Difference spatial distribution function analysis of aqueous solutions. II. Hydration structures of dimethyl ether, 180 degrees ethyl methyl ether and 0 degrees ethyl methyl ether solutions

Monte Carlo simulations are systematically presented to demonstrate the inf luence of the hydrophobic group's steric bulk on hydration structure. We ha ve simulated a dimethyl ether (DME), two conformations for ethyl methyl eth er (0 degrees EME and 180 degrees EME), and 0 degrees ethanol solutions. Sp atial distribution function (SDF), g(00)(x,y,z) and difference SDF (DSDF), Delta g(00)(x,y,z), obtained from MC simulation in an infinitely dilute aqu eous solution of ether show the three-dimensional probability of an atom-at om pair distribution between solute and solvent atoms. Based on the results of SDF in an infinitely dilute aqueous solution of ether, the distribution of hydration water molecules can be divided into hydrogen acceptor (HA) an d hydrophobic hydration (NH) regions, and the spatial orientation of the hy drogen-bonded water in the HA region is found to form a triple-layer struct ure, as it does in alcohol solutions. From the results of an analysis of th e DSDF Delta g(00)(x,y,z) between the SDFs of EME and DME, it is apparent t hat the distribution changes of hydration water molecules in ether solution s are essentially similar to those in the alcohol solutions, Further, we sh ow that the hydration water molecules are distributed mainly in the stable area in the binding energy's (BE) contour maps for each region.