Consider the following reaction sequence: Ethyl 3-oxobutanoate NaBH ₄ A conc. H ₂ SO ₄, B The major product 'B' is:

Step-by-step solution

NaBH ₄ is a mild reducing agent that selectively reduces the ketone group to a secondary alcohol but does not reduce the ester group. Therefore, ethyl 3-oxobutanoate is reduced to ethyl 3-hydroxybutanoate (Product A). Heating the -hydroxy ester (A) with concentrated H ₂ SO ₄ leads to acid-catalyzed dehydration. The elimination of a water molecule occurs to form a double bond that is conjugated with the ester carbonyl group, making it highly stable. This yields ethyl but-2-enoate as the major product (Product B). Co