Question

Explain Reimer Tiemann reaction of Phenols.

Hint:

This is a specific method to synthesize Salicylaldehyde. If CCl$_4$ is used instead of CHCl$_3$, the product is Salicylic Acid (Kolbe-like product).

Answer 1

1. Reaction: When phenol is treated with chloroform (CHCl$_3$) in the presence of aqueous sodium hydroxide (NaOH) at 340K, followed by acid hydrolysis.
2. Mechanism: The reaction involves an electrophilic substitution where the electrophile is dichlorocarbene (:CCl$_2$).
3. Product: An aldehyde group (-CHO) is introduced, predominantly at the ortho position to the phenolic -OH group.
4. Equation:
Phenol + CHCl$_3$ + 3NaOH $\to$ Salicylaldehyde (2-Hydroxybenzaldehyde) + 3NaCl + 2H$_2$O.