But-2-ene
- Interactive image
- (cis): Interactive image
- (trans): Interactive image
- CHEBI:48363 checkY
- (cis): CHEBI:48366
- (trans): CHEBI:48365
- 203-452-9
- EM2932000 1718756
- S1SK37516R checkY
- (cis): L35ORC9C05 checkY
- (trans): 017NGL487F checkY
- InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3 checkYKey: IAQRGUVFOMOMEM-UHFFFAOYSA-N checkY
- InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3Key: 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
- −42.6·10−6 cm3/mol (cis)
- −43.3·10−6 cm3/mol (trans)
- Health 1: Exposure would cause irritation but only minor residual injury. E.g. turpentine
- Flammability 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. propane
- Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen
- Special hazards (white): no code
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 isomers 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 of crude oil or the dimerization of ethylene. Its main uses are in the production of high-octane gasoline (petrol) on alkylation units and butadiene,[4] although some but-2-ene is also used to produce the solvent butanone via hydration reaction to butan-2-ol 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 but-2-ene mixture is 70% (Z)-but-2-ene (cis-isomer) and 30% (E)-but-2-ene (trans-isomer). Butane 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.[4]
References
[edit ]- ^ a b c d e Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
- ^ a b c d e Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
- ^ 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.
- ^ a b 2-Butene (PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, February 1995.
- ^ Chemical Safety Information from Intergovernmental Organizations Archived December 9, 2009, at the Wayback Machine