Hydrogen Peroxide-Assisted Alkaline Defluorination of the Fumigant and Potent Greenhouse Gas, Sulfuryl Fluoride: Hydrogen Peroxide as a Nucleophilic Reagent.

Sulfuryl fluoride (SOF, SF) is an effective and increasingly popular fumigant for treating buildings and commodities in international trade but has come under scrutiny as a potent greenhouse gas. Passage of vent gases through an alkaline spray has been proposed for scrubbing SF, but base hydrolysis is insufficiently fast and generates equal yields of fluoride and fluorosulfate, the latter of unknown environmental hazard. We report here that alkaline hydrogen peroxide (HO) markedly accelerates SF removal and gives nearly quantitative yield of fluoride, with fluorosulfate produced in less than 3.5% yield. The other major products are sulfate, peroxymonosulfate, and oxygen. The oxidation state of S was unchanged. Hydroxyl and superoxide radical scavengers had no effect on the rate. The reaction proceeds by sequential nucleophilic displacement of fluoride by hydroperoxide ion (HO) to form a transient diperoxysulfate species that rapidly undergoes intramolecular redox rearrangement to give sulfate and singlet oxygen. Peroxymonosulfate, produced through side reactions, can fully defluorinate SF as well, although more slowly. Two new peaks were detected in the F-NMR spectrum corresponding to intermediates. Fluoride can be removed conventionally, and the other products are innocuous or short-lived. Thus, HO-assisted alkaline defluorination promises to be an effective method for scrubbing spent SF fumes and preventing SF from reaching the atmosphere. This study highlights the benefits of HO and peroxymonosulfate as nucleophiles in remediation chemistry.