What happens when a haloalkane is treated with alcoholic KOH under reflux?

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What happens when a haloalkane is treated with alcoholic KOH under reflux?

When a haloalkane is treated with alcoholic KOH under reflux, elimination takes precedence and you form an alkene. The strong base in an alcoholic solvent abstracts a beta-hydrogen, the carbon–halogen bond breaks as the electrons form a double bond, and the halide leaves as a halide ion. Heating helps push this dehydrohalogenation path, and the anti-periplanar arrangement often guides which hydrogen is removed to give the more substituted alkene (the usual Zaitsev outcome when possible). The alcoholic medium makes OH− a stronger base relative to a nucleophile, so substitution to alcohol is less favored under these conditions, while elimination to the alkene is promoted.

When a haloalkane is treated with alcoholic KOH under reflux, elimination takes precedence and you form an alkene. The strong base in an alcoholic solvent abstracts a beta-hydrogen, the carbon–halogen bond breaks as the electrons form a double bond, and the halide leaves as a halide ion. Heating helps push this dehydrohalogenation path, and the anti-periplanar arrangement often guides which hydrogen is removed to give the more substituted alkene (the usual Zaitsev outcome when possible). The alcoholic medium makes OH− a stronger base relative to a nucleophile, so substitution to alcohol is less favored under these conditions, while elimination to the alkene is promoted.

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