The structure of Cl- solutions in ethylene glycol studied by neutron diffraction

Abstract

The method of isotopic substitution in neutron diffraction is applied to study the coordination environment of Cl- in a 0.999(3) molal solution of NaCl in fully deuterated ethylene glycol (EG). It is shown that the EG molecules act as monodentate ligands to give a Cl(EG)4- complex that comprises Cl- . D-O hydrogen bonds which are approximately linear and of length 2.14(3) AA. The results are compared with those obtained for the Cl- coordination complex in aqueous and methanolic solution. It is found that there is a reduction from approximately=6 to approximately=4 in the number of ligands binding to Cl- on changing the solvent from water to EG and that, for all three solvents, the Cl- . D-O hydrogen bond is typically linear. The effect of a small hydrogen imbalance between the solutions used for isotopic substitution experiments is briefly considered.