Dinitrogen tetroxide

Dinitrogen tetroxide
	Nitrogen dioxide at −196 °C, 0 °C, 23 °C, 35 °C, and 50 °C. (NO; 2) converts to the colorless dinitrogen tetroxide (N; 2O; 4) at low temperatures, and reverts to NO; 2 at higher temperatures.
Names
	IUPAC name Dinitrogen tetroxide
Identifiers
CAS Number	10544-72-6 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:29803 ;
ChemSpider	23681 ;
ECHA InfoCard	100.031.012
EC Number	234-126-4;
Gmelin Reference	2249
PubChem CID	25352;
RTECS number	QW9800000;
UNII	M9APC3P75A ;
UN number	1067
CompTox Dashboard (EPA)	DTXSID00893116 ;
	InChI InChI=1S/N2O4/c3-1(4)2(5)6 Key: WFPZPJSADLPSON-UHFFFAOYSA-N ; InChI=1/N2O4/c3-1(4)2(5)6 Key: WFPZPJSADLPSON-UHFFFAOYAS;
	SMILES [O-][N+](=O)[N+]([O-])=O;
Properties
Chemical formula	N2O4
Molar mass	92.010 g·mol−1
Appearance	White solid, colorless liquid, orange gas
Density	1.44246 g/cm3 (liquid, 21 °C)
Melting point	−11.2 °C (11.8 °F; 261.9 K) and decomposes to NO2
Boiling point	21.69 °C (71.04 °F; 294.84 K)
Solubility in water	Reacts to form nitrous and nitric acids
Vapor pressure	96 kPa (20 °C)
Magnetic susceptibility (χ)	−23.0·10−6 cm3/mol
Refractive index (nD)	1.00112
Structure
Molecular shape	Planar, D2h
Dipole moment	small, non-zero
Thermochemistry
Std molar; entropy (S⦵298)	304.29 J/K⋅mol
Std enthalpy of; formation (ΔfH⦵298)	+9.16 kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H270, H314, H330, H335, H336
Precautionary statements	P220, P244, P260, P261, P264, P271, P280, P284, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P320, P321, P363, P370+P376, P403, P403+P233, P405, P410+P403, P501
NFPA 704 (fire diamond)	3 0 0 OX
Flash point	Non-flammable
Safety data sheet (SDS)	External SDS
Related compounds
Related nitrogen oxides	Nitrous oxide; Nitric oxide; Dinitrogen trioxide; Nitrogen dioxide; Dinitrogen pentoxide;
Related compounds	Phosphorus tetroxide; Arsenic tetroxide; Antimony tetroxide;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N₂O₄. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide. Its molar mass is 92.011 g/mol.

Dinitrogen tetroxide is a powerful oxidizer that is hypergolic (spontaneously reacts) upon contact with various forms of hydrazine, which has made the pair a common bipropellant for rockets.