Theoretical study on the degradation mechanism of propranolol in aqueous solution initiated by hydroxyl and sulfate radicals

In this paper, density functional theory (DFT) calculation was carried out to explore hydroxyl (center dot OH) and sulfate radicals (SO4 center dot-)-initiated oxidative degradation of propranolol (PRO) in an aqueous solution. It was found that the most favorable pathways for the reactions between PRO and center dot OH are center dot OH addition (ADD) reactions related to C1, C2, and C4 sites of PRO and hydrogen atom abstraction (HAA) channels involving C10-H, C11-H, and C13-H bonds. The plausible subsequent reactions of the favorable initial intermediates include hydroxylation, naphthalene ring cleavage, ether bond and C-N bonds breakage, and their combination. SO4 center dot- was found to have stronger oxidizing performance than center dot OH in the aqueous degradation of PRO. Single electron transfer (SET) reaction between PRO and SO4 center dot- is not feasible. Water molecules and dissolved oxygen in water participate in aqueous degradation of PRO.