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Butene, also known asbutylene, is analkene with the formulaC4H8. The wordbutene may refer to any of the individual compounds. They are colourless gases that are present incrude oil as a minor constituent in quantities that are too small for viable extraction. Butene is therefore obtained bycatalytic cracking of long-chain hydrocarbons left during refining of crude oil. Cracking produces a mixture of products, and the butene is extracted from this byfractional distillation.[1]
Butene can be used as themonomer forpolybutene, but thispolymer is more expensive than alternatives with shorter carbon chains such aspolypropylene. Polybutene is therefore used in more specialized applications. Butenes are more commonly used to make copolymer (mixed with another monomer such as ethylene).
Butenes are major constituents ofraffinates, the C4 fractions in oil processing. The raffinates containing butadiene are considered carcinogenic and mutagenic.[2] They can be used asfeedstocks for further processing (e. g., onalkylation units), or used as industrial fuel. Their mixing intoLPG for nonindustrial uses sometimes occurs but is generally prohibited.[3]
Among the molecules which have thechemical formulaC4H8 fourisomers arealkenes. All four of thesehydrocarbons have fourcarbonatoms and onedouble bond in theirmolecules, but have differentchemical structures. TheIUPAC and common names, respectively, of thesechemical compounds are:
| Common name(s) | IUPAC name | Structure | Skeletal formula | 3D model |
|---|---|---|---|---|
| 1-butene, α-butylene | But-1-ene |  |  |  |
| cis-2-butene,cis-β-butylene | (2Z)-but-2-ene |  |  |  |
| trans-2-butene,trans-β-butylene | (2E)-but-2-ene |  |  |  |
| isobutene, isobutylene | 2-methylprop-1-ene |  |  |  |
In the chemical structures above, the small blue numbers in the structure images are the numbering of the atoms in the main backbone chain of the molecules. Other organic compounds have the formula C4H8, namelycyclobutane andmethylcyclopropane, but are not alkenes and do not fall under the namebutene. There are also cyclic alkenes with four carbon atoms overall such ascyclobutene and two isomers ofmethylcyclopropene, but they do not have the formula C4H8 and are not discussed here.
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