Stereoselective synthesis of 2-dienyl-substituted pyrrolidines using an eta4-dienetricarbonyliron complex as the stereodirecting element: Elaboration to the pyrrolizidine skeleton

Primary amines react with keto-aldehyde functionality located in the side-chain of an eta4-dienetricarbonyliron complex to provide the corresponding pyrrolidines in excellent diastereoselectivity. Two of the pyrrolidine products, 1i and 1k, have been elaborated into pyrrolizidines using a 1,5-C-H insertion and radical cyclization strategy, respectively.     

Die Bestimmung des Phosgens

Ohne Zusammenfassung     

The status of process analytical instrumentation : Recommended practices and future trends

The use of process analytical instrumentation with particular reference to the oil and petrochemical industries, is reviewed, taking into account the involvement of process engineering, laboratory, operations, maintenance, and instrument engineering functions. Selection of analyzers providing process monitoring, safety control or environment protection must be based on proper appreciation of their financial contribution to process and plant operation (pay-back ratio). All aspects of the operating environment affect the operating pay-back ratio. The overall systems concept is vital. Present practices of analyzer system protection by installation in local cabinets and analyzer houses are reviewed and arguments are given for more informed practices. Construction, design, location, safety and ventilation are considered. Analyzer calibration is described in detail. Laboratory practices, maintenance procedures, maintenance training and the need for better motivation by management are discussed, as are the potential benefits of total automation. Types of process analyzers and new design and development trends are reviewed. The importance of engineering and design standards and of system and analyzer design documentation is emphasized.     

Determination of fatty acid methyl esters: Elimination of tissue-derived contamination and artefacts and preparation of a support-coated acid-modified polyester liquid phase

Fatty acid methyl esters made by transesterification of extracted plasma lipids with methanolic hydrochloric acid were found to contain substances which interfered with quantitation by gas-liquid chromatography. A method to eliminate most interfering materials and a procedure that allows reproducible wetting of an inert support with acid-modified ethylene glycol succinate are reported. Hydrocarbon contamination and artefacts produced during transesterification from substances native to tissue matrices were identified by gas chromatography/mass spectrometry and removed by chromatography over 6% hydrated alumina. Ethylene glycol succinate was treated with orthophosphoric acid to improve wetting of silanized supports and extend the thermal stability of the polymer. Quantitation was achieved by using synthetic triheptadecanoin as an internal standard.     

Mapping the cooperativity pathways in spin crossover complexes

Crystal packing energy calculations are applied to the [Fe(PM-L)₂(NCS)₂] family of spin crossover (SCO) complexes (PM-L = 4-substituted derivatives of the N-(2-pyridylmethylene)-4-aminobiphenyl ligand) with the aim of relating quantitatively the cooperativity of observed SCO transitions to intermolecular interactions in the crystal structures. This approach reveals a linear variation of the transition abruptness with the sum of the magnitudes of the interaction energy changes within the first molecular coordination sphere in the crystal structure. Abrupt transitions are associated with the presence of significant stabilising and destabilising changes in intermolecular interaction energies. While the numerical trend established for the PM-L family does not directly extend to other classes of SCO complex in which the intermolecular interactions may be very different, a plot of transition abruptness against the range of interaction energy changes normalised by the largest change shows a clustering of complexes with similar transition abruptness. The changes in intermolecular interactions are conveniently visualised using energy difference frameworks, which illustrate the cooperativity pathways of an SCO transition.

The abruptness of spin crossover (SCO) is related to intermolecular energy changes occurring over the course of an SCO transition. Crossover is abrupt when SCO-induced strain is accommodated synergistically in a few key interactions.     

(Series Editor) Transform Techniques in Chemistry,P.R. Griffiths,D. Hercules (Eds.), in: Modern Analytical Chemistry Series,Plenum, New York,NY (1978), 385 pp. $47.40

Concentration potentials in zinc sulphate, copper sulphate, nickel sulphate and cobalt sulphate solutions across liquid membranes based on myristates and laurates of zinc, copper, nickel and cobalt and caprate and caprylate of copper have been studied in concentration cells in which the liquid membrane separates the two solutions of the same electrolyte. The behaviour of the cell with heavy metal soap liquid ion-exchange membranes becomes more and more nernstian as the number of carbon atoms in the hydrocarbon chain of the fatty acid soap increases. Concentration potential values with copper, zinc, nickel or cobalt soap follow the order of their insolubility in water. The failure to record the theoretical potentials as calculated by Nernst's equation has been explained by considering the transport of water across organic phase by hydrated ions and the dissolution of heavy metal soaps in aqueous solutions. Liquid membranes based on heavy metal myristate soaps when used in concentration cells could measure the activities of zinc, copper, nickel and cobalt ions in the concentration range of 10^?4–10^?1M.     

Results of the pilot experiment to search for inelastic interactions of WIMPs with 73Ge

A pilot search for the excitation of ⁷³Ge to the first excited state at 13.26 keV by spin-dependent interactions of Weakly Interacting Massive Particles (WIMPs) was performed. The first experimental results have been analyzed with a new method. The background for these reactions is ≤0.0012 events/(keV kg(⁷³Ge) d). Although there is no theory for E2 excitations by WIMPs, this very large suppression of the background may promise an enlarged version of this experiment to be competitive. It is appropriate to propose an experiment with several kg of enriched ⁷³Ge detectors based on these results.