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Question #44915

Difficulty: 8/10 | 🟢 Free

The Question

Consider the azo coupling reactions of 3-aminophenol with benzenediazonium chloride ( $\ce{PhN2+Cl-}$ ) under two different pH conditions at $273-278\text{ K}$ :

Reaction I: 3-aminophenol + $\ce{PhN2+Cl-} \xrightarrow{\text{pH} = 4.5}$ Major Product $\mathbf{P}$

Reaction II: 3-aminophenol + $\ce{PhN2+Cl-} \xrightarrow{\text{pH} = 9.5}$ Major Product $\mathbf{Q}$

Identify the correct IUPAC names for the major products $\mathbf{P}$ and $\mathbf{Q}$ .

Options

A.
$\mathbf{P}$ : 5-amino-2-(phenyldiazenyl)phenol ; $\mathbf{Q}$ : 3-amino-4-(phenyldiazenyl)phenol
B.
$\mathbf{P}$ : 3-amino-4-(phenyldiazenyl)phenol ; $\mathbf{Q}$ : 5-amino-2-(phenyldiazenyl)phenol
C.
$\mathbf{P}$ : 3-amino-2-(phenyldiazenyl)phenol ; $\mathbf{Q}$ : 3-amino-4-(phenyldiazenyl)phenol
D.
$\mathbf{P}$ : 5-amino-2-(phenyldiazenyl)phenol ; $\mathbf{Q}$ : 3-amino-2-(phenyldiazenyl)phenol

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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

Electrophilic Substitution Control|Azo Coupling Regioselectivity|Coupling Reactivity

Why This Question Is Tricky

Common Mistakes

The core trap tests the student's understanding of pH-dependent chemoselectivity and steric control in Electrophilic Aromatic Substitution.

Students often memorize that $\ce{-OH}$ or $\ce{-NH2}$ are activating, but fail to account for their pH-dependent ionization states ( $\ce{-O-}$ vs $\ce{-OH}$ , and $\ce{-NH2}$ vs $\ce{-NH3+}$ ).

Furthermore, they must apply the steric constraint of the bulky diazonium electrophile, which heavily favors para coupling over ortho coupling, avoiding the highly hindered position 2 between the two substituents.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Electrophilic Substitution Control
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free