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Abstract: Our results demonstrate that the equatorial C–H groups of 1,3-dioxane form hydrogen-bond-like C–H⋯O interactions more readily than do the axial C–H groups. The peak frequency of the strong axial C–H stretch band of 1,3-dioxane in a dilute D2O solution possesses an unusual non-monotonic pressure dependence, which indicates enhanced C–H⋯O hydrogen bond formation at high pressure. We performed density functional theory calculations to predict the relative energies and total interaction energies of 1,3-dioxane/(water) n clusters and found that the equatorial C–H groups are more favorable sites for hydrogen bonding than are the axial C–H groups. [Copyright &y& Elsevier]

We have investigated the effect of pressure versus C–H–O interactions in 1,4-dioxane/D2O mixtures. Hydrogen bond-like C–H–O interaction may be a distinct possibility to understand the origin of the spectral features observed under high pressure. Based on the results of density functional theory calculations, the structural identification of the pressure-induced hydrophobic isomers is complicated by the presence of more than one stable isomeric form. This study demonstrates that high pressure can be used as a valuable means of triggering hydrogen bond-like C–H–O interactions. [Copyright &y& Elsevier]