NMR Studies on Molecular Interactions Involved in Alkali Metal Halide–Amide–Glycol Ternary Systems

Abstract

Abstract Interactions in a ternary solution of alkali metal halide–amide–glycol have been investigated on the basis of NMR measurement of chemical shifts of OH proton of glycol and amidic protons of acetamide. Measurements were carried out with various alkali metal halides (MX, M=Li, Na, K, X=Cl, Br, I) and glycols (mono-, di-, tri-, and tetraethylene glycol). The dependency of the chemical shifts on solute concentration was examined with a ternary solution of potassium iodide–acetamide–ethylene glycol. The addition of alkali metal halide to respective glycols or glycolic solutions of acetamide gave rise to a change in chemical shift values. The observed changes were related to the ionic sizes of cations and anions of alkali metal halides and to the number of oxyethylene units in a glycol molecule. It was found that a large ion induces a higher magnetic field shift of resonance positions of glycolic OH proton and amidic proton at trans position than a small ion, the magnitude of the shift change being almost proportional to the concentration of ion, and halogen anion formed in glycolic solution tending to interact with hydrogen at trans position rather than at cis position. From a comparison with the values for chemical shifts of water proton in aqueous alkali metal halide solution, it is suggested that the contribution of alkali metal halide to the chemical shift changes in glycolic solution is similar to those in aqueous solution.