Elucidating the molecular fundamentals of hydrotropic solutions

Hydrotropism is the improvement of solubility of compounds by adding a co-solute. This is an important method to improve water solubility for drug compounds in the pharmaceutical sciences. However, the mechanism of hydrotropism is not understood to date, since structural models of the solution based on experimental data are not easily accessible. Here we propose to investigate the solution structure of caffeine - sodium benzoate in water by neutron total scattering. Caffeine solubility can be raised 20fold by the addition of the co-solute, and preliminary NMR data shows a 2:1 caffeine:benzoate binding model with strong binding energy. Data collection of this model system on SANDALS will enable us to generate a structural model of the disordered solution phase using DISSOLVE and elucidate the mechanism of hydrotropism in this system.