Dinitrogen pentoxide

Dinitrogen pentoxide

Names
IUPAC name Dinitrogen pentaoxide
Other names Nitric anhydride Nitronium nitrate Nitryl nitrate DNPO Anhydrous nitric acid
Identifiers
CAS Number	10102-03-1 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:29802 Y
ChemSpider	59627 Y
ECHA InfoCard	100.030.227
EC Number	233-264-2
PubChem	66242
UNII	6XB659ZX2W N
InChI InChI=1S/N2O5/c3-1(4)7-2(5)6 Y Key: ZWWCURLKEXEFQT-UHFFFAOYSA-N Y InChI=1/N2O5/c3-1(4)7-2(5)6 Key: ZWWCURLKEXEFQT-UHFFFAOYAN
SMILES [O-][N+](=O)O[N+]([O-])=O
Properties
Chemical formula	N2O5
Molar mass	108.01 g/mol
Appearance	white solid
Density	1.642 g/cm3 (18 °C)
Melting point	41 °C (106 °F; 314 K)
Boiling point	47 °C (117 °F; 320 K) sublimes
Solubility in water	reacts to give HNO3
Solubility	soluble in chloroform negligible in CCl4
Magnetic susceptibility (χ)	−35.6·10−6 cm3/mol (aq)
Dipole moment	1.39 D
Structure
Crystal structure	hexagonal
Molecular shape	planar, C2v (approx. D2h) N–O–N ≈ 180°
Thermochemistry
Std molar entropy (So298)	178.2 J K−1 mol−1 (s) 355.6 J K−1 mol−1 (g)
Std enthalpy of formation (ΔfHo298)	−43.1 kJ/mol (s) +11.3 kJ/mol (g)
Gibbs free energy (ΔfG˚)	114.1 kJ/mol
Hazards
Main hazards	strong oxidizer, forms strong acid in contact with water
NFPA 704	0 3 0 OX
Flash point	Non-flammable
Related compounds
Related nitrogen oxides	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).
N  (what is YN ?)
Infobox references

Dinitrogen pentoxide is the chemical compound with the formula N₂O₅. Also known as nitrogen pentoxide, N₂O₅ is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It 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dangerous oxidizer that once was used as a reagent when dissolved in chloroform for nitrations but has largely been superseded by NO₂BF₄ (nitronium tetrafluoroborate).

N₂O₅ is a rare example of a compound that adopts two structures depending on the conditions: most commonly it is a salt, but under some conditions it is a polar molecule:

N₂O₅ was first reported by Deville in 1840, who prepared it by treating AgNO₃ with Cl₂. A recommended laboratory synthesis entails dehydrating nitric acid (HNO₃) with phosphorus(V) oxide:

In the reverse process, N₂O₅ reacts with water (hydrolyses) to produce nitric acid. Thus, dinitrogen pentoxide is the anhydride of nitric acid:

N₂O₅ exists as colourless crystals that sublime slightly above room temperature. The salt eventually decomposes at room temperature into NO₂ and O₂.

Solid N₂O₅ is a salt, consisting of separated anions and cations. The cation is the linear nitronium ion NO₂⁺ and the anion is the planar nitrate NO₃⁻ ion. Thus, the solid could be called nitronium nitrate. Both nitrogen centers have oxidation state +5.