But-2-ene is an acyclic
alkene with four
carbon atoms. It is the simplest alkene exhibiting
''cis''/''trans''-isomerism (also known as (''E''/''Z'')-isomerism); that is, it exists as two geometric
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
s ''cis''-but-2-ene ((''Z'')-but-2-ene) and ''trans-''but-2-ene ((''E'')-but-2-ene).
It is a
petrochemical, produced by the
catalytic cracking
Fluid Catalytic Cracking (FCC) is the conversion process used in petroleum refineries to convert the high-boiling point, high-molecular weight hydrocarbon fractions of petroleum (crude oils) into gasoline, olefinic gases, and other petroleum prod ...
of
crude oil
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...
or the dimerization of
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds).
Ethylene i ...
. Its main uses are in the production of
gasoline (petrol) and
butadiene,
[.] although some but-2-ene is also used to produce the solvent
butanone via
hydration to
2-butanol
2-Butanol, or ''sec''-butanol, is an organic compound with formula C H3CH( OH)CH2CH3. Its structural isomers are 1-butanol. isobutanol, and ''tert''-butanol. 2-Butanol is chiral and thus can be obtained as either of two stereoisomers designated ...
followed by
oxidation.
The two isomers are extremely difficult to separate by
distillation because of the proximity of their
boiling point
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
The boiling point of a liquid varies depending upon the surrounding envir ...
s (~4 °C for ''cis'' and ~1 °C for ''trans''
Chemical Safety Information from Intergovernmental Organizations
). However, separation is unnecessary in most industrial settings, as both isomers behave similarly in most of the desired reactions. A typical industrial but-2-ene mixture is 70% (''Z'')-but-2-ene (''cis''-isomer) and 30% (''E'')-but-2-ene (''trans''-isomer). Butane
Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name but ...
and but-1-ene are common impurities, present at 1% or more in industrial mixtures, which also contain smaller amounts of isobutene, butadiene and butyne.
References
External links
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{{DEFAULTSORT:Butene, 2-
Alkenes