In Liquefied petroleum gas: 1075
|Molar mass||56.11 g·mol−1|
|Density||0.5879 g/cm3, liquid|
|Melting point||−140.3 °C (−220.5 °F; 132.8 K)|
|Boiling point||−6.9 °C (19.6 °F; 266.2 K)|
|GHS signal word||DANGER|
|P210, P377, P381, P403|
|EU classification||Extremely flammable (F+)|
|S-phrases||(S2), S9, S16, S33|
|Flash point||flammable gas|
|465 °C (869 °F; 738 K)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Isobutylene (or 2-methylpropene) is a hydrocarbon of industrial significance. It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. At standard temperature and pressure it is a colorless flammable gas.
Isobutylene is used as an intermediate in the production of a variety of products. It is reacted with methanol and ethanol in the manufacture of the gasoline oxygenates methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), respectively. Alkylation with butane produces isooctane, another fuel additive. Isobutylene is also used in the production of methacrolein. Polymerization of isobutylene produces butyl rubber (polyisobutylene). Antioxidants such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are produced by Friedel-Crafts alkylation of phenols using isobutylene.
Polymer and chemical grade isobutylene is typically obtained by dehydrating tertiary butyl alcohol or catalytic dehydrogenation of isobutane. Gasoline oxygenates MTBE and ETBE are generally produced by reacting methanol or ethanol with isobutylene contained in butene streams from olefin steam crackers or refineries. Isobutylene is not isolated before the reaction as separating the ethers from the remaining butenes is simpler.
Isobutylene is a highly flammable gas and presents an explosion danger. Usually stored as a compressed, liquefied gas, if released it may produce an oxygen-deficient atmosphere that presents an asphyxiation hazard.
- The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN 091191028X, 5024.
- Isobutene, International Chemical Safety Card 1027, Geneva: International Programme on Chemical Safety, April 2000
- Olah, George A.; Molnár, Árpád, Hydrocarbon Chemistry, Wiley-Interscience, ISBN 978-0-471-41782-8.