isopropanol, isopropyl alcohol, or 2-propanol (Īˌsəprōˈpənōl, Īˌsəprōˈpĭl) [key], (CH3)2CHOH, a colorless liquid that is miscible with water. It melts at - 89°C and boils at 82.3°C. It is poisonous if taken internally. It is a major component of rubbing alcohols. Isopropanol is a secondary alcohol. It is one of the cheapest alcohols and has replaced ethanol for many uses because of its similar solvent properties. Isopropanol is made commercially by dissolving propylene gas in sulfuric acid and then hydrolyzing the sulfate ester that is formed; the propylene is a byproduct of petroleum refining. Isopropanol was formerly obtained largely by catalytic reduction of acetone; oxidation of isopropanol is now the major source of acetone.