Isopropyl alcohol, also known as isopropanol, is a colorless, flammable organic compound with the molecular formula C3H8O. This liquid substance has a characteristic alcohol-like odor and mixes well with most solvents, including water. Isopropyl alcohol is relatively nontoxic and is utilized for a variety of purposes, most notably as a solvent and as a cleaning agent. Although it is more utilized in the industry, most people know isopropyl alcohol as “rubbing alcohol,” which is a mixture of isopropyl alcohol and water and can be found in many pharmacies and grocery stores.
Propylene is an organic gas that is a byproduct of natural gas processing. Indirect hydration of propylene was the only method used to produce isopropyl alcohol worldwide up until the first commercial direct-hydration process was introduced in 1951. Indirect hydration is also called the sulfuric acid process since it requires a reaction with sulfuric acid. This is a two-step process: the reaction between propylene and sulfuric acid to produce monoisopropyl and diisopropyl sulfates, followed by a reaction with water that hydrolyzes these intermediates into isopropyl alcohol.
Isopropyl alcohol dissolves a wide range of non-polar compounds. It also evaporates quickly, leaves nearly zero oil traces, compared to ethanol, and is relatively non-toxic, compared to alternative solvents. Thus, it is used widely as a solvent and as a cleaning fluid, especially for dissolving oils.
Rubbing alcohol, hand sanitizer, and disinfecting pads typically contain a 60–70% solution of isopropyl alcohol or ethanol in water. Water is required to open up membrane pores of bacteria, which acts as a gateway for isopropyl alcohol. A 75% v/v solution in water may be used as a hand sanitizer. Isopropyl alcohol is used as a water-drying aid for the prevention of otitis externa, better known as swimmer's ear.
As a biological specimen preservative, isopropyl alcohol provides a comparatively non-toxic alternative to formaldehyde and other synthetic preservatives. Isopropyl alcohol solutions of 70–99% are used to preserve specimens.