The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presence of alcoholic KOH, alkenes are major products. Explain.

Explanation

In aqueous KOH, KOH is almost completely ionized to give `OH^(-)` ions. The `OH^(-)` being strong nucleophile, results into substitution reaction on alkyl chlorides to form alcohols. Moreover, in aqueous solution, the `OH^(-)` ions are highly hydrated (solvated). The hydration reduces the basic character of `OH^(-)` ions which therefore, fails to abstract a hydrogen from the `beta`-carbon of the alkyl chloride to form an alkene.
On the other hand, an alcoholic solution of KOH contains alkoxide (`RO^(-)`) ions which being stronger base than `OH^(-)` ions preferentially eliminates a molecule of HCl from an alkyl halide to form alkenes.