Calculation of Solute Partition Coefficient Using the A-P Scheme

Abstract

Although many models have been developed for solute partition coefficient (or solvation Gibbs free energy, ΔG_solv), how to develop models for rapid and accurate solvation energy predictions still remains challenging. In this work, a relation named the A-P scheme based on the Q–e scheme in radical copolymerizations and the Arrhenius equation for chemical kinetics is for the first time proposed to correlate the partition coefficients with supposed nonpolar and polar contributions from solute and solvent molecules. When compounds used as a solute or a solvent were allocated a parameter A denoting nonpolar contribution and another parameter P meaning polar contribution, the partition coefficients (or solvation Gibbs energies) of any solute/solvent pair can be calculated with the A-P scheme. Further, 6238 experimental solvation Gibbs energies were used to test the A-P scheme, resulting in a root means square (rms) error of 2.89 kJ·mol⁻¹, lower than the chemical accuracy of 4.18 kJ·mol⁻¹. Unlike other empirical approaches or quantitative structure–property relationship (QSPR) models, the proposed new scheme in this paper is not restricted to a specific solvent or solute and has markedly less computational intensity in predicting solute partition coefficient (or solvation Gibbs free energy). Therefore, the A-P scheme proposed in this work is feasible in rapid and accurate calculation of solvation Gibbs energies.

Graphical Abstract