(367c) Electrostatic and Induction Effects in Solubility of Water in Alkane

Alkane solubility in water has received intense scrutiny but the converse problem, which is of technological and scientific interest, has received much less attention. Experiments show that at 298 K and 1 atm pressure, the transfer free energy of water from its vapor to liquid normal alkanes(C5 to C12) is negative. Earlier it was found that with the united-atom TraPPE model for alkanes and the SPC/E model for water, one had to artificially enhance the attractive alkane-water cross interaction to capture this behavior. In this talk, I will discuss the importance of electrostatic and induction effects in solubility of water in alkanes, which is commonly ignored for water-alkane interactions. We calculated the transfer free energy using the polarizable AMOEBA and the non-polarizable CHARMM General (CGenFF) forcefields. We find that with CGenFF, the transfer free energy is positive and the error relative to experiments is about 1.5 kBT. With AMOEBA, the transfer free energy is negative and deviations relative to experiments are between 0.25 kBT (AMOEBA14) and 0.5 kBT (AMOEBA03). Quantum chemical calculations in a continuum solvent suggest that zero point effects may account for some of the deviation.