But-2-ene

But-2-ene Other names 2-Butene β-Butylene Identifiers InChI InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3 InChIKey IAQRGUVFOMOMEM-UHFFFAOYAW Standard InChI InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3 Standard InChIKey IAQRGUVFOMOMEM-UHFFFAOYSA-N CAS number [107-01-7] EC number 203-452-9 ChemSpider 11719 Properties Chemical formula C4H8 Molar mass 56.106 g/mol Hazards EU index number 601-012-00-4 GHS pictograms GHS signal word DANGER GHS hazard statements H220 GHS precautionary statements P210, P377, P381, P403 Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

(E)-But-2-ene Other names trans-But-2-ene Identifiers InChI InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3+ InChIKey IAQRGUVFOMOMEM-ONEGZZNKBD Standard InChI InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3+ Standard InChIKey IAQRGUVFOMOMEM-ONEGZZNKSA-N CAS number [624-64-6] EC number 210-855-3 ChemSpider 56442 Properties Chemical formula C4H8 Molar mass 56.106 g/mol Melting point −105.5 ºC Boiling point 0.9 ºC Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

(Z)-But-2-ene Other names cis-But-2-ene Identifiers InChI InChI=1/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3- InChIKey IAQRGUVFOMOMEM-ARJAWSKDBO Standard InChI InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3/b4-3- Standard InChIKey IAQRGUVFOMOMEM-ARJAWSKDSA-N CAS number [590-18-1] EC number 209-673-7 ChemSpider 4449912 Properties Chemical formula C4H8 Molar mass 56.106 g/mol Melting point −138.9 ºC Boiling point 3.7 ºC Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

But-2-ene is an acyclic alkene with four carbon atoms. It is the simplest alkene to shown (E/Z)-isomerism (also known as cis/trans-isomerism).

It is a petrochemical, produced by the catalytic cracking of crude oil. Its main uses are in the production of gasoline (petrol) and butadiene, although some but-2-ene is also used to produce the solvent butanone (methyl ethyl ketone, MEK) via hydration to butan-2-ol and oxidation.

The two isomers are extremely difficult to separate by distillation because of the proximity of their boiling points. Fortunately, separation is unnecessary in industrial usage, as both isomers behave similarly in 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 (ethylacetylene).

External links

• SIDS Initial Assessment Report for 2-Butene from the Organisation for Economic Co-operation and Development (OECD)