H-1 NMR and IR studies were carried out for 1,4-dioxane/H2O mixtures over the whole concentration range at temperatures of 1, 25, and 50 degreesC. H-1 NMR spectra were also acquired for 1,3-dioxane/H2O and 4-methyl-1,3-dioxane/H2O mixtures. All the chemical shift data were measured by referring to an external reference and corrected using in situ bulk susceptibilities as determined on a unified scale. The results are compared with those previously obtained for dimethyl suffoxide/H2O and acetone/H2O mixtures in order to determine the influence of the polar group on the hydrogen bond formation of water at the polar and hydrophobic groups. It was found that an anomalous polarization of the water molecules, which had been observed in the dimethyl sulfoxide/H2O and acetone/H2O Mixtures, did not occur in the three different aqueous dioxane mixtures. Thus, we have concluded that the hydrophobic moiety in an organic solute having a polar group does not play a role in anomalously high polarization of the water molecules. We have also concluded that the hydrogen-bonding basicity of the polar group is an important factor for the anomalous polarization of the water in the water-rich region and that the basicities of the ether oxygens in the three dioxanes are not strong enough to cause the anomalous polarization of water. It was found that the frequencies of IR C-H stretching vibration modes of 1,4-dioxane increase and the absorption intensities of the modes decrease with increasing water concentration. Since these spectroscopic features correspond well to the formation of the blue-shifting C-H...OH2 hydrogen bonds obtained from ab initio calculations for complexations in gas phases, we can categorize the solvation of the C-H groups in the dioxanes in aqueous solutions as blue-shifting C-H...O hydrogen bonding. Thus, we propose for the first time that the hydration of CH groups in organic solutes having a polar group is due to the formation of blue-shifting C-H...OH2 hydrogen bonds. As a picture of the hydration of the C-H groups in 1,4-dioxane, we propose the formation of a bifunctional hydrogen-bonded hydration complex in which each water molecule plays a role as both a proton donor in the conventional O-H...O hydrogen bonding with the ether oxygen and a proton acceptor in the blue-shifting C-H...O hydrogen bonding simultaneously.