COSMO-SAC AS A TOOL FOR PREDICTING BIOCOMPOUNDS SOLUBILITY IN IONIC LIQUIDS: AN INQUIRY ON SUGARS

Ionic liquids (IL) can be used to extract/purify biocompounds from several natural sources. While the number of possible combinations of cations and anions for creating ILs is too large for predicting every possible mixture, estimates of the solubility of biocompounds in ILs can be obtained from a priori calculations with for a specific matrix of interest. Therefore, simulating different combinations of cations and anions that form ILs within a reduced family of target solutes is sought. Furthermore, because pure bioactive compounds and ILs are usually costly, obtaining experimental data is difficult. Thus, a previous selection to narrow the possibilities down is many times necessary. COSMO models are based on ab-initio quantum calculations and could be a fine alternative for this task. In this way, the aim of this study was to test the COSMO-SAC model in the prediction of the solubility of biocompounds in ILs, with a focused outlook on organic acids. Solubility experimental data from literature were predicted using the COSMO-SAC methodology, apparent surface charges were constructed using ab-initio QM (HF+TZVP) using GAMESS. Fusion temperature and enthalpy data were obtained from literature. Calculations were performed using the JCOSMO program for various organic compounds, and an in-depth investigation focusing on organic acids, i.e. phenolic compounds in particular, was performed. Results have been mixed, especially when varying the anion used to form the IL, e.g.caffeic acid (CA) in 1-octyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate ([OMIM]+[BF4]-) and 1-octyl-3-methyl-1H-imidazol-3-ium hexafluorophosphate ([OMIM]+[PF6]-); while COSMO accurately predicts CA’s quasi insolubility in the PF6 solvent, it erroneously indicates a similar behavior in the BF4 one, when experimental data suggests real solubility is more than an order of magnitude higher.