Molecular Structure of the Chloroform−Water and Dichloromethane−Water Interfaces

Abstract

Using equilibrium molecular dynamics simulations, we investigate the structure of chloroform−water and dichloromethane−water interfaces. These systems are analyzed in terms of the orientation of water, chloroform, and dichloromethane molecules as a function of distance from the Gibbs surface. We also calculate order parameters for all molecules across the interface. The results show that the structures may be described in the context of a few distinct regions of the interface, where organic and water molecules generally arrange themselves either to maximize hydrogen-bonding interactions or to minimize the net dipole moment. In cases where molecular arrangements promote hydrogen-bonding interactions, they often do not provide complete dipole compensation. The orientation of organic and water molecules then creates a field across the interface. For the CHCl3−water interface, the field has a uniform direction with the positive end of the dipole pointing toward the bulk water phase. The interfacial field is m...