| 2-Butene | |
|---|---|
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But-2-ene |
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Other names
β-Butylene |
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| Identifiers | |
| CAS number | 107-01-7 |
| ChemSpider | 11719 |
| UNII | S1SK37516R |
| EC-number | 203-452-9 |
| ChEBI | CHEBI:48363 |
| RTECS number | EM2932000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C4H8 |
| Molar mass | 56.106 g/mol |
| Melting point |
-139°C |
| Boiling point |
0.88 °C, 274 K, 34 °F |
| Hazards[1] | |
| GHS pictograms | |
| GHS signal word | DANGER |
| GHS hazard statements | H220 |
| GHS precautionary statements | P210, P377, P381, P403 |
| EU Index | 601-012-00-4 |
| EU classification | Extremely flammable (F+) |
| R-phrases | R12 |
| S-phrases | (S2) S9 S16 S33 |
| NFPA 704 |
4
1
0
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| Flash point | flammable gas |
| Autoignition temperature |
324 °C (615 °F) |
| Related compounds | |
| Related butenes | 1-Butene cis-2-Butene trans-2-Butene Isobutene |
| Related compounds | Butane Butyne |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 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 geometrical isomers cis-2-butene ((Z)-2-butene), shown at the right, and trans-2-butene ((E)-2-butene), not shown.
It is a petrochemical, produced by the catalytic cracking of crude oil. Its main uses are in the production of gasoline (petrol) and butadiene,[2] 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[3]). The more elongated trans-molecule which has a tougher job to get its tail free from the liquid has the higher boiling point, the more rounded cis isomer escapes easier, thus having a lower boiling point. 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.[2]