A Neutron and X‐Ray Diffraction Study of the Binary Liquid Aromatic System Benzene‐Hexafluorobenzene II. The Mixtures

Abstract

Abstract A series of X‐ray and neutron diffraction experiments has been performed on liquid benzene, hexafluorobenzene and their liquid mixtures in order to find out whether packing effects or electrostatic interactions are the structure determining factors. The results for the mixtures are reported together with a qualitative interpretation of the experimental data. By combined analysis of the X‐ray and neutron diffraction experiments it could be proved that a reorientation takes place from a L‐type pair geometry in the pure components to a nearly parallel alignment of the molecules in a 1:1 complex. In a second approach a new quantity ‐ a so‐called excess structure factor ‐ was defined, the analysis of which confirmed the deduced change of orientation. With a stacking distance of 3.7 Å and a separation of 7.6 Å between two consecutive hexafluorobenzene molecules the structure of the equimolar mixture in the liquid phase very closely ressembles the one obtained for the solid phase. It can be concluded that the quadrupolar interaction is the structure determining factor in the investigated liquid aromatic systems.