Potassium azide: Difference between revisions

|Watchedfields = changed

|verifiedrevid = 444179568

|ImageFileL1 =K+.svg

|ImageSizeL1 = 32px

|ImageFileR1 =Azid-Ion.svg

|ImageSizeR1 = 140px

|ImageFile2 = KN3viewCropped.tif

|ImageSize2 = 300px

|IUPACName = Potassium azide

|Section1={{Chembox Identifiers

|CASNo_Ref = {{cascite|correct|??}}

|CASNo = 20762-60-1

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = J3LSB2C8SO

|PubChem = 10290740

|SMILES =[N-]=[N+]=[N-].[K+]

|InChI = 1S/K.N3/c;1-3-2/q+1;-1

|InChIKey = TZLVRPLSVNESQC-UHFFFAOYSA-N

}}

|Section2={{Chembox Properties

|Formula = {{chem2|KN3}}

|MolarMass = 81.1184 g/mol

|Appearance = Colorless crystals<ref name="perry_phillips"/>

|Density = 2.038 g/cm{{su|p=3}} <ref name="perry_phillips"/>

|MeltingPtC = 350

|MeltingPt_notes = (in vacuum)<ref name="perry_phillips">{{cite book | title = Handbook of inorganic compounds | author1 = Dale L. Perry | author2 = Sidney L. Phillips | publisher = CRC Press | year = 1995 | page = 301 | isbn = 0-8493-8671-3 }}</ref>

|BoilingPt = decomposes

|Solubility = 41.4 g/100 mL (0 °C)<br />50.8 g/100 mL (20 °C)<br />105.7 g/100 mL (100 °C)

|SolubleOther = 0.1375 g/100 g in [[ethanol]] (16°C)<ref>{{cite journal | title = IUPAC-NIST Solubility Data Series. 79. Alkali and Alkaline Earth Metal Pseudohalides. | author1 = Jiri Hála | journal = J. Phys. Chem. Ref. Data | volume = 33 | page = 16 | year = 2004 | doi=10.1063/1.1563591}} </ref><br />insoluble in [[diethyl ether|ether]]

}}

|Section3={{Chembox Thermochemistry

|DeltaHf = -1.7 kJ/mol

}}

|Section4={{Chembox Hazards

|MainHazards = Very Toxic, explosive if strongly heated

|NFPA-H = 4 | NFPA-F = 3 | NFPA-R = 3 | NFPA-S =

|LD50 = 27 mg/kg (oral, rat)<ref>{{Cite web |url=https://chem.nlm.nih.gov/chemidplus/rn/20762-60-1 |title=Substance Name: Potassium azide |website=chem.sis.nlm.nih.gov |access-date=2014-08-11 |archive-date=2014-08-12 |archive-url=https://web.archive.org/web/20140812215717/https://chem.nlm.nih.gov/chemidplus/rn/20762-60-1 |url-status=live}}</ref>

}}

|Section5={{Chembox Related

|OtherCations = [[Sodium azide]], [[copper(II) azide]], [[lead(II) azide]], [[silver azide]]

}}

'''Potassium azide''' is the [[inorganic compound]] having the formula {{chem2|KN3}}. It is a white, water-soluble [[salt (chemistry)|salt]]. It is used as a reagent in the laboratory.

It has been found to act as a nitrification inhibitor in soil.<ref>{{cite journal | title = Potassium Azide as a Nitrification Inhibitor | author1 = T. D. Hughes | author2 = L. F. Welch | journal = Agronomy Journal | volume = 62 | pages = 595–599 | year = 1970 | issue = 5 | publisher = American Society of Agronomy | doi=10.2134/agronj1970.00021962006200050013x}}</ref>

==Structure==

{{chem2|KN3}}, {{chem2|RbN3}}, {{chem2|CsN3}}, and {{chem2|TlN3}} adopt the same structures. They crystallize in a tetragonal habit.<ref>{{Cite journal | first1 = M. Y.| last1 = Khilji| last2 = Sherman | first2 = W. F. | first3 = G. R. | last3 = Wilkinson| title = Variable temperature and pressure Raman spectra of potassium azide| journal = Journal of Raman Spectroscopy| volume = 12| issue = 3| pages = 300–303| year = 1982 | doi = 10.1002/jrs.1250120319|bibcode = 1982JRSp...12..300K }}</ref> The azide is bound to eight cations in an eclipsed orientation. The cations are bound to eight terminal N centers.<ref>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}}</ref>

[[File:AzideCoordinationCropped.tif|thumb|left|180px|Coordination sphere of azide in K,Rb,Cs,TlN₃]]

==Synthesis and reactions==

{{chem2|KN3}} is prepared by treating [[potassium carbonate]] with [[hydrazoic acid]], which is generated in situ.<ref>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.</ref> In contrast, the analogous [[sodium azide]] is prepared (industrially) by the "[[Johannes Wislicenus|Wislicenus]] process," which proceeds via the reaction sodium amide with [[nitrous oxide]].<ref name=Ullmann>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}}</ref>

Upon heating or upon irradiation with ultraviolet light, it decomposes into potassium metal and [[nitrogen]] gas.<ref>{{cite journal | author1 = Tompkins, F. C. | author2 = Young, D. A. | title = The Photochemical and Thermal Formation of Colour Centres in Potassium Azide Crystals | journal = Proceedings of the Royal Society of London | series = Series A, Mathematical and Physical Sciences | volume = 236 | issue = 1204 | pages = 10–23 | year = 1982 }}</ref> The decomposition temperatures of the alkali metal azides are: {{chem2|NaN3}} (275&nbsp;°C), {{chem2|KN3}} (355&nbsp;°C), {{chem2|RbN3}} (395&nbsp;°C), {{chem2|CsN3}} (390&nbsp;°C).<ref>E. Dönges "Alkali Metals" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 475</ref>

Under high pressures and high temperatures, potassium azide was found to transform into the K₂N₆ and K₉N₅₆ compounds, both containing hexazine rings: N{{su|b=6|p=2−}} and N₆^4-, respectively.<ref>{{cite journal |last1=Wang |first1=Yu |last2=Bykov |first2=Maxim |last3=Chepkasov |first3=Ilya |last4=Samtsevich |first4=Artem |last5=Bykova |first5=Elena |last6=Zhang |first6=Xiao |last7=Jiang |first7=Shu-qing |last8=Greenberg |first8=Eran |last9=Chariton |first9=Stella |last10=Prakapenka |first10=Vitali B. |last11=Oganov |first11=Artem R. |last12=Goncharov |first12=Alexander F. |title=Stabilization of hexazine rings in potassium polynitride at high pressure |journal=Nature Chemistry |date=21 April 2022 |volume=14 |issue=7 |pages=794–800 |doi=10.1038/s41557-022-00925-0|pmid=35449217 |arxiv=2010.15995 |bibcode=2022NatCh..14..794W |s2cid=226222305}}</ref><ref>{{Cite journal |last1=Laniel |first1=Dominique |last2=Trybel |first2=Florian |last3=Yin |first3=Yuqing |last4=Fedotenko |first4=Timofey |last5=Khandarkhaeva |first5=Saiana |last6=Aslandukov |first6=Andrey |last7=Aprilis |first7=Georgios |last8=Abrikosov |first8=Alexei I. |last9=Bin Masood |first9=Talha |last10=Giacobbe |first10=Carlotta |last11=Bright |first11=Eleanor Lawrence |last12=Glazyrin |first12=Konstantin |last13=Hanfland |first13=Michael |last14=Wright |first14=Jonathan |last15=Hotz |first15=Ingrid |date=2023-03-06|title=Aromatic hexazine [N6]4− anion featured in the complex structure of the high-pressure potassium nitrogen compound K9N56 |url=https://www.nature.com/articles/s41557-023-01148-7 |journal=Nature Chemistry |volume=15 |issue=5 |pages=641–646 |language=en |doi=10.1038/s41557-023-01148-7 |pmid=36879075 |bibcode=2023NatCh..15..641L |s2cid=257377020 |issn=1755-4330}}</ref>

==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]].<ref name=Ullmann/>

{{Azides}}