Home > Community > Use of aqueous KOH and alcoholic KOH in dehydrohalogenation reactions [duplicate]
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Marchen Grith

Use of aqueous KOH and alcoholic KOH in dehydrohalogenation reactions [duplicate]

Bruce Heath  Follow

Aqueous $\ce{KOH}$ is alkaline in nature i.e. it dissociates to produce a hydroxide ion. These hydroxide ions act as a strong nucleophile and replace the halogen atom in an alkyl halide.

$$\ce{RCl + KOH (aq) -> ROH + KCl}$$

This results in the formation of alcohol molecules and the reaction is known as nucleophilic substitution reaction.

Alcoholic, $\ce{KOH}$, specially in ethanol, produces $\ce{C2H5O-}$ ions. The $\ce{C2H5O-}$ ion is a stronger base than the $\ce{OH-}$ ion. Thus,the former abstracts the ß-hydrogen of an alkyl halide to produce alkenes. This reaction is known as elimination reaction.

$$\ce{CH3CH2Br + KOH (alc) -> H2C=CH2 + KBr + H2O}$$

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James Byrd  Follow
A good answer would also mention the order of each reaction (SN1, SN2, E1, or E2) for completeness.More
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