C.L. Khetrapal

Side-band intensities in the deuterium magnetic resonance spectra of oriented molecules spinning near the magic angle

The appearance of spinning side bands in the 2H NMR spectra of oriented molecules is investigated. A theoretical interpretation of the side-band intensities is carried out. Information derived on the director orientation and distribution as a function of spinning speedis reported.

Spectral assignments based on the 13C NMR spectra of mixed liquid crystals of opposite diamagnetic anisotropies

Abstract The proton-decoupled 13 C NMR spectra of mixtures of liquid crystals with opposite diamagnetic anisotropies have been studied in the natural abundance of 13 C. A new method to assign the spectral lines to specific carbons in the liquid crystalline phase has been developed. For this purpose, the assignments of lines in the isotropic media are required, and they were obtained from two-dimensional hetero-COSY experiments. From the spectra in the “critical” mixtures where both the orientations of the liquid crystal directors, with the alignments along and perpendicular to the direction of the magnetic field, “coexist,” the 13 C chemical-shift anisotropies have been determined, assuming uniaxial symmetry.

13C-N.M.R. studies of discotics

Abstract 13C-N.M.R. spectra of benzene-hexa-n-octanoate (a discotic liquid-crystalline material) show significant differences in the isotropic, mesomorphic and solid states. The presence of four molecules per asymmetric unit is required to explain the results in the solid state.

Determination of the sign of the order parameter from MAS spectra of oriented molecules

The use of the intensities of the spinning sidebands in the magic-angle spinning spectra of oriented molecules is proposed for the determination of the signs of the order parameters. The method is demonstrated for benzene and chloroform oriented in nematic phases of liquid crystals. On the basis of the theoretical expressions derived for the various order sidebands, the applicability of the method for different experimental conditions is discussed.

Development of NMR: From the Early Beginnings to the Early 1990s

A gas bag of high safety, responsibility and stability for attachment to a high speed moving vehicle, comprising a hollow bag body, a gas introducing hole means, and at least one restraining member provided in the hollow bag body for restraining the free deformation of said hollow bag body upon the pressing of the occupant thereagainst in the inflated condition, said restraining member having at least one breaking part which is broken when a predetermined tensile force is applied to the restraining member, whereby, when the occupant presses said inflated bag body in the sudden stop of the moving apparatus, at least one breaking part is broken and a rebounding force of the bag body against the occupant can be remarkably reduced.

The rα structure, chemical shift anisotropy, and the abnormal orientation of methyldichlorophosphine from the NMR spectrum☆

NMR studies of methyldichlorophosphine have been undertaken in the nematic phase of mixed liquid crystals of opposite diamagnetic anisotropies. The rα structure is derived. The proton chemical-shift anisotropy has been determined from the studies without the use of a reference compound and without a change of experimental conditions. It is shown that the molecule orients in the liquid crystal with positive diamagnetic anisotropy in such a way that the C3 symmetry axis of the CH3P moiety is preferentially aligned perpendicular to the direction of the magnetic field, unlike other similar systems. This is interpreted in terms of the formation of a weak solvent-solute molecular complex. The heteronuclear indirect spin-spin coupling constants are determined. The sign of the two-bond JPH is found to be positive.