Potassium azide

Chemical compound From Wikipedia, the free encyclopedia

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.

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Potassium azide
Names
IUPAC name
Potassium azide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.039.997 Edit this at Wikidata
EC Number
  • 244-013-1
UNII
  • 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 0.1375 g/100 g in ethanol (16 °C)[2]
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)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
4
3
3
Lethal dose or concentration (LD, LC):
27 mg/kg (oral, rat)[3]
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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It has been found to act as a nitrification inhibitor in soil.[4]

Structure

KN3, RbN3, CsN3, and TlN3 adopt the same structures. They crystallize in a tetragonal habit.[5] The azide is bound to eight cations in an eclipsed orientation. The cations are bound to eight terminal N centers.[6]

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

Synthesis and reactions

KN3 is prepared by treating potassium carbonate with hydrazoic acid, which is generated in situ.[7] In contrast, the analogous sodium azide is prepared (industrially) by the "Wislicenus process," which proceeds via the reaction sodium amide with nitrous oxide.[8]

Upon heating or upon irradiation with ultraviolet light, it decomposes into potassium metal and nitrogen gas.[9] The decomposition temperatures of the alkali metal azides are: NaN3 (275 °C), KN3 (355 °C), RbN3 (395 °C), CsN3 (390 °C).[10]

Under high pressures and high temperatures, potassium azide was found to transform into the K2N6 and K9N56 compounds, both containing hexazine rings: N2−
6 and N64-, respectively.[11][12]

Health hazards

Like sodium azide, potassium azide is very toxic. The threshold limit value of the related sodium azide is 0.07 ppm. The toxicity of azides arise from their ability to inhibit cytochrome c oxidase.[8]

References

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