−89 °C, 184 K, -128 °F
82.5 °C, 356 K, 181 °F
Isopropyl alcohol (also propan-2-ol, 2-propanol or the abbreviation IPA) is a common name for a chemical compound with the molecular formula C3H8O. It is a colorless, flammable chemical compound with a strong odor. It is the simplest example of a secondary alcohol, where the alcohol carbon is attached to two other carbons sometimes shown as (CH3)2CHOH. It is a structural isomer of propanol.
Isopropyl alcohol is produced by combining water and propene. There are two processes for achieving this: indirect hydration via the sulfuric acid process, and direct hydration. The former process, which can use low-quality propene, predominates in the USA while the latter process, which requires high-purity propene, is more commonly used in Europe. These processes give predominantly isopropyl alcohol rather than 1-propanol because the addition of water or sulfuric acid to propene follows Markovnikov's rule.
The indirect process reacts propene with sulfuric acid to form a mixture of sulfate esters. Subsequent hydrolysis of these esters produces isopropyl alcohol. Direct hydration reacts propene and water, either in gas or liquid phases, at high pressures in the presence of solid or supported acidic catalysts. Both processes require that the isopropyl alcohol be separated from water and other by-products by distillation. Isopropyl alcohol and water form an azeotrope and simple distillation gives a material which is 87.9% by weight isopropyl alcohol and 12.1% by weight water. Pure (anhydrous) isopropyl alcohol is made by azeotropic distillation of the "wet" isopropyl alcohol using either diisopropyl ether or cyclohexane as azeotroping agents.
Isopropyl alcohol is readily available. Like acetone, it dissolves a wide range of non-polar compounds. It is also relatively non-toxic and evaporates quickly. Thus it is used widely as a solvent and as a cleaning fluid, especially for dissolving lipophilic contaminants such as oil. Examples include cleaning electronic devices such as contact pins (like those on ROM cartridges), magnetic tape and disk heads (such as those in audio and video tape recorders and floppy disk drives), the lenses of lasers in optical disc drives (e.g. CD, DVD) and removing thermal paste from IC packages (such as CPUs.) It is used to clean LCD and glass computer monitor screens (at some risk to the anti-reflection coating on some screens), and used to give second-hand or worn records newer-looking sheens. Isopropyl alcohol should not be used to clean vinyl records as it may leach plasticizer from the vinyl making it more rigid). Isopropyl alcohol removes smudges, dirt, and fingerprints from cell phones and PDAs. It is effective at removing residual glue from some sticky labels although some other adhesives used on tapes and paper labels are resistant to it. It can also be used to remove stains from most fabrics, wood, cotton, etc. Isopropyl alcohol is also used to remove brake fluid traces from hydraulic disk brake systems, so that the brake fluid (usually DOT 3, DOT 4 or mineral oil) does not contaminate the brake pads, which would result in poor braking. In addition it can also be used to clean paintballs or other oil based products so that they may be reused, commonly known as "repainting".
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