Critical Reflections on the Hydrophobic Effect, its Origins and Manifestation: Water Structure, Chemical Reactivity, Micelles and Gels.

The origins of the Hydrophobic Effect (HE), its biological significance and its experimental basis are critically addressed in this brief review. It is argued that the mechanistic work reported on the HE in recent decades needs to be reassessed, as its conclusions are apparently debatable. Essentially, it is highly inaccurate to view the HE as a repulsive interaction, which is rather an attractive one. It appears inevitable that the HE is indeed a manifestation of the perturbation of the structure of water upon the introduction of hydrocarbon molecules into its interior. There appears to be no other satisfactory explanation for the formation of micellar aggregates and the existence of the critical micelle concentration. Also, the practical significance of the HE on the reactivity of organic compounds ( e.g. cycloadditions) is severely limited by their minuscule solubility levels, itself a manifestation of the HE! Other related phenomena apparently include the formation of gels and the occurrence of certain esterification reactions in water, which are briefly reviewed from a conceptual viewpoint.