Potassium azide

Summary

Potassium azide is the inorganic compound having the formula KN3. It is a white, water-soluble salt. It is used as a reagent in the laboratory.

Potassium azide
K+.svg
Azid-Ion.svg
KN3viewCropped.tif
Names
IUPAC name
Potassium azide
Identifiers
  • 20762-60-1 checkY
3D model (JSmol)
  • Interactive image
ECHA InfoCard 100.039.997 Edit this at Wikidata
  • 10290740
UNII
  • J3LSB2C8SO checkY
  • DTXSID9040267 Edit this at Wikidata
  • InChI=1S/K.N3/c;1-3-2/q+1;-1
    Key: TZLVRPLSVNESQC-UHFFFAOYSA-N
  • [N-]=[N+]=[N-].[K+]
Properties
KN3
Molar mass 81.1184 g/mol
Appearance Colorless crystals[1]
Density 2.038 g/cm3
[1]
Melting point 350 °C (662 °F; 623 K) (in vacuum)[1]
Boiling point decomposes
41.4 g/100 mL (0 °C)
50.8 g/100 mL (20 °C)
105.7 g/100 mL (100 °C)
Solubility soluble in ethanol
insoluble in ether
Thermochemistry
-1.7 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Very Toxic, explosive if strongly heated
NFPA 704 (fire diamond)
4
3
3
Lethal dose or concentration (LD, LC):
27 mg/kg (oral, rat)[2]
Related compounds
Other cations
Sodium azide, copper(II) azide, lead(II) azide, silver azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

It has been found to act as a nitrification inhibitor in soil.[3]

StructureEdit

KN3, RbN3, CsN3, and TlN3 adopt the same structures. They crystallize in a tetragonal habit.[4] The azide is bound to eight cations in an eclipsed orientation. The cations are bound to eight terminal N centers.[5]

 
Coordination sphere of azide in K,Rb,Cs,TlN3.

Synthesis and reactionsEdit

KN3 is prepared by treating potassium carbonate with hydrazoic acid, which is generated in situ.[6] In contrast, the analogous sodium azide is prepared (industrially) by the "Wislicenus process," which proceeds via the reaction sodium amide with nitrous oxide.[7]

Upon heating or upon irradiation with ultraviolet light, it decomposes into potassium metal and nitrogen gas.[8] The decomposition temperatures of the alkali metal azides are: NaN3 (275 °C), KN3 (355 °C), RbN3 (395 °C), CsN3 (390 °C).[9]

Under pressure potassium azide changes structure to form hezaxine with nitrogen in a ring of six atoms: N2−
6
. This is stable at pressures over 20 GPa, but is formed at 45 GPa after heating.[10]

Health hazardsEdit

Like sodium azide, potassium azide is very toxic. The TLV of the related sodium azide is 0.07 ppm. The toxicity of azides arise from their ability to inhibit cytochrome c oxidase.[7]

ReferencesEdit

  1. ^ a b c Dale L. Perry; Sidney L. Phillips (1995). Handbook of inorganic compounds. CRC Press. p. 301. ISBN 0-8493-8671-3.
  2. ^ "Substance Name: Potassium azide". chem.sis.nlm.nih.gov. Archived from the original on 2014-08-12. Retrieved 2014-08-11.
  3. ^ T. D. Hughes; L. F. Welch (1970). "Potassium Azide as a Nitrification Inhibitor". Agronomy Journal. American Society of Agronomy. 62 (5): 595–599. doi:10.2134/agronj1970.00021962006200050013x.
  4. ^ Khilji, M. Y.; Sherman, W. F.; Wilkinson, G. R. (1982). "Variable temperature and pressure Raman spectra of potassium azide". Journal of Raman Spectroscopy. 12 (3): 300–303. Bibcode:1982JRSp...12..300K. doi:10.1002/jrs.1250120319.
  5. ^ Ulrich Müller "Verfeinerung der Kristallstrukturen von KN3, RbN3, CsN3 und TIN3" Zeitschrift für anorganische und allgemeine Chemie 1972, Volume 392, 159–166. doi:10.1002/zaac.19723920207
  6. ^ P. W. Schenk "Alkali Azides from Carbonates" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 475.
  7. ^ a b Horst H. Jobelius, Hans-Dieter Scharff "Hydrazoic Acid and Azides" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_193
  8. ^ Tompkins, F. C.; Young, D. A. (1982). "The Photochemical and Thermal Formation of Colour Centres in Potassium Azide Crystals". Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences. 236 (1204): 10–23.
  9. ^ E. Dönges "Alkali Metals" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 475.
  10. ^ Wang, Yu; Bykov, Maxim; Chepkasov, Ilya; Samtsevich, Artem; Bykova, Elena; Zhang, Xiao; Jiang, Shu-qing; Greenberg, Eran; Chariton, Stella; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F. (21 April 2022). "Stabilization of hexazine rings in potassium polynitride at high pressure". Nature Chemistry. arXiv:2010.15995. doi:10.1038/s41557-022-00925-0. PMID 35449217. S2CID 226222305.