Molecular dynamics computer simulation of the hydration of two simple organic solutes

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The hydration of two simple organic solutes has been studied using the molecular dynamics (MD) computer simulation method. Results of the simulations of a single 1,4-dioxane or 1,3-dioxane molecule dissolved in 122 water molecules are compared with those of a MD simulation of an empty cavity of corresponding size in 216 water molecules. This yields the opportunity to trace the specific effects of the polar and dispersion solute-solvent interactions on the properties of the water molecules in the hydration shell of the solute. The hydration shell properties of 1,4-dioxane (μ) = 0·14 D) are very similar to those of the corresponding cavity, whereas those of 1,3-dioxane (μ) = 1·91 D) show significant deviations. Earlier conclusions that water structure-making and water structure-breaking properties of 1,4-dioxane are about equally balanced, while 1,3-dioxane is definitely structure-breaking, are confirmed. Moreover, it is shown that a slower self-diffusion and reorientation of water molecules upon addition o...