Two forms of aluminium phosphate tridymite from X‐ray powder data

Monoclinic and triclinic (pseudo‐orthorhombic) AlPO₄ tridymites have been refined from X‐ray powder diffraction data using the silica analogues as starting models. The framework structures of both forms of tridymite are made up of six‐membered rings of tetrahedra which differ in the distortion patterns of the ring shapes. Ordered occupation of alternate tetrahedra by Al and P leads to a doubling of the a lattice parameter for monoclinic AlPO₄ tridymite (space group Pc) and loss of the C‐centring with respect to the isotypic silica tridymite (space group Cc). Triclinic AlPO₄ tridymite was refined in the same space group (F1) as the SiO₂ analogue.     

High-performance liquid chromatographic,capillary electrophoretic and capillary electrophoretic-electrospray ionisation mass spectrometric analysis of selected alkaloid groups

Systems for efficient separation of selected alkaloid groups by high performance liquid chromatography (HPLC), capillary electrophoresis (CE) and capillary electrophoresis coupled with electrospray ionisation mass spectrometry (CE-ESI-MS) are described. The optimized HPLC system was applied for the separation of 23 standard indole alkaloids as well as for qualitative and quantitative analyses of crude alkaloid extracts of Rauvolfia serpentina X Rhazya stricta hybrid cell cultures. The developed conditions for CE analysis proved to be efficient for separation of mixtures of standard indole and beta-carboline alkaloids. The described buffer system is also applicable in the combination of CE with electrospray ionisation mass spectrometry. This analytical technique allowed the separation and identification of components of standard indole alkaloid mixture as well as crude extracts of R. serpentina roots, R. serpentina cell suspension cultures and cortex of Aspidosperma quebracho-blanco. The influence of buffer composition and analyte structures on separation is discussed.     

Novel correlation of Schottky constants with lattice energies for II-VI and I-VII compounds

Correlations of computed Schottky constants () with structural and thermodynamic properties showed linear dependences of log K_S on the lattice energies for the Zn-, Cd-, Hg-, Mg-, and Sr-chalcogenides and for the Na- and K-halides. These findings suggest a basic relation between the Schottky constants and the lattice energies for these families of compounds from different parts of the Periodic Table, namely, =−(2.303nRT log K_S)+2.303nRm_b+2.303nRTi_b. is the experimental (Born-Haber) lattice energy (enthalpy), n is a constant approximately equal to the formal valence (charge) of the material, m_b and i_b are the slope and intercept, respectively, of the intercept b (of the log K_S versus linear relation) versus the reciprocal temperature. The results of this work also provide an empirical correlation between the Gibbs free energy of vacancy formation and the lattice energy.     

D-Penicillamine—Production and Properties

The non-naturally occurring amino acid D -penicillamine, originally only of interest as a key substance in the structural elucidation and total synthesis of penicillins is gaining increasing importance as a therapeutic, particularly in the long-term treatment of rheumatoid arthritis. D -Penicillamine which previously was obtained semi-synthetically by degradation of penicillins can now be totally synthesized using a new process which starts from isobutyraldehyde, sulfur, ammonia, and hydrogen cyanide and yields the racemate which is then selectively resolved. The biochemical behavior of D -penicillamine—chelate formation with heavy metal ions, cleavage of disulfide bridges, and condensation with aldehyde groups—affords information related to its therapeutic activity.