JEE Main · 2013 · 07 Apr 2013 · Offline · Alcohols Phenols and Ethers

WhatsApp Email

An unknown alcohol is treated with the "Lucas reagent" to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism:

(A)tertiary alcohol by $S_{N} 1$ ✓ Correct
(B)secondary alcohol by $S_{N} 2$
(C)tertiary alcohol by $S_{N} 2$
(D)secondary alcohol by $S_{N} 1$

Answer: (A)

Solution

The Lucas reagent,

HCl

with

ZnCl X_{2}

, works by letting the alcohol ionise to a carbocation along an

S_{N} 1

path, so the quicker a stable carbocation forms the sooner the turbidity appears. The tertiary carbocation is the most stable of the three, so a tertiary alcohol reacts fastest, by the

S_{N} 1

mechanism.

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option

Practise more: all JEE Main PYQs on Alcohols Phenols and Ethers →

More JEE Main questions on Alcohols Phenols and Ethers

Given below are two statements :

Statement I: Phenol on treatment with $CHCl_{3} /$ aq. KOH under refluxing condition, followed by acidification produces $p$ -hydroxy benzladehyde as the major product and $o$ -hydroxy benzaldehyde as the minor product.

Statement II …
JEE Main 2026View solution →
3,3-Dimethyl-2-butanol cannot be prepared by:
A.
B.
C.
D.
E.
Choose the correct answer from the options given below:
JEE Main 2026View solution →
A mixed ether ( P ), when heated with excess of hot concentrated hydrogen iodide produces two different alkyl iodides which when treated with aq. NaOH give compounds (Q) and (R). Both (Q) and (R) give yellow precipitate with NaOI. Identify the mixed ether (P):
JEE Main 2026View solution →
Consider the following two reactions A and B .
(A) (see structure)
(B) (see structure)

Numerical value of [molar mass of $x +$ molar mass of y ] is ______。
JEE Main 2026View solution →
From the following, how many compounds contain at least one secondary alcohol?
JEE Main 2026View solution →
Consider the following reaction sequence

vapour density 47]
Compound (y) develops characteristic colour with neutral $FeCl_{3}$ solution.
Identify the INCORRECT statement from the following for the above sequence.
JEE Main 2026View solution →