Prediction of ethenzamide solubility in organic solvents by explicit inclusions of intermolecular interactions within the framework of COSMO-RS-DARE

The solubility of ethenzamide (Et) in six organic solvents has been found to be very imprecisely predicted by COSMO-RS approach leading to error of computed mole fractions between 360% for methanol (MeOH) up to 600% in the case of ethyl acetate (EtAc). This paper suggests that the origin of such failure is to be addressed to the lack of inclusion in the default approach very important intermolecular interactions of Et. The results of quantum chemistry computations including contributions coming from the electron correlation and zero vibrational point correction performed on representative set of coformers suggest existence of binary clusters in all considered solutions with the following trend of affinities Et-Et > Et-S ≈ S-S, where S stands for solvent molecule. For proper characteristics of such kind of interactions Dimerization, Aggregation, and Reaction Extension (COSMO-RS-DARE) was used. This led to very accurate prediction of Et solubility in each of the solvent for which experimental data were available. This approach requires introduction of new affinity parameter, which value was fitted to experimental data. Fortunately, it has been found that this parameter is linearly dependent with the values of Gibbs free energy of reactions leading to homo-molecular complexes in either of studied solutions. This fortunate circumstance allows for very accurate prediction of Et solubility in virtually any solvent or solvent mixture. Ethenzamide solubility via COMSO-RS-DARE intra- and inter-molecular interactions in organic solvents. [Display omitted] •very low accuracy of COSMO-RS approach for Ethenzamide computations has been noticed.•inclusion of intermolecular interaction involving this drug significantly was emphasized.•application of COSMO-RS-DARE approach improved significantly predicted values of mole fraction.•intermolecular parameter inherent to COSMO-RS-DARE was obtained by fitting to experimental data.•the COSMO-RS-DARE parameter is linearly correlated with Gibbs free energy of Ethenzamide dimerization in bulk solutions.