To expand on Nizar Matar's answer, dioxane is a 6-membered ring like cyclohexane, and it's three dimensional structure inter-converts between the chair and boat conformations. While the dioxane in the chair conformation would be symmetrical, and thus non-polar, the molecule with also occupy the boat conformation and be very polar. Also, there are other conformations (twisted boat) that exist, allowing for more non-symmetrical geometries to exist, lending more polarity to the ensemble as a whole.

1,4-dioxane is highly polar solvent with a polarity index = 4.8 . It is more polar than ethyl acetate & also more polar than MEK (i.e. methyl ethyl ketone). The ring structure of dioxane is NOT flat. Had it been planar, then it would have been nonpolar.

Thanks for this good question.

To expand on Nizar Matar's answer, dioxane is a 6-membered ring like cyclohexane, and it's three dimensional structure inter-converts between the chair and boat conformations. While the dioxane in the chair conformation would be symmetrical, and thus non-polar, the molecule with also occupy the boat conformation and be very polar. Also, there are other conformations (twisted boat) that exist, allowing for more non-symmetrical geometries to exist, lending more polarity to the ensemble as a whole.

I agree with the above ans's

I agree with answers and explanations by Charles and Dr. Nizar Matar

I disagree with everyone. Dioxane has a dielectric constant of only 2.25, less than that of toluene. The diplole moment is only 0.45 D. ET(30) of dioxane is only 36, less than ethylbenzene. This makes is a non-polar solvent, despite being miscable with water and a strong eluent in chromatography. The Snyder polarity is related to eluent strength.