Revealing the specific solute–solvent interactions via the measurements of the NMR spin–spin coupling constants

Abstract

The solvent induced changes of one-bond spin–spin coupling constants (SSCCs) are investigated for a set of substituted methanes in solvents with various ε dielectric constants. Solute–solvent systems with varying types of ε-dependences for the solute SSCCs are outlined. Aliphatic hydrocarbon solvents and their halogen-substituted derivatives comprise the subset, where the SSCC is linearly dependent on the solvent reaction field, f(ε)=2(ε−1)/(2ε+1), hence indicating the absence of specific solute–solvent interactions. In such solvents, SSCCs depend only on bulk dielectric properties of the medium, and, the magnitudes of the solvent sensitivities of SSCCs are fully determined by the initial values of “pure” SSCCs that correspond to the isolated solute molecules. The solvents involved in the second subset have a relatively chaotic distribution of the SSCC/f(ε) relationship, with possible groupings by their chemical nature. There, the conventional linear SSCC/f(ε) dependence is perturbed by additional interactions, such as hydrogen bonding, specific association processes, lone electron pairs, and conjugation.