Sulfuryl fluoride
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| Sulfuryl fluoride | |
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| IUPAC name | Sulfuryl fluoride |
| Other names | Sulfonyl fluoride; Sulfur dioxide difluoride;
Sulphuryl fluoride; Sulfuryl difluoride |
| Identifiers | |
| CAS number | [2699-79-8] |
| Properties | |
| Molecular formula | SO2F2 |
| Molar mass | 102.06 g/mol |
| Appearance | colourless gas |
| Density | 1.623 g/cm³ at 0 °C |
| Melting point |
-135.7 °C |
| Boiling point |
-55.2 °C |
| Solubility in water | low |
| Solubility in other solvents | SO2 |
| Structure | |
| Coordination geometry |
tetrahedral |
| Hazards | |
| Main hazards | toxic |
| Related compounds | |
| Related compounds | SO2Cl2, SO2ClF, SF6, SO3 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Sulfuryl fluoride is the chemical compound with the formula SO2F2. This inorganic gas has properties more similar to sulfur hexafluoride than sulfuryl chloride, being resistant to hydrolysis even up to 150 °C. So inert is this material that suspended molten "sodium metal retains its shiny metallic appearance."[1]
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[edit] Structure and preparation
The molecule is tetrahedral with C2v symmetry. The S-O distance is 140.5 pm, S-F is 153.0 pm. As predicted by VSEPR, the O-S-O angle is more open than the F-S-F angle, 124° and 97°, respectively.[1]
It is prepared by direct reaction of fluorine with sulfur dioxide:
- SO2 + F2 → SO2F2
A laboratory-scale synthesis begins with the preparation of potassium fluorosulfite:[2]
- SO2 + KF → KSO2F
This salt is then chlorinated to give sulfuryl chloride fluoride:
- KSO2F + Cl2 → SO2ClF + KCl
Further heating (180 °C) of potassium fluorosulfite with the sulfuryl chloride fluoride gives the desired product:[3]
- SO2ClF + KSO2F → SO2F2 + KCl + SO2
Heating metal fluorosulfonate salts also gives this molecule:[1]
- Ba(OSO2F)2 → BaSO4 + SO2F2
[edit] Use as a fumigant
SO2F2 is of interest as a fumigant with the phase-out of methyl bromide and in view of the risks of phosphine.[4]
Originally developed by the Dow Chemical Company, SO2F2 (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, powder-post beetles, bark beetles, and bedbugs.
Sulfuryl fluoride is currently marketed by two distinct manufacturers, under three different brand names. Vikane (Dow) has been commercially available since the early 1960s, with Zythor (marketed by competitor EnSystex II of North Carolina) 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. [1]
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. 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 sulfuryl fluoride is the only effective treatment for drywood termites. (Heat is the only other approved method for whole structure treatment for termites in California.[5]) Because it leaves no residue sulfuryl fluoride provides no protection from future infestations, although heavy reinfestation can take several years since drywood termites have slower growing colonies than ground termites.
[edit] Safety considerations
Sulfuryl fluoride must be transported in a vehicle marked with "Inhalation Hazard 2" placards. Most U.S. states also require a license or certification for the individual applying the fumigant.
[edit] References
- ^ a b c Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Seel, F. "Potassium Fluorosulfite" Inorganic Syntheses 1967, IX, pages 113-115.
- ^ Seel, F. "Sulfuryl Chloride Fluoride and Sufluryl Fluoride" Inorganic Syntheses 1967, IX, pages 11-113.
- ^ Bell, C. H. "Fumigation in the 21st century" "Crop Protection, 2000, 19, 563-569. ISSN 0261-2194. AN 2000:895590
- ^ Termites Fact Sheet
