Question

Phenol on treatment with chloroform in the presence of NaOH, a -CHO group is introduced at ortho position of benzene ring. The reaction is known as

• A. Kolbe's reaction
• B. Reimer-Tiemann reaction
• C. Gattermann-Koch reaction
• D. Stephen reaction
• E. Sandmeyer reaction

Hint:

Reimer-Tiemann introduces \(-CHO\) group in phenol.

Answer 1

The Correct Option is B

Step 1: Understanding Name Reactions of Phenol:
This question asks to identify a specific name reaction involving phenol. It is crucial to be familiar with the reactants, reagents, and products of common named organic reactions.
Step 2: Analyzing the Given Reaction:
Reactants: Phenol and chloroform (CHCl\(_3\)).
Reagent: Sodium hydroxide (NaOH), a strong base.
Product described: A -CHO (formyl) group is introduced onto the benzene ring, primarily at the ortho position, to form o-hydroxybenzaldehyde (salicylaldehyde).
This set of reactants and products precisely describes the Reimer-Tiemann reaction. The reactive intermediate in this reaction is dichlorocarbene (:\text{CCl}_2).
Step 3: Differentiating from Other Name Reactions:

(A) Kolbe's reaction (or Kolbe-Schmitt reaction): This reaction involves treating sodium phenoxide with carbon dioxide (CO\(_2\)) under pressure. It introduces a carboxylic acid group (-COOH) to form salicylic acid.
(C) Gattermann-Koch reaction: This reaction formylates benzene (not phenol) using carbon monoxide (CO) and HCl in the presence of a catalyst like AlCl\(_3\)/CuCl.
(D) Stephen reaction: This is a method to prepare aldehydes from nitriles (R-CN) using SnCl\(_2\)/HCl followed by hydrolysis.
(E) Sandmeyer reaction: This reaction converts a primary aromatic amine, via its diazonium salt, into an aryl halide, cyanide, etc., using copper(I) salts.
Step 4: Final Answer:
The described reaction is the Reimer-Tiemann reaction.