Difference Spatial Distribution Function Analysis of Aqueous Solutions. II. Hydration Structures of Dimethyl Ether, 180°Ethyl Methyl Ether and 0°Ethyl Methyl Ether Solutions

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Monte Carlo simulations are systematically presented to demonstrate the influence of the hydrophobic group's steric bulk on hydration structure. We have simulated a dimethyl ether (DME), two conformations for ethyl methyl ether (0°EME and 180°EME), and 0°ethanol solutions. Spatial distribution function (SDF), g_<OO>(x, y, z) and difference SDF (DSDF), △g_<OO>(x, y, z), obtained from MC simulation in an infinitely dilute aqueous solution of ether show the three-dimensional probability of an atom-atom 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) and hydrophobic hydration (HH) regions, and the spatial orientation of the hydrogen-bonded water in the HA region is found to form a triple-layer structure, as it does in alcohol solutions. From the results of an analysis of the DSDF △g_<OO>(x, y, z) between the SDFs of EME and DME, it is apparent that the distribution changes of hydration water molecules in ether solutions are essentially similar to those in the alcohol solutions. Further, we show that the hydration water molecules are distributed mainly in the stable area in the binding energy's (BE) contour maps for each region.
公益社団法人日本薬学会の論文
2000-01-01