2-Butene

2-Butene
cis
trans
cis
trans
Names
Preferred IUPAC name
But-2-ene
Other names
β-Butylene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.003.140
EC Number 203-452-9
RTECS number EM2932000
UNII
Properties
C4H8
Molar mass 56.106 g/mol
Density 0.641 g/mL (cis, at 3.7 °C)[1]
0.626 g/mL (trans, at 0.9 °C)[2]
Melting point -138.9 ºC (cis)[1]
-105.5 °C (trans)[2]
Boiling point 3.7 ºC (cis)[1]
0.9 °C (trans)[2]
  • -42.6·10−6 cm3/mol (cis)
  • -43.3·10−6 cm3/mol (trans)
Hazards[3]
GHS pictograms
GHS signal word DANGER
H220
P210, P377, P381, P403
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propaneHealth code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
4
1
0
Flash point −72 °C (−98 °F)[1][2]
325 °C (617 °F; 598 K)[1][2]
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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Infobox references

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,[4] 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[5]). 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.[4]

References

  1. 1 2 3 4 5 Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  2. 1 2 3 4 5 Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  3. ↑ cis-2-Butene, International Chemical Safety Card 0397, Geneva: International Programme on Chemical Safety, March 1996 . trans-2-Butene, International Chemical Safety Card 0398, Geneva: International Programme on Chemical Safety, March 1996 .
  4. 1 2 2-Butene (PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, February 1995 .
  5. ↑ Chemical Safety Information from Intergovernmental Organizations Archived December 9, 2009, at the Wayback Machine.
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