Transfer of the K+ cation across a water/dichloromethane interface: a steered molecular dynamics study with implications in cation extraction.

In this paper we report the characterization of the dichloromethane (DCM)/water interface in terms of density profile, width, and surface structure. The use of steered molecular dynamics (SMD) to study the transfer of the K(+) cation from the organic layer to the water layer is also described. The corresponding free energy is in semiquantitative agreement with published experimental and theoretical results. The transference of the K(+) cation from the water layer toward the DCM layer occurs with concomitant water transport as a water microdroplet that detaches itself from the water layer after ca. 16 Å of penetration into the organic layer by breaking the thin water thread that unites both. Complexation of the water microdroplet by a polyethylene-glycol type podand induces the loss of water molecules from the water microdroplet to bulk DCM and, eventually, to the water layer.