Disulfur decafluoride

Disulfur decafluoride (S2F10) is a chemical compound discovered in 1934 by Denbigh and Whytlaw-Gray.[4] Each sulfur atom of the S2F10 molecule is octahedral, and surrounded by five fluorine atoms.[5] S2F10 is highly toxic, with toxicity four times that of phosgene.

Disulfur decafluoride
Ball-and-stick model of disulfur decafluoride
Space-filling model of disulfur decafluoride
Names
Preferred IUPAC name
Disulfur decafluoride
Systematic IUPAC name
Decafluoro-1λ6,2λ6-disulfane
Other names
sulfur pentafluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.024.732
EC Number
  • 227-204-4
MeSH Disulfur+decafluoride
RTECS number
  • WS4480000
UNII
UN number 3287
Properties
S2F10
Molar mass 254.1 g/mol
Appearance colorless liquid
Odor like sulfur dioxide[1]
Density 2.08 g/cm3
Melting point −53 °C (−63 °F; 220 K)
Boiling point 30.1691 °C (86.3044 °F; 303.3191 K)
insoluble[2]
Vapor pressure 561 mmHg (20 °C)[1]
Hazards
Main hazards Poisonous
NFPA 704 (fire diamond)
Lethal dose or concentration (LD, LC):
2000 mg/m3 (rat, 10 min)
1000 mg/m3 (mouse, 10 min)
4000 mg/m3 (rabbit, 10 min)
4000 mg/m3 (guinea pig, 10 min)
4000 mg/m3 (dog, 10 min)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.025 ppm (0.25 mg/m3)[1]
REL (Recommended)
 C 0.01 ppm (0.1 mg/m3)[1]
IDLH (Immediate danger)
 1 ppm[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

It is a colorless liquid with a burnt match smell similar to sulfur dioxide.[1]

Production

Disulfur decafluoride is produced by photolysis of SF5Br:[6]

2 SF5Br → S2F10 + Br2

Disulfur decafluoride arises by the decomposition of sulfur hexafluoride. It is produced by the electrical decomposition of sulfur hexafluoride (SF6)—an essentially inert insulator used in high voltage systems such as transmission lines, substations and switchgear. S2F10 is also made during the production of SF6.

Properties

The S-S bond dissociation energy is 305 ± 21 kJ/mol, about 80 kJ/mol stronger than the S-S bond in diphenyldisulfide.

At temperatures above 150 °C, S
2F
10 decomposes slowly (disproportionation) to SF
6 and SF
4:

S2F10 → SF6 + SF4

S
2F
10 reacts with N
2F
4 to give SF
5NF
2. It reacts with SO
2 to form SF
5OSO
2F in the presence of ultraviolet radiation.

S
2F
10 + N
2F
4 → 2 SF
5NF
2

In the presence of excess chlorine gas, S
2F
10 reacts to form sulfur chloride pentafluoride (SF
5Cl):

S
2F
10 + Cl
2 → 2 SF
5Cl

The analogous reaction with bromine is reversible and yields SF
5Br.[7] The reversibility of this reaction can be used to synthesize S
2F
10 from SF
5Br.[8]

Ammonia is oxidised by S
2F
10 into NSF
3.[9]

Toxicity

S
2F
10 was considered a potential chemical warfare pulmonary agent in World War II because it does not produce lacrimation or skin irritation, thus providing little warning of exposure. Disulfur decafluoride is a colorless gas or liquid with a SO2-like odor.[10] It is about 4 times as poisonous as phosgene. Its toxicity is thought to be caused by its disproportionation in the lungs into SF
6, which is inert, and SF
4, which reacts with moisture to form sulfurous acid and hydrofluoric acid.[11] Disulfur decafluoride itself is not toxic due to hydrolysis products, since it is hardly hydrolysed by water and most aqueous solutions.

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References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0579". National Institute for Occupational Safety and Health (NIOSH).
  2. http://www.chemicalbook.com/ChemicalProductProperty_EN_CB0751782.htm
  3. "Sulfur pentafluoride". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. Denbigh, K. G.; Whytlaw-Gray, R. (1934). "The Preparation and Properties of Disulphur Decafluoride". Journal of the Chemical Society. 1934: 1346–1352. doi:10.1039/JR9340001346.
  5. Harvey, R. B.; Bauer, S. H. (June 1953). "An Electron Diffraction Study of Disulfur Decafluoride". Journal of the American Chemical Society. 75 (12): 2840–2846. doi:10.1021/ja01108a015.
  6. . doi:10.1016/S0022-1139(97)00096-1. Cite journal requires |journal= (help); Missing or empty |title= (help)
  7. Cohen, B.; MacDiarmid, A. G. (December 1965). "Chemical Properties of Disulfur Decafluoride". Inorganic Chemistry. 4 (12): 1782–1785. doi:10.1021/ic50034a025.
  8. Winter, R.; Nixon, P.; Gard, G. (January 1998). "A new preparation of disulfur decafluoride". Journal of Fluorine Chemistry. 87 (1): 85–86. doi:10.1016/S0022-1139(97)00096-1.
  9. Mitchell, S. (1996). Biological Interactions of Sulfur Compounds. CRC Press. p. 14. ISBN 978-0-7484-0245-8.
  10. "Sulfur Pentaflu". 1988 OSHA PEL Project. CDC NIOSH.
  11. Johnston, H. (2003). A Bridge not Attacked: Chemical Warfare Civilian Research During World War II. World Scientific. pp. 33–36. ISBN 978-981-238-153-8.
  • Christophorou, L. G.; Sauers, I. (1991). Gaseous Dielectrics VI. Plenum Press. ISBN 978-0-306-43894-3.
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