RELATIVE POLARITY OF 1,3-DIOXANE AND 1,4-DIOXANE STUDIED BY THE REACTION FIELD-THEORY AND VIA COMPUTER-SIMULATIONS

We show that neither the dipole moment of a molecule nor the static dielectric constant of a solvent are satisfactory descriptors of polarity. According to the usual definition of molecular polarity, 1,3-dioxane is polar while 1,4-dioxane is not. The electric fields at the center of a 1,3-dioxane molecule dissolved in 1,4-dioxane and in 1,3-dioxane (pure liquid) were estimated by means of Monte Carlo statistical mechanics simulations and were found to be similar. This led us to emphasize and discuss one aspect of the limitations of the reaction field theory. Finally, we make use of the relationship between the polarity of solvent and the magnetic relaxation rate of dissolved monoatomic Xe-131 to corroborate our conclusions. The relaxation rates of Xe-131 dissolved in 1,3-dioxane and 1,4-dioxane were measured and were also found to be similar.