Fundamentholfundamenthol
NEET2022Chemistry
Q.

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 + ZnCl, known as Lucas Reagent.

Statement II:

Primary alcohols are most reactive and immediately produce turbidity at room temperature on reaction with Lucas Reagent.

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

  1. A

    Both Statement I and Statement II are incorrect.

  2. B

    Statement I is correct but Statement II is incorrect.

  3. C

    Statement I is incorrect but Statement II is correct

  4. D

    Both Statement I and Statement II are correct

Solution

The Lucas test does distinguish 1, 2, and 3 alcohols by their rates of reaction with conc. HCl and ZnCl, so Statement I is correct.

The reaction proceeds via a carbocation intermediate. Tertiary carbocations are most stable, so 3 alcohols give immediate turbidity, 2 alcohols react within about 5 minutes, and 1 alcohols essentially do not react at room temperature.

Statement II reverses the reactivity order; primary alcohols are the least reactive, not the most. So Statement II is incorrect.

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