Quantitative Bestimmung der Catechine und Hydroxyzimts?uren in pflanzlichen Lebensmitteln

Zusammenfassung Die Problematik der Bestimmung von Catechinen und Hydroxyzimtsäuren in pflanzlichen Lebensmitteln wird diskutiert und gezeigt, daß es notwendig ist, eine ausreichende Vorreinigung (Säulen-Chromatographie an Polyamid und Dünnschicht-Chromatographie an Cellulose bzw. Kieselgel) mit einem geeigneten Bestimmungsverfahren (Spektralphotometrie mit Vanillin/Salzsäure bzw. direkt) zu kombinieren. Beispiele werden beschrieben.Plenarvortrag anläßlich der Tagung Spurenanalyse, 2.–5. April 1973 in Erlangen.     

Optisch aktive übergangsmetall-komplexe : XXV. Substituenteneinflüsse auf die intramolekulare epimerisierung von tetragonal-pyramidalen molybdanund wolfram-komplexen

The synthesis, IR, ¹H NMR and UV spectra of optically active square pyramidal cyclopentadienyldicarbonyl-molybdenum and -tungsten complexes with Schiff bases, derived from methyl-substituted pyridine carbaldehyde(2) and S-(—)-α-methylbenzylamine, are described. The epimerisation of these complexes, measured polarimetrically at 75–97°C in DMF, follows a 1^st order rate law and represents a regular pentatopal skeletal rearrangement. The inductive effect of a methyl group in the para position of a pyridine ring leads to a retardation of the epimerisation compared to unsubstituted complexes. The rate constants decrease even more if an ortho methyl group is introduced into the pyridine system, since additional steric effects are introduced. If the metal complex contains a 4,6-dimethyl-substituted Schiff base as a chelating ligand, the contributions of a 4- and a 6-methyl group are additive. A benzene ring fused to the 5,6-positions of the pyridine system also leads to stabilisation of the configuration.     

Immobilization of η-cyclopentadienyltris(dimethylamido)zirconium polymerization catalysts on a chlorosilane- and HMDS-modified mesoporous silica surface: a new concept for supporting metallocene amides towards heterogeneous single-site-catalysts

The modification of a mesoporous silica surface with Si(Ind)(CH₃)₂Cl and the immobilization of CpZr(NMe₂)₃ on this surface was studied via IR-spectroscopy. To reduce side reactions, the indenyl-modified silica was reacted with hexamethyldisilazane (HMDS) under IR-control before the CpZr(NMe₂)₃-immobilization. The role of the hydroxyl group protection with HMDS is discussed. The surface modifications have been repeated via Schlenk technique at the same conditions and the surface modifications were studied with ¹³C CP MAS–NMR, ¹H MAS–NMR, elemental-, SEM- and BET-analysis. The surface species of the resulting catalysts are discussed. The precatalysts have been treated with methylaluminoxane (MAO) (Al:Zr (mol:mol)=500:1) and the resulting Zr contents (leaching-effect) are discussed. All catalysts have been tested in ethylene and propylene polymerization.     

Efficient indirect electrochemical in-situ regeneration of nadh:electrochemically driven enzymatic reduction of pyruvate catalyzed by d-ldh

Using [Cp(Me)₅Rh(bipy)C1]C1 (1) as redox catalyst for the continous NADH regeneration it was possible to perform an electrochemically driven enzymatic reduction of pyruvate to D-lactate catalyzed by D-LDH at a rate of 5 turnovers per hour. This is by a factor of 20 faster than the best results obtained until now. Current yields of 50 to 70 % may be obtained.     

Zur Chemie von Sulfiden und Seleniden primärer Phosphane — Die (1-Hydroxyalkyl)-organyl-phosphansulfide und -selenide,neue Verbindungsklassen

Investigation into Sulfides and Selenides of Primary Phosphines — The (1-Hydroxyalkyl)-organyl-phosphine Sulfides and Selenides, New Classes of Compounds Primary phosphines react with S₈ and Se₈, respectively, forming organylphosphine monosulfides, and monoselenides, respectively, RP(X)H₂ (X = S, Se) which are well characterized by ³¹P NMR spectroscopy. Organylphosphine monosulfides are detected in the reaction mixture of primary phosphines with 2,4-diaryl-1,3,2,4-dithiadiphosphetane-2,4-disulfides, too. The reaction of primary phosphines with sulfur or selenium proceeds in presence of most of the ketones without formation of any side product. The (1-hydroxyalkyl)-organyl-phosphine sulfides and selenides, respectively, RP(X)(H)C(OH)R¹R², are yielded generally in crystalline form. The X-ray crystal structure analysis of the (1-hydroxy-1-methyl-ethyl)-phenyl-phosphane sulfide (R = Ph, R¹ = R² = Me) has shown that in the crystal the molecules are chained via intermolecular O? H …? S hydrogen bridging bonds (O …? S = 328 pm). Aldehydes react with primary phosphines and sulfur forming bis(1-hydroxyalkyl)-phenyl-phosphine sulfides, RP(S)[CH(OH)R¹]₂. ¹H, ¹³C, and ³¹P NMR spectroscopic investigations allow to detect and to identify stereoisomers in some cases. Quantumchemical calculations reflect correctly which of the carbonyl compounds are able to react with the organylphosphine monosulfide formed as intermediate.