Question:
Which of these intermediates is formed during the Reimer-Tiemann reaction of phenol with chloroform and NaOH?
Which of these intermediates is formed during the Reimer-Tiemann reaction of phenol with chloroform and NaOH?
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The Reimer–Tiemann reaction puts an aldehyde group (–CHO) onto phenol to make salicylaldehyde. To understand it you must know which reactive intermediate does the attacking.
Updated On: Jun 24, 2026
- Nitrene
- Free radical
- Carbonium ion
- Dichlorocarbene
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The Correct Option is D
Solution and Explanation
Concept:
The Reimer–Tiemann reaction puts an aldehyde group (–CHO) onto phenol to make salicylaldehyde. To understand it you must know which reactive intermediate does the attacking.
Step 1:
When chloroform (CHCl3) is mixed with strong base (NaOH), the base removes a proton and then two chloride ions leave, generating a very reactive species called dichlorocarbene (:CCl2).
Step 2:
This electron-poor dichlorocarbene then attacks the phenol ring (which is electron-rich because of the –OH group). After further reaction with the base and water, the –CHO group is formed, giving salicylaldehyde.
Step 3:
So the key intermediate is dichlorocarbene, not a nitrene (no nitrogen involved), not a free radical, and not a carbonium ion.
Answer: Option (4) — Dichlorocarbene.
The Reimer–Tiemann reaction puts an aldehyde group (–CHO) onto phenol to make salicylaldehyde. To understand it you must know which reactive intermediate does the attacking.
Step 1:
When chloroform (CHCl3) is mixed with strong base (NaOH), the base removes a proton and then two chloride ions leave, generating a very reactive species called dichlorocarbene (:CCl2).
Step 2:
This electron-poor dichlorocarbene then attacks the phenol ring (which is electron-rich because of the –OH group). After further reaction with the base and water, the –CHO group is formed, giving salicylaldehyde.
Step 3:
So the key intermediate is dichlorocarbene, not a nitrene (no nitrogen involved), not a free radical, and not a carbonium ion.
Answer: Option (4) — Dichlorocarbene.
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