Synthesised commercially purification of tert-Butyl alcohol (CAS NO. ) is the hydration of 2-methylpropene in dilute H₂SO₄. Dried with CaO, K₂CO₃, CaSO₄ or MgSO₄, filtered and fractionally distd. Dried further by refluxing with, and distilling from, either magnesium activated with iodine, or small amounts of calcium, sodium or potassium, under nitrogen. Passage through a column of type 4A molecular sieve is another effective method of drying. So, also, refluxing with tert-butyl phthalate or succinate. Other methods include refluxing with excess aluminium tert-butylate, or standing with CaH₂, and distilling as needed. Further purification is achieved by fractional crystn by partial freezing, taking care to exclude moisture. tert-Butyl alcohol samples containing much water can be dried by adding benzene, so that the water distils off as a tertiary azeotrope, b 67.3 °C. Traces of isobutylene have been removed from dry tert-butyl alcohol by bubbling dry pre-purified nitrogen through for several hours at 40-50 °C before using. It form azeotropic mixtures with a large number of compounds. It has also been purified by distn from CaH₂ into Linde 4A molecular sieves which had been activated at 350 °C for 24h.

Rapid purification: Dry tert-butanol with CaH₂ (5% w/v), distil and store over 3A molecular sieves.