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Isobutylene

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Isobutylene
Skeletal formula
Skeletal formula
Space-filling model
Space-filling model
Ball-and-stick model
Names
IUPAC name
2-Methylpropene
Other names
Isobutene
γ-Butylene
2-Methylpropylene
Methylpropene
2-Methylprop-1-ene
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.003.697 Edit this at Wikidata
EC Number
  • 204-066-3
RTECS number
  • UD0890000
UNII
UN number 1055
In Liquefied petroleum gas: 1075
  • InChI=1S/C4H8/c1-4(2)3/h1H2,2-3H3 checkY
    Key: VQTUBCCKSQIDNK-UHFFFAOYSA-N checkY
  • InChI=1/C4H8/c1-4(2)3/h1H2,2-3H3
  • CC(=C)C
Properties
C4H8
Molar mass 56.106 g/mol
Appearance Colorless gas
Density 0.5879 g/cm3, liquid
Melting point −140.3 °C
Boiling point −6.9 °C (19.6 °F; 266.2 K)
Insoluble
Hazards
GHS labelling:
Flam. Gas 1Press. Gas
Danger
H220
P210, P377, P381, P403
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
4
0
Flash point flammable gas
Explosive limits 1.8–9.6%
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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.

Uses

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.

Manufacture

Isobutylene can be isolated from refinery streams by reaction with sulfuric acid, but the most common industrial method for its production is by catalytic dehydrogenation of isobutane.[3] In the 1990s, the production of isobutylene increased dramatically as the demand for oxygenates such as MTBE grew.

Safety

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.[2]

See also

References

  1. ^ The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN 091191028X, 5024.
  2. ^ a b Isobutene, International Chemical Safety Card 1027, Geneva: International Programme on Chemical Safety, April 2000
  3. ^ Olah, George A.; Molnár, Árpád, Hydrocarbon Chemistry, Wiley-Interscience, ISBN 978-0-471-41782-8.
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