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| Names | |||
|---|---|---|---|
| IUPAC name Sulfuryl fluoride | |||
| Other names Sulfonyl fluoride; Sulfur dioxide difluoride; Sulphuryl fluoride; Sulfuryl difluoride; Vikane; Zythor | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.018.437 | ||
| UNII | |||
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| Properties | |||
| SO2F2 | |||
| Molar mass | 102.06 g/mol | ||
| Appearance | colourless gas | ||
| Odor | odorless[1] | ||
| Density | 4.172 g/L (gas), 1.632 g/mL (liquid under compressed gas at 0 °C) | ||
| Melting point | −124.7 °C (−192.5 °F; 148.5 K) | ||
| Boiling point | −55.4 °C (−67.7 °F; 217.8 K) | ||
| 0.2% (0°C)[1] | |||
| Solubility in other solvents | SO2 | ||
| Vapor pressure | 15.8 atm (21°C)[1] | ||
| Structure | |||
| tetrahedral | |||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | neurotoxin | ||
| NFPA 704 (fire diamond) | |||
| Lethal dose or concentration (LD, LC): | |||
LC50 (median concentration) | 991 ppm (rat, 4 hr)[2] | ||
LCLo (lowest published) | 1200 ppm (mouse, 1 hr) 5000 ppm (rabbit, 1 hr)[2] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 5 ppm (20 mg/m3)[1] | ||
REL (Recommended) | TWA 5 ppm (20 mg/m3) ST 10 ppm (40 mg/m3)[1] | ||
IDLH (Immediate danger) | 200 ppm[1] | ||
| Related compounds | |||
Otheranions | SO2Cl2, SO2ClF | ||
Othercations | SeO2F2 | ||
Related compounds | SF6, SO3 SO2F3− CrO2F2 | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Sulfuryl fluoride (also spelledsulphuryl fluoride) is aninorganic compound with theformula SO2F2. It is an easily condensed gas and has properties more similar tosulfur hexafluoride thansulfuryl chloride, being resistant tohydrolysis even up to 150 °C.[3] It is neurotoxic and a potentgreenhouse gas, but is widely used as a fumigant insecticide to controltermites.
The molecule is tetrahedral with C2vsymmetry. The S-O distance is 140.5 pm, S-F is 153.0 pm. As predicted byVSEPR, the O-S-O angle is more open than the F-S-F angle, 124° and 97°, respectively.[3]
One synthesis begins with the preparation of potassium fluorosulfite:[4]
This salt is then chlorinated to givesulfuryl chloride fluoride:
Heating thesulfuryl chloride fluoride with potassium fluorosulfite at 180 °C gives the desired product:[5]
Heating metalfluorosulfonate salts also gives this molecule:[3]
It can be prepared by direct reaction offluorine withsulfur dioxide:
On a laboratory scale, sulfuryl fluoride has been conveniently prepared from 1,1'-sulfonyldiimidazole, in the presence ofpotassium fluoride and acid.[6][7]
Sulfuryl fluoride is unreactive toward molten sodium metal.[3] Similarly it is slow to hydrolyze, but eventually converts tosulfur trioxide.[8][9]
Sulfuryl fluoride gas is a precursor to fluorosulfates andsulfamoyl fluorides:[10]
Originally developed by theDow Chemical Company, sulfuryl fluoride is in widespread use as a structuralfumigantinsecticide to control drywoodtermites, particularly in warm-weather portions of the southwestern and southeastern United States and in Hawaii. It has a non-specificmode of action (IRAC group 8C). Less commonly, it can also be used to controlrodents,powderpost beetles,deathwatch beetles,bark beetles, andbedbugs. Its use has increased as a replacement formethyl bromide, which was phased out because of harm to the ozone layer. It is an alternative to the use ofphosphine, which is acutely toxic.[11]
During application, the building is enclosed and filled with the gas for a period of time, usually at least 16–18 hours, sometimes as long as 72 hours. The building must then be ventilated, generally for at least 6 hours, before occupants can return. California regulations are such that the tent will be on for three to five days, which includes ventilation. In the US, sulfuryl fluoride must be transported in a vehicle marked with "Inhalation Hazard 2" placards.[12][13] Most states require a license or certification for the individual applying the fumigant.
The concentration is continuously monitored and maintained at the specified level using electronic equipment. Possible leakages are also checked by low range electronic detectors. Reentry to the home is allowed when the concentration level is at or below 5 ppm.[14] Sulfuryl fluoride is colorless and odorless, however, during the fumigation process, a warning agent calledchloropicrin is first released into the building to ensure that no occupants remain. Tent fumigation is the most effective treatment for the extermination of known and unknown infestations of wood-destroying insects. Heat is the only other approved method for whole structure treatment for termites in California.[15] Sulfuryl fluoride provides no protection from future infestations, although heavy re-infestation can take several years since drywood termites have slower growing colonies than ground termites.
Sulfuryl fluoride is marketed in the U.S. by three manufacturers, under four different brand names.Vikane (Dow) (EPA Reg. No. 62719- 4-ZA) has been commercially available since the early 1960s, withZythor (marketed by competitor Ensystex of North Carolina) (EPA Reg. No. 81824- 1-AA) being more recently introduced gradually as its use is approved by individual states (in Florida circa 2004, but not in California until October 2006, for example). Sulfuryl fluoride has been marketed as a post-harvest fumigant for dry fruits, nuts, and grains under the trade nameProFume (U.S. EPA Reg. No. 62719- 376-AA).[16] Most recently Drexel Chemical Company has registeredMaster Fume (EPA Reg. No. 19713-596-AA) for the structural market, competing againstVikane andZythor.[17]
Inhalation of sulfuryl fluoride is hazardous and may result in respiratory irritation,pulmonary edema, nausea, abdominal pain, central nervous system depression, numbness in the extremities, muscle twitching, seizures, and death.[18][19][20] These high exposures occurred when people entered into structures illegally during fumigation or after insufficient aeration. Epidemiological studies showed that fumigation workers who used sulfuryl fluoride showed neurological effects, which included reduced performance on cognitive tests and pattern memory tests, and reduced olfactory function.[21]
In 1987, an elderly couple was exposed to sulfuryl fluoride in their house already cleared for reentry.[21] While the fumigation company opened windows and doors, and aerated the house with fans, sulfuryl fluoride level was not measured. It was not detected when the air was sampled 12 days after aeration. The couple experienced weakness, nausea and shortness of breath that evening. The man suffered a seizure and died the following day. His wife's condition got worse with pulmonary edema, and she died after a cardiovascular arrest 6 days later.
In 2015, a 10-year-old boy suffered severe brain damage and lost function of his left arm and leg after his home was treated with sulfuryl fluoride and insufficiently aerated, prompting a criminal investigation by the Department of Justice and the Florida Department of Agricultural and Consumer Services.[22] Two pest control workers later pled guilty to charges of misuse of the pesticide resulting in the boy's poisoning, and were each sentenced to one year in prison.[23]
In 2016, a 24-year-old man who allegedly entered an apartment that was being fumigated inFremont, California to commit a burglary was exposed to sulfuryl fluoride andchloropicrin and died shortly thereafter. According to a police officer, he experienced labored breathing and was sweating before he collapsed just a few steps from the first floor window of the apartment he allegedly burglarized.[24]
In April 2024, In Pompano Beach Florida, two company pesticide workers died. The owner was also hospitalized but survived.[25]
Based on the first high frequency, high precision, in situ atmospheric and archived air measurements, sulfuryl fluoride has an atmospheric lifetime of 30–40 years,[8] much longer than the 5 years earlier estimated.[26]
Sulfuryl fluoride has been reported to be a greenhouse gas which is about 4000–5000 times more efficient in trapping infrared radiation (per kg) than carbon dioxide (per kg).[8][27][28] The amount of sulfuryl fluoride released into the atmosphere is about 2000 metric tons per year.[8] The most important loss process of sulfuryl fluoride is dissolution of atmospheric sulfuryl fluoride in the ocean followed by hydrolysis.
Sulfuryl fluoride, a gas fumigant, was the pesticide used to fumigate, sources told CNN.
