In β-elimination, under the influence of a highly basic metal hydroxide mixed with ethanol, here alcoholic KOH the halogen atom attached to the α-carbon atom and a hydrogen atom attached to the β-carbon atom are removed, resulting in the formation of alkene. KOH (alcoholic potash) is a dehydrohalogenation agent that interacts with an alkyl halide to produce an alkene.
When 1-Chlorobutane reacts with alcoholic potash, the hydrogen atom from the β-carbon is removed. Also, halogen is a leaving group in this reaction and chlorine which is a type of halogen is removed from 1-Chlorobutane, resulting in the formation of 1-butene. The chemical reaction is: