einfriertemperaturen stimmen mit dilatometrisch gemessenen — gleiche thermische Vorbehandlung vorausgesetzt — überein.

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Summary The specific heat of some commercially available samples of polyvinyl chloride (suspension PVC, emulsion PVC, high impact PVC, and a copolymerisate of vinylchloride and vinylacetate) was measured in the temperature range from 20 (or –50) to 140 °C, using an adiabatic calorimeter. Special attention was paid to the influence of thermal history of the samples. Investigations of annealed samples gave simple curves with a steep slope in the glass transition range, in agreement with the results of other authors. Measurements with samples quenched in ice water showed specific heat curves with a minimum at the beginning of the glass transition range caused by enthalpy relaxation. Above the glass transition range crystallization occurred accompanied by heat effects of about –1,3 cal/g (exothermal). From this the fraction of crystalline PVC was estimated to be about 3%. The melting point of the PVC crystallites as determined by differential thermal analysis was 156 or 170 °C. With high impact PVC the melting of traces of polyethylene was observed between 102 and 125 °C. The glass transition temperatures as determined by calorimetry agreed with those determined by dilatometric measurements, provided thermal pretreatment being equal in both cases.

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Mit 14 Abbildungen und 5 Tabellen     

Asymmetric [2,3]-rearrangement of glycine-derived allyl ammonium ylids

The first examples of highly enantioselective [2,3]-sigmatropic rearrangements of acyclic allylic ammonium ylids are reported. Thus, a range of N-{2'-[(N'-allyl-N',N'-dialkyl)ammonium]}acetyl camphor sultams undergo rearrangement at 0 degrees C in DME solution with high diastereofacial control (up to 99:1 dr) to give allylglycines in generally high yield. The power of the method has been demonstrated in a rapid and efficient synthesis of (R)-allyl glycine.     

Fractionation of partly hydrolyzed polyvinyl acetate

Vinyl acetate–vinyl alcohol copolymers were fractionated in order to obtain their degree of hydrolysis distributions. In the method employed for fractionation, the differences in molecular weight of copolymer did not affect the fractional separation. Degree of hydrolysis distributions was found to be broad, with a pronounced maximum at a low degree of hydrolysis. Viscosity measurements were performed both for the precipitated fractions and unfractionated polymer. The Huggins constant was found to increase with a decrease in the degree of hydrolysis of polyvinyl acetate. These results were interpreted in terms of a polymer molecular association. From values of Huggins constants, comparative information about copolymer “blockiness” is also established.     

Non relativistic continuum wave functions for two coulomb centres

We give the continuum wave function solutions to the Schrödinger equation for an electron moving field of two point nuclei, as an expansion in terms of one centre Coulomb wave functions in a prolate elliptical coordinate system. These solutions may be chosen to have a convenient asymptotic behaviour, and tend to the conventional solutions of the Helmholtz equation in the limit that the nuclear charge goes to zero. In symmetric systems, where both nuclei have the same charge the angular wave functions are found to be identical with those occurring in the free case, and the expansion coefficients for the corresponding radial solutions are given for selected values of electron energy and nuclear separation.[/p]