1.Dipole moment data shows that 1,3-dioxane and its substituted forms containing nonpolar substituents at the second carbon atom have the armchair configuration.2.The molecules of 2-bromomethyl-1,3-dioxane and 2-ethoxy-4-methyl-1,3-dioxane have the armchair configuration with the polar groups in the equatorial position. Free rotation of the CH2Br groups is possible in the case of 2-bromomethyl-1,3-dioxane.