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Chemistry · Alcohols, Ethers and Phenols

NEET (UG) 2024 — Question 77

Which one of the following alcohols reacts instantaneously with Lucas reagent?

  1. Option A:
    Option A figure
  2. Option B:
    Option B figure
  3. Option C:
    Option C figure
  4. Option D:
    Option D figure
    Correct
  5. Option E:
    CH3−CH2−CH2−CH2OH\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2\text{OH}
  6. Option F:
    CH3−CH2−CH−OH∣CH3\begin{array}{c} \text{CH}_3 - \text{CH}_2 - \text{CH} - \text{OH} \\ \mid \\ \text{CH}_3 \end{array}
  7. Option G:
    CH3−CH−CH2OH∣CH3\begin{array}{c} \text{CH}_3 - \text{CH} - \text{CH}_2\text{OH} \\ \mid \\ \text{CH}_3 \end{array}
  8. Option H:
    CH3∣CH3−C−OH∣CH3\begin{array}{c} \text{CH}_3 \\ \mid \\ \text{CH}_3 - \text{C} - \text{OH} \\ \mid \\ \text{CH}_3 \end{array}
    Correct

Answer: D, H

Step-by-step solution

Lucas reagent is a mixture of concentrated HCl\ce{HCl} and anhydrous ZnClX2\ce{ZnCl2}. With Lucas reagent, alcohols react via SN1S_N1 substitution, and the rate depends on carbocation stability. Tertiary alcohols form the most stable tertiary carbocations, so they react instantaneously, giving immediate turbidity due to the insoluble alkyl chloride. Among the options, D is (CHX3)X3COH\ce{(CH3)3COH} (2-methylpropan-2-ol), which is a tertiary alcohol. Therefore, the alcohol that reacts instantaneously with Lucas reagent is D.

Answer key and solution verified before publishing.

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Exam
NEET (UG) 2024
Paper
2024 paper
Subject
Chemistry
Chapter
Alcohols, Ethers and Phenols
Topic
Physical properties, Tests & Uses of alcohols
Which one of the following alcohols reacts instantaneously with Lucas… | NEET (UG) 2024 PYQ with Solution · DhiX AI