Palladium Catalyzed Cross-Couplings of Organozincs in Ionic Liquids.-Negishi cross-coupling between aryl halides or nonaflates and zinc bromides is achieved under mild conditions using an ionic liquid and a new ionic phosphine ligand. Moreover, the solvent allows a facile work-up.
The reaction of anhydroerythritol (AnEryt) and methyl-β-Dgalactopyranoside (Me-β-D-Galp) with dichloro[hydridotris-(pyrazolyl)borato]oxorhenium(V) [(tpb)ReOCl 2 ] in methanol/ triethylamine results in the formation of blue crystals of the diolato complexes [(tpb)ReO(AnErytH −2 )] (1) and [(tpb)Re-O(Me-β-D-Galp3,4H −2 )] (2). The amounts of anti-1 and syn-1 isomers are investigated by means of NMR spectroscopy and depend on the solvent chosen. For 2, the generally rigid pyr-
The design of reactors with a dispersed gas in a liquid phase, e.g., bubble columns, is often based on rather roughly estimated parameters. To obtain a better understanding of the influence and interaction of the fluid dynamics and the mass transfer in the presence of a chemical reaction of NO and Fe(EDTA) in the liquid phase, the complex system of a bubbly flow is here reduced to single-bubble investigations. For this purpose, mass transfer is investigated with and without chemical reaction to be able to differentiate between various influencing factors and determined enhancement caused by the chemical reaction. Two experimental setups are applied, namely, the first one with two moving cameras where the velocity is adapted to the rising velocity of the bubble, and the second one is a countercurrent-flow cell.
-Reactive bubble columns are widely used in the chemical, petrochemical, biochemical and metal industries. While the reactive mass transfer around a single spherical shaped bubble is quite well described in literature, the influence of hydrodynamic interactions, such as bubble bouncing or coalescence on mass transfer -with and without chemical reaction -is not well understood. As to this, high resolution simulations and sophisticated experimental analysis based on high-speed camera images and local color changes gives a new firm basis. In this work, a new system is presented, based on Nitric Oxide (NO) gas absorbed in a Fe II -solution. The reaction rate can be adjusted by the addition of ligands and the resulting local color change is detected. The impact of the colliding bubbles leads to a deformation of the bubble shapes and creates a fast movement of the bubble interfaces, which, finally, leads to an increased mass transfer. The results of five tested ligands reveal the high potential of the reactive Fe II (NO) system to investigate basic phenomena affecting yield and selectivity of mixing-sensitive chemical reactions.Résumé -Transfert de masse réactive de bulles simples et de bulles rebondissantes dans les solutions ferriques aqueuses -Une étude de faisabilité -Les colonnes à bulles réactives sont largement utilisées dans les industries chimiques, pétrochimiques, biochimiques et métalliques. Bien que le transfert de masse réactif autour d'une seule bulle de forme sphérique soit assez bien décrit dans la littérature, l'influence des interactions hydrodynamiques, comme le rebond des bulles ou la coalescence sur le transfert de masse -avec ou sans réaction chimique -n'est pas bien comprise. Pour ce faire, des simulations de haute résolution et des analyses expérimentales sophistiquées basées sur des images de caméras à haute vitesse et des changements de couleur locaux donnent une nouvelle base solide. Dans ce travail, un nouveau système est présenté, basé sur l'oxyde nitrique (NO) gazeux absorbé dans une solution de Fe II . La vitesse de réaction peut être ajustée par addition de ligands et le changement de couleur local résultant est détecté. L'impact des bulles de collision entraîne une déformation des formes de bulles et crée un mouvement rapide des interfaces de bulles, ce qui conduit finalement à un transfert de masse accru. Les résultats de cinq ligands testés révèlent le haut potentiel du système réactif Fe II (NO) pour étudier les phénomènes fondamentaux affectant le rendement et la sélectivité des réactions chimiques sensibles au mélange.
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