Isobutylene

Isobutylene

Names
Preferred IUPAC name 2-Methylprop-1-ene
Other names 2-Methylpropene Isobutene γ-Butylene 2-Methylpropylene Methylpropene
Identifiers
CAS Number	115-11-7 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:43907 N
ChemSpider	7957 Y
ECHA InfoCard	100.003.697
EC Number	204-066-3
PubChem	8255
RTECS number	UD0890000
UNII	QA2LMR467H Y
UN number	1055 In Liquefied petroleum gas: 1075
InChI InChI=1S/C4H8/c1-4(2)3/h1H2,2-3H3 Y Key: VQTUBCCKSQIDNK-UHFFFAOYSA-N Y InChI=1/C4H8/c1-4(2)3/h1H2,2-3H3
SMILES CC(=C)C
Properties
Chemical formula	C4H8
Molar mass	56.106 g/mol
Appearance	Colorless gas
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)
Solubility in water	Insoluble
Magnetic susceptibility (χ)	-44.4·10−6 cm3/mol
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H220
GHS precautionary statements	P210, P377, P381, P403
EU classification (DSD)	Extremely flammable (F+)
R-phrases	R12
S-phrases	(S2), S9, S16, S33
NFPA 704	4 1 0
Flash point	flammable gas
Autoignition temperature	465 °C (869 °F; 738 K)
Explosive limits	1.8–9.6%
Related compounds
Related butenes	1-Butene cis-2-Butene trans-2-Butene
Related compounds	Isobutane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

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.