Answer the questions on the basis of passage given below:

As aldehydes & ketones possess the carbonyl functional group, they show similar reactions. They exhibit nucleophilic addition reactions, reduction, oxidations, reactions due to ∝-Hydrogen atom, and many other reactions, like Cannizzaro reaction to electrophilic substitution reactions (in case of aromatic aldehydes & ketones). These reactions help in the preparation of a number of important compounds, like acetic acid, vinyl acetate, polymers and in perfume and dye industries. Nucleophilic addition reactions form cyanohydrins. acetals, alcohols and N-substituted derivatives like imine, oxime, semicarbazone, phenylhydrazone & Schiff's base. Reactions due to ∝-hydrogen atoms help in formation of aldols and a, B-unsaturated aldehydes & ketones.

Complete the following equation:

The correct answer is option 3.

The given reactant is 3-Oxobutanoic acid and the reagents and catalysts shows that it is Clemmensen reduction reaction. 

3-Oxobutanoic acid (also known as acetoacetic acid) undergoes Clemmensen reduction to form butanoic acid.

Clemmensen reduction involves the reduction of carbonyl compounds (aldehydes or ketones) using zinc amalgam (Zn/Hg) in the presence of **hydrochloric acid (HCl). It reduces the carbonyl group (C=O) of aldehydes and ketones to a methylene group (CH_2)

Reaction of 3-Oxobutanoic Acid: In the case of 3-oxobutanoic acid, the carbonyl group in the ketone position (\(\text{-CO-}\)) is reduced to a methylene group \(\text{-CH_2-}\), while the carboxylic acid group (\(\text{-COOH}\)) remains unaffected under Clemmensen conditions.

The reaction can be represented as:

Thus, the product of the Clemmensen reduction of 3-oxobutanoic acid is butanoic acid.

Mechanism :