Quantitative Bestimmungen mittels cyclischer Voltammetrie an der Phasengrenze zweier mischbarer Elektrolytl?sungen

Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.

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Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet     

Infrared intensities of the external modes of crystalline nitrous oxide

The absorption intensities of two infrared active lattice modes of crystalline N₂O have been measured. Both the frequencies and intensities of the external modes of N₂O have been found to be very similar to those of CO₂, and most of the differences between the spectra of CO₂ and N₂O can be explained by the differences in the quadrupole moments.     

Die Kopplungskonstante 1JPP von Diphosphat-Anionen mit P?P-Gerüst

One-Bond P? P Coupling Constant of Diphosphate Anions The coupling constant ¹J_PP of diphosphate anions depends upon the electronegativities of the substituents at phosphorus. The simple linear relationship which has been established also holds for other P? P compounds involving tetra-coordinate phosphorus, with the exception of compounds with bulky substituents.     

Chromatographic detection of scandium

Scandium was readily detected by paper chromatography using methyl acetate as the solvent and quinalizarin for the developer. The reddish-violet color formed with scandium resembled the colers obtained with thorium, titanium, zirconium and the rare earths, but the difference in R_F values gave definite separation of these elements. Positive chromatographs were obtained by using 0.01 ml of solution 0.005M respect to scandium.     

Eine einfache Methode zur Bestimmung von Spurenmengen Kobalt (II)-ionen auf katalytischer Grundlage

Zusammenfassung Es wird eine Methode beschrieben, nach der, gegebenenfalls unter Zuhilfenahme von Testlösungen, Spurenmengen von Co²⁺ in einem Konzentrationsbereich von 10 mg bis zu 0,001 mg herab in 1 ml sich recht genau auf Grund der Katalyse der H₂O₂-Indigocarminreaktion in Gegenwart von Calciumcarbonat als Träger bestimmen lassen. Da das Volumen der Versuchslösung stets 60 ml beträgt (siehe oben), beläuft sich die kleinste noch bestimmbare Co²⁺-Konzentration auf 10^–6 g Co²⁺ in 60 ml was einer Verdünnung von 16·10⁷ entspricht. In bezug auf diese Empfindlichkeit steht die Methode den colorimetrischen bzw. spektrophotometrischen^1,6 und auch den komplexchemischen⁷ Verfahren nicht nach. Sie bietet aber im Vergleich mit diesen insofern gewisse Vorteile, als man die störenden Fremdionen meist nicht zu entfernen braucht, was auf eine beträchtliche Zeitersparnis hinauskommt. Schließlich ist die katalytische Methode, für die mit entsprechenden Abänderungen auch eine Temperatur von 30° C genügen würde, in ihrer Handhabung und Ausführung sehr einfach und bedarf, abgesehen vom Thermostaten, keiner kostspieligen Apparatur.     

Beiträge zur Chemie des Phosphors. 167 [1, 2]. Konstitutions- und Konfigurationsisomere von Pentaphosphan(7), P5H7

Contributions to the Chemistry of Phosphorus. 167. Constitutional and Configurational Isomers of Pentaphosphane(7), P₅H₇ Phosphane mixtures containing 10—15 P-% of pentaphosphane(7), P₅H₇, are obtained by thermolysis of diphosphane, P₂H₄, or as residue from distillation of crude diphosphane [3]. According to the complete analysis of the ³¹P{¹H}-NMR spectrum on the basis of selective population transfer experiments, P₅H₇ exists as a mixture of three diastereomers of n-P₅H₇ — 1a (erythro, erythro), 1b (erythro, threo), 1c (threo, threo) — and of the constitutional isomer 2-phosphinotetraphosphane 2 (iso-P₅H₇, largest relative isomeric abundance). The correlation between the diastereomers and the observed spin systems results from the preferred gauche orientation of neighboring free electron pairs, the dependence of ¹J(PP) on dihedral angles, and the ³J(PP) long range couplings. From the ³¹P-NMR data of the phosphane molecules P_nH_n+2 with n = 1—5 general relationships for the δ(³¹P) values and the ¹J(PP) coupling constants of chain-type phosphorus hydrides as a function of their structural parameters are derived.     

Photodissociation of state-selected cluster ions studied by mass-selective, pulsed-field threshold ionization spectroscopy

Delayed pulsed-field ionization of long-lived high Rydberg states yields vibrationally and partly rotationally resolved spectra of polyatomic molecular ions and of cluster ions when the resulting threshold ions are measured as a function of the excitation energy. The field ionized threshold ions are monitored and separated from the non-energy-selected ions in a reflecting field mass spectrometer with high mass resolution. The decay of the molecular or cluster ion core is monitored by the appearance of threshold ions at the daughter ion mass as a function of the selectively excited vibrational state. In this way, upper limits for dissociation thresholds of neutral and ionized dimers are obtained which are smaller than recent theoretical values from the literature. The appearance of daughter fragment ions after delayed pulsed-field ionization indicates that high Rydberg orbits are not destroyed by the dissociation of the core. Possible applications of our technique for the production of state-selected ions are discussed.     

Characterization of intermolecular beta-sheet peptides by mass spectrometry and hydrogen isotope exchange

The self-assembly of beta-sheet peptide domains resulting in the formation of fibrillar aggregates (amyloids) is a feature of various neurodegenerative disorders. In order to evaluate mass spectrometric methods for the characterization of intermolecular beta-sheet structures the hydrogen/deuterium exchange behaviour of model peptides DPKGDPKG-(VT)(n)-GKGDPKPD-amide (n = 3,4,5,6,7,8), (VT)(n)-peptides, composed of a central beta-sheet-forming domain and N- and C-terminal nonstructured octapeptide sequences, was measured by electrospray ionization mass spectrometry (ESI-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The kinetic analysis of the hydrogen/deuterium exchange (HX) shows that intermolecular beta-sheet structures contain slowly exchanging protons (k 相似文献   

Preparation,structure and catalytic properties of a binuclear Pd(0) complex with bridging silylene ligands

In contrast to the N-heterocyclic carbene (NHC) 1, the homologous N-heterocyclic silylene (NHS) 4 acts as a bridging ligand to Pd(0), giving rise to the dinuclear complex 5 which is catalytically active in Suzuki reactions.