Gattermann koch

Gattermann Koch Reaction (Organic Chemistry)

1. GATTERMANN – KOCH REACTION By- Manish Sahu M.Sc. Chemistry (Final) Sp.- Physical Chemistry

2. SYNOPSIS Introduction Definition History Formylation Gattermann -Koch Formylation Mechanism Uses Conclusion Reference

3. INTRODUCTION The Gattermann-Koch reaction is a chemical reaction in which aromatic compounds are formylated by a mixture of CO and HCl in the presence of Anhydrous AlCl 3 . This reaction is known as Gattermann-Koch reaction .

4. DEFINITION A synthesis of an aldehyde from an aromatic Hydrocarbon , Hydrogen , Carbon monoxide , Hydrogen chloride , in the presence of the catalyst Anhydrous Aluminium chloride .

5. HISTORY The Gattermann-Koch reaction , named after the German Chemists LUDWIG GATTERMANN and JULIUS ARNOLD KOCH . It was discovered in 1897 . Ludwig Gatteramnn

6. FORMYLATION Substitution of formyl group that is , aldehyde group ( - CHO ) into aromatic ring is known as formylaton .

7. GATTERMANN-KOCH FORMYLATION Formyl chloride is unstable. Hence the reaction takes place under a high pressure with a mixture of CO , HCl in the presence of a catalyst AlCl 3. Product is Benzaldehyde. CuCl

8. MECHANISM The CO and HCl reacts to form an unstable formyl chloride. CO + HCl + AlCl 3 → [ HC + = O ↔ HC ≡ O + ] AlCl - 4

9. The Mechanism of this reaction, the formyl cation ( HC + = O ) is the active electrophlic species . The function of cuprous chloride is to co-ordinate with CO to provide its higher local concentration . Unlike the Gattermann reaction , this reaction is not applicable to phenol and phenolic ether substrates .

10. USES It is the method of synthesizing aromatic aldehyde by the action of a mixture of CO and HCl on aromatic hydrocarbon . Use aluminium chloride as catalyst some time Aluminium Bromide using a small amount of monochloride of copper .

11. CONCLUSION In Gattermann - Koch reaction , formylation of benzene take place to form benzaldehyde . In this reaction , benzene is reacted with CO and HCl in presence of anhydrous AlCl 3 . AlCl 3 abstracts Cl - ion and initiates H + ion , which attack on carbon atom in CO. Due to this carbon aquires positive charge , hence attack on benzene ring to form arenium ion , which loses proton to form benzaldehyde .

12. REFERENCE Advanced Organic Chemistry By :- “Dr. Jagdamba Singh” “Dr. L. D. S. Yadav” Advanced Organic Chemistry By :- “S. K. Gosh”