HYDRATION OF METHANOL IN AQUEOUS-SOLUTION

We present neutron diffraction data on a 1:9 molar ratio methanol-water mixture in which isotope substitution is used to isolate the methyl hydrogen (M) to water hydrogen (H) pair correlation function. Spherical harmonic analysis of the data confirms the existence of a definite hydration shell of water molecules at a distance of approximately 3.7 angstrom from the carbon atom in the methanol molecule. The water molecules in this shell form a disordered cage but retain the roughly tetrahedral local coordination found in pure water. Some degree of polarization of the water molecules in this shell is also apparent.