Isobutylene (or 2-methylpropene) is a

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

. It is a four-carbon branched

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

(olefin), one of the four

isomers of butylene Butene, also known as butylene, is an alkene with the formula . The word ''butene'' may refer to any of the individual compounds. They are colourless gases that are present in crude oil as a minor constituent in quantities that are too small for ...

. It is a colorless flammable gas, and is of considerable industrial value.

Production

Polymer and chemical grade isobutylene is typically obtained by dehydrating tertiary butyl alcohol (TBA) or

catalytic Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...

dehydrogenation of isobutane.. Gasoline additives

methyl tert-butyl ether Methyl ''tert''-butyl ether (MTBE), also known as ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used a ...

(MTBE) and

ethyl tert-butyl ether Ethyl ''tertiary''-butyl ether (ETBE), also known as ethyl ''tert''-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than eth ...

(ETBE), respectively, are produced by reacting

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

with isobutylene contained in butene streams from olefin steam crackers or refineries, or with isobutylene from dehydrated TBA. Isobutylene is not isolated from the olefin or refinery butene stream before the reaction, as separating the ethers from the remaining butenes is simpler. Isobutylene can also be produced in high purities by "back-cracking" MTBE or ETBE at high temperatures and then separating the isobutylene by distillation from methanol. Isobutylene is a byproduct in the ethenolysis of

diisobutene Diisobutene (also known as Diisobutylene and Isooctene) refers to a pair of organic compounds with the overall formula C8H16. The isomers have the same carbon skeleton but differ in the location of the C=C bond. Both are colorless liquids with ver ...

to prepare neohexene: :(CH₃)₃C-CH=C(CH₃)₂ + → (CH₃)₃C-CH= + (CH₃)₂C=

Uses

Isobutylene is used in the production of a variety of products. It is alkylated with butane to produce

isooctane 2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH3)3CCH2CH(CH3)2. It is one of several isomers of octane (C8H18). This particular isomer is the standard 100 point on the octane rating scal ...

or dimerized to diisobutylene (DIB) and then hydrogenated to make

, a fuel additive. Isobutylene is also used in the production of methacrolein.

Polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...

of isobutylene produces

butyl rubber Butyl rubber, sometimes just called butyl, is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the homop ...

(polyisobutylene or PIB). Antioxidants such as

butylated hydroxytoluene Butylated hydroxytoluene (BHT), also known as dibutylhydroxytoluene, is a lipophilic organic compound, chemically a derivative of phenol, that is useful for its antioxidant properties. BHT is widely used to prevent free radical-mediated oxidation ...

(BHT) and butylated hydroxyanisole (BHA) are produced by Friedel-Crafts alkylation of

phenol Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire. The molecule consists of a phenyl group () ...

s with isobutylene. ''tert''-Butylamine is produced commercially by amination of isobutylene using

zeolite Zeolites are a group of several microporous, crystalline aluminosilicate minerals commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a meta ...

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

s: : Applications are found in the calibration of photoionization detectors.

Safety

Isobutylene is a highly flammable gas.

References

External links

* * {{Hydrocarbons Alkenes

Production

Uses

Safety

See also

References

External links