A chemical equilibrium modelling strategy for tuning the apparent equilibrium constants of the chemical systems.

Abstract In many equilibrium systems, it is customary to use a simplified, apparent equilibrium reaction instead of the complete reaction model. The resulting apparent equilibrium constants are altered or controlled by changes of the chemical system, usually modifying the total concentration of auxiliary reagents, but the variation of other parameters such the intensity of light in photo-controlled reactions, types and concentration of solvents or composition of mixed solvents, the ionic strength of the chemical media, etc. is also possible. The main goal of this work is to propose a chemical equilibrium modelling based strategy to control the conditions governing equilibrium systems in order to tune the apparent constants. Indeed, by extracting the analytic relationship between the parameters of the complete model and apparent model, the magnitude of the apparent constant(s) can be predicted. At first, a basic strategy for calculating the tunable range of apparent constants of chemical equilibria is proposed. Next, three case studies for tuning the apparent constants are investigated in detail: inclusion complexes with cyclodextrin, aqueous micellar solutions for investigating the solvent effects and the boric acid/Mannitol system that allows the tuning of the apparent protonation constant. In all examples tuning the apparent constant is possible by regulating the chemical composition. Graphical abstract Image 1 Highlights • For many equilibrium systems it is customary to use a simplified apparent, instead of a complete complex equilibrium system. • By the thermodynamic laws and equilibrium models, the exact analytic relationship between complete and apparent models of equilibrium systems can be extracted. • The extracted relationship formula determine the external parameter (s) for controlling the apparent models of equilibrium systems. • By controlling the conditions, the apparent constant of equilibrium systems could be tuned in the desired value. [ABSTRACT FROM AUTHOR]