Fluorine azide

Fluorine azide or triazadienyl fluoride (FN3) is a yellow green gas composed of nitrogen and fluorine with formula FN3.[1] It is counted as an interhalogen compound, as the azide functional group is termed a pseudohalogen. It resembles ClN3, BrN3, and IN3 in this respect.[2] The bond between the fluorine atom and the nitrogen is very weak, leading to this substance being very unstable and prone to explosion.[3] Calculations show the F–N–N angle to be around 102° with a straight line of 3 nitrogen atoms.[4]

Fluorine azide
Names
Other names
triazadienyl fluoride
Identifiers
3D model (JSmol)
Properties
FN3
Molar mass 61.019 g/mol
Appearance Yellow green gas
Melting point −139 °C (−218 °F; 134 K)
Boiling point −30 °C (−22 °F; 243 K)
Explosive data
Shock sensitivity Extreme
Friction sensitivity Extreme
Hazards
Main hazards Extremely sensitive explosive
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth (blue): no hazard codeReactivity code 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazards (white): no code
0
4
Related compounds
Other cations
 Hydrazoic acid
Chlorine azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

The gas boils at –30° and melts at –139 °C.[5]

It was first made by John F. Haller in 1942.[6]

Reactions

Fluorine azide can be made by reacting hydrazoic acid and fluorine gas.[5]

Another way to form it is by reacting sodium azide with fluorine.[7]

Fluorine azide decomposes without explosion at normal temperatures to make dinitrogen difluoride:

2 FN3 → N2F2 + 2 N2.[1]

At higher temperatures such as 1000 °C fluorine azide breaks up into nitrogen monofluoride radical:[7]

FN3 → FN{a1Δ} + N2.

Solid or liquid FN3 explodes, releasing much heat. A thin film burns at the rate of 1.6 km/s.[8] Because the explosion hazard is great only very small quantities of this substance should be handled at a time. A 0.02 g limit is recommended for experiments.[9]

N3F adducts can be formed with the Lewis acids boron trifluoride (BF3) and arsenic pentafluoride (AsF5) at -196 °C. These molecules bond with the Nα atom.[10]

Properties

Spectroscopy
parameter value[9] unit
A 48131.448 MHz
B 5713.266 MHz
C 5095.276 MHz
μa 1.1
μb 0.7

Shape

The nitrogen atoms in this molecule can be labelled with Greek letters: Nα for nitrogen attached to fluorine, Nβ for the intermediate nitrogen, and Nγ for the terminal nitrogen.[10] The terminal nitrogen can also be labelled Nω.[3]

Distances between atoms are F-N 0.1444 nm, FN-NN 0.1253 nm and FNN-N 0.1132 nm.[9]

Physical

N3F has a density of 1.3 g/cm3.[11]

N3F adsorbs on to solid surfaces of potassium fluoride, but not onto lithium fluoride or sodium fluoride. This property was being investigated so that N3F could boost the energy of solid propellants.[11]

The ultraviolet photoelectric spectrum shows ionisation peaks at 11.01, 13,72, 15.6, 15.9, 16.67, 18.2, and 19.7 eV. Respectively these are assigned to the orbitals: π, nN or nF, nF, πF, nN or σ, π and σ.[3]

References
  1. Gipstein, Edward; John F. Haller (1966). "Absorption Spectrum of Fluorine Azide". Applied Spectroscopy. 20 (6): 417–418. Bibcode:1966ApSpe..20..417G. doi:10.1366/000370266774386470. ISSN 0003-7028.
  2. Saxena, P. B. (2007-01-01). Chemistry of Interhalogen Compounds. Discovery Publishing House. p. 96. ISBN 9788183562430. Retrieved 16 June 2014.
  3. Rademacher, Paul; Andreas J. Bittner; Gabriele Schatte; Helge Willner (1988). "Photoelectron Spectrum and Electronic Structure of Triazadienyl Fluoride, N3F". Chemische Berichte. 121 (3): 555–557. doi:10.1002/cber.19881210325. ISSN 0009-2940.
  4. Peters, Nancy J. S.; Leland C. Allen; Raymond A. Firestone (1988). "Fluorine azide and fluorine nitrate: structure and bonding". Inorganic Chemistry. 27 (4): 755–758. doi:10.1021/ic00277a035. ISSN 0020-1669.
  5. Gholivand, Khodayar; Gabriele Schatte; Helge Willner (1987). "Properties of triazadienyl fluoride, N3F". Inorganic Chemistry. 26 (13): 2137–2140. doi:10.1021/ic00260a025. ISSN 0020-1669.
  6. Lowe, Derek (21 October 2008). "Things I Won't Work With: Triazadienyl Fluoride". In the Pipeline. Retrieved 15 June 2014.
  7. Benard, D. J.; B. K. Winker; T. A. Seder; R. H. Cohn (1989). "Production of nitrogen monofluoride (a1Δ) by dissociation of fluorine azide". The Journal of Physical Chemistry. 93 (12): 4790–4796. doi:10.1021/j100349a022. ISSN 0022-3654.
  8. Seder, T.A.; D.J. Benard (1991). "The decomposition of condensed phase fluorine azide". Combustion and Flame. 85 (3–4): 353–362. doi:10.1016/0010-2180(91)90139-3. ISSN 0010-2180.
  9. Christen, Dines.; H. G. Mack; G. Schatte; H. Willner (1988). "Structure of triazadienyl fluoride, FN3, by microwave, infrared, and ab initio methods". Journal of the American Chemical Society. 110 (3): 707–712. doi:10.1021/ja00211a007. ISSN 0002-7863.
  10. Schatte, G.; H. WIllner (1991). "Die Wechselwirkung von N3F mit Lewis-Säuren und HF. N3F als möglicher Vorläufer für die Synthese von N3+-Salzen = The interaction of N3F with Lewis acids and HF•N3F as possible precursor for the synthesis of N3+ salts". Zeitschrift für Naturforschung B (in German). 46 (4): 483–489. ISSN 0932-0776.
  11. Brener, Nathan E.; Kestner, Neil R.; Callaway, Joseph (December 1990). Theoretical Studies of Highly Energetic CBES Materials: Final Report for the Period 2 March 1987 to 31 May 1987 (PDF). Louisiana State University, Department of Physics and Astronomy. pp. 21–27. Retrieved 25 June 2014.
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