Selenium hexafluoride

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Selenium hexafluoride
Selenium-hexafluoride-2D.png Selenium-hexafluoride-3D-balls.png
Identifiers
CAS number 7783-79-1 YesY
PubChem 24558
RTECS number VS9450000
Jmol-3D images Image 1
Properties
Molecular formula SeF6
Molar mass 192.9534 g/mol
Appearance colourless gas
Density 7.887 g/cm3[1]
Melting point −34.6 °C (−30.3 °F; 238.6 K)[1]
Boiling point −46.6 °C (−51.9 °F; 226.6 K) sublimes
Solubility in water insoluble
Refractive index (nD) 1.895
Structure
Crystal structure Orthorhombic, oP28
Space group Pnma, No. 62
Coordination
geometry
octahedral (Oh)
Dipole moment 0
Thermochemistry
Std enthalpy of
formation
ΔfHo298
1030 kJ/mol[2]
Hazards
Main hazards toxic, corrosive
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Selenium hexafluoride is the inorganic compound with the formula SeF6. It is a colourless gas described as having a "repulsive" odor.[3] It is not widely encountered and has no commercial applications.[4]

Structure, preparation, and reactions[edit]

Like many compounds of selenium, SeF6 is hypervalent. The compound has octahedral molecular geometry with Se-F bond length 168.8 pm.

SeF6 can be prepared from the elements[5] or by the reaction of bromine trifluoride (BrF3) with selenium dioxide. The crude product is purified by sublimation.

The relative reactivity of the hexafluorides of S, Se, and Te follows the order TeF6 > SeF6 > SF6, the latter being completely inert toward hydrolysis until high temperatures. SeF6 also resists hydrolysis.[2] The gas can be passed through 10% NaOH or KOH without change, but reacts with gaseous ammonia at 200 °C.[6]

Safety[edit]

Although selenium hexafluoride is quite inert and slow to hydrolyze, it is toxic even at low concentrations,[7] especially by longer exposition. In the U.S., OSHA and ACGIH standards for selenium hexafluoride exposure is an upper limit of 0.05 ppm in air averaged over an eight-hour work shift. Additionally, selenium hexafluoride is designated as IDLH chemical with a maximum allowed exposure limit of 2 ppm.[8]

References[edit]

  1. ^ a b Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. 
  2. ^ a b Wiberg, E.; Holleman, A. F. (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5. 
  3. ^ "Material Safety". Retrieved 2010-07-24. 
  4. ^ Langner, B. E. (2005), "Selenium and Selenium Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a23_525 
  5. ^ Yost, D. M.; Simons, J. H. (1939). "Sulfur, Selenium, and Tellurium Hexafluorides". Inorganic Syntheses 1: 121–122. doi:10.1002/9780470132326.ch44. 
  6. ^ Krebs, B.; Bonmann, S.; Eidenschink, I. (1994). "Selenium-Inorganic Chemistry". In King, R. B. Encyclopedia of Inorganic Chemistry. John Wiley & Sons. ISBN 0-471-93620-0. 
  7. ^ "Medical Management Guidelines for Selenium Hexafluoride (SeF6)". CDC ATSDR. Retrieved 2010-07-24. 
  8. ^ Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)

External links[edit]