Hydrazoic acid
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Names | |
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IUPAC name
Hydrogen azide
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Other names
Hydrogen azide
Azoimide Azic acid | |
Identifiers | |
3D model (JSmol)
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ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.029.059 |
EC Number |
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773 | |
PubChemCID
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UNII | |
CompTox Dashboard(EPA)
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Properties | |
HN3 | |
Molar mass | 43.029g·mol−1 |
Appearance | colorless, highly volatile liquid |
Density | 1.09 g/cm3 |
Melting point | −80 °C (−112 °F; 193 K) |
Boiling point | 37 °C (99 °F; 310 K) |
highly soluble | |
Solubility | soluble inalkali,alcohol,ether |
Acidity(pKa) | 4.6[1] |
Conjugate base | Azide |
Structure | |
approximately linear | |
Hazards | |
Occupational safety and health(OHS/OSH): | |
Main hazards
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Highly toxic, explosive, reactive |
GHSlabelling: | |
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Danger | |
H200,H319,H335,H370 | |
P201,P202,P260,P261,P264,P270,P271,P280,P281,P304+P340,P305+P351+P338,P307+P311,P312,P321,P337+P313,P372,P373,P380,P401,P403+P233,P405,P501 | |
NFPA 704(fire diamond) | |
Related compounds | |
Othercations
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Sodium azide Lithium azide Potassium azide |
Ammonia Hydrazine | |
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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Hydrazoic acid,also known ashydrogen azide,azic acidorazoimide,[2]is a compound with the chemical formulaHN3.[3]It is a colorless, volatile, and explosive liquid at room temperature and pressure. It is a compound ofnitrogenandhydrogen,and is therefore apnictogen hydride.Theoxidation stateof the nitrogen atoms in hydrazoic acid is fractional and is -1/3.[citation needed]It was first isolated in 1890 byTheodor Curtius.[4]The acid has few applications, but itsconjugate base,theazideion, is useful in specialized processes.
Hydrazoic acid, like its fellowmineral acids,is soluble in water. Undiluted hydrazoic acid is dangerously explosive[5]with astandard enthalpy of formationΔfHo(l, 298K) = +264 kJ/mol.[6]When dilute, the gas and aqueous solutions (<10%) can be safely prepared but should be used immediately; because of its low boiling point, hydrazoic acid is enriched upon evaporation and condensation such that dilute solutions incapable of explosion can form droplets in the headspace of the container or reactor that are capable of explosion.[7][8]
Production
[edit]The acid is usually formed by acidification of an azide salt likesodium azide.Normally solutions of sodium azide in water contain trace quantities of hydrazoic acid in equilibrium with the azide salt, but introduction of a stronger acid can convert the primary species in solution to hydrazoic acid. The pure acid may be subsequently obtained byfractional distillationas an extremely explosive colorless liquid with an unpleasant smell.[2]
- NaN3+ HCl → HN3+ NaCl
Its aqueous solution can also be prepared by treatment ofbarium azidesolution with dilutesulfuric acid,filtering the insolublebarium sulfate.[9]
It was originally prepared by the reaction of aqueoushydrazinewithnitrous acid:
- N2H4+ HNO2→ HN3+ 2 H2O
With thehydraziniumcation[N2H5]+this reaction is written as:
- [N2H5]++ HNO2→ HN3+ H2O + [H3O]+
Other oxidizing agents, such ashydrogen peroxide,nitrosyl chloride,trichloramineornitric acid,can also be used to produce hydrazoic acid from hydrazine.[10]
Destruction prior to disposal
[edit]Hydrazoic acid reacts with nitrous acid:
- HN3+ HNO2→ N2O + N2+ H2O
This reaction is unusual in that it involves compounds with nitrogen in four different oxidation states.[11]
Reactions
[edit]In its properties hydrazoic acid shows some analogy to the halogen acids, since it forms poorly soluble (in water) lead, silver and mercury(I) salts. The metallic salts all crystallize in the anhydrous form and decompose on heating, leaving a residue of the pure metal.[2]It is a weak acid (pKa= 4.75.[6]) Its heavy metal salts are explosive and readily interact with thealkyl iodides.Azides of heavieralkali metals(excludinglithium) oralkaline earth metalsare not explosive, but decompose in a more controlled way upon heating, releasing spectroscopically-pureN2gas.[12]Solutions of hydrazoic acid dissolve many metals (e.g.zinc,iron) with liberation of hydrogen and formation of salts, which are calledazides(formerly also called azoimides or hydrazoates).
Hydrazoic acid may react with carbonyl derivatives, including aldehydes, ketones, and carboxylic acids, to give an amine or amide, with expulsion of nitrogen. This is calledSchmidt reactionor Schmidt rearrangement.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Schmidt_Reaktion_%C3%9Cbersicht_Carbons%C3%A4uren1.svg/350px-Schmidt_Reaktion_%C3%9Cbersicht_Carbons%C3%A4uren1.svg.png)
![](https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/Schmidt_Reaktion_%C3%9Cbersicht_Ketone1.svg/400px-Schmidt_Reaktion_%C3%9Cbersicht_Ketone1.svg.png)
Dissolution in the strongest acids produces explosive salts containing the aminodiazonium ion[H2N=N=N]+⇌ [H2N−N≡N]+,for example:[12]
- HN=N=N + H[SbCl6] → [H2N=N=N]+[SbCl6]−
The ion[H2N=N=N]+isisoelectronictodiazomethaneH2C=N+=N−.
The decomposition of hydrazoic acid, triggered by shock, friction, spark, etc. produces nitrogen and hydrogen:
- 2 HN3→ H2+ 3 N2
Hydrazoic acid undergoes unimolecular decomposition at sufficient energy:
- HN3→ NH + N2
The lowest energy pathway produces NH in the triplet state, making it a spin-forbidden reaction. This is one of the few reactions whose rate has been determined for specific amounts of vibrational energy in the ground electronic state, by laser photodissociation studies.[13]In addition, these unimolecular rates have been analyzed theoretically, and the experimental and calculated rates are in reasonable agreement.[14]
Toxicity
[edit]Hydrazoic acid is volatile and highly toxic. It has a pungent smell and its vapor can cause violentheadaches.The compound acts as a non-cumulative poison.
Applications
[edit]2-Furonitrile,a pharmaceutical intermediate and potential artificial sweetening agent has been prepared in good yield by treatingfurfuralwith a mixture of hydrazoic acid (HN3) andperchloric acid(HClO4) in the presence of magnesium perchlorate in thebenzenesolution at 35 °C.[15][16]
Theall gas-phase iodine laser(AGIL) mixes gaseous hydrazoic acid withchlorineto produce excitednitrogen chloride,which is then used to causeiodineto lase; this avoids the liquid chemistry requirements ofCOIL lasers.
References
[edit]- ^Pradyot Patnaik.Handbook of Inorganic Chemicals.McGraw-Hill, 2002,ISBN0-07-049439-8
- ^abcChisholm, Hugh,ed. (1911). .Encyclopædia Britannica.Vol. 3 (11th ed.). Cambridge University Press. pp. 82–83.This also contains a detailed description of the contemporaneous production process.
- ^Dictionary of Inorganic and Organometallic Compounds.Chapman & Hall.
- ^Curtius, Theodor(1890)."Ueber Stickstoffwasserstoffsäure (Azoimid) N3H "[On hydrazoic acid (azoimide) N3H].Berichte der Deutschen Chemischen Gesellschaft.23(2): 3023–3033.doi:10.1002/cber.189002302232.
- ^Furman, David; Dubnikova, Faina; van Duin, Adri C. T.; Zeiri, Yehuda; Kosloff, Ronnie (2016-03-10). "Reactive Force Field for Liquid Hydrazoic Acid with Applications to Detonation Chemistry".The Journal of Physical Chemistry C.120(9): 4744–4752.Bibcode:2016APS..MARH20013F.doi:10.1021/acs.jpcc.5b10812.ISSN1932-7447.S2CID102029987.
- ^abCatherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 15: The group 15 elements".Inorganic Chemistry, 3rd Edition.Pearson. p. 449.ISBN978-0-13-175553-6.
- ^Gonzalez-Bobes, F. et al Org. Process Res. Dev. 2012, 16, 2051-2057.
- ^Treitler, D. S. et al Org. Process Res. Dev. 2017, 21, 460-467.
- ^L. F. Audrieth, C. F. Gibbs Hydrogen Azide in Aqueous and Ethereal Solution "Inorganic Syntheses 1939, vol. 1, pp. 71-79.
- ^Greenwood, Norman N.;Earnshaw, Alan (1997).Chemistry of the Elements(2nd ed.).Butterworth-Heinemann.p. 432.ISBN978-0-08-037941-8.
- ^Greenwood, pp. 461–464.
- ^abEgon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). "The Nitrogen Group".Inorganic chemistry.Academic Press. p. 625.ISBN978-0-12-352651-9.
- ^Foy, B.R.; Casassa, M.P.; Stephenson, J.C.; King, D.S. (1990). "Overtone-excitedHN
3(X1A') - Anharmonic resonance, homogeneous linewidths, and dissociation rates ".Journal of Chemical Physics.92:2782–2789.doi:10.1063/1.457924. - ^Besora, M.; Harvey, J.N. (2008). "Understanding the rate of spin-forbidden thermolysis ofHN
3andCH
3N
3".Journal of Chemical Physics.129(4): 044303.doi:10.1063/1.2953697.PMID18681642. - ^P. A. Pavlov; Kul'nevich, V. G. (1986). "Synthesis of 5-substituted furannitriles and their reaction with hydrazine".Khimiya Geterotsiklicheskikh Soedinenii.2:181–186.
- ^B. Bandgar; Makone, S. (2006). "Organic reactions in water. Transformation of aldehydes to nitriles using NBS under mild conditions".Synthetic Communications.36(10): 1347–1352.doi:10.1080/00397910500522009.S2CID98593006.
External links
[edit]Media related toHydrogen azideat Wikimedia Commons
- OSHA: Hydrazoic AcidArchived2008-04-04 at theWayback Machine