|Preferred IUPAC name
3D model (JSmol)
|25196 1140 1141|
CompTox Dashboard (EPA)
|Molar mass||56.106 g/mol|
|Density||0.641 g/mL (cis, at 3.7 °C)|
0.626 g/mL (trans, at 0.9 °C)
|Melting point|| −138.9 °C (−218.0 °F; 134.2 K) (cis)|
-105.5 °C (trans)
|Boiling point|| 0.8 to 3.7 °C (33.4 to 38.7 °F; 273.9 to 276.8 K) (Z = 3.7 °C)|
(E = 0.8 °C)
|GHS Signal word||Danger|
|P210, P377, P381, P403|
|NFPA 704 (fire diamond)|
|Flash point||−72 °C (−98 °F)|
|325 °C (617 °F; 598 K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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 isomers cis-2-butene ((Z)-2-butene) and trans-2-butene ((E)-2-butene).
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 gasoline (petrol) and butadiene, although some 2-butene is also used to produce the solvent butanone via hydration 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)-2-butene (cis-isomer) and 30% (E)-2-butene (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.