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Chemistry Question 66 – JEE-MAIN 2025

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Given below are two statements : Statement (I) : Alcohols are formed when alkyl chlorides are treated with aqueous potassium hydroxide by elimination reaction. Statement (II) : In alcoholic potassium hydroxide, alkyl chlorides form alkenes by abstracting the hydrogen from the β-carbon. In the light of the above statements, choose the most appropriate answer from the options given below :

The nature of the solvent (aqueous vs. alcoholic) significantly influences the reaction pathway of alkyl halides with potassium hydroxide.

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Ninja Strategy•Reagent-Mechanism Mapping

Quickly recall that aqueous KOH leads to substitution (alcohols) and alcoholic KOH leads to elimination (alkenes), then check if the statements correctly map the products and mechanisms.

Step 1: Differentiate between aqueous and alcoholic KOH reactions✦ Active

Aqueous potassium hydroxide (KOH(aq)) acts as a nucleophile, promoting nucleophilic substitution reactions with alkyl halides to form alcohols.

Alcoholic potassium hydroxide (KOH(alc)) acts as a strong base, promoting elimination reactions (dehydrohalogenation) with alkyl halides to form alkenes.

Step 2: Evaluate Statement (I)○ Expand

Statement (I) claims that alcohols are formed from alkyl chlorides with aqueous KOH by elimination reaction. While alcohols are formed, the reaction mechanism is nucleophilic substitution, not elimination. Therefore, Statement (I) is incorrect.

Step 3: Evaluate Statement (II)○ Expand

Statement (II) states that in alcoholic KOH, alkyl chlorides form alkenes by abstracting hydrogen from the β-carbon. This accurately describes the elimination reaction (dehydrohalogenation) mechanism. Therefore, Statement (II) is correct.

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