(CAS NO. ) is prepared commercially by dissolution of propene in H₂SO₄, followed by hydrolysis of the sulfate ester. Major impurities are water, lower alcohols and oxidation products such as aldehydes and ketones. Purification of isopropanol follows substantially the same procedure as for n-propyl alcohol.

Isopropanol forms a constant-boiling mixture, b 80.3 °C, with water. Most of the water can be removed from this 91% isopropanol by refluxing with CaO (200gL) for several hours, then distilling. The distillate can be dried further with CaH₂, magnesium ribbon, BaO, CaSO₄, calcium, anhydrous CuSO₄ or Linde type 5A molecular sieves. Distn from sulfanilic acid removes ammonia and other basic impurities. Peroxides [indicated by liberation of iodine from weakly acid (HCl) solns of 2% KI] can be removed by refluxing with solid stannous chloride or with NaBH₄ then fractionally distilling. To obtain isopropanol containing only 0.002M of water, sodium (8g/L) has been dissolved in material dried by distn from CaSO₄, 35mL of isopropyl benzoate has been added and, after refluxing for 3h, the alcohol has been distd through a 50 cm Vigreux column. 

Other purification steps for isopropanol include refluxing with solid aluminium isopropoxide, refluxing with NaBH₄ for 24h. and the removal of acetone by treatment with, and distn from 2,4-dinitrophenylhydrazine. Peroxides re-form in isopropanol if it is stood for several days.