Solvent extraction of alkaline earth metal picrates with poly- and bis(crown ether)s

Summary Solvent extraction of alkaline earth metal picrates with poly- and bis(crown ether)s containing benzo-15-crown-5- and benzo-18-crown-6 moieties was carried out in a water-chloroform system. The poly- and bis(crown ether)s showed larger extractability for the metal picrates than the corresponding monocyclic crown ethers. Especially, poly- and bis(benzo-15-crown-5), and bis(benzo-18-crown-6) were found to have relatively high extractability and selectivity for Ba²⁺ and Sr²⁺, respectively.

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Lösungsmittelextraktion von Erdalkalipikraten mit Hilfe von Poly- und Bis-Kronenethern

Zusammenfassung Poly- und Bis-Kronenether mit Benzo-15-krone-5- und Benzo-18-krone-6-Einheiten wurden zur Extraktion von Erdalkalipikraten im Wasser-Chloroform-System verwendet. Die genannten Ether zeigten eine bessere Extraktionsfähigkeit für die Pikrate als die entsprechenden monocyclischen Kronenether. Im Falle von Ba²⁺ und Sr²⁺ ergab sich eine besonders gute Extrahierbarkeit und Selektivität mit Poly- und Bis(benzo-15-krone-5)- und Bis(benzo-18-krone-6)-Ethern.

     

Two-channel separable potential model for the low-energy hyperon-nucleon interaction

A two-channel separable potential model is given such that the T-matrix is given in the form of a N/D matrix. This model is used to examine the relationships between the three different definitions for a resonance in the two-channel problem, particularly for a ³S₁ Λp resonance. In order to obtain a phenomenological hyperon-nucleon (YN) scattering T-matrix in the present model, a least-squares fit is performed to the existing available data for the $\text{I =}\text{1}\text{2}\text{YN}$ scattering cross sections and angular distributions at low energies using the s- and p-wave N/D solutions which carry sixteen independent parameters. Several solution sets of potential parameters are found, for which we can obtain good fits to the Λp → Λp, Σ^?p → Λn and ΣN → ΣN data, particularly to the cross-section data for these processes. The p-wave contributions are estimated, and particularly the possibility of p-wave YN resonances is pointed out for the solutions for which we do not assume a ³₁ Λp resonance.     

General route to 2-alkyl-2-butenolactones via the retro-Diels-Alder reaction

Various 2-alkyl-2-butenolactones were simply prepared from cyclopentadiene-maleic anhydride adducts through the retro-Diels-Alder reaction. The procedure was applied for the synthesis of dehydrolappaol A dimethyl ether.     

Numerische Berechnung der natürlichen Konvektion in einem waagerechten Kanal mit ungleichen Endtemperaturen

The paper reports a finite difference solution for the natural counterflow generated in a horizontal adiabatic duct with different end-temperatures. Ducts with circular and rectangular cross-section are considered. The natural counterflow is modeled as fully-developed. The numerical results demonstrate that the flow consists of a strong axial counterflow superimposed on four secondary eddies situated in the four quadrants of the cross-section. The paper documents the temperature variation around the wall of a pipe, in a moderate Rayleigh number range not documented previously. The use of the wall temperature information in thermal stress analysis is discussed. The numerical results are also used to assess the applicability of analytical predictions for the flow field in ducts with rectangular cross-section.     

Evaluation of mass discrimination effects in the quantitative analysis of polydisperse polymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using uniform oligostyrenes

Mass discrimination effects in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) were quantitatively investigated using equiweight and equimolar mixtures of uniform polystyrene (PS) oligomers. Uniform PS oligomers were separated by preparative super-critical fluid chromatography (SFC) from commercial standard PS samples. The separated PS oligomers, with degrees of polymerization n = 2–25, have absolutely no molecular weight distributions. Equiweight and equimolar mixtures of uniform PS oligomers were accurately prepared by weighing by microbalance, and their spectra were recorded using a MALDI-TOF mass spectrometer. In the lower molecular weight region (less than about 10³) the oligomers with lower molecular weights give lower mass spectral intensities, with no correlation with laser power. In contrast, higher laser powers yield a decrease of mass spectral intensities in the higher molecular weight region. These results clearly show that mass discrimination effects occur at lower and higher molecular weights depending on the laser power, and provide quantitative information about the discrimination. Using the data on equiweight and equimolar mixtures of PS oligomers, it was possible to calibrate the MALDI-TOF mass spectral data for an analysis of molecular weight distribution of a standard monodisperse PS sample with number-averaged molecular weight of 10³, and to compare it with the molecular weight distribution measured by analytical SFC. The result from the calibrated MALDI-TOF mass spectrum, however, does not agree perfectly with that from the SFC results, because undetectable peaks in MALDI-TOF mass spectra at lower and higher molecular weights could not be included in the calibration of peak intensities. Copyright © 2001 John Wiley & Sons, Ltd.     

Photochemical reaction of 2-cyclopentenone with ethers : The mechanism of solvent addition

Photochemical addition of several ethers to 2-cyclopentenone has been studied under various conditions, especially in the presence of a few aromatic ketones. The mechanism of the ether addition is suggested to be via direct abstraction of hydrogen by excited 2-cyclopentenone rather than due to a chemical process involving aromatic ketyl radicals.     

UV photoelectron spectra and sum rule consideration: Out-of-plane orbitals of unsaturated compounds with planar-skeleton structure

He(l) photoelectron spectra are presented for various planar unsaturated aliphatic compounds such as mono- and di-methyl substituted ethylenes, alkyl aldehydes, chloro-substituted aldehydes, ketones and alkyl acids. Each photoelectron spectrum is resolved into individual bands by considering the band shape, the relative intensity and the number of p-type localized MO's (LO's). The sum rule previously proposed on vertical ionization energies by the present authors is applied to the photoelectron bands associated with out-of-plane LO's. In each compound, a partial sum P(a″) is obtained over all the out-of-plane LO's and it is shown that the calculated P(a″) value is in good agreement with the experimental one which may be obtained by an appropriate sum of vertical ionization energies with negative signs.     

Polythiazolines

Polythioureas having pendant hydroxyl groups were prepared by the polyaddition reaction of bisaminoalcohols and diisothiocyanates. The polythioureas had inherent viscosities in the range of 0.22–1.08 dl/g and gave transparent films by solution casting. These polythioureas were converted to polythiazolines by treatment with poly(phosphoric acid) or to poly(thiazoline–oxazolines) by treatment with a mixture of poly(phosphoric acid) and a polar solvent.