Reimer Tiemann reaction – Crack Chemistry

Reimer Tiemann reaction | Organic Reaction Mechanism

This is one of the very very important naming reactions in organic chemistry especially for students pursuing Higher Secondary and Bachelor’s Degree in Chemistry subjects.
This reaction is about Ortho-Formylation in aromatic alcohols.
Simply we can say, Reimer Tiemann Reaction is used in the conversation of Phenol into Salicylaldehyde.
This reaction is important because it contains the most important Reaction intermediate. That is Carbene.
 
Lets See…,

Reaction Mechanism:-

Reimer Tiemann Reaction :-

General Reaction:-

  When the Phenol and Chloroform are reacted in presence of a strong base like Potassium Hydroxide is forms Salicylaldehyde.
The general reaction is given below in the image
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General Reaction

Formation of Carbene:-

 
First of all, the carbene is formed by the reaction of KOH ( Potassium Hydroxide ) with Chloroform, it forms trichloromethyl carbanion.
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Chloroform reacting With KOH

Then the formed trichloromethyl carbanion will be Converted into Carbene ( dichloromethylene )

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Carbene

Formation of Phenoxide ion:-

The Phenol is reacted with KOH and the base will obstruct the proton from the Phenol and it ends up in the formation of a Phenoxide ion.
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Convertion of Phenol to Phenoxide ion

The reaction of Carbene and Phenoxide ion:-

 
In this part, Phenoxide ion is reacted with Carbene intermediate in presence of KOH (Strong base).
Finally, it forms Salicylaldehyde.

 

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Reaction between Carbene & Phenoxide ion
Reimer Tiemann Reaction, crackchemistry, organic chemistry, reaction mechanisms
KCl – Elimination

After Adding the KOH base in the above process, KCl (Potassium Chloride) will eliminate. It forms -OH in the respective chain.

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Proton Transfer

In this above step,

The proton transfer takes place. That is Proton of one Alcohol group is shifted to another group.
So Conversion of Phenol ( any aromatic alcohol ) into Salicylaldehyde is known as Reimer Tiemann Reaction.

Key Notes :-

This reaction is also get done in Aromatic alcohols with Heteroatom’s like Thiolate etc..,
• The intermediate formed in this reaction is a very short-living Species called Carbene
• The temperature of the reaction is carried out in 60°C.
• It is position specific reaction ( Ortho – Formylation )
• The IUPAC name of the product formed in this reaction is 2-hydroxy Benzaldehyde.

Frequently Asked Questions:-

Here i give 5 frequently asked questions in this above reaction. Try to answer it.

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