Solute-solvent interactions from relaxation data by a novel procedure

Abstract

The use of the Bellamy plot in infra-red spectroscopy is extended into the realm of dielectric relaxation studies. The mean relaxation times of a given molecule in a series of solvents are plotted against the mean relaxation times of a suitable reference molecule in the same solvents. The use of these reference-molecule relaxation time plots (RMRT plots) is illustrated for solutions of trichloromethane in several solvents. The plots are then applied to solutions of 2-nitrophenol in several solvents with nitrobenzene as reference molecule, and to solutions of 8-hydroxyquinoline in several solvents with 1-nitronaphthalene as reference molecule. The specific interaction between 1,4-dioxan and the hydroxyl compound is distinctly revealed in each case despite the presence of the strong intramolecular hydrogen bond in the solute molecules. Taking other physical evidence into account, the most comprehensive explanation for 2-nitrophenol is the formation of a bifurcated hydrogen bond between the chelated molecule and the solvent. For 8-hydroxyquinoline the possibility of chelate ring fission and orthodox intermolecular hydrogen bond formation is not eliminated.