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  • 1.
    Andersson, Marit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Olin, Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of lead in household refuse fly-ash by X-ray fluorescence spectrometry and a modified standard-addition technique1991In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 38, no 4, p. 385-390Article in journal (Refereed)
    Abstract [en]

    Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.

  • 2.
    Andersson, Pher
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Bäckvall, Jan-E.
    Synthesis of Furanoid Terpenes via an Efficient Palladium-Catalyzed Cyclization of 4,6-Dienols1991In: J. Org. Chem., Vol. 56, no 18, p. 5349-5353Article in journal (Refereed)
  • 3.
    Bergens, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Determination of Aromatic Amines and Nitro Compounds by Voltammetry and Amperometric Detection in Liquid Chromatography1991Licentiate thesis, monograph (Other academic)
  • 4. Bäckvall, Jan-E.
    et al.
    Andersson, Pher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Stereocontrolled Oxaspirocyclization of Conjugated Dienes via Palladium Catalysis1991In: J. Org. Chem. Soc, Vol. 56, no 7, p. 2274-2276Article in journal (Refereed)
  • 5.
    Bäckvall, Jan-Erling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Stone, Guy
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Syntheses of (±)-α- and (±)- γ- Lycorane via a Stereocontrolled Organopalladium Route1991In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 56, no 9, p. 2988-2993Article in journal (Refereed)
    Abstract [en]

    Total syntheses of (+/-)-alpha-and (+/-)-gamma-lycorane are described. The key steps in the syntheses are the stereocontrolled palladium-catalyzed intramolecular 1,4-chloroamidation of 12 to 13 and the subsequent anti-stereoselective copper-catalyzed S(N)2' reaction of allylic chloride 13 with [3,4-(methylenedioxy)phenyl]magnesium bromide to give 14. Hexahydroindole 14 has the required relative stereochemistry between carbons 3a, 7, and 7a for alpha-lycorane (1a) and was transformed to the latter via 15 and 16. The epimeric gamma-lycorane (2) was obtained by performing the Bischler-Napieralski cyclization on 14, which led to a highly stereoselective isomerization to give exclusively 17. Compound 17 was subsequently transformed to 2. The overall yield from ester 8 to (+/-)-alpha- and (+/-)-gamma-lycorane was 40 and 36%, respectively.

  • 6. Eriksson, Lars
    et al.
    Werner, Per-Erik
    Berger, Rolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Oorganisk kemi.
    Meerschaut, Alain
    Structure refinement of TlCu7Se4 from X-ray powder profile data1991In: Journal of Solid State Chemistry, Vol. 90, p. 61-68Article in journal (Refereed)
    Abstract [en]

    The structure of TlCu7Se4 (synthetic crookesite) has been refined from X-ray powder data using the Rietveld technique. The compound is isostructural with NH4Cu7S4 and TlCu7S4, although successful refinements from two independent data sets occurred in I4/m rather than I -4 previously suggested for this structure type. Positional parameters of natural crookesite were refined from slightly inferior single-crystal data to R(F)= 8.5%.

  • 7.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    ABINITIO CALCULATIONS OF THE FUNDAMENTAL OH FREQUENCY OF BOUND OH- IONS1991In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 95, no 5, p. 3578-3588Article in journal (Refereed)
    Abstract [en]

    In contrast to the OH stretching frequencies of bound H2O molecules, which are always found at lower wave numbers compared to the free molecule, the experimentally determined frequency of the OH- ion can be either lower or higher than the free-ion value. Optimized geometries and fundamental stretching frequency of OH- have been calculated here by ab initio methods at the Hartree-Fock and second-order Moller-Plesset levels for a number of cation-OH-, HOH...OH-, cation-OH-.q-, and cation-OH-.OH2 complexes for Li+, Mg2+, and Al3+. The importance of electrostatic effects on the OH- frequency has been assessed by comparison with calculations of different point-charge and homogenous-field OH- systems. As long as the interaction is not dominated by electronic overlap, the frequency shift is found to be largely determined by electrostatic forces: with increasing field strength the OH- frequency rises to a maximum and then decreases. The OH- dipole moment and Mulliken charges vary monotonically with the field strength, whereas the equilibrium OH distance goes through a minimum and the bond electron density through a maximum. In strongly polarizing fields, such as in the optimized Al3+.OH- and Mg2+.OH-...OH2 systems, the OH- frequency falls below the free-ion value. Ar experimentally observed frequency downshift for an OH- ion in the condensed phase cannot be used as a criterion for the existence of H bonding. The OH- ion acts as an H-bond donor only when strongly polarized by a neighbor on its oxygen side.

  • 8.
    HERMANSSON, KERSTI
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    KNUTS, SÖREN
    LINDGREN, JAN
    THE OH VIBRATIONAL-SPECTRUM OF LIQUID WATER FROM COMBINED ABINITIO AND MONTE-CARLO CALCULATIONS1991In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 95, no 10, p. 7486-7496Article in journal (Refereed)
    Abstract [en]

    The infrared vibrational OH stretching spectrum of isotopically isolated HDO molecules in liquid water has been calculated by ab initio methods at the MP2 level for a number of geometrical configurations taken from a Monte Carlo simulation. Each vibrating water molecule with its environment was described by a pentamer supermolecule, surrounded by a large number of point charges representing polarized water molecules. The anharmonic stretching potentials (MP2 force constants up to fifth order) for 40 uncoupled OH water vibrators were calculated. The average computed r(e) distance found for liquid water is 0.01 angstrom longer than the free-water value. The frequencies were obtained by solving the one-dimensional Schrodinger equation variationally for each OH potential curve. Using the squared dipole moment derivatives, which vary by a factor of 7 over the frequency band, the density-of-states histograms were converted to intensities. The resulting computed average frequency downshift is approximately 260 cm-1, compared to approximately 310 cm-1 (experimental), with a bandwidth in good agreement with experiment. The remaining discrepancy between theoretical and experimental frequency shifts is to a large part due to the charge transfer within the water clusters. This charge transfer gives rise to an electrostatic field which, at the site of the vibrating H atom, counteracts the downshift induced by the other environmental effects. The agreement between experiment and theory is very satisfactory when this charge transfer effect is corrected for or when point-charge embedded heptamer clusters are considered.

  • 9.
    Larsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Tegenfeldt, Jörgen
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    REORIENTATION OF WATER-MOLECULES IN SOLID HYDRATES - CORRELATION WITH SPECTROSCOPIC AND STRUCTURAL DATA1991In: Journal of the Chemical Society, Faraday Transactions, ISSN 0956-5000, E-ISSN 1364-5455, Vol. 87, no 8, p. 1193-1200Article in journal (Refereed)
    Abstract [en]

    A review is presented of experimentally known activation energies, E(a), for the 180-degrees flip motion of the H2O molecule about its two-fold axis in 30 different solid hydrates. The relationship between E(a) and other parameters characterizing a hydrogen bond is discussed. Diagrams correlating E(a) with the hydrogen-bond length, R(o ... x, stretching frequency, nu-OH, librational twist frequency, nu-tw, and deuterium quadrupole coupling constant, e2qQ/h, are presented. The dependence of these correlations on the coordination of the water molecule is discussed, and it is clear that the number of atoms coordinating the water molecule is one of the main factors determining the flip activation energy E(a). The activation energy and the librational twist frequency display a strong correlation, with an associated correlation coefficient of 0.90.

  • 10. Murakami, Masahiro
    et al.
    Andersson, Pher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Suginome, Michinori
    Ito, Yoshihiko
    Intramolecular Bis-Silylation of Carbon -Carbon Double Bonds Leading to Stereoselective Synthesis of 1,2,4-Triols1991In: J. Am. Chem. Soc, no 113, p. 3987-3988Article in journal (Refereed)
  • 11. van Elp, J
    et al.
    Potze, R
    Eskes, H
    Berger, R
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Oorganisk kemi.
    Sawatzky, G.A.
    Electronic structure of MnO1991In: Phys Rev B, Vol. 44, no 4, p. 1530-1537Article in journal (Refereed)
    Abstract [en]

    The electronic structure of MnO has been investigated using high-energy spectroscopies. An experimental gap of 3.9 eV is found. By comparing the experimental results to a configuration-interaction cluster model, values for the different parameters in a model Hamiltonian are found.

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