Binary mutual diffusion coefficients of aqueous cyclic ethers at 25 degrees C. Tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1,3-dioxane, tetrahydropyran, and trioxane

Taylor dispersion and differential refractometry are used to measure mutual diffusion coefficients (D) for the binary mixtures 1,4-dioxane + water, 1, 3-dioxolane + water, and tetrahydrofuran + water at 25 degrees C. For each of these systems the plot of D against composition shows a pronounced minim um. Activity and viscosity data for aqueous 1,4-dioxane are used to discuss the strong composition dependence of D in terms of changes in the mobiliti es and thermodynamic driving forces. Diffusion coefficients are also report ed for dilute aqueous solutions of 1,3-dioxane, tetrahydropyran, and trioxa ne. The limiting diffusion coefficients of the infinitely dilute aqueous et hers are discussed in terms of ring size, number and relative location of t he oxygens, and the ether partial molar volume. A second or a third oxygen in the five- or six-membered rings reduces the ether partial molar volumes by about 10 cm(3).mol(-1) and increases the limiting diffusion coefficients by (0.14 to 0.21) x 10(-5) cm(2).s(-1).