Nitric oxide

Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula (N=O or NO). Nitric oxide is also a heteronuclear diatomic molecule, a class of molecules whose study spawned early modern theories of chemical bonding.

Nitric oxide
Names
IUPAC name
Nitrogen monoxide
Systematic IUPAC name
Oxidonitrogen(•) (additive)
Other names
Nitrogen oxide
Nitrogen(II) oxide
Oxonitrogen
Nitrogen monoxide
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.030.233
EC Number
  • 233-271-0
451
KEGG
RTECS number
  • QX0525000
UNII
UN number 1660
  • InChI=1S/NO/c1-2 Y
    Key: MWUXSHHQAYIFBG-UHFFFAOYSA-N Y
  • InChI=1/NO/c1-2
    Key: MWUXSHHQAYIFBG-UHFFFAOYAI
  • [N]=O
Properties
NO
Molar mass 30.006 g·mol−1
Appearance Colourless gas
Density 1.3402 g/L
Melting point −164 °C (−263 °F; 109 K)
Boiling point −152 °C (−242 °F; 121 K)
0.0098 g / 100 ml (0 °C)
0.0056 g / 100 ml (20 °C)
1.0002697
Structure
linear (point group Cv)
Thermochemistry
210.76 J/(K·mol)
90.29 kJ/mol
Pharmacology
R07AX01 (WHO)
License data
Inhalation
Pharmacokinetics:
good
via pulmonary capillary bed
2–6 seconds
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
  • Fatal if inhaled
  • Causes severe burns
  • Causes eye damage
  • Corrosive to the respiratory tract
GHS labelling:
Danger
H270, H280, H314, H330
P220, P244, P260, P280, P303+P361+P353+P315, P304+P340+P315, P305+P351+P338+P315, P370+P376, P403, P405
NFPA 704 (fire diamond)
Lethal dose or concentration (LD, LC):
315 ppm (rabbit, 15 min)
854 ppm (rat, 4 h)
2500 ppm (mouse, 12 min)
320 ppm (mouse)
Safety data sheet (SDS) External SDS
Related compounds
Related nitrogen oxides
Dinitrogen pentoxide

Dinitrogen tetroxide
Dinitrogen trioxide
Nitrogen dioxide
Nitrous oxide
Nitroxyl (reduced form)
Hydroxylamine (hydrogenated form)

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 ?)
Infobox references

An important intermediate in industrial chemistry, nitric oxide forms in combustion systems and can be generated by lightning in thunderstorms. In mammals, including humans, nitric oxide is a signaling molecule in many physiological and pathological processes. It was proclaimed the "Molecule of the Year" in 1992. The 1998 Nobel Prize in Physiology or Medicine was awarded for discovering nitric oxide's role as a cardiovascular signalling molecule.

Nitric oxide should not be confused with nitrogen dioxide (NO2), a brown gas and major air pollutant, or with nitrous oxide (N2O), an anesthetic gas.

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