The calculation considered the total F in the initial PFAS (0.5 mM) to reflect the general efficacy of oxidation. In comparison, the "molecular oxidative deF" in Tables and As expected, the five structures without a C-H bond for HO• attack allowed <5% of defluorination (Table , entries 2, 6, 11, 22, and 24), whereas NBP-H allowed up to 25% of defluorination at [S2O8 2-]:[NBP-H]=100:1 (Table , entry 4). The previous study did not identify the oxidation product from NBP-H. In this work, following the established "H-abstraction" mechanism by HO•, we predicted that the branched terminal •CF(CF3)-O-RF radical (Scheme 1a) would bind with another HO• to yield HO-CF(CF3)-O-RF. This structure with one -F and one -OH on the same carbon would undergo HF elimination to yield the ester, CF3CO-O-RF, which would further hydrolyze under the alkaline condition to afford CF3COO -(TFA, inert to HO• as shown in Table ) and HO-RF. The HO-RF, in this case, would further undergo HF elimination and subsequent hydrolysis to yield TP1. With TP1 as the analytical standard, we verified our prediction and quantified the formation of both TP1 and TFA (Table Oxidation of PFESAs by SO4 -•. When the oxidant was switched to SO4 -•, all structures containing -COO -allowed significant defluorination (Table , entries 1, 3, 5, 10, and 15). As expected, fully fluorinated NBP-F and 2+2 PFESA were not reactive (Table , entries 21 and 23). Following the established "decarboxylation" mechanism by SO4 -•, we predicted that NBP-COOH would yield the same •CF(CF3)-O-RF radical (Scheme 1b) as from the reaction between NBP-H and HO•. The carbon radical would bind with another SO4 -• to yield -O3S-O-CF(CF3)-O-RF, which would further hydrolyze under the acidic condition to HO-CF(CF3)-O-RF. The following steps would yield TP1 and TFA as described above. However, SO4 -• could further decarboxylate TP1 following the same set of mechanisms to yield TP2 and another equivalent of TFA. We verified our prediction and quantified the generation of TP1, TP2, and TFA from both NBP-COOH (Table , zone C) and NBP-H (Table , zone B). The SO4 -• oxidation of TP1 also generated the expected TP2 and TFA (Table