HO-CH2-CH2-OH =H2SO4=> HO-CH2-CH2-OSO3H =H2SO4=> HO3SO-CH2-CH2-OSO3H
The mono- and disulphonated dioxanes thereby obtained react with excess of free dioxane to form an ether, for example:
HO-CH2-CH2-OSO3H + HO-CH2-CH2-OH ==> HO-CH2-CH2-O-CH2-CH2-OH
Formed di- ethylene glycol ether can be sulphonated further. When one of the ends gets sulphonated, the other end (free alcohol) substitutes the sulphone group to give a cyclic ether - dioxane. This last step (cyclisation) is fast since it's intramolecular.
Although dioxane is the favored product, note that there's a possibility that reaction also forms larger cyclic and linear poly-ethers. The former type of compounds are known as crown ethers, which are not healthy to have around...
Materials to prepare dioxane are easy to get. As ethylene glycol I've used a brand of antifreeze that told to be an aqueous solution of ethylene glycol (also had some blue dye), glycol was dried prior to use, by heating slowly to 198oC.
Whole procedure is done outside!
Distilation is ceased when reaction mixture becomes black, starts to foam alot and evolve SO2.
With increased temperature and concentration of H2SO4, rates of some byreactions will increase: first, dehydration of ethylene glycole to form acetaldehyde and second, oxidation-reduction reactions which leads to charring of reaction mixture and evolution of SO2.
Next, product is salted out: powdered potassium carbonate is added to the colorless distillate until solution separates in two layers. Upper dioxane layer is separated and dried first by dry potassium carbonate and then by potassium hydroxide. On addition of potassium hydroxide, solution becomes orange-brown because acetaldehyde (a byproduct) polymerises in basic conditions. First pieces of KOH dissolves on stirring (an additional layer separates), while following pieces remains unchanged.
Dried product is transfered to another flask, a peasize piace of metallic sodium is added and dioxane is destilled collecting a fraction of 100-103oC. Yield is 12 g (51% from theoretical).
Dioxane is a colorless liquid, mixes with water, ethanole and diethyl ether. mp = 11,7oC; bp = 101,3oC; dencity at 20oC = 1,03375.