| Sulfuryl fluoride | |
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Sulfuryl fluoride |
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Other names
Sulfonyl fluoride; Sulfur dioxide difluoride; Sulphuryl fluoride; Sulfuryl difluoride |
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| Identifiers | |
| CAS number | 2699-79-8 |
| PubChem | 17607 |
| ChemSpider | 16647 |
| ChEBI | CHEBI:39287 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | SO2F2 |
| Molar mass | 102.06 g/mol |
| Appearance | colourless gas |
| Density | 4.172 g/L (gas), 1.632 g/mL (liquid under compressed gas at 0 °C) |
| Melting point |
-124.7 °C, 148 K, -192 °F |
| Boiling point |
-55.4 °C, 218 K, -68 °F |
| Solubility in water | low |
| Solubility in other solvents | SO2 |
| Structure | |
| Coordination geometry |
tetrahedral |
| Hazards | |
| Main hazards | toxic |
| NFPA 704 |
0
3
1
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| Related compounds | |
| Related compounds | SO2Cl2, SO2ClF, SF6, SO3 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
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. So inert is this material that suspended molten "sodium metal retains its shiny metallic appearance."[1]
Contents |
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:
A laboratory-scale synthesis begins with the preparation of potassium fluorosulfite:[2]
This salt is then chlorinated to give sulfuryl chloride fluoride:
Further heating (180 °C) of potassium fluorosulfite with the sulfuryl chloride fluoride gives the desired product:[3]
Heating metal fluorosulfonate salts also gives this molecule:[1]
Use of SO2F2 as a fumigant has increased rapidly as it replaces methyl bromide, now being phased out because of harm to the ozone layer, and as an alternative to the risks of phosphine.[4]
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, bark beetles, and bedbugs.
Sulfuryl fluoride is currently marketed by three distinct 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). [1] Most recently Drexel Chemical Company has registered Master Fume (EPA Reg. No. 19713-596-AA) for the structural market, competing against Vikane and Zythor.[5]
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.[6]) 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.
Sulfuryl fluoride is toxic in humans and following inhalation may cause symptoms of fluoride poisoning. Symptoms may include weakness, nausea, vomiting, hypotension, metabolic acidosis, hypocalcemia, cardiac dysrhythmia, pulmonary edema, and death.[7][8][9] Medical treatment may consist of giving calcium, correcting acidosis with sodium bicarbonate, and hemodialysis.[7] They would have been advised to follow Nitschke[10] as post treatment with phenobarbital was effective in rats, whereas post treatment to restore calcium was not effective.
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.
Based on the first high frequency, high precision, in situ atmospheric and archived air measurements of sulfuryl fluoride it was determined that sulfuryl fluoride has an atmospheric lifetime of 30–40 years,[11] much longer than the 5 years earlier estimated.[12] Moreover, 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).[11][13][14] It is important to note, however, that amounts of sulfuryl fluoride released into the atmosphere (about 2000 metric tons per yr[11]) 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.[11][15]