Related Experiment Video
Updated: Dec 21, 2025

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
Published on: August 5, 2016
Inelastic neutron scattering study of tetramethylpyrazine in the complex with chloranilic acid
M Prager1, A Pawlukojc, L Sobczyk
1Institut für Festkörperforschung, Forschungzzentrum Jülich, D-52425 Jülich, Germany.
Abstract:
The tunnel splitting of the methyl librational ground states in the hydrogen bonded tetramethylpyrazine-chloranilic acid (TMP-CLA) complex are determined for temperatures T≤28 K by high resolution neutron spectroscopy. Three tunnel modes are resolved at T = 2.4 K. Their relative intensities show that the crystal structure must be different from the proposed space group. Tunnelling and methyl librational modes from the measured density of states are combined into rotational potentials. There are discrepancies of activation energies calculated for these potentials and those obtained from quasielastic scattering of neutrons at T≥50 K due to structural differences in the two respective temperature regimes. Rotational potentials in TMP-CLA are significantly weaker as in pure TMP.
Related Concept Videos
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Mass Spectrometry: Alkyl Halide Fragmentation
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
Chirality at Nitrogen, Phosphorus, and Sulfur
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Radicals: Electronic Structure and Geometry
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...

