Infrared spectroscopic studies of hydrogen bonding in triethylammonium salts. Part 3.—Strong hydrogen bonding

Abstract

Infrared absorption spectra of solutions of a number of strongly hydrogen-bonded triethyl-ammonium salts Et₃N⁺H⋯A^– have been obtained. Special attention has been paid to changes in the band parameters of the ν_N⁺H stretching mode. A comparison is made between Fermi resonance of internal modes of the triethylammonium ion and a new type of strong resonance coupling of internal modes in which the intermolecular bending mode of the hydrogen-bonded complex Et₃N⁺H⋯A^– participates. The zero, first and second moments of the ν_N⁺H stretching-mode bands have been measured. The inter-relation between these values has been checked over the permissible range of interionic hydrogen-bonding strengths in the ion pairs Et₃N⁺H⋯A^–. Hydrogen-bond energies of the triethylammonium salts studied have been estimated by a spectral method.