Infrared study of the solvation of halide ions by water and N-methyl acetamide

Abstract

Infrared spectra in the O—H and N—H stretching regions have been used to measure the interaction between halide ions (Cl^–, Br^–, I^– as tetra-alkylammonium salts) and water or N-methyl acetamide (NMA) in tetrachloromethane. Formation constants for the monosolvates (at 22.5°C) have been estimated. Frequency shifts were approximately proportional to the free energy of hydrogen-bond formation and to the widths of the monosolvate bands. Formation constants for the monoaquo complexes and the NMA complexes were similar to those previously reported for the corresponding methanol solvates; however, the sensitivity of the N—H frequency was less than that of the O—H frequency.