Chemistry:Chlorine pentafluoride

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Short description: Chemical compound
Chlorine pentafluoride
3D model (JSmol)
RTECS number
  • FO2975000
Molar mass 130.445 g mol−1
Appearance colorless gas
Density 4.5 kg/m3 (g/L)
Melting point −103 °C (−153 °F; 170 K)
Boiling point −13.1 °C (8.4 °F; 260.0 K)
Square pyramidal
310.73 J K−1 mol−1
−238.49 kJ mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chlorine pentafluoride is an interhalogen compound with formula ClF5. This colourless gas is a strong oxidant that was once a candidate oxidizer for rockets. The molecule adopts a square pyramidal structure with C4v symmetry,[1] as confirmed by its high-resolution 19F NMR spectrum.[2] It was first synthesized in 1963.[3]


Some of the earliest research on the preparation was classified.[4][5] It was first prepared by fluorination of chlorine trifluoride at high temperatures and high pressures:[4]

ClF3 + F2 → ClF5
ClF + 2F2 → ClF5
Cl2 + 5F2 → 2ClF5
CsClF4 + F2 → CsF + ClF5

NiF2 catalyzes this reaction.[6]

Certain metal fluorides, MClF4 (i.e. KClF4, RbClF4, CsClF4), react with F2 to produce ClF5 and the corresponding alkali metal fluoride.[5]


In a highly exothermic reaction, ClF5 reacts with water to produce chloryl fluoride and hydrogen fluoride:[7]

ClF5 + 2 H2OClO2F + 4 HF

It is also a strong fluorinating agent. At room temperature it reacts readily with all elements (including otherwise "inert" elements like platinum and gold) except noble gases, nitrogen, oxygen and fluorine.[2]


Rocket propellant

Chlorine pentafluoride was once considered for use as an oxidizer for rockets. As a propellant, it is similar to ClF3, but has a higher maximum specific impulse.[4] However, due to the hazardous nature of chlorine pentafluoride, it has yet to be used in a large scale rocket propulsion system.

See also


  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 833. ISBN 978-0-08-037941-8. 
  2. 2.0 2.1 Pilipovich, D.; Maya, W.; Lawton, E.A.; Bauer, H.F.; Sheehan, D. F.; Ogimachi, N. N.; Wilson, R. D.; Gunderloy, F. C. et al. (1967). "Chlorine pentafluoride. Preparation and Properties". Inorganic Chemistry 6 (10): 1918. doi:10.1021/ic50056a036. 
  3. Smith D. F. (1963). "Chlorine Pentafluoride". Science 141 (3585): 1039–1040. doi:10.1126/science.141.3585.1039. PMID 17739492. 
  4. 4.0 4.1 4.2 Clark, John D. (1972). Ignition! An Informal History of Liquid Rocket Propellants. Rutgers University Press. pp. 87–88. ISBN 0-8135-0725-1. 
  5. 5.0 5.1 Smith D. F. (1963). "Chlorine Pentafluoride". Science 141 (3585): 1039–1040. doi:10.1126/science.141.3585.1039. PMID 17739492. Bibcode1963Sci...141.1039S. 
  6. "On the Synthesis of Chlorine Pentafluoride". Journal of Fluorine Chemistry 17 (4): 381–383. 1981. doi:10.1016/S0022-1139(00)81783-2. 
  7. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 834. ISBN 978-0-08-037941-8. 

External links