Ultraviolet photolysis of acetophenone and its degradation products in aerated aqueous solution

Direct photolysis (lambda greater than or equal to 200nn) of acetophenone in aerated aqueous solution (10(-4)mol.dm(-3), pH = 6) gave 2 - hydroxyl and 3 - hydroxyl acetophenone as the main intermediates. The photolysis was greatly depressed when the solution was degassed using N-2 during the irradiation. This suggests that the photodegradation proceeds via the attack of aromatic ring by reactive oxygen species which are formed from the reaction of dissolved oxygen with the excited organic substrate, It was also observed that the intermediates of hydroxyl acetophenone could undergo further photolysis to produce dihydroxyl acetophenone, and the first order apparent rate constant for the photo - disappearance follows the order: acetophenone > 3 - hydroxyl acetophenone > 4 - hydroxyl acetophenone > 2 - hydroxyl acetophenone.