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Claisen Condensation

Definition: What is Claisen Condensation?

The Claisen condensation is an organic reaction used to form a carbon-carbon bond between two ester molecules or one ester molecule with another carbonyl compound in the presence of a strong base (alkoxide). The product formed is a beta-keto ester.During the reaction, an enolate is formed when the alpha-hydrogenis removed from the ester. If the ester lacks an alpha-hydrogen, as in the case with most aromatic carbonyl compounds, then it is incapable of forming the enolate. Such type of condensation reaction is called crossed or mixed Claisen condensation [1 -3].

Examples of Claisen Condensation Reaction

Claisen Condensation Examples

Mechanism of Claisen Condensation Reaction [4 – 7]

Claisen Condensation Mechanism

Claisen Schmidt Condensation

In case of Claisen Schmidt Condensation, an aldehyde or a ketone having an alpha-hydrogen is used to react with an aromatic carbonyl compound without any alpha-hydrogen.

FAQs

Q.1. Why cannot methanoate esters undergo Claisen self-condensations?

Ans.Methanoate esters (HCOOR) don’t have an alpha-hydrogen and therefore, cannot form the nucleophilic enolate.

Q.2.What type of esters can undergo Claisen condensation reactions?

Ans. Only those esters that contain alpha-hydrogen can undergo Claisen Condensation reaction.

Q.3. What is a beta-keto ester?

Ans. A beta-keto ester is a compound which is formed by joining a ketone and an ester with a carbon between them.

References

  1. Definition and mechanism – Name-reaction.com
  2. Definition –Chem.ucla.edu
  3. Definition – Chem.ucalgary.ca
  4. Mechanism – Chemhelper.com
  5. Mechanism – Chem.libretexts.org
  6. Mechanism – Organic-chemistry.org
  7. Mechanism – Clutchprep.com

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