Hydrogen Peroxide-Assisted\nAlkaline Defluorination\nof the Fumigant and Potent Greenhouse Gas, Sulfuryl Fluoride: Hydrogen\nPeroxide as a Nucleophilic Reagent

Sulfuryl fluoride (SO<sub>2</sub>F<sub>2</sub>, SF) is\nan effective\nand increasingly popular fumigant for treating buildings and commodities\nin international trade but has come under scrutiny as a potent greenhouse\ngas. Passage of vent gases through an alkaline spray has been proposed\nfor scrubbing SF, but base hydrolysis is insufficiently fast and generates\nequal yields of fluoride and fluorosulfate, the latter of unknown\nenvironmental hazard. We report here that alkaline hydrogen peroxide\n(H<sub>2</sub>O<sub>2</sub>) markedly accelerates SF removal and gives\nnearly quantitative yield of fluoride, with fluorosulfate produced\nin less than 3.5% yield. The other major products are sulfate, peroxymonosulfate,\nand oxygen. The oxidation state of S was unchanged. Hydroxyl and superoxide\nradical scavengers had no effect on the rate. The reaction proceeds\nby sequential nucleophilic displacement of fluoride by hydroperoxide\nion (HO<sub>2</sub><sup>–</sup>) to form a transient diperoxysulfate\nspecies that rapidly undergoes intramolecular redox rearrangement\nto give sulfate and singlet oxygen. Peroxymonosulfate, produced through\nside reactions, can fully defluorinate SF as well, although more slowly.\nTwo new peaks were detected in the <sup>19</sup>F-NMR spectrum corresponding\nto intermediates. Fluoride can be removed conventionally, and the\nother products are innocuous or short-lived. Thus, H<sub>2</sub>O<sub>2</sub>-assisted alkaline defluorination promises to be an effective\nmethod for scrubbing spent SF fumes and preventing SF from reaching\nthe atmosphere. This study highlights the benefits of H<sub>2</sub>O<sub>2</sub> and peroxymonosulfate as nucleophiles in remediation\nchemistry.