Dissecting steric and polar substituent effects in linear free energy Relationships: Re-Assessment of the Taft equation with Temperature-Dependent kinetic modeling
Résumé
Kinetic models are vital for developing process flow diagrams that support cost, risk, and environmental assessments, but constructing them is time-consuming, particularly when screening multiple substituents or solvents. Linear Free Energy Relationships (LFERs) can reduce experimental effort, yet most existing formulations neglect temperature effects. In this work, we quantify the temperature dependence (20–50 °C) of Taft’s polar (σ*) and steric (Es) substituent parameters for methyl, ethyl, n-propyl, and 2-chloroethyl groups using kinetic data from esterification and saponification of levulinate derivatives in aqueous media. Both σ* and Es varied linearly with temperature, with the strongest sensitivity observed for 2-chloroethyl (–0.007 °C−1 for σ*, 0.008 °Csup>−1 for Es). Incorporating these temperature coefficients into LFER-based kinetic models enhances their predictive accuracy for reaction rates, enabling more efficient process design in biomass valorization and related chemical systems.
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