Solubility prediction of bio-oil derived chemicals in aqueous media by Localized Molecular Orbital-Energy Decomposition Analysis (LMO-EDA) and COSMO-RS predictions

Abstract

A series of hydrogen bonding complexes which include Glycolaldehyde⋯water, Furfural⋯water, Acetic acid⋯water and Furanone⋯water were for the first time analyzed by Localized Molecular Orbital-Energy Decomposition Analysis (LMO-EDA) for the prediction of solubility. Stable equilibrium structures of complexes in gas phase were determined by second-order Møller–Plesset perturbation theory (MP2) with 6-311++G(d,p) basis set. Initially conformer analysis was performed on all the solutes and the complexes to choose the minimum energy conformer. It has been found that the most stable structure of Glycolaldehyde and Acetic acid made a cyclic complex with water and was bonded together by two H-bonds which make them unique as compared to Furanone and Furfural. Thereafter with the minimum energy conformer of the solute, the COSMO (COnductor like Screening MOdel) model displaying the distribution of screening charges on a molecular surface was obtained. Subsequently a qualitative analysis based on the sigma profile explained the high distribution coefficients of Glycolaldehyde and Acetic acid. LMO-EDA based Interaction energy and its constituent energy terms (Electrostatic Energy, Exchange Energy, Repulsion Energy, Polarization Energy, and dispersion Energy) were then determined, where the reported and predicted solubility parameters of water in these compounds were found to be: Acetic acid>Glycolaldehyde>Furanone>Furfural. The same trend was also confirmed when comparing the COSMO-RS predicted Infinite Dilution Activity Coefficients (IDAC) of the components in water. An inverse relation was thus obtained between the predicted IDAC values and the LMO-EDA based interaction energies.