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 hydrophobic, and their odors are usually weak or ...

with the

chemical formula In chemistry, 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 symbol ...

. It is a four-carbon branched

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

(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 ''tert''-Butyl alcohol is the simplest tertiary alcohol, with a formula of (CH3)3COH (sometimes represented as ''t''-BuOH). Its isomers are 1-butanol, isobutanol, and butan-2-ol. ''tert''-Butyl alcohol is a colorless solid, which melts near r ...

(TBA) or

catalytic Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

dehydrogenation In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At ...

of isobutane (Catofin or similar processes).. Gasoline additives

methyl tert-butyl ether Methyl ''tertiary''-butyl ether (MTBE), also known as methyl tert-butyl ether and ''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 sol ...

(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 ethan ...

(ETBE), respectively, are produced by reacting methanol or

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

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 or Isobutylene is a byproduct in the

ethenolysis In organic chemistry, ethenolysis is a chemical process in which internal olefins are degraded using ethylene () as the reagent. The reaction is an example of cross metathesis. The utility of the reaction is driven by the low cost of ethylen ...

of diisobutylene to prepare

neohexene Neohexene is the hydrocarbon compound with the chemical formula . It is a colorless liquid, with properties similar to other hexenes. It is a precursor to commercial synthetic musk perfumes. Preparation and reactions Neohexene is prepared by ...

: :

\ce +  \longrightarrow \ce + \ce

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 sc ...

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

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

methacrolein Methacrolein, or methacrylaldehyde, is an unsaturated aldehyde. It is a clear, colorless, flammable liquid. Methacrolein is one of two major products resulting from the reaction of isoprene with OH in the atmosphere, the other product being ...

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 ho ...

(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 oxidat ...

(BHT) and

butylated hydroxyanisole Butylated hydroxyanisole (BHA) is a synthetic, waxy, solid petrochemical. Its antioxidant properties have caused it to be widely used as a preservative in food, food packaging, animal feed, cosmetics, pharmaceuticals, rubber, and petroleum produ ...

(BHA) are produced by Friedel-Crafts alkylation of

phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...

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

zeolite Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These p ...

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

s: :NH3 + CH2=C(CH3)2 -> H2NC(CH3)3

Safety

Isobutylene is a highly flammable gas.

References

External links

* * {{Hydrocarbons Alkenes

Production

Uses

Safety

See also

References

External links