Explanation

The molecular formula of compound A is C₈H₈O₂. This immediately suggests that A is most likely a substituted benzaldehyde or aromatic aldehyde.

Now consider the reaction with concentrated NaOH. The formation of a substituted benzyl alcohol as one of the two products clearly indicates that compound A undergoes the Cannizzaro reaction.

Cannizzaro reaction is shown only by aldehydes which do not have α-hydrogen. Hence, compound A must be an aromatic aldehyde without α-hydrogen.

Among the given options:

• 2-hydroxy acetophenone is a ketone → does not undergo Cannizzaro reaction
• 4-hydroxy benzylaldehyde contains phenolic –OH but still possible, however it gives multiple aldol products
• 4-methyl benzoic acid is a carboxylic acid → no aldol or Cannizzaro reaction
• 4-methoxy benzaldehyde is an aromatic aldehyde with no α-hydrogen

Now consider cross-Aldol condensation with acetophenone. Benzaldehyde derivatives without α-hydrogen give only one cross-aldol product with acetophenone.

Thus, 4-methoxy benzaldehyde satisfies both conditions:

• Gives Cannizzaro reaction with conc. NaOH
• Gives a single cross-aldol product with acetophenone

Therefore, the compound A is:

4-methoxy benzaldehyde

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