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Question #44352

Difficulty: 8/10 | 🟢 Free

The Question

Compound \textbf{P} (3-hydroxybenzoic acid) is treated with excess aqueous bromine to yield a tribrominated aromatic compound \textbf{Q}. \textbf{Q} is then subjected to two separate reactions: Reaction 1: \textbf{Q} is heated with excess $\ce{CH3OH}$ and a catalytic amount of concentrated $\ce{H2SO4}$ to give \textbf{R}. Reaction 2: \textbf{Q} is treated with one equivalent of diazomethane ( $\ce{CH2N2}$ ) in ether to give \textbf{S}. Identify \textbf{R} and \textbf{S}.

Options

A.
\textbf{R}: 2,4,6-tribromo-3-hydroxybenzoic acid, \textbf{S}: methyl 2,4,6-tribromo-3-hydroxybenzoate
B.
\textbf{R}: methyl 2,4,6-tribromo-3-hydroxybenzoate, \textbf{S}: methyl 2,4,6-tribromo-3-hydroxybenzoate
C.
\textbf{R}: 2,4,6-tribromophenol, \textbf{S}: 2,4,6-tribromoanisole
D.
\textbf{R}: 2,4,6-tribromo-3-hydroxybenzoic acid, \textbf{S}: 2,4,6-tribromo-3-methoxybenzoic acid

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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

Electrophilic Substitution Activation/Deactivation|Esterification Steric Hindrance

Why This Question Is Tricky

Common Mistakes

The question tests three advanced traps: 1) Regioselectivity and ipso-substitution: Students often falsely assume all hydroxybenzoic acids decarboxylate with bromine water, but meta-isomers do not because the ipso carbon lacks resonance stabilization from the -OH group. 2) The Ortho Effect: Recognizing that di-ortho substituted benzoic acids resist Fischer esterification due to steric crowding in the tetrahedral transition state. 3) Diazomethane Mechanism: Understanding that CH2N2 esterification bypasses this steric hindrance via an SN2 mechanism and selectively reacts with the more acidic -COOH proton over the phenolic -OH.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Haloalkanes and Haloarenes - Class 12
Concept	Electrophilic Substitution Activation/Deactivation
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free