Solvation of Ethanol, Phenol, and o-Methoxyphenol in Dilute Aqueous Solutions under Normal and Supercritical Conditions

Abstract

The structure of 2 wt % aqueous solutions of ethanol, phenol, and o-methoxyphenol (guaiacol) was modeled in NVT ensemble using the classical molecular dynamics method at densities of 0.997 and 0.133 g/cm³ corresponding to the normal (298 K, 0.1 MPa) and supercritical (673 K, 23.0 MPa) conditions. The self-diffusion coefficients were calculated for individual components in solutions; the radial distribution functions were calculated for the oxygen atoms of water molecules, oxygen atoms of hydroxyl groups, and centers of mass in phenol molecules. The possibility of clusterization of solute molecules was analyzed. The data obtained suggest heterogeneity of solutions, in which clusters of different compositions and structures can exist. Clusterization of up to seven ethanol and phenol molecules can occur under normal conditions, and dimerization was detected under SC conditions. The structural features of solutions under normal and SC conditions were compared. The difference in the formation of hydration shells of ethanol and phenols molecules was demonstrated. Stable shells of water molecules form around ethanol molecules under normal conditions. For phenols, the solvation shells are unstable, with a pronounced tendency toward clusterization of organic molecules.