Question #bbbea

1 Answer
Dec 19, 2017

Aqueous KOH gives alcohols because of substitution reaction. While alcoholic KOH gives alkenes due to elimination reaction.

Explanation:

Alkyl chlorides with Aq.KOH :--
When an alkyl chlorides treated with Aq.KOH in solution KOH is almost ionized to give OH— ions which being a strong nucleophile, brings about a substitution reaction and give alcohols.

Ex. RCl+KOH(Aq) =ROH+KCl

Alkyl chlorides with alco.KOH :--
In contrast,an alcoholic solution of KOH contains alkoxide (RO–) ions which being a much stronger base than OH- ions eliminates a mol ecule of HCl from an alkyl chlorides to form alkenes.

Ex. CH3CH2CH2Cl+KOH(alc.) = CH3CH=CH2 +HCl