2-Butene

{{chembox

|Verifiedfields = changed

|Watchedfields = changed

|verifiedrevid = 477212869

|Name = 2-Butene

|ImageFileL1 = Cis-2-Buten.svg

|ImageCaptionL1 = cis

|ImageFileR1 = Trans-2-Buten.svg

|ImageCaptionR1 = trans

|ImageFileL2 = Cis-but-2-ene-3D-balls.png

|ImageCaptionL2 = cis

|ImageFileR2 = Trans-but-2-ene-3D-balls.png

|ImageCaptionR2 = trans

|PIN = But-2-ene

|OtherNames = β-Butylene

|Section1 = {{Chembox Identifiers

|index1_label = (cis)

|index2_label = (trans)

|InChI = 1/C4H8/c1-3-4-2/h3-4H,1-2H3

|StdInChI_Ref = {{stdinchicite|correct|chemspider}}

|StdInChI = 1S/C4H8/c1-3-4-2/h3-4H,1-2H3

|InChIKey = IAQRGUVFOMOMEM-UHFFFAOYAW

|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

|StdInChIKey = IAQRGUVFOMOMEM-UHFFFAOYSA-N

|PubChem1 = 5287573

|ChemSpiderID1_Ref = {{chemspidercite|changed|chemspider}}

|ChemSpiderID1 = 4449912

|SMILES1 = C/C=C\C

|InChI1= 1S/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3-

|InChIKey1 = IAQRGUVFOMOMEM-ARJAWSKDSA-N

|PubChem2 = 62695

|ChemSpiderID2_Ref = {{chemspidercite|changed|chemspider}}

|ChemSpiderID2 = 56442

|SMILES2 = C/C=C/C

|InChI2 = 1S/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3+

|InChIKey2 = IAQRGUVFOMOMEM-ONEGZZNKSA-N

|ChEBI_Ref = {{ebicite|correct|EBI}}

|ChEBI = 48363

|ChEBI1 = 48366

|ChEBI2 = 48365

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = S1SK37516R

|UNII1_Ref = {{fdacite|correct|FDA}}

|UNII1 = L35ORC9C05

|UNII2_Ref = {{fdacite|correct|FDA}}

|UNII2 = 017NGL487F

|SMILES = C(=CC)C

|CASNo = 107-01-7

|CASNo_Ref = {{cascite|correct|CAS}}

|CASNo1 = 590-18-1

|CASNo1_Ref = {{cascite|correct|CAS}}

|CASNo2 = 624-64-6

|CASNo2_Ref = {{cascite|correct|CAS}}

|EC_number = 203-452-9

|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID = 11719

|RTECS = EM2932000 1718756

|Beilstein = 1718755 1361341

|Gmelin = 25196 1140 1141

}}

|Section2 = {{Chembox Properties

|Formula = C₄H₈

|MolarMass = 56.106 g/mol

|Density = 0.641 g/ml (cis, 3.7 °C){{GESTIS|ZVG=490242}}
0.626 g/ml (trans, 0.9 °C){{GESTIS|ZVG=490266}}

|MeltingPtC = -138.9

|MeltingPt_notes = (cis)
−105.5 °C (trans)

|BoilingPtC = 0.8 to 3.7

|BoilingPt_notes = (Z = 3.7 °C)
(E = 0.8 °C)

|MagSus = {{Plainlist|

• −42.6·10⁻⁶ cm³/mol (cis)
• −43.3·10⁻⁶ cm³/mol (trans)

}}

}}

|Section3 = {{Chembox Hazards

|Hazards_ref = {{ICSC-ref|03|97|name=cis-2-Butene|date=March 1996}}. {{ICSC-ref|03|98|name=trans-2-Butene|date=March 1996}}.

|GHSPictograms = {{GHS02|Flam. Gas 1}}{{GHS exclamation mark|Press. Gas}}

|GHSSignalWord = DANGER

|HPhrases = {{H-phrases|220}}

|PPhrases = {{P-phrases|210|377|381|403}}

|NFPA-H = 1

|NFPA-F = 4

|NFPA-R = 0

|FlashPtC = -72

|FlashPt_ref =

|AutoignitionPtC = 325

|AutoignitionPt_ref =

}}

|Section4 = {{Chembox Related

|OtherFunction = 1-Butene
cis-2-Butene
trans-2-Butene
Isobutene

|OtherFunction_label = butenes

|OtherCompounds = Butane
Butyne

}}

}}

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)-but-2-ene) and trans-2-butene ((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,{{SIDS-ref|id=107017|name=2-Butene|date=February 1995}}. although some 2-butene is also used to produce the solvent butanone via hydration reaction 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[http://www.inchem.org|InChem: Chemical Safety Information from Intergovernmental Organizations] {{webarchive|url=https://web.archive.org/web/20091209074235/http://www.inchem.org/ |date=December 9, 2009 }}). 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)-but-2-ene (cis-isomer) and 30% (E)-but-2-ene (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.