Elimination Reaction

In an elimination reaction a halogenoalkane loses a molecule of hydrogen halide (HX) and forms an alkene. The hydrogen and the halogen are removed from neighbouring carbon atoms.The reagent is potassium hydroxide dissolved in ethanol, and the mixture is heated. In these conditions the hydroxide ion acts as a base, removing a proton, rather than as a nucleophile.For example: CH₃CH₂Br + KOH → CH₂=CH₂ + KBr + H₂O.If the halogen is not at the end of the chain, more than one alkene can form. 2-bromobutane gives a mixture of but-1-ene and but-2-ene, and but-2-ene can exist as E and Z isomers.Elimination is a useful way to make alkenes, which can then be used to make polymers.