Dinitrogen pentoxide
Dinitrogen pentoxide (also known as nitrogen pentoxide or nitric anhydride) is the chemical compound with the formula N2O5. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.
| Names | |
|---|---|
| IUPAC name
Dinitrogen pentoxide | |
| Other names
Nitric anhydride Nitronium nitrate Nitryl nitrate DNPO Anhydrous nitric acid | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.030.227 |
| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| N2O5 | |
| Molar mass | 108.01 g/mol |
| Appearance | white solid |
| Density | 2.0 g/cm3 |
| Boiling point | 33 °C (91 °F; 306 K) sublimes |
| reacts to give HNO3 | |
| Solubility | soluble in chloroform negligible in CCl4 |
| −35.6×10−6 cm3 mol−1 (aq) | |
| 1.39 D | |
| Structure | |
| Hexagonal, hP14 | |
| P63/mmc No. 194 | |
a = 0.54019 nm, c = 0.65268 nm | |
Formula units (Z) |
2 |
| planar, C2v (approx. D2h) N–O–N ≈ 180° | |
| Thermochemistry | |
Heat capacity (C) |
143.1 J K−1 mol−1 (s) 95.3 J K−1 mol−1 (g) |
Std molar entropy (S⦵298) |
178.2 J K−1 mol−1 (s) 355.7 J K−1 mol−1 (g) |
Std enthalpy of formation (ΔfH⦵298) |
−43.1 kJ/mol (s) +13.3 kJ/mol (g) |
Gibbs free energy (ΔfG⦵) |
113.9 kJ/mol (s) +117.1 kJ/mol (g) |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
strong oxidizer, forms strong acid in contact with water |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
| Nitrous oxide Nitric oxide Dinitrogen trioxide Nitrogen dioxide Dinitrogen tetroxide | |
Related compounds |
Nitric acid |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
Dinitrogen pentoxide is an unstable and potentially dangerous oxidizer that once was used as a reagent when dissolved in chloroform for nitrations but has largely been superseded by nitronium tetrafluoroborate (NO2BF4).
N2O5 is a rare example of a compound that adopts two structures depending on the conditions. The solid is a salt, nitronium nitrate, consisting of separate nitronium cations [NO2]+ and nitrate anions [NO3]−; but in the gas phase and under some other conditions it is a covalently-bound molecule.