Gattermann Reaction

It is used in the synthesis of aromatic ring compounds such as aromatic halides and aromatic aldehydes. It is similar to the Friedel-Crafts reaction. It is named after German Chemist Ludwig Gattermann. It is also known as Gattermann Formylation. In Gattermann Reaction for the formation of aromatic halide diazonium salt reacts with copper powder in presence of corresponding halogen acid. It is a substitution reaction. 

Gattermann Reaction can be written as Follows -  

How is Diazonium Salt Formed? 

Aromatic amine reacts with nitrous acid and mineral acid to form diazonium salt and produces water as a side product. This reaction is known as Diazotization Reaction.

Reaction can be written as follows- 

ArNH₂               +            HNO₂                    +      HX        🡪          RN₂+X-       +         H₂O           

Aromatic amine nitrous acid        mineral acid        Diazonium salt      water

Diazotization of Aniline

It is done by treating aniline with sodium nitrate and HCl at the temperature of 273K. the reaction involved is given below – 

Synthesis of Aromatic Aldehyde by Gattermann Reaction 

Gattermann Reaction Mechanism 

The mechanism of the Gattermann Reaction is explained for the formation of aromatic aldehydes. The reaction takes place by following four steps – 

Step 1. Formation of Formimino Chloride 

Hydrogen cyanide reacts with hydrogen chloride and forms chloride. 

The reaction can be written as follows – 

Step 2. Formation of Electrophile 

Formimino chloride reacts with lewis acid catalysts (such as AlCl3) and forms cations. The reaction is given below – 

Step 3. Attack of Electrophile on Benzene Ring 

Formimino cation (electrophile) attacks benzene rings and forms benzylamine. The reaction is given below -

Step 4. Hydrolysis of Benzylamine 

Hydrolysis of benzylamine takes place in this step. Which results in the formation of benzaldehyde. The reaction is given below – 

Applications of Gattermann Reaction 

• It is used for the formation of chlorobenzene and bromobenzene. 

• It is used for the formation of benzaldehydes. 

• Products of Gattermann Reaction such as benzaldehydes and haloarenes etc. are used in various fields such as pharmaceuticals, agricultural, medicinal etc. 

• It is used in the formation of aromatic halides and aromatic aldehydes. 

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Talking about the Gattermann Reaction, when the synthesis of any aromatic ring compounds like aromatic halides and aromatic aldehydes. There is one more reaction that is somewhat similar to the Gattermann Reaction, and it is known as the Friedel Crafts reaction. This reaction is named after the famous chemist, the German Ludwig Gattermann. It is sometimes also known as Gattermann Formulation. While using this reaction, when we are forming aromatic halide diazonium salt is reacted with copper powder in the presence of corresponding halogen acid. It is also a substitution reaction.

The Formation of Diazonium Salt

Only when the aromatic amine is reacted with mineral acid and nitrous acid, the diazonium salt is formed. This whole process also has a side product that is water. The whole reaction is known as Diazotization Reaction. This reaction can also be written as the following chemical equation:

ArNH₂ + HNO₂ + HX + RN₂ +X^- + H₂O

The Mechanism of Gattermann Reaction

There are a certain number of steps that need to be followed in order to complete the Gattermann Reaction. This process consists of 4 steps, which are given below:

• Step 1 - The forming the Formimino Chloride

The first and foremost step in order to create a Gattermann Reaction is to create a Formimino Chloride. In this, hydrogen chloride reacts with hydrogen cyanide which in turn forms Formimino chloride.

• Step 2 - The forming of Electrophile

The next step is to create Electrophile. As a result, the formimino chloride is reacted with a lewis acid catalyst and helps in the formation of forming cation, which is also known as Electrophile.

• Step 3 - When the Electrophile attacks on Benzene Ring

The third step explains how the Formimino cation (Electrophile) attacks benzene rings and in the result forms benzylamine.

• Step 4 - When the Benzylamine is Hydrolysed

The fourth step is also one of the most interesting and important steps. In this step, the hydrolysis of Benzylamine occurs. Which in turn produces benzaldehyde.

Now, let us discuss some of the major applications of the Gattermann Reaction.

The applications are given below:

• It can be used to form aromatic halides and aromatic aldehydes.

• There are many products of the Gattermann Reaction, such as benzaldehydes and haloarenes, etc. These elements in turn are used in various applications or fields of agriculture, pharmaceuticals, medicine, etc.

• It is also used to form benzaldehydes.

• It is also used to form chlorobenzene and bromobenzene.

All these applications are also the use-cases of the Gattermann Reaction. These uses are the majority in the chemical field.