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Hydrazoic acid

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Hydrazoic acid
Structure, bonding and dimensions of the hydrogen azide molecule
Hydrazoic acid
Hydrazoic acid
Names
IUPAC name Hydrogen azide
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.059 Edit this at Wikidata
PubChem CID
CompTox Dashboard (EPA)
InChI
  • InChI=1S/HN3/c1-3-2/h1HKey: JUINSXZKUKVTMD-UHFFFAOYSA-N
  • InChI=1/HN3/c1-3-2/h1HKey: JUINSXZKUKVTMD-UHFFFAOYAO
SMILES
  • ==
Properties
Chemical formula HN3
Molar mass 43.03 g/mol
Appearance colorless, highly volatile liquid
Density 1.09 g/cm
Melting point −80 °C (−112 °F; 193 K)
Boiling point 37 °C (99 °F; 310 K)
Solubility in water highly soluble
Solubility soluble in alkali, alcohol, ether
Acidity (pKa) 4.6
Structure
Molecular shape approximately linear
Hazards
Occupational safety and health (OHS/OSH):
Main hazards Highly toxic, explosive
Related compounds
Other cations Sodium azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

Hydrazoic acid, also known as hydrogen azide or azoimide, is a colorless, volatile, and extremely explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, having chemical formula HN3. It was first isolated in 1890 by Theodor Curtius. It is used primarily for preservation of stock solutions, and as a reagent.

Chemistry

It is soluble in water, and the solution dissolves many metals (e.g. zinc, iron) with liberation of hydrogen and formation of salts (azides, formerly also called azoimides or hydrazoates).

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.

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 = 4.6-4.7).

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

HN=N=N + HSbCl
6 →

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

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(s) + HCl(aq) → HN3(aq) + NaCl(aq)

Can also be prepared by treatment of barium azide solution with dilute sulfuric acid, filtering the insoluble barium sulfate.

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.

References

  1. Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
  2.  Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)
  3. Dictionary of Inorganic and Organometallic Compounds. Chapman & Hall.
  4. Curtius, Theodor (1890). Berichte. 23: 3023. {{cite journal}}: Missing or empty |title= (help)
  5. ^ Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). "The Nitrogen Group". Inorganic chemistry. Academic Press. p. 625. ISBN 0123526515.
  6. Booth, Harold Simmons (1939). Inorganic Synthesis Vol.1. MCGRAW-HILL. doi:10.1002/9780470132326. ISBN 9780470131602.

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