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 (•OH) and sulfate radicals (SO4•-)-initiated oxidative degradation of propranolol (PRO) in an aqueous solution. It was found that the most favorable pathways for the reactions between PRO and •OH are •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 CN bonds breakage, and their combination. SO4•- was found to have stronger oxidizing performance than •OH in the aqueous degradation of PRO. Single electron transfer (SET) reaction between PRO and SO4•- is not feasible. Water molecules and dissolved oxygen in water participate in aqueous degradation of PRO.