Direct Determination of the Relationship between the Intramolecular Oxygen-Hydrogen Bond Length and Its Stretching Vibrational Frequency of the Methanol Molecule in the Liquid State.

Time-of-flight (TOF) neutron diffraction measurements on pure liquid deuterated methanol and concentrated methanolic LiClO 4 and LiTFSA solutions have been carried out to investigate the effect of intermolecular hydrogen bonds on the intramolecular O-D distance ( r OD ) of the methanol molecule in the liquid state. Intramolecular parameters for the methanol molecule are determined by the least-squares fitting analysis of the neutron total interference term observed in the high- Q region. Attenuated total reflection (ATR) IR spectra have been measured for methanolic solutions of natural abundance to determine the gravitational center frequency (ν OH ) of the stretching vibrational band of the methanol molecule. The relationship between r OD and ν OH is approximated well by a linear function. The value dν OH /d r OD = -17000 ± 3000 cm -1 Å -1 has been derived from the slope of the fitted function. It has been revealed that the O-D bond length of the methanol molecule is sensitively affected by the intermolecular hydrogen bonding interaction.