AbstractThe present work reports chemical shift measurements for t‐BuOH/H2O, dioxane/H2O, CH3CN/H2O, THF/H2O and DMSO/H2O as well as for aqueous solutions of n‐Bu4NBr and KBr containing bis(methylsulfonyl)methane (1) as a probe for solute/solvent interactions. For each ternary mixture the behaviour of the water resonance [v(H2O)] and the methylene proton chemical shift [v(CH2)] of 1 is given as a function of solvent composition. The trends of v(H2O) are not affected by the presence of 1. Furthermore, the direction of the solvent‐induced shift of v(CH2) in the water‐rich range is no general measure for the change in the solvent structural integrity. The shifts of v(CH2) are determined by polar interactions (involving 1 as a hydrogen bonding donor as revealed by C‐D stretching frequency shifts for 1‐d2) and nonpolar interactions (including hydrophobic bonding). For dioxane/water especially there is strong evidence for preferential solvation of 1 by the apolar organic cosolvent. The data clearly reveal the complex features of aqueous ternaries. The solvent effects on v(CH2) are discussed in combination with kinetic and thermodynamic data for some slow proton transfer reactions. For DMSO/H2O the v(H2O) values at various mole fractions of water are linearly correlated with Cox's data for the free enthalpies of transfer of a series of solutes from water to the corresponding DMSO/H2O mixtures.