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Th 1H-NMR-spectra of benzene and benzene-1-13C in the isotropic phase (CCl4solution) as well as in the nematic phase of a liquid crystal are analysed and the resulting direct and indirect couplings presented. The comparison of observed direct couplings with values calculated from known Raman structural data shows deviations of up to 9% relative to the HH(orto)-coupling. This corresponds to an apparent increase of the carbon-proton distance of 0.03 A. Possible reasons are discussed such as anisotropy of the indirect couplings, solvent effects on indirect couplings and intramolecular vibrations. The conclusion is reached that the consideration of intramolecular vibrational motion perfectly explains the discrepancies.

Nematic liquids are used as solvents for NMR investigations. By this method a partial orientation of the solute molecules is obtained, causing splittings of the NMR signals by intramolecular direct dipole-dipole interactions. The high resolution spectra of benzene, some derivatives of benzene, and 4-chlorobenzoic acid are reported. As solvents nematic melts of 4.4′-di-n-hexoxy- and 4.4′-di-n-heptoxyazoxybenzene and 4-n-butoxybenzoic acid were used. The linewidth remains small despite the very strong direct dipole-dipole interactions that could be observed in some cases. With benzene and 1.3.5-trichlorobenzene the anisotropy of the screening has been determined. It was found Δσ = σξξ— (σξξ+ σηη)/2 = -2.88 x 10-6for benzene and △σ= -4.91 x 10-6for 1.3.5-trichlorobenzene (ξ-axes normal to molecular plane).

Die direkte und vollständige Analyse komplexer kernmagnetischer Resonanzspektren vom Typ A2B2nach einem früher angegebenen Verfahren wird ausführlich beschrieben.

The analysis of the proton magnetic resonance spectra of a 3-protonsystem with C2-symmetry and of a special 4-protonsystem (rotating methylgroup and one interacting proton) is given in terms of the magnetic dipole-dipole couplings and the chemical shifts. The application to the spectrum of 3,5-dichloro-benzoic acid, dissolved in nematic 6-n-hexyloxy-2-naphthoic acid, and to 2,3,5,6- and 2,3,4,6-tetrachloro-anisole and 2,3,5,6-tetrachloro-toluene, dissolved in nematic 4,4-di-n-hexyloxy- or -heptyloxy-azoxybenzene gives information on the molecular orientation and the anisotropy of the chemical shifts. The ratio of the proton-proton distances of the toluene compound is determined.