Before You Begin

Question #45084

Difficulty: 8/10 | 🟢 Free

The Question

Consider the acid-catalyzed Fischer esterification of the following 2,6-disubstituted benzoic acids (s) with excess $\ce{CH3OH}$ (l) in the presence of catalytic $\ce{H2SO4}$ at 298 K: (I) 2,6-Difluorobenzoic acid (II) 2,6-Dimethoxybenzoic acid (III) 2,6-Dichlorobenzoic acid (IV) 2,6-Dimethylbenzoic acid

Let $k_1, k_2, k_3,$ and $k_4$ be their respective initial rate constants. Which of the following represents the correct decreasing order of the esterification rates?

Options

A.
$k_1 > k_2 > k_3 > k_4$
B.
$k_3 > k_1 > k_2 > k_4$
C.
$k_4 > k_2 > k_3 > k_1$
D.
$k_1 > k_3 > k_4 > k_2$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Cahn-Ingold-Prelog (CIP) Priority|Esterification Steric Hindrance

Why This Question Is Tricky

Common Mistakes

This question tests the 'Ortho Effect' in esterification kinetics.

Students often erroneously apply electronic effects (predicting EWGs accelerate and EDGs decelerate the reaction, leading to $k_1 > k_3 > k_4 > k_2$ ) or correlate rates with CIP priority.

The hidden variable is that the transition state geometry is entirely gated by steric B-strain.

Furthermore, students must correctly evaluate the effective steric bulk of $\ce{-OCH3}$ versus $\ce{-Cl}$ , recognizing that the conformational flexibility of the methoxy group makes it less sterically demanding than a chlorine atom at the ortho position.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2
Concept	Cahn-Ingold-Prelog (CIP) Priority
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free