An organic compound with the molecular formula C₉H₁₀O forms 2, 4-DNP dervative, reduces Tollens’ reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1, 2-benzenedicarboxylic acid. Identify the compound.

(i) Since the given compound with M.F. C9H10O forms a 2, 4-DNP derivative and reduces Tollens’ reagent, it must an aldehyde. 

(ii) Since it undergoes Cannizzaro reaction, therefore, CHO group is directly attached to the benzene ring.

(iii)   Since on vigorous oxidation, it gives 1, 2-benzenedicarboxylic acid, therefore, it must be an ortho-substituted benzaldehyde. The only o-substituted aromatic aldehyde having M.F. C₉H₁₀O is 2-ethylbenzaldehyde. All the reactions can now be explained on the basis of this structure.