Proton solvation in methanol solutions of HCl

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 C_HCl>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.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2261–2268, October, 1992.