Question

What is electrophile in Reimer Tiemann Reaction?

Answer 1

Explanation of Reimer Tiemann reaction -

1. Phenol is reacted with ${\mathrm{CHCl}}_3$ (Chloroform) in the presence of $\mathrm{NaOH}$ Sodium Hydroxide.
2. The introduction of the Formyl group occurs to the ortho position of the -OH group.

Example of Reimer Tiemann reaction-

1. The conversion of Phenol to Salicylaldehyde (2-hydroxy benzaldehyde) is an example of a Reimer Tiemann reaction.

Reimer Tiemann Reaction Mechanism-

1. Deprotonation of Chloroform ${\mathrm{CHCl}}_3$ by $\mathrm{NaOH}$ solution leads to the formation of chloroform carbanion ${\mathrm{CCl}}_3^{-}$.
2. This ${\mathrm{CCl}}_3^{-}$ undergoes alpha elimination and forms Dichlorocarbene as a product. As dichlorocarbene acts as an electrophile in this reaction.
3. The aqueous $\mathrm{NaOH}$ also cause deprotonation of Phenol and forms Phenoxide ions.
4. The negative charge on Phenoxide ion delocalized over the Benzene ring causes it more nucleophilic.
5. Now, this nucleophile attack on electrophile dichlorocarbene leads to the formation of an intermediate Dichloromethyl substituted Phenol.
6. This intermediate undergoes hydrolysis to form Ortho-hydroxybenzaldehyde.

Thus, dichlorocarbene acts as an electrophile in this reaction.