Identification of active sites in gold-catalyzed hydrogenation of acrolein

The active sites of supported gold catalysts, favoring the adsorption of C=O groups of acrolein and subsequent reaction to allyl alcohol, have been identified as edges of gold nanoparticles. After our recent finding that this reaction preferentially occurs on single crystalline particles rather than multiply twinned ones, this paper reports on a new approach to distinguish different features of the gold particle morphology. Elucidation of the active site issue cannot be simply done by varying the size of gold particles, since the effects of faceting and multiply twinned particles may interfere. Therefore, modification of the gold particle surface by indium has been used to vary the active site characteristics of a suitable catalyst, and a selective decoration of gold particle faces has been observed, leaving edges free. This is in contradiction to theoretical predictions, suggesting a preferred occupation of the low-coordinated edges of the gold particles. On the bimetallic catalyst, the desired allyl alcohol is the main product (selectivity 63%; temperature 593 K, total pressure p(total) = 2 MPa). From the experimentally proven correlation between surface structure and catalytic behavior, the edges of single crystalline gold particles have been identified as active sites for the preferred C=O hydrogenation.     

Synthesis and characterization of a new benzofulvene polymer showing a thermoreversible polymerization behavior

A new polymer based on a functionalized benzofulvene moiety has been synthesized by spontaneous polymerization of the monomer in the solid state. This polymer shows a very high molar mass, high solubility in the most common organic solvents, and thermoreversible polymerization properties. An interesting application in synthesis is reported.     

Asymmetric synthesis of α-hydroxy-esters via ester enolates

3-Phenylpropionates of chiral alcohols derived from (+)-camphor are oxidized by Mo0₅· Py·HMPT (MoOPH) with high diastereoselectivity.     

Metabolism of Pyrene and Chrysene in Epithelial Human Bronchial and Hamster Lung Cells

Abstract

The metabolism of pyrene and chrysene in epithelial human bronchial and in hamster lung cells has been studied and found to be very similar in both systems, although it differs from that observed in rat lung microsomes. Metabolite profiles have been analyzed by means of capillary GC and by GC/MS.     

Testing and improvement of micro-optical-switch dynamics

The experimental and theoretical investigations presented in this paper have been performed on a micro-opto-electro-mechanical switch developed for switching and attenuation of light in optical fibers. It is demonstrated that high-speed cine photomicrography together with model-based evaluation of the image sequences is a powerful diagnostic tool for reliability testing of dynamic processes in micro-electro-mechanical systems.     

Indirecte Bestimmung von Kali und Natron

Ohne Zusammenfassung     

Reagenspapiere

Ohne Zusammenfassung     

Nachweis kleiner Mengen Methanol in ?thanol

Ohne Zusammenfassung     

Einige Anwendungen der Salicyls?ure in der analytischen Chemie

Ohne Zusammenfassung