The Orientation of the Water Molecules in the Hydration Sphere of F− and in the Hydrophobic Hydration Sphere

Abstract

AbstractNuclear magnetic relaxation rates of 19F in aqueous KF solutions and of the proton in aqueous solutions of formic acid, HCOOD, of pro‐pionic acid, CHD2CD2COOD, and of methanol, CHD2OD are reported. The solvent water is 16OD2 to which suitable amounts of 17OD2 or 16OH2 are added. From the intermolecular relaxation rate of the solute nucleus (19F or H), caused by the dipole‐dipole interaction with the magnetic nuclei in the solvent, the orientation of the water molecules in the hydration sphere of the solute particle has been derived. Our results regarding the angle of the electric dipole moment of the H2O molecule relative to a radial reference axis are: βo = 50° for F−. βo = 96° for formic acid, βo = 107.5° for propionic acid and βo = 102.5° for methanol.