When 2-oxo-2-phenylacetaldehyde is treated with aqueous NaOH, it undergoes intramolecular cannizzaro reaction in which one carboxyl group is reduced to alcohol and other carboxyl group is reduced to sodium salt of carboxylic acid. Mechanism Firstly, base NaOH attacks on carboxyl carbon of aldehyde (as aldehyde is more electrophilic)
Second step involves migration of H+ion on ketone carbon.