JEE Challenger
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ChemEasyAdv 2007 • Paper 2

Reagents for Reimer-Tiemann Formylation

Comprehension Passage

Reimer-Tiemann reaction introduces an aldehyde group onto the aromatic ring of phenol, ortho to the hydroxyl group. This reaction involves electrophilic aromatic substitution. This is a general method for the synthesis of substituted salicylaldehydes as depicted below:

p-cresol→reagentintermediate (I)→aq. HCl2-hydroxy-5-methylbenzaldehyde\text{p-cresol} \xrightarrow{\text{reagent}} \text{intermediate (I)} \xrightarrow{\text{aq. HCl}} \text{2-hydroxy-5-methylbenzaldehyde}

Which one of the following reagents is used in the above reaction?

Options

A

aq. NaOH+CH3Cl\text{NaOH} + \text{CH}_3\text{Cl}

B

aq. NaOH+CH2Cl2\text{NaOH} + \text{CH}_2\text{Cl}_2

C

aq. NaOH+CHCl3\text{NaOH} + \text{CHCl}_3

Correct
D

aq. NaOH+CCl4\text{NaOH} + \text{CCl}_4

Topics & Concepts

Alcohols, Phenols and EthersReimer-Tiemann ReactionPhenolsFormylation

Step-by-Step Solution

The classical Reimer-Tiemann formylation of phenols to form ortho-hydroxybenzaldehydes utilizes chloroform (CHCl3\text{CHCl}_3) in aqueous sodium hydroxide (NaOH\text{NaOH}).

In basic medium, chloroform undergoes α\alpha-elimination to generate dichlorocarbene (:CCl2:\text{CCl}_2), the active electrophile.

Correct Answer: C

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