Question:
Which of the following alcohols on addition of Lucas reagent reacts fast and turns the reagent turbid instantly.
Which of the following alcohols on addition of Lucas reagent reacts fast and turns the reagent turbid instantly.
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Tertiary alcohols give the most stable carbocation, so the turbidity appears at once.
Updated On: Oct 1, 2026
- n - Butyl alcohol
- sec - Butyl alcohol
- iso - Butyl alcohol
- tert - Butyl alcohol
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Lucas reagent is anhydrous \(\text{ZnCl}_2\) in concentrated HCl. The alcohol is converted to an alkyl chloride, which is insoluble and makes the solution turbid.
Step 2: Reactivity:
The rate depends on the stability of the carbocation formed: tertiary > secondary > primary. Tertiary alcohols give turbidity instantly, secondary in about 5 minutes, and primary only on heating.
Step 3: Options:
n-Butyl alcohol and iso-butyl alcohol are primary. sec-Butyl alcohol is secondary. tert-Butyl alcohol is tertiary, so it reacts fastest.
Final Answer:
tert-Butyl alcohol, option (D). \[ \boxed{\text{tert-Butyl alcohol}} \]
Lucas reagent is anhydrous \(\text{ZnCl}_2\) in concentrated HCl. The alcohol is converted to an alkyl chloride, which is insoluble and makes the solution turbid.
Step 2: Reactivity:
The rate depends on the stability of the carbocation formed: tertiary > secondary > primary. Tertiary alcohols give turbidity instantly, secondary in about 5 minutes, and primary only on heating.
Step 3: Options:
n-Butyl alcohol and iso-butyl alcohol are primary. sec-Butyl alcohol is secondary. tert-Butyl alcohol is tertiary, so it reacts fastest.
Final Answer:
tert-Butyl alcohol, option (D). \[ \boxed{\text{tert-Butyl alcohol}} \]
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