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)

dichloro carbine

Answer 2

Phenol reacts with chloroform and $NaOH$ to give $o-$ hydroxy benzaldehyde or salicylaldehyde. In this reaction dichlorocarbene $\left(: C C l_{2}\right)$ electrophile is generated. This reaction is called Reimer-Tiemann reaction.
$OH ^{-}+ CHCl _{3} \rightarrow HOH +\underset{\text { unstable }}{ CCl _{3}^{-}}: CCl _{3}^{-} \rightarrow Cl ^{-}+\underset{\text { dichlorocarbene }}{: CCl _{2}}$