The most reactive alcohol towards Lucas reagent is:
Correct answer: C. 2 - methyl - 2 - butanol
- A. 2 - butanol
- B. 2 - methyl - 1 - butanol
- C. 2 - methyl - 2 - butanol
- D. 2,2 - dimethyl - 1 - butanol
Explanation
The reactivity of alcohols towards Lucas reagent (a mixture of concentrated HCl and ZnCl₂) depends on the stability of the carbocation formed during the reaction. Alcohols react with Lucas reagent via an SN1 mechanism, where the rate-determining step is the formation of a carbocation after the hydroxyl group leaves.Tertiary alcohols form the most stable carbocations and react the fastest.Secondary alcohols are moderately reactive.Primary alcohols form the least stable carbocations and are the least reactive.Analysis of the options:2-butanol: A secondary alcohol; reacts slower than tertiary alcohols.2-methyl-1-butanol: A primary alcohol; reacts very slowly due to the instability of the primary carbocation.2-methyl-2-butanol: A tertiary alcohol; forms a highly stable tertiary carbocation, so it reacts the fastest.2,2-dimethyl-1-butanol: A primary alcohol; forms an unstable primary carbocation, so it reacts very slowly.Conclusion:2-methyl-2-butanol, being a tertiary alcohol, is the most reactive alcohol towards Lucas reagent.
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About Alcohols
Alcohols contain a hydroxyl group attached to a saturated carbon atom and are classified as primary, secondary or tertiary. Their nomenclature, hydrogen bonding, acidity, oxidation, dehydration, reaction with sodium and conversion to haloalkanes are covered, along with the distinction between alcohols and phenols, where the hydroxyl group is attached directly to an aromatic ring.
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