Study of Reorientational Motion in Solid State of 1, 2, 3-trichlorobenzene and Hexachlorobenzene by Pure Quadrupole Resonance

Abstract

Abrupt increases accompanying the elevation of temperature were observed in the line widths of pure quadrupole resonance spectrum of l, 2, 3-trichlorobenzene and hexachlorobenzene. The results suggest a possibility of reorientational motion of these molecules in temperature ranges far lower than the melting points. In consideration of hexagonal symmetry of hexachlorobenzene, it was concluded that there was occurring a reorientational motion around the hexagonal axis of this molecule. Its hindering potential barrier was estimated at 12.6>W≥9.9 Kcal/mole by means of pure quadrupole resonance alone. Although 1, 2, 3-trichlorobenzene has no symmetry about the normal axis of the molecular plane, measurements of proton magnetic resonance and dielectric constant, in addition to the pure quadrupole resonance suggested the possibility of the reorientational motion around the normal axis of the molecule, which covers only two neighboring equilibrium positions. From temperature dependence of the line width of pure quadrupole resonance spectrum, the mean height of its hindering potential barrier was estimated at 6.0>W≥5.0 Kcal/mole.