Heck reactions in monoglyme and diglyme using BmimCl as pre‐ligand

Heck reactions between iodobenzene and methyl acrylate were carried out in monoglyme and diglyme as solvents, using different ligands and palladium sources, and good to high yields were obtained in the production of (E)‐substituted olefins. The ionic liquid BmimCl was successfully utilized as pre‐ligand to substitute triphenylphosphine. Copyright © 2007 John Wiley & Sons, Ltd.     

Vorkommen und quantitative Bestimmung der Milchs?ure im Wein

Ohne Zusammenfassung     

Direct analysis of drugs by continuous-flow fast-atom bombardment and tandem mass spectrometry

The techniques of continuous-flow fast-atom bombardment (CF-FAB) and tandem mass spectrometry (MS/MS) are combined and applied to the analysis of small molecular mass drugs (mol.wt less than 500 Da). The approach involves the interfacing of a CF-FAB inlet with a triple-stage quadrupole mass spectrometer, enabling the acquisition of collision-activated decomposition mass spectra of the drugs after FAB ionization. The relationship between a stable sample surface on the CF-FAB probe tip and the quality of the mass spectrum is discussed, as are practical methods for obtaining and maintaining surface stability. CF-FAB MS/MS spectra for several drugs are presented, including penicillin G, phentolamine, cocaine and benzoylecgonine. Minimum detection limits range from 50-500 pg injected, depending on the compound. The reproducibility of the integrated areas of peaks from repetitive injections is approximately five per cent. Data are also presented for the direct CF-FAB MS/MS analysis of cocaine and benzoylecgonine in spiked urine samples.     

Ligand-free Suzuki-Miyaura reactions in PEG 300

In this work, we present ligand-free Suzuki cross-coupling reactions in PEG 300 under thermal conditions at 55 °C with good yields of conversion; better results were obtained with low reaction time. In 1 hour, 1-iodo-4-nitrobenzene and phenylboronic acid reached 98% of the yield and 9700 of TON. Better results were obtained with Pd(0) sources. The reaction system was recycled up to three times with good activity.     

Self‐assembled Monolayers of Alkylphosphonic Acids on Aluminum Oxide Surfaces – A Theoretical Study

Density‐functional based calculations were used to investigate self‐assembled monolayers of different alkylphosphonic acids on corundum α‐Al₂O₃ (0001), bayerite β‐Al(OH)₃ (001) and boehmite γ‐AlOOH (010) surface models. Mono‐, bi‐, and tridentate adsorption modes were considered. In addition, the organization of single adsorbed molecules was compared to the organization at full surface coverage. The height (thickness) of the self‐assembled monolayers is always shorter than the length of the phosphonic acid molecules due to tilting of the alkyl chains. Tilt angles at full surface coverage are very similar to the tilt angle of a single adsorbed molecule, which indicates that the density of the self‐assembled monolayers is limited by the density of adsorption sites. The lateral interactions between alkyl chains are evidenced by small torsions of the adsorbed molecules, which may serve to minimize the repulsion forces between interchain hydrogen atoms. Similar tilt angles were obtained for mono‐, bi‐, and tridentate adsorptions. Hence, the coordination mode cannot be characterized by the molecule tilting.     

Motif Reconstruction in Clusters and Layers: Benchmarks for the Kawska–Zahn Approach to Model Crystal Formation

A recently developed atomistic simulation scheme for investigating ion aggregation from solution is transferred to the morphogenesis of metal clusters grown from the vapor and layers deposited on a substrate surface. Both systems are chosen as benchmark models for intense motif reorganization during aggregate/layer growth. The applied simulation method does not necessarily involve global energy minimization after each growth event, but instead describes crystal growth as a series of structurally related configurations which may also include local energy minima. Apart from the particularly favorable high‐symmetry configurations known from experiments and global energy minimization, we also demonstrate the investigation of transient structures. In the spirit of Ostwald’s step rule, a continuous evolution of the aggregate/layer structure during crystal growth is observed.     

Coherence during scattering of fast H atoms from a LiF(001) surface

The coherence for diffraction effects during grazing scattering of fast hydrogen and helium atoms from a LiF(001) surface with energies up to some keV is investigated via the coincident detection of two-dimensional angular distributions for scattered projectiles with their energy loss. For keV H atoms, we identify electronic excitations of the target surface as the dominant mechanism for decoherence, whereas for He atoms this contribution is small. The suppression of electronic excitations owing to the band gap of insulators plays an essential role for preserving quantum coherence and thus for the application of fast atom diffraction as a surface analytical tool.