Reimer-Tiemann reaction
Phenol reacts with chloroform in aqueous NaOH at 340 K, and hydrolysis of the product gives salicylaldehyde.
PhenolC₆H₅OHPhenol - Step 1
(i) CHCl₃, aq. NaOH, 340 K (ii) H⁺
Salicylaldehydeo-HOC₆H₄CHOAldehyde
How it works
- Chloroform and base generate dichlorocarbene (:CCl₂), the electrophile.
- The phenoxide ring attacks the carbene at the ortho position.
- Hydrolysis of the dichloromethyl group gives CHO and, on acidification, salicylaldehyde.
What it makes
Salicylaldehyde (2-hydroxybenzaldehyde).
Where it fails
Mainly the ortho product. Carbon tetrachloride in place of chloroform gives salicylic acid.
Class 12, Chapter 7 Alcohols, Phenols and Ethers
Reimer-Tiemann reaction: quick answers
What is the reactive species?
Dichlorocarbene.
What is formed if CCl4 is used instead of CHCl3?
Salicylic acid.
Why is the product ortho?
The phenoxide ion directs the electrophile to the ortho position here.