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NEET CHEMISTRYMedium

Given below are two statements: Statement I: In Lucas test, primary, secondary, and tertiary alcohols are distinguished on the basis of their reactivity with conc. HCl+ZnCl2HCl + ZnCl_2, known as Lucas Reagent. Statement II: Primary alcohols are most reactive and immediately produce turbidity at room temperature on reaction with Lucas Reagent.

In light of the above statements, choose the most appropriate answer from the options given below:

A

Statement I is incorrect but Statement II is correct.

B

Both Statement I and Statement II are correct.

C

Both Statement I and Statement II are incorrect.

D

Statement I is correct but Statement II is incorrect.

Step-by-Step Solution

  1. Statement I is Correct: The Lucas test differentiates alcohols based on their rate of reaction with the Lucas reagent (concentrated HClHCl and anhydrous ZnCl2ZnCl_2). The reaction involves the substitution of the hydroxyl group (-OH) with chloride (-Cl) to form an alkyl halide.
  2. Statement II is Incorrect: The reaction proceeds via a carbocation intermediate. Stability of carbocations is 3∘>2∘>1∘3^{\circ} > 2^{\circ} > 1^{\circ}. Consequently, the reactivity order is Tertiary > Secondary > Primary.
  • Tertiary alcohols react immediately, producing turbidity (due to insoluble alkyl halide) at room temperature.
  • Secondary alcohols take about 5 minutes to produce turbidity.
  • Primary alcohols do not react appreciably at room temperature and require heating to produce turbidity.
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