Integrating Solvent Effects into the Prediction of Kinetic Constants Using a COSMO-Based Equation of State.

Abstract

While kinetic generators produce thermo-kinetic data for detailed gas-phase kinetic models, adapting these models for liquid-phase applications poses challenges due to the need for solvent-dependent thermodynamic properties. To bridge this gap, solvation energies are used to incorporate solvent effects into gas-phase thermo-kinetic data. However, such an adaptation depends on calculating liquid-phase data of unconventional solutes such as free radicals and transition states, which are not accessible with classical equations of states. To address this issue, this work proposes a flexible framework based on an equation of state that integrates all the latest advances of this model family and is called the tc-PR EoS. Combined with a quantum-based continuum solvation model (COSMO-RS) through an advanced mixing rule, the proposed model is made predictive by employing group contribution methods to estimate the pure compound input parameters required to perform thermodynamic calculations with the model. These parameters can be calculated for closed-shell molecules, free radicals, and transition states, with an average deviation of less than 10% with respect to the benchmark database containing experimental data as well as data obtained from quantum-based calculations and QSPR-type correlations. The tc-PR/COSMO-RS model is able to predict the solvation free energies of activation for H-abstraction reactions with an accuracy of approximately 0.2 kcal/mol, offering a high-throughput and accurate solution for integrating solvation effects into detailed kinetic models in the liquid phase.