Nuclear magnetic resonance of oriented molecules in lyotropic liquid crystalline media: p-cresol

Proton-proton distance ratios and order parameters for partially oriented p-cresol in a lyotropic mesophase derived from potassium laurate are obtained. The order parameters are the largest yet found for an ordered solute in a nematic-like lyotropic system. The dipolar couplings and structural data were independent of the rotational potential from 0–200 cal mol^?1.     

Nuclear magnetic resonance coupled microseparations

The increased separation efficiency afforded by reducing the size of the separation column has resulted in 'microseparations' becoming an important component in many chemical and biochemical applications. The coupling of microseparations with NMR detection is an area of increasing interest owing to the high structural information of NMR. In order to couple efficiently with the separation, the NMR detector must be reduced in size to correspond to that of the separation peak. This paper summarizes some of the approaches used in coupling NMR detection with pressure-driven and electrophoretic microseparations, the design of small NMR detectors and applications of this technology.     

Nuclear magnetic resonance relaxation titration

Summary Quantitative determination of the concentration of paramagnetic ions in aqueous solutions is performed by NMR relaxation titration. By measurement of the nuclear spin-lattice relaxation time T ₁ or the nuclear spin-spin relaxation time T₂ redox titrations and complexometric determinations of the concentration of paramagnetic ions are possible. Also the precipitation of ions from the solution can be followed by this method. The use of a magnetic indicator in this analytical method is shown. The sensitivity of the method goes down to concentrations as low as 10^–3 M. The accuracy of NMR relaxation titration is better than 1%. A number of applications of the method are given.

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Kernmagnetische Relaxationstitration

Zusammenfassung Quantitative Bestimmungen von paramagnetischen Ionen in wäßrigen Lösungen können mit Hilfe der kernmagnetischen Relaxationstitration durchgeführt werden. Durch Messung der Kernspin-Gitter-Relaxationszeit T ₁ oder der Kernspin-Kernspin-Relaxationszeit T ₂ als Funktion der Ionenkonzentration sind Redoxtitrationen oder komplexometrische Titrationen möglich. Der quantitative Ablauf von Fällungen kann ebenfalls verfolgt werden. Die Verwendung von magnetischen Indicatoren bei der Relaxationstitration wird beschrieben. Bestimmungen von Ionenkonzentrationen bis herab zu 10^–3 M Lösungen sind z.Z. möglich. Die Methode erlaubt eine Genauigkeit der Konzentrationsbestimmung von 1% und besser. Die Anwendung der Methode wird an einer Reihe von Beispielen gezeigt.

     

Nuclear magnetic resonance studies on dipeptides

Dipeptides of different amino acids have been studied by NMR in aqueous solutions at different pH values. The results obtained are discussed in terms of the different contributions to the chemical shift of the α-CH protons.     

Nuclear magnetic resonance of paramagnetic metalloporphyrins

The present article reviews and discusses proton magnetic resonance studies on metalloporphyrins which provide good models for heme proteins in their physical and chemical properties. Emphasis is given on the discussion of the₁Hnmr work done in our laboratory.     

Nuclear magnetic resonance of benzobisheterocyclic compounds

The nuclear magnetic resonance spectra of forty-nine benzobisheterocyclic compounds, containing various heterocycles, were determined. The observed spectral data made possible the elucidation of the structure and also clarified the influences of the heterocyclic substituents and of heterocyclic rings on chemical shift values of the aromatic protons.     

Nuclear magnetic resonance studies of the molecular structures of phosphabenzene and arsabenzene partially oriented in a nematic solvent

The molecular structures of phosphabenzene and arsabenzene partially oriented in the nematic liquid crystal crystal EBBA were studied by NMR. The structures were in excellent agreement with the combined electron diffraction and microwave spectroscopic studies except the angle relating to the β hydrogens. Improved values for this parameter were suggested. The absolute signs of the J_PH of phosphabenzene and some information on the ³¹P chemical shift anisotropies were also obtained.     

Nuclear magnetic resonance of oriented molecules in lyotropic liquid crystalline media: Pyridine, 4-cyanopyridine and benzonitrile

Proton distance ratios for pyridine, benzonitrile and 4-cyanopyridine have been obtained in a potassium laurate lyotropic mesophase and compare favorably with values for different thermotropic solvents. Order matrices indicate a preference for the C_2v symmetry axis of the molecules to be aligned along the optical axis of the mesophase.