Functions of Hydrotropes in Solutions

Hydrotropes affect a several‐fold increase of the solubility of sparingly soluble solutes under normal conditions. Their water‐solubility can significantly enhance the solubility of organic solutes such as esters, alcohols, aldehydes, ketones, hydrocarbons, and fats. While the study of hydrotropes is pioneered by a biochemist, greater appreciation of their role and applicability has happened rather in chemistry and chemical engineering than in biology. Hydrotropes are widely used in drug solubilization, as extraction agents for fragrances, as agents to increase the rate of heterogeneous reactions, and for separation of close‐boiling liquid mixtures through extractive distillation and liquid‐liquid extraction. Applications of hydrotropy and its mechanism are discussed and the scope for future work is presented in this review. Hydrotropes are water‐soluble surface‐active compounds that at higher concentration enhance the solubilities of organic reactants in aqueous phases. Besides being cheap, nontoxic, and environmentally friendly, aqueous hydrotropic solutions possess physicochemical characteristics required to be an alternative reaction media. Applications of hydrotropy and its mechanism are reviewed and discussed.