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Topic summary

Nitric oxide

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)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard100.030.233EC Number
  • 233-271-0
451
KEGG
RTECS number
  • QX0525000
UNII
UN number1660
  • InChI=1S/NO/c1-2
    Key: MWUXSHHQAYIFBG-UHFFFAOYSA-N
  • InChI=1/NO/c1-2
    Key: MWUXSHHQAYIFBG-UHFFFAOYAI
  • [N]=O
Properties NOMolar mass30.006 g·mol Appearance Colourless gas Density1.3402 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 C∞v) Thermochemistry 210.76 J/(K·mol) +90.29 kJ/mol Pharmacology R07AX01 (WHO) License data
InhalationPharmacokinetics: good via pulmonary capillary bed 2–6 seconds Hazards Occupational safety and health (OHS/OSH):
Main hazards
Very toxic, corrosive, oxidizer GHS labelling: DangerH270, H314, H330P220, P244, P260, P280, P303+P361+P353+P315, P304+P340+P315, P305+P351+P338+P315, P370+P376, P403, P405NFPA 704 (fire diamond)
3
0
3
OX
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 SDSRelated 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).
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Nitric oxide (nitrogen oxide, nitrogen mono-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 heteronucleardiatomic molecule, a class of molecules whose study spawned early modern theories of chemical bonding.

An important intermediate in industrial chemistry, nitric oxide forms in combustion systems and can be generated by lightning in thunderstorms. High temperatures of hydrogen combustion in an oxygen-rich environment, with atmospheric nitrogen present, can also result in breaking of N≡N bonds, forming toxic NOx if no exhaust scrubbing is done. 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. Its impact extends beyond biology, with applications in medicine, such as the development of sildenafil (Viagra), and in industry, including semiconductor manufacturing.

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

Wikipedia source