Insight into the weak interaction between organic primary amine and propionic acid or phenol solvents in solvent extraction

Abstract

The essence of solvent extraction is to change the interaction degree between extracted molecules and solvents in the system. The study of solvent extraction at the molecular level has important guiding significance for further design. Here, taking the extraction of organic weak acid (phenol/propionic acid) by primary amines N1923 through hydrogen bond association as an example, the quantitative calculation parameters of reactive molecules were discussed, such as the charge distribution, potential distribution, average local ionization energy (ALIE) distribution and abbreviated Fukui function, while the polar index and polar area percentage were calculated. Moreover, the region and intensity of weak interaction were analyzed and visualized by electronic density difference and Van der Waals (VDW) radius. At the same time, the electron density of the critical point of bond (BCP) and the corresponding predicted value of hydrogen bonding energy are calculated. Finally, the solubility energy of primary amines and the Gibbs free energy of extraction reaction were calculated, and the results show that the interaction between organic amine and propionic acid is stronger by the hydrogen bond mechanism. This study provides a set of systematic cases to analyze the interaction between extraction molecules. It provides a new perspective for understanding the essence of solvent extraction, thus promoting the theoretical development of separation science.