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2-Butene

2-Butene
Names Preferred IUPAC name
But-2-ene
Other names
β-Butylene
Identifiers
3D model (JSmol)
1718755 1361341 ChEBI
ChemSpider
ECHA InfoCard100.003.140EC Number
  • 203-452-9
25196 1140 1141
RTECS number
  • EM2932000 1718756
UNII
  • InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3
    Key: IAQRGUVFOMOMEM-UHFFFAOYSA-N
  • InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3
    Key: IAQRGUVFOMOMEM-UHFFFAOYAW
  • (cis): InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3-
    Key: IAQRGUVFOMOMEM-ARJAWSKDSA-N
  • (trans): InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3+
    Key: IAQRGUVFOMOMEM-ONEGZZNKSA-N
  • C(=CC)C
  • (cis): C/C=C\C
  • (trans): C/C=C/C
Properties C4H8Molar mass56.108 g·mol Density0.641 g/ml (cis, 3.7 °C)
0.626 g/ml (trans, 0.9 °C) Melting point−138.9 °C (−218.0 °F; 134.2 K) (cis)
−105.5 °C (trans) Boiling point0.8 to 3.7 °C (33.4 to 38.7 °F; 273.9 to 276.8 K) (Z = 3.7 °C)
(E = 0.8 °C)
  • −42.6·10 cm/mol (cis)
  • −43.3·10 cm/mol (trans)
Hazards GHS labelling: DangerH220P210, P377, P381, P403NFPA 704 (fire diamond)
1
4
0
Flash point−72 °C (−98 °F; 201 K) 325 °C (617 °F; 598 K) Related compounds
Related butenes
1-Butene
cis-2-Butene
trans-2-Butene
Isobutene
Related compounds
Butane
Butyne
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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2-Butene 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 isomerscis-2-butene ((Z)-but-2-ene) and trans-2-butene ((E)-but-2-ene).

It is a petrochemical, produced by the catalytic cracking of crude oil or the dimerization of ethylene. Its main uses are in the production of high-octanegasoline (petrol) on alkylation units and butadiene, although some 2-butene is also used to produce the solvent butanone via hydration reaction to 2-butanol followed by oxidation.

The two isomers are extremely difficult to separate by distillation because of the proximity of their boiling points (~4 °C for cis and ~1 °C for trans). However, separation is unnecessary in most industrial settings, as both isomers behave similarly in most of the desired reactions. A typical industrial 2-butene mixture is 70% (Z)-but-2-ene (cis-isomer) and 30% (E)-but-2-ene (trans-isomer). Butane and 1-butene are common impurities, present at 1% or more in industrial mixtures, which also contain smaller amounts of isobutene, butadiene and butyne.

Wikipedia source