Chlorine pentafluoride

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Chlorine pentafluoride
Chlorine-pentafluoride-2D-dimensions.png
Chlorine-pentafluoride-3D-balls.png
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Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.734 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
RTECS number
  • FO2975000
UNII
  • InChI=1S/ClF5/c2-1(3,4,5)6 X mark.svgN
    Key: KNSWNNXPAWSACI-UHFFFAOYSA-N X mark.svgN
  • FCl(F)(F)(F)F
Properties
ClF5
Molar mass 130.445 g mol−1
Appearancecolorless 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)
Hydrolyzes
Structure
Square pyramidal
Thermochemistry
Std molar
entropy (S⦵298)
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]

Contents

Preparation

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]

Reactions

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

ClF
5 + 2 H
2O → ClO
2F + 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]

Uses

Rocket propellant

Chlorine pentafluoride was once considered for use as an oxidizer for rockets. As a propellant, it has a higher maximum specific impulse than ClF3, but with the same difficulties in handling. [4] Due to the hazardous nature of chlorine pentafluoride and the large amounts of hydrogen fluoride in the exhaust, it has yet to be used in a large scale rocket propulsion system.

See also

References

  1. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 833. ISBN   978-0-08-037941-8.
  2. 1 2 Pilipovich, D.; Maya, W.; Lawton, E.A.; Bauer, H.F.; Sheehan, D. F.; Ogimachi, N. N.; Wilson, R. D.; Gunderloy, F. C.; Bedwell, V. E. (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. Bibcode:1963Sci...141.1039S. doi:10.1126/science.141.3585.1039. PMID   17739492. S2CID   39767609.
  4. 1 2 3 Clark, John Drury (23 May 2018). Ignition!: An Informal History of Liquid Rocket Propellants. Rutgers University Press. pp. 87–88. ISBN   978-0-8135-9918-2.
  5. 1 2 Smith D. F. (1963). "Chlorine Pentafluoride". Science . 141 (3585): 1039–1040. Bibcode:1963Sci...141.1039S. doi:10.1126/science.141.3585.1039. PMID   17739492. S2CID   39767609.
  6. ↑ Šmalc A, Žemva B, Slivnik J, Lutar K (1981). "On the Synthesis of Chlorine Pentafluoride". Journal of Fluorine Chemistry. 17 (4): 381–383. 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.
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