Disulfur decafluoride

Disulfur decafluoride

Names
Preferred IUPAC name Disulfur decafluoride
Systematic IUPAC name Decafluoro-1λ6,2λ6-disulfane
Other names Sulfur pentafluoride TL-70 Agent Z
Identifiers
CAS Number	5714-22-7
3D model (JSmol)	Interactive image
ChemSpider	56348
ECHA InfoCard	100.024.732
EC Number	227-204-4
MeSH	Disulfur+decafluoride
PubChem CID	62586
RTECS number	WS4480000
UNII	5XG19I842O
UN number	3287
CompTox Dashboard (EPA)	DTXSID2073356
InChI InChI=1S/F10S2/c1-11(2,3,4,5)12(6,7,8,9)10 Key: BPFZRKQDXVZTFD-UHFFFAOYSA-N
SMILES FS(F)(F)(F)(F)S(F)(F)(F)(F)F
Properties
Chemical formula	S2F10
Molar mass	254.10 g·mol−1
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)
Solubility in water	insoluble[2]
Vapor pressure	561 mmHg (20 °C)[1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Poisonous
NFPA 704 (fire diamond)	4 0 0 OX
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	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

Disulfur decafluoride is a chemical compound with the formula S₂F₁₀. It was 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] and one sulfur atom. The two sulfur atoms are connected by a single bond. In the S₂F₁₀ molecule, the oxidation state of each sulfur atoms is +5, but their valency is 6 (they are hexavalent). S₂F₁₀ is highly toxic, with toxicity four times that of phosgene.

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) into 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 four 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]

See also

• Phosgene
• Perfluoroisobutene
• Bis(trifluoromethyl) disulfide

References

• Christophorou, L. G.; Sauers, I. (1991). Gaseous Dielectrics VI. Plenum Press. ISBN 978-0-306-43894-3.

External links

• "Sulfur Pentaflu". 1988 OSHA PEL Project. CDC NIOSH. 28 February 2020.