Applications of NMR spectroscopy of chiral association complexes 5. Stereodynamics and diastereotopism in chiral 1,3-dienes \documentclass{article}\pagestyle{empty}\begin{document}${\rm HOCMe}_{\rm 2} \rlap{--} ({\rm CCl =\!= CCl\rlap{--})}_{\rm 2} {\rm X}$\end{document}

The barriers to partial rotation around the central single bond in chiral dienes \documentclass{article}\pagestyle{empty}\begin{document}${\rm HOCMe}_{\rm 2} \rlap{--} ({\rm CCl =\!= CCl\rlap{--})}_{\rm 2} {\rm X}$\end{document} have been determined by coalescence of either ¹H NMR signals (X = CH₂OCH₃) or ¹³C NMR signals (X = H). In the presence of the optically active shift reagent (+) ? Eu(hfbc)₃ all ¹H signals were split at temperatures where the interconversion of enantiomers is slow. The temperature dependence of these spectra also yielded free activation enthalpies for the enantiomerizations which were in agreement with the ones obtained without Eu(hfbc)₃. The assignment of the four methyl resonances appearing in the presence of (+) ? Eu(hfbc)₃ at low temperature was possible by gradually increasing the rate of enantiomerization or gradually replacing the optically active auxiliary compound by the racemic one.     

Regelflächen im zentroaffinen Raum

Special theories exist for ruled surfaces in euclidean and affine spaces, which are fitted to the peculiarities of those surfaces. This paper deals with ruled surfaces in the 3-dimensional centro-affine space. The first part contains a theory about cones, which is needed subsequently.     

High resolution mass spectrometry of trimethylamine

High resolution shows that the four principal fragment peaks of trimethylamine are singlets. Close studies of the metastable transitions in the spectrum have established the origin of almost all fragment peaks.     

Beitrag zur Kenntnis des Systems La−C−N

An isothermal section at 1,200°C of the partial system La–LaN–LaC₂ was examined by X-ray and metallographic techniques. There is no evidence of an appreciable solid solubility of carbon in LaN or of nitrogen in La₂C₃ or LaC₂ at 1,200°C. There are indications however that at higher temperatures, especially that of the electric arc, the solubility of carbon in LaN might be appreciable or that a carbonitride phase of Lanthanum might exist. LaC₂ reacts with nitrogen under pressure at 1,200°C to form a new carbonitride phase with the composition La₁C_0,88N_0,77.

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