Chemistry REIMER- TIEMANN REACTION

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REIMER- TIEMANN REACTION

Reimer -Tiemann Reaction :

An alkaline solution of phenol is refluxed with chloroform at `60^oC`, distilling off the excess of chloroform and acidifying the residual liquid with sulphuric acid. As a result, `o` - hydroxy and `p`- hydroxy benzaldehyde are formed, which are separated by steam- distillation.

Mechanism of Reimer-Tiemann Reaction :

If both the `o` - positions are blocked, `p`-hydroxy benzaldehyde is the main product. With blocked `p`- position, `o`- hydroxy benzaldehyde and cyclohexadienones are formed. shown in Fig 1c.

Cyclohexadienone derivative remains unhydrolysed as it has a neopentylic system, which involves lot of steric crowding.

When phenol is refluxed with `C Cl_4` in alkaline medium, salicylic acid is formed as shown in Fig 1d.