Nitric oxide

Nitric oxide
Skeletal formula showing two lone pairs and one three-electron bond	Space-filling model of nitric oxide
Names
	IUPAC name Nitrogen monoxide
	Systematic IUPAC name Oxidonitrogen(•) (additive)
	Other names Nitrogen oxide; Nitrogen(II) oxide; Oxonitrogen; Nitrogen monoxide
Identifiers
CAS Number	10102-43-9 ;
3D model (JSmol)	Interactive image;
3DMet	B00122;
ChEBI	CHEBI:16480 ;
ChEMBL	ChEMBL1200689 ;
ChemSpider	127983 ;
DrugBank	DB00435 ;
ECHA InfoCard	100.030.233
EC Number	233-271-0;
Gmelin Reference	451
IUPHAR/BPS	2509;
KEGG	D00074 ;
PubChem CID	145068;
RTECS number	QX0525000;
UNII	31C4KY9ESH ;
UN number	1660
CompTox Dashboard (EPA)	DTXSID1020938 ;
	InChI InChI=1S/NO/c1-2 Key: MWUXSHHQAYIFBG-UHFFFAOYSA-N ; InChI=1/NO/c1-2 Key: MWUXSHHQAYIFBG-UHFFFAOYAI;
	SMILES [N]=O;
Properties
Chemical formula	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)
Solubility in water	0.0098 g / 100 ml (0 °C) ; 0.0056 g / 100 ml (20 °C)
Refractive index (nD)	1.0002697
Structure
Molecular shape	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
ATC code	R07AX01 (WHO)
License data	EU EMA: by INN;
Routes of; administration	Inhalation
	Pharmacokinetics:
Bioavailability	good
Metabolism	via pulmonary capillary bed
Biological half-life	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:
Pictograms
Signal word	Danger
Hazard statements	H270, H280, H314, H330
Precautionary statements	P220, P244, P260, P280, P303+P361+P353+P315, P304+P340+P315, P305+P351+P338+P315, P370+P376, P403, P405
NFPA 704 (fire diamond)	3 0 3 OX
	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; 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). verify (what is ?) Infobox references

Nitric oxide (nitrogen oxide or nitrogen monoxide^[1]) 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.^[6]

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.^[7] It was proclaimed the "Molecule of the Year" in 1992.^[8] The 1998 Nobel Prize in Physiology or Medicine was awarded for discovering nitric oxide's role as a cardiovascular signalling molecule.^[9]

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.^[6]

^ ^a ^b Nomenclature of Inorganic Chemistry, IUPAC Recommendations (PDF). International Union of Pure and Applied Chemistry. 2005. p. 69.
^ "Nitric Oxide (CHEBI:16480)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
^ ^a ^b ^c "Nitrogen monoxide - Registration Dossier - ECHA". Retrieved 2020-11-02.
^ ^a ^b ^c ^d "Safety Data Sheet - Nitric Oxide, compressed - Registration Dossier" (PDF). Retrieved 2020-11-02.
^ ^a ^b "Nitric oxide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ ^a ^b Cite error: The named reference G&E was invoked but never defined (see the help page).
^ Hou, Y. C.; Janczuk, A.; Wang, P. G. (1999). "Current trends in the development of nitric oxide donors". Current Pharmaceutical Design. 5 (6): 417–441. doi:10.2174/138161280506230110111042. PMID 10390607.
^ Culotta, Elizabeth; Koshland, Daniel E. Jr. (1992). "NO news is good news". Science. 258 (5090): 1862–1864. Bibcode:1992Sci...258.1862C. doi:10.1126/science.1361684. PMID 1361684.
^ "The Nobel Prize in Physiology or Medicine 1998". NobelPrize.org. Retrieved 2022-06-17.

[Nomenclature_2005-1] Nomenclature of Inorganic Chemistry, IUPAC Recommendations (PDF). International Union of Pure and Applied Chemistry. 2005. p. 69.

[2] "Nitric Oxide (CHEBI:16480)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.

[ECHA-3] "Nitrogen monoxide - Registration Dossier - ECHA". Retrieved 2020-11-02.

[SDS-4] "Safety Data Sheet - Nitric Oxide, compressed - Registration Dossier" (PDF). Retrieved 2020-11-02.

[IDLH-5] "Nitric oxide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).

[G&E-6] Cite error: The named reference G&E was invoked but never defined (see the help page).

[7] Hou, Y. C.; Janczuk, A.; Wang, P. G. (1999). "Current trends in the development of nitric oxide donors". Current Pharmaceutical Design. 5 (6): 417–441. doi:10.2174/138161280506230110111042. PMID 10390607.

[pmid1361684-8] Culotta, Elizabeth; Koshland, Daniel E. Jr. (1992). "NO news is good news". Science. 258 (5090): 1862–1864. Bibcode:1992Sci...258.1862C. doi:10.1126/science.1361684. PMID 1361684.

[9] "The Nobel Prize in Physiology or Medicine 1998". NobelPrize.org. Retrieved 2022-06-17.

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