Before You Begin

Question #44435

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following multi-step reaction sequence performed on 4-acetylbenzoic acid:

$\ce{4-Acetylbenzoic acid ->[\text{1. } \ce{CH3MgBr} \text{ (1.0 eq), THF, 273 K}][\text{2. } \ce{CH3I} \text{ (1.0 eq), DMF, } \Delta] \text{Intermediate } X ->[\ce{NaBH4} \text{ (excess)}][\ce{CH3OH}, \text{ 298 K}] \text{Major Product } Y }$

Identify the major organic product $Y$ .

Options

A.
Methyl 4-(1-hydroxyethyl)benzoate (Racemic)
B.
Methyl 4-(2-hydroxypropan-2-yl)benzoate
C.
4-(2-methoxypropan-2-yl)benzoic acid
D.
4-(1-hydroxyethyl)benzyl alcohol (Racemic)

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Nucleophilic Addition Sterics|Grignard Reagent Sensitivity|Carboxylic Acid Strength

Why This Question Is Tricky

Common Mistakes

This problem tests the kinetic hierarchy of Grignard reagents and chemoselectivity.

Students often impulsively attack the electrophilic ketone carbonyl with the Grignard reagent (forming a tertiary alcohol).

However, the acid-base reaction with the carboxylic acid proton is kinetically superior.

By strictly limiting the Grignard reagent to 1.0 equivalent, the nucleophilic addition path is rendered moot.

The subsequent steps test the SN2 reactivity of the resulting carboxylate salt and the chemoselective reduction limits of NaBH4 (which reduces ketones but leaves esters intact).

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Aldehydes, Ketones, and Carboxylic Acids - Class 12
Concept	Nucleophilic Addition Sterics
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free