Butene

Butenes (including butylenes ) are a group of four isomeric hydrocarbons with the general empirical formula C4H8, which have a C-C double bond. They belong to the most alkenes. Two of the isomers differ in cis -trans isomerism.

Butenes are under standard conditions colorless, flammable gas with a density greater than air. Negative pressure can liquefy the isomers. You have narcotic effects and asphyxiation in high concentrations. With air to form an explosive mixture.

Structure and Properties

Thermodynamic properties

Butenes are easily liquefied gases whose application and implementation is often carried out at elevated pressure as a liquid or in the supercritical state.

Synthesis

Michael Faraday discovered in 1825 as butenes gaseous component in the distillation of crude oil (see also: LPG ). Butenes can be obtained by cracking of petroleum as a mixture of isomers. They are obtained by thermal reaction ( dehydration ) of n -butane or isobutane.

Use

Due to the CC double bond they are interesting and important starting materials for chemical syntheses. They are used for the preparation of compounds such as 2- butanol, 2 -butanone is used ( by oxo - synthesis) and 1,3-butadiene and a starting material for preparation of plastics (for example, butyl rubber and polyisobutylene ). Suitable alkylating agents they serve, for example, for the synthesis of additives for anti-knock fuels ( 2,2,4- trimethylpentane ( isooctane) ). Isobutene is for the synthesis of methyl tert- butyl ether (MTBE ) or ethyl tert -butyl ether ( ETBE), are required. And tert-butyl ester can be prepared via the reaction of acids and isobutene ( carbon). This synthesis route offers specifically appropriate when in the esterification with tert -butanol as a competing reaction dominated by dehydration.