Hydrazoic acid

Hydrazoic acid
Names
IUPAC name
Hydrogen azide
Identifiers
7782-79-8 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:29449 YesY
ChEMBL ChEMBL186537 YesY
ChemSpider 22937 YesY
ECHA InfoCard 100.029.059
PubChem 24530
Properties
HN3
Molar mass 43.03 g/mol
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 in alkali, alcohol, ether
Acidity (pKa) 4.6 [1]
Structure
approximately linear
Hazards
Main hazards Highly toxic, explosive, reactive
R-phrases R3, R27/28
S-phrases S33, S36/37, S38
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
0
4
2
Related compounds
Other cations
 Sodium azide
Ammonia
Hydrazine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Hydrazoic acid, also known as hydrogen azide or azoimide,[2] is a compound with the chemical formula HN3.[3] It is a colorless, volatile, and explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, and is therefore a pnictogen hydride. It was first isolated in 1890 by Theodor Curtius.[4] The acid has few applications, but its conjugate base, the azide ion, is useful in specialized processes.

Hydrazoic acid is soluble in water. Undiluted hydrazoic acid is dangerously explosive[5] with a standard enthalpy of formation ΔfHo (l, 298K) = +264 kJmol−1).[6] When dilute, the gas and aqueous solutions (<10%) can be safely handled.

Production

The acid is usually formed by acidification of an azide salt like sodium 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 by fractional distillation as an extremely explosive colorless liquid with an unpleasant smell.

NaN3 + HCl → HN3 + NaCl

Its aqueous solution can also be prepared by treatment of barium azide solution with dilute sulfuric acid, filtering the insoluble barium sulfate.[7]

It was originally prepared by the reaction of aqueous hydrazine with nitrous acid.

N2H5+ + HNO2 → HN3 + H+ + 2 H2O

Other oxidizing agents, such as hydrogen peroxide, NOCl, NCl3 or nitric acid, can also be used.[8]

Reactions

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. It is a weak acid (pKa = 4.75.[6]) Its heavy metal salts are explosive and readily interact with the alkyl iodides. Azides of heavier alkali metals (excluding lithium) or alkaline earth metals are not explosive, but decompose in a more controlled way upon heating, releasing spectroscopically-pure N
2 gas.[9] Solutions of hydrazoic acid dissolve many metals (e.g. zinc, iron) with liberation of hydrogen and formation of salts, which are called azides (formerly also called azoimides or hydrazoates).

Dissolution in the strongest acids produces explosive salts containing the H
2N=N=N+
 ion, for example:[9]

HN=N=N + HSbCl
6 → [H
2N=N=N]+
[SbCl
6]−

The ion H
2N=N=N+
 is isoelectronic to diazomethane.

The decomposition of hydrazoic acid, triggered by shock, friction, spark, etc. goes as follows:

2HN
3 → H
2 + 3N
2

Toxicity

Hydrazoic acid is volatile and highly toxic. It has a pungent smell and its vapor can cause violent headaches. The compound acts as a non-cumulative poison.

Applications

2-Furonitrile, a pharmaceutical intermediate and potential artificial sweetening agent has been prepared in good yield by treating furfural with a mixture of hydrazoic acid (HN3) and perchloric acid in the presence of magnesium perchlorate in the benzene solution at 35 °C.[10][11]

The all gas-phase iodine laser (AGIL) mixes gaseous hydrazoic acid with chlorine to produce excited nitrogen chloride, which is then used to cause iodine to lase; this avoids the liquid chemistry requirements of COIL lasers.

References

  1. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ↑  Chisholm, Hugh, ed. (1911). "Azoimide". Encyclopædia Britannica. 3 (11th ed.). Cambridge University Press.
  3. ↑ Dictionary of Inorganic and Organometallic Compounds. Chapman & Hall.
  4. ↑ 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.
  5. ↑ 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. doi:10.1021/acs.jpcc.5b10812. ISSN 1932-7447.
  6. 1 2 Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 15: The group 15 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 449. ISBN 978-0-13-175553-6.
  7. ↑ L . F. Audrieth, C. F. Gibbs Hydrogen Azide in Aqueous and Ethereal Solution" Inorganic Syntheses 1939, vol. 1, pp. 71-79.
  8. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 432. ISBN 0-08-037941-9.
  9. 1 2 Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). "The Nitrogen Group". Inorganic chemistry. Academic Press. p. 625. ISBN 0-12-352651-5.
  10. ↑ P. A. Pavlov; Kul'nevich, V. G. (1986). "Synthesis of 5-substituted furannitriles and their reaction with hydrazine". Khimiya Geterotsiklicheskikh Soedinenii. 2: 181–186.
  11. ↑ 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.
This article is issued from Wikipedia - version of the 10/19/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.