Hydrazoic acid
Hydrazoic acid, also known as hydrogen azide, azic acid or azoimide, is a compound with the chemical formula HN3. 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. The oxidation state of the nitrogen atoms in hydrazoic acid is fractional and is -1/3. It was first isolated in 1890 by Theodor Curtius. The acid has few applications, but its conjugate base, the azide ion, is useful in specialized processes.
| Names | |
|---|---|
| IUPAC name
Hydrogen azide | |
| 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 | |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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SMILES
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| Properties | |
| HN3 | |
| Molar mass | 43.029 g·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 in alkali, alcohol, ether |
| Acidity (pKa) | 4.6 |
| Conjugate base | Azide |
| Structure | |
Molecular shape |
approximately linear |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Highly toxic, explosive, reactive |
| GHS labelling: | |
| 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) |
4
0
3 |
| Related compounds | |
Other cations |
Sodium azide Lithium azide Potassium azide |
Related nitrogen hydrides |
Ammonia Hydrazine |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
Hydrazoic acid, like its fellow mineral acids, is soluble in water. Undiluted hydrazoic acid is dangerously explosive with a standard enthalpy of formation ΔfHo (l, 298K) = +264 kJ/mol. 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.