Dioxane is undertood to be 1,4-dioxane and the latter name should be used more properly. Like tetrahydropyran (THP), dioxane is a 6-membered ring ether and its structure is related to that of cyclohexane. Consider the boat form of this molecule. Would you think that the boat form should be more or less destabilized in the case of the dioxane as compared to the cyclohexane? [Hint: Think about the nature of the interaction between the electronegative O-atoms.]