Gattermann Reaction


What is 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 - 

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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 – 

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Synthesis of Aromatic Aldehyde by Gattermann Reaction 

 

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Gattermann Reaction Mechanism 

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

Step 1. Formation of Formimino Chloride 

Hydrogen cyanide reacts with hydrogen chloride and forms formimino chloride. 

Reaction can be written as follows – 

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Step 2. Formation of Electrophile 

Formimino chloride reacts with lewis acid catalyst (such as AlCl3) and forms formimino cation. Reaction is given below – 

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Step 3. Attack of Electrophile on Benzene Ring 

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

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Step 4. Hydrolysis of Benzylamine 

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

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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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