Abstract
The thermal and mechanical properties of organic compounds are well known to be strongly correlated with the orientational freedom of its molecules or its molecular groups such as NH{sub 3}, CH{sub 3}, CH{sub 4}... For this reason, the study of the rotational behaviour of methyl groups in the solid state as a function of temperature is of great interest. With decreasing temperature, the rotations change from classical hoping to processes where quantum mechanical rotations become important. By quantum mechanical rotations, we mean the low-temperature counterpart, for with tunneling is the dominant mode of motion. However, the interpretation of tunnelling lines is critical when it is not straightforward to relate them to specific vibrational modes and particularly so when the molecule contains crystallographically inequivalent groups. The aim of this work is to interpret such spectra (obtained from inelastic neutron scattering) from structural data. The lack of structural knowledge at low temperatures, makes therefore a limited interpretation of the spectra obtained from polycrystalline samples. In a first step it is essential to solve crystalline structure of compounds by single crystal X-rays and neutron diffraction. Indeed X-ray diffraction is necessary to locate the skeleton (C, N, O and localised H atoms). Moreover neutron
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Citation Formats
Kaiser Morris, E.
Dynamics and disorder of methyl group in the different phases of 2,6-dimethyl pyrazine, 4-methyl pyridine and 4-methyl pyridine N-oxide; Dynamique et desordre du groupe methyle dans les differentes phases de la 2,6-dimethyl pyrazine, 4-methyl pyridine et 4-methyl pyridine N-oxyde.
France: N. p.,
1997.
Web.
Kaiser Morris, E.
Dynamics and disorder of methyl group in the different phases of 2,6-dimethyl pyrazine, 4-methyl pyridine and 4-methyl pyridine N-oxide; Dynamique et desordre du groupe methyle dans les differentes phases de la 2,6-dimethyl pyrazine, 4-methyl pyridine et 4-methyl pyridine N-oxyde.
France.
Kaiser Morris, E.
1997.
"Dynamics and disorder of methyl group in the different phases of 2,6-dimethyl pyrazine, 4-methyl pyridine and 4-methyl pyridine N-oxide; Dynamique et desordre du groupe methyle dans les differentes phases de la 2,6-dimethyl pyrazine, 4-methyl pyridine et 4-methyl pyridine N-oxyde."
France.
@misc{etde_308953,
title = {Dynamics and disorder of methyl group in the different phases of 2,6-dimethyl pyrazine, 4-methyl pyridine and 4-methyl pyridine N-oxide; Dynamique et desordre du groupe methyle dans les differentes phases de la 2,6-dimethyl pyrazine, 4-methyl pyridine et 4-methyl pyridine N-oxyde}
author = {Kaiser Morris, E}
abstractNote = {The thermal and mechanical properties of organic compounds are well known to be strongly correlated with the orientational freedom of its molecules or its molecular groups such as NH{sub 3}, CH{sub 3}, CH{sub 4}... For this reason, the study of the rotational behaviour of methyl groups in the solid state as a function of temperature is of great interest. With decreasing temperature, the rotations change from classical hoping to processes where quantum mechanical rotations become important. By quantum mechanical rotations, we mean the low-temperature counterpart, for with tunneling is the dominant mode of motion. However, the interpretation of tunnelling lines is critical when it is not straightforward to relate them to specific vibrational modes and particularly so when the molecule contains crystallographically inequivalent groups. The aim of this work is to interpret such spectra (obtained from inelastic neutron scattering) from structural data. The lack of structural knowledge at low temperatures, makes therefore a limited interpretation of the spectra obtained from polycrystalline samples. In a first step it is essential to solve crystalline structure of compounds by single crystal X-rays and neutron diffraction. Indeed X-ray diffraction is necessary to locate the skeleton (C, N, O and localised H atoms). Moreover neutron diffraction is the unique tool to precise the position of H atoms of methyl groups. The exam of the nuclear density of these protons the Fourier maps allows us to evaluate the crystal potential experienced by this rotor. Inelastic neutron scattering allows on single crystals allows the complete characterizations of quantum excitations (author) 75 refs.}
place = {France}
year = {1997}
month = {Dec}
}
title = {Dynamics and disorder of methyl group in the different phases of 2,6-dimethyl pyrazine, 4-methyl pyridine and 4-methyl pyridine N-oxide; Dynamique et desordre du groupe methyle dans les differentes phases de la 2,6-dimethyl pyrazine, 4-methyl pyridine et 4-methyl pyridine N-oxyde}
author = {Kaiser Morris, E}
abstractNote = {The thermal and mechanical properties of organic compounds are well known to be strongly correlated with the orientational freedom of its molecules or its molecular groups such as NH{sub 3}, CH{sub 3}, CH{sub 4}... For this reason, the study of the rotational behaviour of methyl groups in the solid state as a function of temperature is of great interest. With decreasing temperature, the rotations change from classical hoping to processes where quantum mechanical rotations become important. By quantum mechanical rotations, we mean the low-temperature counterpart, for with tunneling is the dominant mode of motion. However, the interpretation of tunnelling lines is critical when it is not straightforward to relate them to specific vibrational modes and particularly so when the molecule contains crystallographically inequivalent groups. The aim of this work is to interpret such spectra (obtained from inelastic neutron scattering) from structural data. The lack of structural knowledge at low temperatures, makes therefore a limited interpretation of the spectra obtained from polycrystalline samples. In a first step it is essential to solve crystalline structure of compounds by single crystal X-rays and neutron diffraction. Indeed X-ray diffraction is necessary to locate the skeleton (C, N, O and localised H atoms). Moreover neutron diffraction is the unique tool to precise the position of H atoms of methyl groups. The exam of the nuclear density of these protons the Fourier maps allows us to evaluate the crystal potential experienced by this rotor. Inelastic neutron scattering allows on single crystals allows the complete characterizations of quantum excitations (author) 75 refs.}
place = {France}
year = {1997}
month = {Dec}
}