A neutron inelastic scattering study of the chloroethanes

Abstract

Neutron inelastic scattering measurements are reported for six chloroethane samples. Absolute theoretical intensities have been calculated for vibrational inelastic events which are in good agreement with the experimental results. In some cases the calculated intensities show a dependence on the symmetry species of the normal modes concerned and this is also confirmed experimentally. The measured torsional frequencies for CH3CCI3 and CHaCHC12 lead to new values of the barriers to internal rotation in these molecules.A discussion is given of the analysis of the low energy scattering with particular emphasis on the difficulties of obtaining unambiguous quantitative data concerning molecular motion in the liquid state. Simple self-diffusion coefficients are obtained for the chloroethanes studied.

1,1-Dichloroethane: A Molecular Crystal Structure without van der Waals Contacts?

“…In this C s -symmetric molecule, two Cl atoms are located at the same carbon atom, and therefore they are less exposed, compared to 12DCE, to intermolecular contacts. Despite numerous studies of 11DCE by nuclear magnetic resonance, , infrared, Raman, − and microwave spectroscopy, neutron inelastic scattering, electron diffraction, and other methods, the exceptional and largest among all chloroethane isomers difference in the melting points of ca. 61 K between 11DCE and 12DCE has not been explained, on the molecular level.…”

Neutron inelastic scattering spectrum and valence force field for benzenetricarbonylchromium

“…intensities through the protons displacements in each normal vibration. In many cases excellent agreement has been found between the calculated and observed neutron spectra [4][5][6][7][8]. Generally speaking, I.N.S.…”

Rotational spectrum, structure and internal rotation in CH3CCl3

“…This large difference was attributed to intermolecular forces within the crystal. Furthermore, two neutron inelastic scattering studies in liquid and solid phases gave a value of 300(12) cm À1 for the torsional frequency [7,8]. To complicate the situation, relative intensity measurements in the microwave spectrum gave a barrier, V 3 = 1.74 (30) kcal mol À1 [9] in good agreement with the thermodynamic determination.…”