Question

What is/are the product/s formed when Benzaldehyde and Ethanal react in the presence of dil. NaOH followed by heating the intermediate product formed?

• A. 2-Methylpent-2-enal \& But-2-enal
• B. 3-Phenylprop-2-enal \& But-2-enal
• C. Only product is But-2-enal
• D. Only product is 2-Phenylprop-2-enal

Hint:

In condensations involving aldehydes like benzaldehyde and ethanal, after NaOH-induced condensation, heating leads to the formation of conjugated enones, which are typically $\beta$-unsaturated aldehydes.

Answer 1

The Correct Option is B

The reaction between Benzaldehyde and Ethanal in the presence of dilute sodium hydroxide (NaOH) typically follows the benzoin condensation mechanism, where the aldehydes undergo condensation to form a $\beta$-hydroxy aldehyde, which, upon heating, undergoes dehydration to form an α,β-unsaturated aldehyde. 

1. Reaction Mechanism: - First, benzaldehyde and ethanal undergo condensation in the presence of NaOH to form an intermediate $\beta$-hydroxy aldehyde. - Upon heating, this intermediate undergoes dehydration to form a conjugated enone, which is a product containing a carbon-carbon double bond (C=C) conjugated with a carbonyl group (C=O). 

2. Products: - The product of this reaction will include 3-Phenylprop-2-enal (an aromatic compound with a phenyl group attached to the carbon chain), formed by the condensation of benzaldehyde and ethanal. - The second product, But-2-enal, is formed due to the loss of the water molecule in the final step, and it also contains a conjugated double bond. 

Thus, the correct products formed are 3-Phenylprop-2-enal and But-2-enal, which corresponds to option (B).