questions
1)why Benzaldehyde and acetone can't do self condensation in claisen-schmidt reaction condensation?
2)In the second step of same reaction why do we add ethanol to form dibenzalideneacetone ?
Answer choices?
To answer your questions, we need to understand the Claisen-Schmidt condensation reaction. This reaction involves the condensation of an aromatic aldehyde (such as Benzaldehyde) with a carbonyl compound (such as acetone) to form an α,β-unsaturated carbonyl compound (such as dibenzalacetone). Let's address each question separately:
1) Benzaldehyde and acetone cannot undergo self-condensation in the Claisen-Schmidt condensation reaction. This is because self-condensation requires the presence of alpha-hydrogens, which are hydrogen atoms attached to a carbon adjacent to the carbonyl group. In the case of benzaldehyde and acetone, neither of them has alpha-hydrogens available for the self-condensation reaction. As a result, the reaction will not proceed under these conditions.
2) In the second step of the reaction, ethanol is added to form dibenzalacetone. Ethanol serves as a solvent in this step, helping to dissolve the reactants and facilitate the reaction. Additionally, ethanol can act as a nucleophile in the presence of a strong base such as sodium hydroxide (NaOH), which is commonly used in the Claisen-Schmidt condensation reaction. The reaction involves the loss of a hydroxide ion from the ethanol molecule, generating an ethoxide ion (C₂H₅O⁻). This ethoxide ion can then attack the carbon of the carbonyl group, resulting in the formation of the α,β-unsaturated compound dibenzalacetone. The presence of ethanol helps to maintain the reaction conditions and ensure the completion of the condensation reaction.
In summary, Benzaldehyde and acetone cannot undergo self-condensation in the Claisen-Schmidt reaction due to the absence of alpha-hydrogens. Ethanol is added in the second step to serve as a solvent and provide the necessary nucleophilic medium for the formation of dibenzalacetone.