Theoretical insight into the initial reaction of ozone with peroxide: Single electron transfer or adduct formation

Abstract According to previous studies, the first step for the reaction of ozone (O3) with peroxymonosulfate (PMS) may be the single electron transfer from PMS to O3 or the adduct formation. Thus, the initial reaction of O3 with PMS has been theoretically verified by the quantum chemical calculations. Based on the theoretical results, the energy barrier for the single electron transfer (Ea,e) from PMS to O3 was 99.6 kcal·mol−1. Then, with a much lower forward energy barrier (Ea,f) (2.3 kcal·mol−1, the reverse energy barrier (Ea,r) was 11.3 kcal·mol−1), the formation of adduct (O3SO52−) from the electrophilic addition of O3 to the peroxy group of PMS was kinetically feasible. To confirm the initial reaction of O3 with other peroxides, peracetic acid (PAA) has been further studied. In the case of PAA, Ea,e was 106.5 kcal·mol−1, and Ea,f and Ea,r for the formation of adduct (CH3C(O)OO4−) were 3.8 kcal·mol−1 and 11.8 kcal·mol−1, respectively. Moreover, with the cases of H2O2 and C6H5O2H, it’s predictable that the reaction types were independent of the substituent groups in the peroxides. In other words, the adduct formation might be the initial step for the reaction of O3 with PMS, PAA, and even all peroxides.