Dinitrogen tetroxide

Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russia 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
Full structural formula
Space-filling model

Nitrogen dioxide at −196 °C, 0 °C, 23 °C, 35 °C, and 50 °C. (NO
2
) converts to the colorless dinitrogen tetroxide (N
2
O
4
) at low temperatures, and reverts to NO
2
at higher temperatures.
Names
IUPAC name
Dinitrogen tetraoxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.031.012
EC Number
  • 234-126-4
2249
RTECS number
  • QW9800000
UNII
UN number 1067
  • InChI=1S/N2O4/c3-1(4)2(5)6 Y
    Key: WFPZPJSADLPSON-UHFFFAOYSA-N Y
  • InChI=1/N2O4/c3-1(4)2(5)6
    Key: WFPZPJSADLPSON-UHFFFAOYAS
  • [O-][N+](=O)[N+]([O-])=O
Properties
N2O4
Molar mass 92.011 g/mol
Appearance Colourless 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)
Reacts to form nitrous and nitric acids
Vapor pressure 96 kPa (20 °C)[1]
−23.0·10−6 cm3/mol
1.00112
Structure
Planar, D2h
small, non-zero
Thermochemistry
304.29 J/K⋅mol[2]
+9.16 kJ/mol[2]
Hazards
GHS labelling:
Danger
H270, H280, H314, H330, H335, H336
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)
Flash point Non-flammable
Safety data sheet (SDS) External MSDS
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)

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.


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