If aqueous solution, KOH is almost completely ionized to give `OH^(-)` ions which being a strong nucleophile brings about a substitution reaction on alkyl halides to form alcohols. Further in the aqueous solution, `OH^(-)`ions are highly solvated (hydrated). This solvation reduces the basic character of `OH^(-)` ions which, therefore, fails to abstract a hydrogen from the p-carbon of the alkyl chloride to form alkenes. ln contrast, an alcoholic solution of KOH contains alkoxide `(RO^(-))` ion which being a much stronger base than `OH^(-)` ions perferentially eliminates of HCl from an alkyl chloride to form alkenes.
