HYDRATION OF METHANOL IN AQUEOUS-SOLUTION

We present neutron diffraction data on a 1:9 molar ratio methanol-wate r mixture in which isotope substitution is used to isolate the methyl hydrogen (M) to water hydrogen (H) pair correlation function. Spherica l harmonic analysis of the data confirms the existence of a definite h ydration shell of water molecules at a distance of approximately 3.7 a ngstrom from the carbon atom in the methanol molecule. The water molec ules in this shell form a disordered cage but retain the roughly tetra hedral local coordination found in pure water. Some degree of polariza tion of the water molecules in this shell is also apparent.