Proton solvation in methanol solutions of HCl

Abstract

The MFTIR IR spectra of solutions of HCl in methanol were obtained in the 900–4000 cm−1 frequency range. It was found that each proton binds two molecules of methanol. The spectra exhibit intense, continuous absorption (CA) with an intensity coefficient at 2000 cm−1 of 174±10 liter/(mole·cm), which is in agreement with the corresponding coefficient for H5O 2 + . The optical densities of CA are linear functions of the concentration of HCl at 900–1600 cm−1; there is no linearity at higher frequencies for CHCl>4 M, and there are less than two molecules of MeOH for each (MeOH)2H+ ion. The results obtained are in agreement with the model in which CA arises in solutions of strong acids because of the interaction of proton vibrations in a strong symmetric H bond with the vibrations of other groups of the proton disolvate.