Chemical Equilibrium and Kinetics in the Autocatalytic Reaction System 2,2,2-Trifluoroacetic Acid–Propan-1-ol–Water–Propyl 2,2,2-Trifluoroacetate

The esterification reaction of alcohols and acids is a fundamental method for synthesizing esters. Such reactions can occur via a nucleophilic substitution mechanism, facilitated by the protonation of the oxygen atom in the carbonyl group of the acid. The scientific literature extensively addresses systems in which one of the reactants is a weak acid, necessitating the use of an external catalyst for the reaction to proceed. In contrast, systems that involve a strong acid as one of the reactants exhibit autocatalytic behavior. A notable example is the esterification reaction between an alcohol and trifluoroacetic acid (TFA), which possesses an acidity comparable to that of strong mineral acids. Despite the investigation of such reactions across various systems, experimental data on the chemical equilibrium and kinetics remain limited. Additionally, the theoretical foundations of autocatalytic esterification kinetics and the existing models for such systems are not universally applicable. This study focuses on the chemical equilibrium and kinetics of the esterification reaction between TFA and propan-1-ol (Pol) without the introduction of an external catalyst. Data on the equilibrium constant were obtained within a temperature range from 30 to 70 °C. The results indicate that a reaction system with initial TFA concentrations of up to a 0.3 mole fraction (x_TFA/x_Pol ≤ 3/7) falls within the homogeneous area of chemical equilibrium compositions. The temperature dependence of the Van't Hoff equation parameters indicates that the reaction is endothermic within this area. Kinetic data were collected for the homogeneous equilibrium area within a temperature range from 30 to 80 °C. Existing models of autocatalytic esterification do not adequately describe the reaction kinetics, primarily because they treat the reaction rate coefficient as a constant. To address this limitation, the present study proposes a model that accounts for the dependence of the activation energy on the TFA concentration. Such an approach provides an adequate description of the experimental data.