Nitric oxide
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| Names | |||
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| IUPAC name
Nitrogen monoxide | |||
| Systematic IUPAC name
Oxidonitrogen(•) (additive) | |||
| Other names
Nitrogen oxide Nitrogen(II) oxide Oxonitrogen Nitrogen monoxide | |||
| Identifiers | |||
3D model (JSmol) |
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| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| DrugBank | |||
| ECHA InfoCard | 100.030.233 | ||
| EC Number |
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| 451 | |||
| KEGG | |||
PubChem CID |
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| RTECS number |
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| UNII | |||
| UN number | 1660 | ||
CompTox Dashboard (EPA) |
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| 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) | |||
Refractive index (nD) |
1.0002697 | ||
| Structure | |||
| linear (point group C∞v) | |||
| Thermochemistry | |||
Std molar entropy (S⦵298) |
210.76 J/(K·mol) | ||
Std enthalpy of formation (ΔfH⦵298) |
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 |
Very toxic, corrosive, oxidizer | ||
| GHS labelling: | |||
| Danger | |||
| H270, 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): | |||
LC50 (median concentration) |
315 ppm (rabbit, 15 min) 854 ppm (rat, 4 h) 2500 ppm (mouse, 12 min) | ||
LCLo (lowest published) |
320 ppm (mouse) | ||
| Safety data sheet (SDS) | External SDS | ||
| Related compounds | |||
Related nitrogen oxides |
Dinitrogen pentoxide Dinitrogen tetroxide | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |||
Nitric oxide (nitrogen oxide, nitrogen monooxide, 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.
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. 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 anesthetic gas.