Probing solute-solvent interactions using difluorobenzene isomers in water-monohydric-alcohol mixtures

Isomers, particularly those with similar geometries, provide an interesting mechanism for studying solute-solvent interactions via their diffusion properties. Here nuclear magnetic resonance (NMR) was used to measure the self-diffusion of difluorobenzene isomers in water-monohydric-alcohol systems (i.e., methanol, ethanol, and tert-butanol), at a range of mole fractions for each solvent system. The diffusion behaviour of the difluorobenzene isomers was different to the previously studied dihydroxybenzene and diaminobenzene isomers. While there is immediate usefulness to mixture analysis by the separation of similar molecules such as isomers using solvent modulation, the comparable structure of the three sets of disubstituted benzene isomers allows a comparison of solvent effects on diffusion. It was found that the different positions and functional groups had a significant effect on the diffusion of the isomers. The effect of substituent position, and the type of functional group on the interaction with the mixed solvent has been examined here.