Spectroscopic Evidence for Hydrogen Bonds: Comparison of Proton-Attracting Properties of Liquids. IV

Abstract

The strengths of deuterium bridges formed between heavy water and forty‐two different basic solvents are compared by measurements of the perturbations which the solvents produce on the OD vibrational band of heavy water which occurs at 3.59 μ in heavy water vapor and at 4.00 μ in liquid heavy water. The solvents were selected from the following classes: ketones, ethers, esters, glycols, nitriles, amides, ketoximes and amines. The proton‐attracting properties of twenty‐five solvents are compared by measurement of the strengths of the hydrogen bonds which they form by sharing the proton of hydrogen chloride. Heavy water was found more satisfactory for strong and moderately weak bases; hydrogen chloride, for extremely weak bases. The shifts which the different liquids produce upon the D2O band and the HCl band are compared with the shifts which the same solvents produce on the OD vibrational band of CH3OD. A linear relation was found in each case, with frequent but small variations from linearity. Basicity constants were known from other measurements for nineteen of the solvents used with D2O. The shifts which these solvents produce on the D2O band were found to be directly proportional to the logarithms of their basicity constants. The method used here promises to be practical for comparing basicities of numerous types of compounds. The close relation existing between the hydrogen bond theory and modern theories of acids and bases is discussed.