1.

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.

Answer»

Solution :In aqueous solution, KOH is almost completely ionised to give `OH^(-)`ions which being a STRONG nucleophile brings about a substitution reaction on alkyl halides to FORM alcohols. Also, `OH^(-)`ions are highly solvated. This solvation reduces the basic character of `OH^(-)`ions which, therefore, fail to ABSTRACT a HYDROGEN from the `beta`-carbon of the alkyl chloride to form an alkene.
In contrast, an alcoholic solution of KOH contains ALKOXIDE `(RO^(-))` ions which is a much stronger base than `OH^(-)`ions. It preferentially eliminates a molecule of HCl from an alkyl chloride to form alkenes.


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