Sulfonyl fluoride; Sulfur dioxide difluoride; Sulphuryl fluoride; Sulfuryl difluoride; Vikane
|Molar mass||102.06 g/mol|
|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)|
|Solubility in other solvents||SO2|
|Vapor pressure||15.8 atm (21°C)|
LC50 (Median lethal concentration)
|991 ppm (rat, 4 hr)|
|US health exposure limits (NIOSH):|
|TWA 5 ppm (20 mg/m3)|
|TWA 5 ppm (20 mg/m3) ST 10 ppm (40 mg/m3)|
IDLH (Immediate danger)
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Sulfuryl fluoride (also spelled sulphuryl fluoride) is the inorganic compound with the formula SO2F2. This easily condensed gas has properties more similar to sulfur hexafluoride than sulfuryl chloride, being resistant to hydrolysis even up to 150 °C.
Structure, preparation, reactions
One synthesis begins with the preparation of potassium fluorosulfite:
- SO2 + KF → KSO2F
This salt is then chlorinated to give sulfuryl chloride fluoride:
- KSO2F + Cl2 → SO2ClF + KCl
Further heating at 180 °C of potassium fluorosulfite with the sulfuryl chloride fluoride gives the desired product:
- SO2ClF + KSO2F → SO2F2 + KCl + SO2
- Ba(OSO2F)2 → BaSO4 + SO2F2
- SO2 + F2 → SO2F2
Use as a fumigant
Originally developed by the Dow Chemical Company, sulfuryl fluoride is in widespread use as a structural fumigant insecticide to control drywood termites, particularly in warm-weather portions of the southwestern and southeastern United States and in Hawaii. Less commonly, it can also be used to control rodents, powderpost beetles, deathwatch beetles, bark beetles, and bedbugs. Its use has increased as a replacement for methyl bromide, which was phased out because of harm to the ozone layer. It is an alternative to the use of phosphine, which is acutely toxic.
Sulfuryl fluoride is marketed by three manufacturers, under four different brand names. Vikane (Dow) (EPA Reg. No. 62719- 4-ZA) has been commercially available since the early 1960s, with Zythor (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). Dow recently has begun marketing sulfuryl fluoride as a post-harvest fumigant for dry fruits, nuts, and grains under the trade name ProFume (EPA Reg. No. 62719- 376-AA).  Most recently Drexel Chemical Company has registered Master Fume (EPA Reg. No. 19713-596-AA) for the structural market, competing against Vikane and Zythor.
During application, the building is enclosed in a tight tent 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. The concentration is continuously monitored and maintained at the specified level using electronic equipment. Possible leakages are also checked by low range electronic detectors. Uniphos Envirotronic  is one of the manufacturer and supplier of such monitors and leak detectors. Reentry to the home is allowed when the concentration level is at or below 5 ppm. Sulfuryl fluoride is colorless, odorless, and leaves no residue. During the fumigation process, a warning agent called Chloropicrin (similar to tear gas, but more toxic) is first released into the building to ensure that no occupants remain. Some pest control experts claim tent fumigation is the only 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.) Because it leaves no residue, 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.
In the US, sulfuryl fluoride must be transported in a vehicle marked with "Inhalation Hazard 2" placards. Most states require a license or certification for the individual applying the fumigant.
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, much longer than the 5 years earlier estimated.
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). It is important to note, however, that amounts of sulfuryl fluoride released into the atmosphere (about 2000 metric tons per yr) are far, far lower than the amounts of CO2 released by hydrocarbon-burning vehicles, industry, and other processes (about 30 billion metric tons per year). The most important loss process of sulfuryl fluoride is dissolution of atmospheric sulfuryl fluoride in the ocean followed by hydrolysis.
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- Sulfuryl Fluoride Technical Fact Sheet - National Pesticide Information Center
- Sulfuryl Fluoride General Fact Sheet - National Pesticide Information Center
- Sulfuryl Fluoride Pesticide Information Profile - Extension Toxicology Network
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