Hydrotropes are a diverse class of molecules first described
by Neuberg [1,2] almost a century ago. They are characterized
by an amphiphilic molecular structure and an ability to
dramatically increase the solubility of sparingly soluble organic
molecules in water, often by several orders of magnitude [3,4].
The most common molecular characteristics of a hydrotropic
molecule are a saturated hydrocarbon ring and an ionic moiety;
however, hydrotropes can adopt many forms. Fig. 1 illustrates a
small sample of the diverse molecules classified as hydrotropes.
They have been well studied since their discovery and Friberg
and Blute [5] report a detailed description of their historical
development and industrial applications. Several recent review
articles [6–8] also touch on the importance of hydrotropes and
their many synergistic properties when combined with other
amphiphilic molecules. Despite this extensive study and the
numerous commercial and pharmaceutical applications many
ambiguities regarding their classification and molecular association
still exist.