In elimination reactions, the reactivity of alkyl halides is in decreasing order:

When haloalkanes with beta -hydrogen atom are boiled with alcoholic solution of KOH, they undergo elimination of hyarogen halide resulting in the formation of alkenes. These reactions are called beta -elimination reactions or dehydrohalogenation reactions. These reactions follow Saytzeff's rule. Substitution and elimination reactions often compete with each other. Mostly bases behave as nucleophiles and therefore can engage in substitution or elimination reactions depending upon the alkyl halide and the reaction conditions. In the elimination reactions, the reactivity of alkyl halides follow the sequence

The most reactive alkyl halide is :

In Wurtz reaction of alkyl halides, the reactivity of alkyl halides follows the decreasing order,

The reactivity of alkyl halides for Wurtz reaction is: