An effective force field to reproduce the solubility of MTBE in water

摘要

In this work, a force field has been developed for methyl tert-butyl ether (MTBE) in the pure liquid by adjusting the intermolecular parameters to reproduce three target thermodynamic properties: the dielectric constant, the surface tension and the density of the liquid. In addition to these three properties, the new force field was able to reproduce the experimental values for the heat of vaporization, the vapor pressure, the self-diffusion and the viscosity, with relative errors smaller than 5%. Moreover, the target properties were also calculated as a function of temperature, in the 288.15 to 313.15 K range. A remarkable agreement with experimental data was found. Finally, by combining the NEWFFP force field for MTBE with the TIP4P/epsilon force field for water, the solubility of MTBE in water as a function of temperature was obtained. The results follow the experimental line with a deviation which is less than 7%. The decrease in the solubility with temperature is explained by the formation, at low temperature, of stable, short-lived MTBE-water clusters that are clearly identified. These clusters contain one, two and three MTBE molecules that form hydrogen bonds with water molecules. At temperatures above 298.15 K no clusters are found, in agreement with the experimentally observed negative slope of the solubility versus temperature behavior.