Application of Organized Microstructures to Study Keto-Enol Equilibrium of β-Dicarbonyl Compounds

Keto-enol tautomerism has been the subject of continuous interest in chemistry. Enols and enolate ions are essential intermediates in many important chemical reactions, and a number of biological transformations also involve enol formation. Enolization, moreover, has long been of interest as an example of tautomeric rearrangement. One of the things that one would like to know about enols is the magnitude of keto (KH) / enol (EH) equilibrium constants (KH EH, KE). This tautomeric equilibrium has been studied for many years and a large number of methods have been applied for investigating the keto-enol conversion. We review some of the work that we have been doing in the field of keto-enol / enolate equilibria characterization and on enol reactivity in constrained media, such as aqueous solutions of surfactants forming micelles or cyclodextrins. A recently developed method of studying keto-enol equilibrium that combines the UV-vis spectroscopy and aqueous solutions of organized microstructures will be presented. The emphasis of the exposition is the comparative analysis of the several methods used in continuing research to evaluate keto-enol equilibrium constants, by paying detailed attention to the difficulties, and advantages / disadvantages of this new method in comparison with previous others. Therefore, after a brief description of common properties of 1,3- dicarbonyl compounds and of micro-organized media, we report studies of keto-enol / enolate equilibria and the methods and techniques used.