Question

Reaction of phenol with chloroform/sodium hydroxide to give $o-$ hydroxy benzaldehyde involves the formation of

• A. dichloro carbine
• B. trichloro carbene
• C. chlorine atoms
• D. chlorine molecules

Answer 1

Answer: (A)

Phenol reacts with chloroform and $NaOH$ to give $o-$ hydroxy benzaldehyde or salicylaldehyde. In this reaction dichlorocarbene $\left(:CC{l}_2\right)$ electrophile is generated. This reaction is called Reimer-Tiemann reaction.
$O{H}^{-}+CHC{l}_3\to HOH+\underset{\text{ unstable }}{CC{l}_3^{-}}:CC{l}_3^{-}\to C{l}^{-}+\underset{\text{ dichlorocarbene }}{:CC{l}_2}$