1,4-Dichlorobut-2-ene are organochlorine compounds with the formula ClCH2CH\dCHCH2Cl. Cis and trans isomers exist. These compounds are intermediates in the industrial production of chloroprene. They are main impurity in technical grade chloroprene.

Production of chloroprene

Chloroprene is a monomer for the production of synthetic rubbers such as Neoprene. It is produced from butadiene in a three-step process. The first step is the liquid- or vapour-phase chlorination of butadiene to a mixture of 3,4-dichlorobut-1-ene and 1,4-dichlorobut-2-ene (both isomers). In the second step, the mixture of 1,4-dichlorobut-2-ene and 3,4-dichlorobut-1-ene is isomerized to 3,4-dichlorobut-1-ene by heating to temperatures of 60–120 °C in the presence of a catalyst. Finally, dehydrochlorination (elimination of hydrogen chloride) of 3,4-dichlorobut-1-ene with dilute sodium hydroxide solution in the presence of polymerization inhibitors gives crude chloroprene.

Other reactions

1,4-Dichlorobut-2-ene is a precursor to various heterocycles. The (E)-isomer is also one of the starting materials for the poriferic natural product sceptrin.