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991.
Max Vecchi Willy Walther Ernst Glinz Thomas Netscher Rudolf Schmid Michel Lalonde Walter Vetter 《Helvetica chimica acta》1990,73(4):782-789
Separation and Quantitation of All Eight Stereoisomers of α-Tocopherol by Chromatography The results of the analysis of several derivatives of (all-rac)-α-tocopherol by HPLC on a chiral stationary phase and by capillary GC on a achiral stationary phase are reported. Consecutive application of both methods to the ethyl-ether derivative allows the separation and quantification of all eight possible stereoisomers of (all-rac)-α-tocopherol. 相似文献
992.
Zusammenfassung Lösungen von Kartoffelamylopektin und Kartoffelamylosen zeigen in einer Apparatur, welche die Empfindlichkeit= 1 besitzt, keine Strömungsdoppelbrechung. Durch Vergleich der Rotationsdiffusionskonstante, welche aus der durch die Empfindlichkeit der Apparatur geschätzten Maxwellschen Konstante folgt, und des für kugelige Teilchen berechneten Wertes findet man, daß sowohl das Amylopektin wie auch die Amylose Moleküle besitzen, die nicht wesentlich von der Kugelgestalt abweichen. 相似文献
993.
Isolation and Structure Elucidation of 36 Diterpenoids from Leaf-Glands of Plectranthus edulis (VATKE ) T.T. AYE Analysis of the polar diterpenoids from the yellow glands of the title plant from Kenya and Abyssinia led to the identification of several novel abietanoids. Main compound is the known edulon A ( 40 ), a 5(4→3) abeo-abietane. Minor compounds include 6 different royleanones, 15 spirocoleons, 3 vinylogous quinones, 8 acylhydroquinones (as their 6,7-dioxo compounds or the tautomeric disophenols), 2 naphthaquinones (as the 1,10-seco-abietanoids), and deacetyledulon A. The known coleon-A-lactone (37) now has also been found in Plectranthus edulis. The intermediacy of the γ-enollactol 44 , combined with a leaving group on C(3) is postulted to explain the biogenesis of the unusual 4H-5-oxaaceanthrylen skeleton of edulon A. 相似文献
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996.
Robert K. Müller Kurt Bernhard Hans Mayer August Rüttimann Max Vecchi 《Helvetica chimica acta》1980,63(6):1654-1664
Contribution to the Analytical Separation and the Synthesis of 3-Hydroxy-4-oxocarotenoids (3RS,3′RS)-Astaxanthin (= 3,3′-dihydroxy-β,β-carotene-4,4′-dione, 1:1-mixture of racemate and meso-form; 1 ) can be separated into its optical isomers (3S,3′S)- 1a , (3R,3′R)- 1b and meso-(3R,3′S)- 1c via the corresponding diastereomeric di-(?)-camphanates. Some aspects of the configurational stability of astaxanthin are discussed. - HPLC. analysis of the (?)-camphanates of 3-hydroxy-4-oxocarotenoids provides, in suitable cases and supported by spectroscopic data, an analytical method for the simultaneous determination of constitution and chirality. 相似文献
997.
Effects of FeCl3 as oxidizing agent on the conduction mechanisms in polypyrrole (PPy)/pc–ZnO hybrid heterojunctions grown by oxidative chemical vapor deposition 下载免费PDF全文
Alejandra Castro‐Carranza Jairo C. Nolasco Stephanie Bley Max Rückmann Florian Meierhofer Lutz Mädler Tobias Voss Jürgen Gutowski 《Journal of Polymer Science.Polymer Physics》2016,54(15):1537-1544
P‐type polypyrrole (PPy) films are deposited on glass and on n‐type polycrystalline ZnO (pc–ZnO) substrates by oxidative chemical vapor deposition under three different amounts of FeCl3 used as oxidizing agents to form hybrid heterojunctions. Their microstructure, morphology, and electrical characteristics are studied. Particularly, current–voltage characteristics of the PPy/pc–ZnO heterojunctions are analyzed by defining an electrical equivalent circuit. The extracted parameters, together with the estimated heterojunction barrier height and the HOMO energy level of the PPy, indicate that a thermionic emission of holes at the heterojunction determines the saturation current of the diode at low voltage. For larger FeCl3 amounts, the diode ideality factor increases indicating an increment of recombination by tunneling of charge carriers occurring at the heterojunction. This is attributed to a narrowing of the space charge region due to an increment of the number of charge carriers with a growing amount of FeCl3. At high voltages, the PPy thickness influences the ohmic and space–charge limited current mechanisms at the bulk region. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1537–1544 相似文献
998.
Dr. Gleb A. Silantyev Moritz Förster Bastian Schluschaß Josh Abbenseth Dr. Christian Würtele Christian Volkmann Prof. Dr. Max C. Holthausen Prof. Dr. Sven Schneider 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5966-5970
The coupling of electron- and proton-transfer steps provides a general concept to control the driving force of redox reactions. N2 splitting of a molybdenum dinitrogen complex into nitrides coupled to a reaction with Brønsted acid is reported. Remarkably, our spectroscopic, kinetic, and computational mechanistic analysis attributes N−N bond cleavage to protonation in the periphery of an amide pincer ligands rather than the {Mo−N2−Mo} core. The strong effect on electronic structure and ultimately the thermochemistry and kinetic barrier of N−N bond cleavage is an unusual case of a proton-coupled metal-to-ligand charge transfer process, highlighting the use of proton-responsive ligands for nitrogen fixation. 相似文献
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1000.