2-butene

2-Butene

cis trans
cis trans
Names
Preferred IUPAC name But-2-ene
Other names β-Butylene
Identifiers
CAS Number	107-01-7 Y 590-18-1 (cis) Y 624-64-6 (trans) Y
3D model (Jmol)	Interactive image (cis): Interactive image (trans): Interactive image
ChEBI	CHEBI:48363 Y
ChemSpider	11719 Y 4449912 (cis) N 56442 (trans) N
ECHA InfoCard	100.003.140
EC Number	203-452-9
PubChem	5287573 (cis) 62695 (trans)
RTECS number	EM2932000
UNII	S1SK37516R Y
InChI InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3 Y Key: IAQRGUVFOMOMEM-UHFFFAOYSA-N Y InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3 Key: IAQRGUVFOMOMEM-UHFFFAOYAW (cis): InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3- Key: IAQRGUVFOMOMEM-ARJAWSKDBO (trans): InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3+ Key: IAQRGUVFOMOMEM-ONEGZZNKBD (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
SMILES C(=CC)C (cis): C/C=C\C (trans): C/C=C/C
Properties
Chemical formula	C4H8
Molar mass	56.106 g/mol
Density	0.641 g/mL (cis, at 3.7 °C) 0.626 g/mL (trans, at 0.9 °C)
Melting point	-138.9 ºC (cis) -105.5 °C (trans)
Boiling point	3.7 ºC (cis) 0.9 °C (trans)
Magnetic susceptibility (χ)	-42.6·10−6 cm3/mol (cis) -43.3·10−6 cm3/mol (trans)
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H220
GHS precautionary statements	P210, P377, P381, P403
EU classification (DSD)	Extremely flammable (F+)
R-phrases	R12
S-phrases	(S2) S9 S16 S33
NFPA 704	4 1 0
Flash point	−72 °C (−98 °F)
Autoignition temperature	325 °C (617 °F; 598 K)
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).
N  (what is YN ?)
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, 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). 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.