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
Appearancecolorless gas
Odor sweet
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/(mol·K)
−238.49 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Fatal if inhaled. Causes permanent blindness and severe skin and respiratory tract burns. [1]
GHS labelling:
GHS-pictogram-rondflam.svg GHS-pictogram-bottle.svg GHS-pictogram-acid.svg GHS-pictogram-skull.svg
Danger
H270, H280, H314, H330
P220, P244, P260, P264, P271, P280, P284, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P320, P321, P363, P370+P376, P403, P403+P233, P405, P410+P403, P501
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, [2] as confirmed by its high-resolution 19F NMR spectrum. [3] It was first synthesized in 1963. [4]

Contents

Preparation

Some of the earliest research on the preparation was classified. [5] [6] It was first prepared by fluorination of chlorine trifluoride at high temperatures and high pressures: [5]

ClF3 + F2 → ClF5
ClF + 2 F2 → ClF5
Cl2 + 5 F2 → 2 ClF5
Cs[ClF4] + F2 → CsF + ClF5

NiF2 catalyzes this reaction. [7]

Certain metal fluorides, M+[ClF4]−, e.g. K+[ClF4]− (potassium tetrafluorochlorate(III)), Rb+[ClF4]− (rubidium tetrafluorochlorate(III)), Cs+[ClF4]− (caesium tetrafluorochlorate(III)), react with F2 to produce ClF5 and the corresponding alkali metal fluoride. [6]

Reactions

In a highly exothermic reaction, ClF5 reacts with water to produce chloryl fluoride and hydrogen fluoride: [8]

ClF5 + 2 H2O → ClO2F + 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. [3]

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. [5] 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.

Safety

Chlorine pentafluoride is highly toxic. It is a strong irritant to skin, eyes and mucous membranes. It is very corrosive. Causes severe and painful skin, eye and respiratory tract burns. May cause lungs damage, toxic pneumonitis and permanent blindness. It is fatal if inhaled or absorbed through skin. Containers with chlorine pentafluoride may explode when heated. Ruptured cylinders may rocket violently. Chlorine pentafluoride causes other symptoms like nausea, vomiting and dyspnea. [1] [9]

Chlorine pentafluoride reacts violently with water or moisture in the air and even water ice at −100 °C (−148 °F) (to produce corrosive hydrofluoric acid and toxic chlorine gas), nitric acid (even at −100° C), metals and organic materials. It is a strong oxidizer. It does not burn, but support burning. On catching fire or heated to decomposition, it emits corrosive and very toxic gases. Vapors from liquefied gas are initially heavier than air and spread along the floor. These are strong oxidizers and will react vigorously or explosively with many materials including fuels. May ignite flammable materials (wood, paper, oil, clothing, etc.). [9]

See also

References

  1. 1 2 https://pubchem.ncbi.nlm.nih.gov/compound/0061654
  2. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 833. ISBN   978-0-08-037941-8.
  3. 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.
  4. ↑ 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.
  5. 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.
  6. 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.
  7. ↑ 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.
  8. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 834. ISBN   978-0-08-037941-8.
  9. 1 2 https://www.chemicalbook.com/ChemicalProductProperty_EN_CB4364157.htm
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