Nitric oxide

Names
	IUPAC name Nitric oxide
	Systematic IUPAC name Oxidonitrogen(•) (additive)
	Other names Nitrogen oxide; Nitrogen monoxide; Nitrogen(II) oxide; Oxonitrogen
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 ;
	show InChI
	show SMILES
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 (So298)	210.76 J/(K·mol)
Std enthalpy of; formation (ΔfH⦵298)	91.29 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
Main hazards	Fatal if inhaled; Causes severe burns; Causes eye damage; Corrosive to the respiratory tract;
Safety data sheet	External SDS
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H270, H280, H330, H314
GHS precautionary statements	P244, P260, P220, P280, P304+340+315, P303+361+353+315, P305+351+338+315, P370+376, 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)
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).
	(what is ?)
	Infobox references

Nitric oxide (nitrogen oxide^[6] 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.^[7]

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.^[8] It was proclaimed the "Molecule of the Year" in 1992.^[9] 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, nor with nitrous oxide (N₂O), an anesthetic.^[7]

Reactions[]

With di- and triatomic molecules[]

Upon condensing to a liquid, nitric oxide dimerizes to dinitrogen dioxide, but the association is weak and reversible. The N–N distance in crystalline NO is 218 pm, nearly twice the N–O distance.^[7]

Since the heat of formation of ·NO is endothermic, NO can be decomposed to the elements. Catalytic converters in cars exploit this reaction:

2 NO → O₂ + N₂.

When exposed to oxygen, nitric oxide converts into nitrogen dioxide:

2 NO + O₂ → 2 NO₂.

This conversion has been speculated as occurring via the ONOONO intermediate.

In water, nitric oxide reacts with oxygen to form nitrous acid (HNO₂). The reaction is thought to proceed via the following stoichiometry:

4 NO + O₂ + 2 H₂O → 4 HNO₂.

Nitric oxide reacts with fluorine, chlorine, and bromine to form the nitrosyl halides, such as nitrosyl chloride:

2 NO + Cl₂ → 2 NOCl.

With NO₂, also a radical, NO combines to form the intensely blue dinitrogen trioxide:^[7]

NO + NO₂ ⇌ ON−NO₂.

Organic chemistry[]

The addition of a nitric oxide moiety to another molecule is often referred to as nitrosylation. The Traube reaction^[10] is the addition of a two equivalents of nitric oxide onto an enolate, giving a diazeniumdiolate (also called a nitrosohydroxylamine).^[11] The product can undergo a subsequent retro-aldol reaction, giving an overall process similar to the haloform reaction. For example, nitric oxide reacts with acetone and an alkoxide to form a diazeniumdiolate on each α position, with subsequent loss of methyl acetate as a by-product:^[12]

This reaction, which was discovered around 1898, remains of interest in nitric oxide prodrug research. Nitric oxide can also react directly with sodium methoxide, ultimately forming sodium formate and nitrous oxide by way of an N-methoxydiazeniumdiolate.^[13]

Coordination complexes[]

Nitric oxide reacts with transition metals to give complexes called metal nitrosyls. The most common bonding mode of nitric oxide is the terminal linear type (M−NO).^[7] Alternatively, nitric oxide can serve as a one-electron pseudohalide. In such complexes, the M−N−O group is characterized by an angle between 120° and 140°. The NO group can also bridge between metal centers through the nitrogen atom in a variety of geometries.

Production and preparation[]

In commercial settings, nitric oxide is produced by the oxidation of ammonia at 750–900 °C (normally at 850 °C) with platinum as catalyst in the Ostwald process:

4 NH₃ + 5 O₂ → 4 NO + 6 H₂O

The uncatalyzed endothermic reaction of oxygen (O₂) and nitrogen (N₂), which is effected at high temperature (>2000 °C) by lightning has not been developed into a practical commercial synthesis (see Birkeland–Eyde process):

N₂ + O₂ → 2 NO

Laboratory methods[]

In the laboratory, nitric oxide is conveniently generated by reduction of dilute nitric acid with copper:

8 HNO₃ + 3 Cu → 3 Cu(NO₃)₂ + 4 H₂O + 2 NO

An alternative route involves the reduction of nitrous acid in the form of sodium nitrite or potassium nitrite:

2 NaNO₂ + 2 NaI + 2 H₂SO₄ → I₂ + 2 Na₂SO₄ + 2 H₂O + 2 NO

2 NaNO₂ + 2 FeSO₄ + 3 H₂SO₄ → Fe₂(SO₄)₃ + 2 NaHSO₄ + 2 H₂O + 2 NO

3 KNO₂ + KNO₃ + Cr₂O₃ → 2 K₂CrO₄ + 4 NO

The iron(II) sulfate route is simple and has been used in undergraduate laboratory experiments. So-called NONOate compounds are also used for nitric oxide generation.

Detection and assay[]

Nitric oxide (white) in conifer cells, visualized using DAF-2 DA (diaminofluorescein diacetate)

Nitric oxide concentration can be determined using a chemiluminescent reaction involving ozone.^[14] A sample containing nitric oxide is mixed with a large quantity of ozone. The nitric oxide reacts with the ozone to produce oxygen and nitrogen dioxide, accompanied with emission of light (chemiluminescence):

NO + O₃ → NO₂ + O₂ + hν

which can be measured with a photodetector. The amount of light produced is proportional to the amount of nitric oxide in the sample.

Other methods of testing include electroanalysis (amperometric approach), where ·NO reacts with an electrode to induce a current or voltage change. The detection of NO radicals in biological tissues is particularly difficult due to the short lifetime and concentration of these radicals in tissues. One of the few practical methods is spin trapping of nitric oxide with iron-dithiocarbamate complexes and subsequent detection of the mono-nitrosyl-iron complex with electron paramagnetic resonance (EPR).^[15]^[16]

A group of fluorescent dye indicators that are also available in acetylated form for intracellular measurements exist. The most common compound is (DAF-2).^[17]

Environmental effects[]

Acid rain deposition[]

Nitric oxide reacts with the hydroperoxy radical (HO₂^•) to form nitrogen dioxide (NO₂), which then can react with a hydroxyl radical (^•OH) to produce nitric acid (HNO₃):

·NO + HO₂^•→ ^•NO₂ + ^•OH

·NO₂ + ^•OH → HNO₃

Nitric acid, along with sulfuric acid, contributes to acid rain deposition.

Ozone depletion[]

·NO participates in ozone layer depletion. Nitric oxide reacts with stratospheric ozone to form O₂ and nitrogen dioxide:

·NO + O₃ → NO₂ + O₂

This reaction is also utilized to measure concentrations of ·NO in control volumes.

Precursor to NO₂[]

As seen in the Acid deposition section, nitric oxide can transform into nitrogen dioxide (this can happen with the hydroperoxy radical, HO₂^•, or diatomic oxygen, O₂). Symptoms of short-term nitrogen dioxide exposure include nausea, dyspnea and headache. Long-term effects could include impaired immune and respiratory function.^[18]

Biological functions[]

NO is a gaseous signaling molecule.^[19] It is a key vertebrate biological messenger, playing a role in a variety of biological processes.^[20] It is a bioproduct in almost all types of organisms, including bacteria, plants, fungi, and animal cells.^[21]

Nitric oxide, an endothelium-derived relaxing factor (EDRF), is biosynthesized endogenously from L-arginine, oxygen, and NADPH by various nitric oxide synthase (NOS) enzymes.^[22] Reduction of inorganic nitrate may also make nitric oxide.^[23] One of the main enzymatic targets of nitric oxide is guanylyl cyclase.^[24] The binding of nitric oxide to the haem region of the enzyme leads to activation, in the presence of iron.^[24] Nitric oxide is highly reactive (having a lifetime of a few seconds), yet diffuses freely across membranes. These attributes make nitric oxide ideal for a transient paracrine (between adjacent cells) and autocrine (within a single cell) signaling molecule.^[23] Once nitric oxide is converted to nitrates and nitrites by oxygen and water, cell signaling is deactivated.^[24]

The endothelium (inner lining) of blood vessels uses nitric oxide to signal the surrounding smooth muscle to relax, resulting in vasodilation and increasing blood flow.^[23] Sildenafil (Viagra) is a drug that uses the nitric oxide pathway. Sildenafil does not produce nitric oxide, but enhances the signals that are downstream of the nitric oxide pathway by protecting cyclic guanosine monophosphate (cGMP) from degradation by cGMP-specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum, allowing for the signal to be enhanced, and thus vasodilation.^[22] Another endogenous gaseous transmitter, hydrogen sulfide (H₂S) works with NO to induce vasodilation and angiogenesis in a cooperative manner.^[25]^[26]

Nasal breathing produces nitric oxide within the body, while mouth breathing does not.^[27]

Occupational safety and health[]

In the U.S., the Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for nitric oxide exposure in the workplace as 25 ppm (30 mg/m³) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 25 ppm (30 mg/m³) over an 8-hour workday. At levels of 100 ppm, nitric oxide is immediately dangerous to life and health.^[28]

References[]

^ "Nitric oxide".
^ "Nitric Oxide (CHEBI:16480)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
^ Jump up to: ^a ^b ^c "Nitrogen monoxide - Registration Dossier - ECHA". Retrieved 2020-11-02.
^ Jump up to: ^a ^b ^c ^d "Safety Data Sheet - Nitric Oxide, compressed - Registration Dossier" (PDF). Retrieved 2020-11-02.
^ Jump up to: ^a ^b "Nitric oxide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ IUPAC nomenclature of inorganic chemistry 2005. PDF.
^ Jump up to: ^a ^b ^c ^d ^e Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ 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. 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.
^
^ Arulsamy, Navamoney; Bohle, D. Scott (2006). "Synthesis of Diazeniumdiolates from the Reactions of Nitric Oxide with Enolates". J. Org. Chem. 71 (2): 572–581. doi:10.1021/jo051998p. PMID 16408967.
^ Traube, Wilhelm (1898). "Ueber Synthesen stickstoffhaltiger Verbindungen mit Hülfe des Stickoxyds". Justus Liebig's Annalen der Chemie (in German). 300: 81–128. doi:10.1002/jlac.18983000108.
^ Derosa, Frank; Keefer, Larry K.; Hrabie, Joseph A. (2008). "Nitric Oxide Reacts with Methoxide". The Journal of Organic Chemistry. 73 (3): 1139–1142. doi:10.1021/jo7020423. PMID 18184006.
^ Fontijn, Arthur.; Sabadell, Alberto J.; Ronco, Richard J. (1970). "Homogeneous chemiluminescent measurement of nitric oxide with ozone. Implications for continuous selective monitoring of gaseous air pollutants". Analytical Chemistry. 42 (6): 575–579. doi:10.1021/ac60288a034.
^ Vanin, A; Huisman, A; Van Faassen, E (2002). Iron dithiocarbamate as spin trap for nitric oxide detection: Pitfalls and successes. Methods in Enzymology. 359. pp. 27–42. doi:10.1016/S0076-6879(02)59169-2. ISBN 9780121822620. PMID 12481557.
^ Nagano, T; Yoshimura, T (2002). "Bioimaging of nitric oxide". Chemical Reviews. 102 (4): 1235–70. doi:10.1021/cr010152s. PMID 11942795.
^ Kojima H, Nakatsubo N, Kikuchi K, Kawahara S, Kirino Y, Nagoshi H, Hirata Y, Nagano T (1998). "Detection and imaging of nitric oxide with novel fluorescent indicators: diaminofluoresceins". Anal. Chem. 70 (13): 2446–2453. doi:10.1021/ac9801723. PMID 9666719.
^ "Centers for Disease Control and Prevention". NIOSH. 1 July 2014. Retrieved 10 December 2015.
^ Liu, Hongying; Weng, Lingyan; Yang, Chi (2017-03-28). "A review on nanomaterial-based electrochemical sensors for H2O2, H2S and NO inside cells or released by cells". Microchimica Acta. 184 (5): 1267–1283. doi:10.1007/s00604-017-2179-2. ISSN 0026-3672. S2CID 21308802.
^ Weller, Richard, Could the sun be good for your heart? TedxGlasgow. Filmed March 2012, posted January 2013
^ Roszer, T (2012) The Biology of Subcellular Nitric Oxide. ISBN 978-94-007-2818-9
^ Jump up to: ^a ^b Perez, Krystle M.; Laughon, Matthew (November 2015). "Sildenafil in Term and Premature Infants: A Systematic Review". Clinical Therapeutics. 37 (11): 2598–2607.e1. doi:10.1016/j.clinthera.2015.07.019. ISSN 0149-2918. PMID 26490498.
^ Jump up to: ^a ^b ^c Stryer, Lubert (1995). Biochemistry, 4th Edition. W.H. Freeman and Company. p. 732. ISBN 978-0-7167-2009-6.
^ Jump up to: ^a ^b ^c T., Hancock, John (2010). Cell signalling (3rd ed.). Oxford: Oxford University Press. ISBN 9780199232109. OCLC 444336556.
^ Szabo, Csaba; Coletta, Ciro; Chao, Celia; Módis, Katalin; Szczesny, Bartosz; Papapetropoulos, Andreas; Hellmich, Mark R. (2013-07-23). "Tumor-derived hydrogen sulfide, produced by cystathionine-β-synthase, stimulates bioenergetics, cell proliferation, and angiogenesis in colon cancer". Proceedings of the National Academy of Sciences of the United States of America. 110 (30): 12474–12479. Bibcode:2013PNAS..11012474S. doi:10.1073/pnas.1306241110. ISSN 1091-6490. PMC 3725060. PMID 23836652.
^ Altaany, Zaid; Yang, Guangdong; Wang, Rui (July 2013). "Crosstalk between hydrogen sulfide and nitric oxide in endothelial cells". Journal of Cellular and Molecular Medicine. 17 (7): 879–888. doi:10.1111/jcmm.12077. ISSN 1582-4934. PMC 3822893. PMID 23742697.
^ Dahl, Melissa (2011-01-11). "'Mouth-breathing' gross, harmful to your health". NBC News. Retrieved 2021-09-06.
^ "Nitric oxide". National Institute for Occupational Safety and Health. Retrieved 2015-11-20.

External links[]

International Chemical Safety Card 1311
"Nitric oxide and its role in health and diabetes". 21 October 2015.
Microscale Gas Chemistry: Experiments with Nitrogen Oxides
Your Brain Boots Up Like a Computer – new insights about the biological role of nitric oxide.
Assessing The Potential of Nitric Oxide in the Diabetic Foot
New Discoveries About Nitric Oxide Can Provide Drugs For Schizophrenia
Nitric Oxide at the Chemical Database
"Immediately Dangerous to Life or Health Concentrations (IDLH): Nitric oxide". National Institute for Occupational Safety and Health. 2 November 2018.

[1] "Nitric oxide".

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

[ECHA-3] Jump up to: ^a ^b ^c "Nitrogen monoxide - Registration Dossier - ECHA". Retrieved 2020-11-02.

[SDS-4] Jump up to: ^a ^b ^c ^d "Safety Data Sheet - Nitric Oxide, compressed - Registration Dossier" (PDF). Retrieved 2020-11-02.

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

[6] IUPAC nomenclature of inorganic chemistry 2005. PDF.

[G&E-7] Jump up to: ^a ^b ^c ^d ^e Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[8] 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. PMID 10390607.

[pmid1361684-9] 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.

[10] 
Not to be confused with Traube purine synthesis.

[11] Arulsamy, Navamoney; Bohle, D. Scott (2006). "Synthesis of Diazeniumdiolates from the Reactions of Nitric Oxide with Enolates". J. Org. Chem. 71 (2): 572–581. doi:10.1021/jo051998p. PMID 16408967.

[12] Traube, Wilhelm (1898). "Ueber Synthesen stickstoffhaltiger Verbindungen mit Hülfe des Stickoxyds". Justus Liebig's Annalen der Chemie (in German). 300: 81–128. doi:10.1002/jlac.18983000108.

[13] Derosa, Frank; Keefer, Larry K.; Hrabie, Joseph A. (2008). "Nitric Oxide Reacts with Methoxide". The Journal of Organic Chemistry. 73 (3): 1139–1142. doi:10.1021/jo7020423. PMID 18184006.

[14] Fontijn, Arthur.; Sabadell, Alberto J.; Ronco, Richard J. (1970). "Homogeneous chemiluminescent measurement of nitric oxide with ozone. Implications for continuous selective monitoring of gaseous air pollutants". Analytical Chemistry. 42 (6): 575–579. doi:10.1021/ac60288a034.

[15] Vanin, A; Huisman, A; Van Faassen, E (2002). Iron dithiocarbamate as spin trap for nitric oxide detection: Pitfalls and successes. Methods in Enzymology. 359. pp. 27–42. doi:10.1016/S0076-6879(02)59169-2. ISBN 9780121822620. PMID 12481557.

[16] Nagano, T; Yoshimura, T (2002). "Bioimaging of nitric oxide". Chemical Reviews. 102 (4): 1235–70. doi:10.1021/cr010152s. PMID 11942795.

[undefined-17] Kojima H, Nakatsubo N, Kikuchi K, Kawahara S, Kirino Y, Nagoshi H, Hirata Y, Nagano T (1998). "Detection and imaging of nitric oxide with novel fluorescent indicators: diaminofluoresceins". Anal. Chem. 70 (13): 2446–2453. doi:10.1021/ac9801723. PMID 9666719.

[18] "Centers for Disease Control and Prevention". NIOSH. 1 July 2014. Retrieved 10 December 2015.

[19] Liu, Hongying; Weng, Lingyan; Yang, Chi (2017-03-28). "A review on nanomaterial-based electrochemical sensors for H2O2, H2S and NO inside cells or released by cells". Microchimica Acta. 184 (5): 1267–1283. doi:10.1007/s00604-017-2179-2. ISSN 0026-3672. S2CID 21308802.

[20] Weller, Richard, Could the sun be good for your heart? TedxGlasgow. Filmed March 2012, posted January 2013

[21] Roszer, T (2012) The Biology of Subcellular Nitric Oxide. ISBN 978-94-007-2818-9

[Perez_2598–2607.e1-22] Jump up to: ^a ^b Perez, Krystle M.; Laughon, Matthew (November 2015). "Sildenafil in Term and Premature Infants: A Systematic Review". Clinical Therapeutics. 37 (11): 2598–2607.e1. doi:10.1016/j.clinthera.2015.07.019. ISSN 0149-2918. PMID 26490498.

[stryer-23] Jump up to: ^a ^b ^c Stryer, Lubert (1995). Biochemistry, 4th Edition. W.H. Freeman and Company. p. 732. ISBN 978-0-7167-2009-6.

[:0-24] Jump up to: ^a ^b ^c T., Hancock, John (2010). Cell signalling (3rd ed.). Oxford: Oxford University Press. ISBN 9780199232109. OCLC 444336556.

[25] Szabo, Csaba; Coletta, Ciro; Chao, Celia; Módis, Katalin; Szczesny, Bartosz; Papapetropoulos, Andreas; Hellmich, Mark R. (2013-07-23). "Tumor-derived hydrogen sulfide, produced by cystathionine-β-synthase, stimulates bioenergetics, cell proliferation, and angiogenesis in colon cancer". Proceedings of the National Academy of Sciences of the United States of America. 110 (30): 12474–12479. Bibcode:2013PNAS..11012474S. doi:10.1073/pnas.1306241110. ISSN 1091-6490. PMC 3725060. PMID 23836652.

[Altaany_879–888-26] Altaany, Zaid; Yang, Guangdong; Wang, Rui (July 2013). "Crosstalk between hydrogen sulfide and nitric oxide in endothelial cells". Journal of Cellular and Molecular Medicine. 17 (7): 879–888. doi:10.1111/jcmm.12077. ISSN 1582-4934. PMC 3822893. PMID 23742697.

[27] Dahl, Melissa (2011-01-11). "'Mouth-breathing' gross, harmful to your health". NBC News. Retrieved 2021-09-06.

[28] "Nitric oxide". National Institute for Occupational Safety and Health. Retrieved 2015-11-20.

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[16]

[17]

[18]

[19]

[20]

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[23]

[24]

[25]

[26]

[27]

[28]

show v t Nitrogen species
Hydrides: NH₃ NH₄⁺ NH₂⁻ N³⁻ NH₂OH N₂H₄ HN₃ N₃⁻
Organic: NR₃ >C=NR -CONR₂ -CN HCN CN⁻ (CN)₂ H₂NCN CH₂N₂ -NO -NO₂
Oxides: N₂O NO (NO)₂ NO₂ (NO₂)₂ NO₃ N₂O₃ N₂O₅ H₄N₂O₄ H₂N₂O₂ N₂O₂²⁻ HNO₂ NO₂⁻ HNO₃ NO₃⁻ HONO₂ ONOO⁻ HONO₃ O₂NOO⁻ NO₄³⁻ HNO NO⁺ NO₂⁺
Halides: NF NF₂ NF₃ NCl₃ NBr₃ NI₃ FN₃ ClN₃ BrN₃ IN₃ NH₂F N₂F₂ NH₂Cl NHCl₂
Chemical formulas

show v t Oxides
Mixed oxidation states	Antimony tetroxide (Sb₂O₄) Cobalt(II,III) oxide (Co₃O₄) Lead(II,IV) oxide (Pb₃O₄) Manganese(II,III) oxide (Mn₃O₄) Iron(II,III) oxide (Fe₃O₄) Silver(I,III) oxide (Ag₂O₂) Triuranium octoxide (U₃O₈) Carbon suboxide (C₃O₂) Mellitic anhydride (C₁₂O₉) Praseodymium(III,IV) oxide (Pr₆O₁₁) Terbium(III,IV) oxide (Tb₄O₇) Dichlorine pentoxide (Cl₂O₅)
+1 oxidation state	Copper(I) oxide (Cu₂O) Caesium oxide (Cs₂O) Dicarbon monoxide (C₂O) Dichlorine monoxide (Cl₂O) Gallium(I) oxide (Ga₂O) Lithium oxide (Li₂O) Potassium oxide (K₂O) Rubidium oxide (Rb₂O) Silver oxide (Ag₂O) Thallium(I) oxide (Tl₂O) Sodium oxide (Na₂O) Water (hydrogen oxide) (H₂O)
+2 oxidation state	Aluminium(II) oxide (AlO) Barium oxide (BaO) Beryllium oxide (BeO) Cadmium oxide (CdO) Calcium oxide (CaO) Carbon monoxide (CO) Chromium(II) oxide (CrO) Cobalt(II) oxide (CoO) Copper(II) oxide (CuO) Dinitrogen dioxide (N₂O₂) Germanium monoxide (GeO) Iron(II) oxide (FeO) Lead(II) oxide (PbO) Magnesium oxide (MgO) Manganese(II) oxide (MnO) Mercury(II) oxide (HgO) Nickel(II) oxide (NiO) Nitric oxide (NO) Palladium(II) oxide (PdO) Silicon monoxide (SiO) Strontium oxide (SrO) Sulfur monoxide (SO) Disulfur dioxide (S₂O₂) Thorium monoxide (ThO) Tin(II) oxide (SnO) Titanium(II) oxide (TiO) Vanadium(II) oxide (VO) Zinc oxide (ZnO)
+3 oxidation state	Actinium(III) oxide (Ac₂O₃) Aluminium oxide (Al₂O₃) Antimony trioxide (Sb₂O₃) Arsenic trioxide (As₂O₃) Bismuth(III) oxide (Bi₂O₃) Boron trioxide (B₂O₃) Cerium(III) oxide (Ce₂O₃) Chromium(III) oxide (Cr₂O₃) Cobalt(III) oxide (Co₂O₃) Dinitrogen trioxide (N₂O₃) Dysprosium(III) oxide (Dy₂O₃) Erbium(III) oxide (Er₂O₃) Europium(III) oxide (Eu₂O₃) Gadolinium(III) oxide (Gd₂O₃) Gallium(III) oxide (Ga₂O₃) Holmium(III) oxide (Ho₂O₃) Indium(III) oxide (In₂O₃) Iron(III) oxide (Fe₂O₃) Lanthanum oxide (La₂O₃) Lutetium(III) oxide (Lu₂O₃) Manganese(III) oxide (Mn₂O₃) Neodymium(III) oxide (Nd₂O₃) Nickel(III) oxide (Ni₂O₃) Phosphorus monoxide (PO) Phosphorus trioxide (P₄O₆) Praseodymium(III) oxide (Pr₂O₃) Promethium(III) oxide (Pm₂O₃) Rhodium(III) oxide (Rh₂O₃) Samarium(III) oxide (Sm₂O₃) Scandium oxide (Sc₂O₃) Terbium(III) oxide (Tb₂O₃) Thallium(III) oxide (Tl₂O₃) Thulium(III) oxide (Tm₂O₃) Titanium(III) oxide (Ti₂O₃) Tungsten(III) oxide (W₂O₃) Vanadium(III) oxide (V₂O₃) Ytterbium(III) oxide (Yb₂O₃) Yttrium(III) oxide (Y₂O₃)
+4 oxidation state	Americium dioxide (AmO₂) Carbon dioxide (CO₂) Carbon trioxide (CO₃) Cerium(IV) oxide (CeO₂) Chlorine dioxide (ClO₂) Chromium(IV) oxide (CrO₂) Dinitrogen tetroxide (N₂O₄) Germanium dioxide (GeO₂) Hafnium(IV) oxide (HfO₂) Lead dioxide (PbO₂) Manganese dioxide (MnO₂) Neptunium(IV) oxide (NpO₂) Nitrogen dioxide (NO₂) Osmium dioxide (OsO₂) Plutonium(IV) oxide (PuO₂) Praseodymium(IV) oxide (PrO₂) Protactinium(IV) oxide (PaO₂) Rhodium(IV) oxide (RhO₂) Ruthenium(IV) oxide (RuO₂) Selenium dioxide (SeO₂) Silicon dioxide (SiO₂) Sulfur dioxide (SO₂) Tellurium dioxide (TeO₂) Terbium(IV) oxide (TbO₂) Thorium dioxide (ThO₂) Tin dioxide (SnO₂) Titanium dioxide (TiO₂) Tungsten(IV) oxide (WO₂) Uranium dioxide (UO₂) Vanadium(IV) oxide (VO₂) Zirconium dioxide (ZrO₂)
+5 oxidation state	Antimony pentoxide (Sb₂O₅) Arsenic pentoxide (As₂O₅) Dinitrogen pentoxide (N₂O₅) Niobium pentoxide (Nb₂O₅) Phosphorus pentoxide (P₂O₅) Protactinium(V) oxide (Pa₂O₅) Tantalum pentoxide (Ta₂O₅) Vanadium(V) oxide (V₂O₅)
+6 oxidation state	Chromium trioxide (CrO₃) Molybdenum trioxide (MoO₃) Rhenium trioxide (ReO₃) Selenium trioxide (SeO₃) Sulfur trioxide (SO₃) Tellurium trioxide (TeO₃) Tungsten trioxide (WO₃) Uranium trioxide (UO₃) Xenon trioxide (XeO₃)
+7 oxidation state	Dichlorine heptoxide (Cl₂O₇) Manganese heptoxide (Mn₂O₇) Rhenium(VII) oxide (Re₂O₇) Technetium(VII) oxide (Tc₂O₇)
+8 oxidation state	Osmium tetroxide (OsO₄) Ruthenium tetroxide (RuO₄) Xenon tetroxide (XeO₄) Iridium tetroxide (IrO₄)
Related	Oxocarbon Suboxide Oxyanion Ozonide Peroxide Superoxide Oxypnictide
Oxides are sorted by oxidation state. Category:Oxides

show v t GABA_A receptor positive modulators
Alcohols	Butanol Chloralodol Chlorobutanol (cloretone) Ethanol (alcohol) (alcoholic drink) Ethchlorvynol Isobutanol Isopropanol Menthol Methanol Methylpentynol Pentanol Petrichloral Propanol tert-Butanol (2M2P) tert-Pentanol (2M2B) Tribromoethanol Trichloroethanol Triclofos Trifluoroethanol
Barbiturates	Allobarbital Alphenal Amobarbital Aprobarbital Barbexaclone Barbital Benzobarbital Benzylbutylbarbiturate Brallobarbital Brophebarbital Butabarbital/Secbutabarbital Butalbital Buthalital Butobarbital Butallylonal Carbubarb Crotylbarbital Cyclobarbital Cyclopentobarbital Difebarbamate Enallylpropymal Ethallobarbital Eterobarb Febarbamate Heptabarb Heptobarbital Hexethal Hexobarbital Metharbital Methitural Methohexital Methylphenobarbital Narcobarbital Nealbarbital Pentobarbital Phenallymal Phenobarbital Phetharbital Primidone Probarbital Propallylonal Propylbarbital Proxibarbital Reposal Secobarbital Sigmodal Spirobarbital Talbutal Tetrabamate Tetrabarbital Thialbarbital Thiamylal Thiobarbital Thiobutabarbital Thiopental Thiotetrabarbital Valofane Vinbarbital Vinylbital
Benzodiazepines	2-Oxoquazepam 3-Hydroxyphenazepam Adinazolam Alprazolam Arfendazam Avizafone Bentazepam Bretazenil Bromazepam Brotizolam Camazepam Carburazepam Chlordiazepoxide Ciclotizolam Cinazepam Cinolazepam Clazolam Climazolam Clobazam Clonazepam Clonazolam Cloniprazepam Clorazepate Clotiazepam Cloxazolam CP-1414S Cyprazepam Delorazepam Demoxepam Diazepam Diclazepam Doxefazepam Elfazepam Estazolam Ethyl carfluzepate Ethyl dirazepate Ethyl loflazepate Etizolam EVT-201 FG-8205 Fletazepam Flubromazepam Flubromazolam Fludiazepam Flunitrazepam Flunitrazolam Flurazepam Flutazolam Flutemazepam Flutoprazepam Fosazepam Gidazepam Halazepam Haloxazolam Iclazepam Imidazenil Irazepine Ketazolam Lofendazam Lopirazepam Loprazolam Lorazepam Lormetazepam Meclonazepam Medazepam Menitrazepam Metaclazepam Mexazolam Midazolam Motrazepam N-Desalkylflurazepam Nifoxipam Nimetazepam Nitrazepam Nitrazepate Nitrazolam Nordazepam Nortetrazepam Oxazepam Oxazolam Phenazepam Pinazepam Pivoxazepam Prazepam Premazepam Proflazepam Pyrazolam QH-II-66 Quazepam Reclazepam Remimazolam Rilmazafone Ripazepam Ro48-6791 Ro48-8684 SH-053-R-CH3-2′F Sulazepam Temazepam Tetrazepam Tolufazepam Triazolam Triflubazam Triflunordazepam (Ro5-2904) Tuclazepam Uldazepam Zapizolam Zolazepam Zomebazam
Carbamates	Carisbamate Carisoprodol Clocental Cyclarbamate Difebarbamate Emylcamate Ethinamate Febarbamate Felbamate Hexapropymate Hydroxyphenamate Lorbamate Mebutamate Meprobamate Nisobamate Pentabamate Phenprobamate Procymate Styramate Tetrabamate Tybamate
Flavonoids	Ampelopsin (dihydromyricetin) Apigenin Baicalein Baicalin Catechin EGC EGCG Hispidulin Luteolin Skullcap constituents (e.g., baicalin) Wogonin
Imidazoles	Etomidate Metomidate Propoxate
Kava constituents	Desmethoxyyangonin Kavain Methysticin Yangonin
Monoureides	Acecarbromal Apronal (apronalide) Bromisoval Carbromal
Neuroactive steroids	Acebrochol Allopregnanolone (brexanolone) Alfadolone Alfaxalone 3α-Androstanediol Androstenol Androsterone Certain anabolic-androgenic steroids Cholesterol DHDOC 3α-DHP 5α-DHP 5β-DHP DHT Etiocholanolone Ganaxolone Hydroxydione Minaxolone ORG-20599 ORG-21465 P1-185 Pregnanolone (eltanolone) Progesterone Renanolone Testosterone THDOC Zuranolone
Nonbenzodiazepines	Cyclopyrrolones: Eszopiclone Pagoclone Pazinaclone Suproclone Suriclone Zopiclone Imidazopyridines: Alpidem DS-1 Necopidem Saripidem Zolpidem Pyrazolopyrimidines: Divaplon Fasiplon Indiplon Lorediplon Ocinaplon Panadiplon Taniplon Zaleplon Others: Adipiplon CGS-8216 CGS-9896 CGS-13767 CGS-20625 CL-218,872 CP-615,003 ELB-139 GBLD-345 Imepitoin JM-1232 L-838,417 Lirequinil (Ro41-3696) NS-2664 NS-2710 NS-11394 Pipequaline ROD-188 RWJ-51204 SB-205,384 SX-3228 TP-003 TPA-023 TP-13 U-89843A U-90042 Viqualine Y-23684
Phenols	Fospropofol Propofol Thymol
Piperidinediones	Glutethimide Methyprylon Piperidione Pyrithyldione
Pyrazolopyridines	Cartazolate Etazolate ICI-190,622 Tracazolate
Quinazolinones	Afloqualone Cloroqualone Diproqualone Etaqualone Mebroqualone Mecloqualone Methaqualone Methylmethaqualone Nitromethaqualone SL-164
Volatiles/gases	Acetone Acetophenone Acetylglycinamide chloral hydrate Aliflurane Benzene Butane Butylene Centalun Chloral Chloral betaine Chloral hydrate Chloroform Cryofluorane Desflurane Dichloralphenazone Dichloromethane Diethyl ether Enflurane Ethyl chloride Ethylene Fluroxene Gasoline Halopropane Halothane Isoflurane Kerosine Methoxyflurane Methoxypropane Nitric oxide Nitrogen Nitrous oxide Norflurane Paraldehyde Propane Propylene Roflurane Sevoflurane Synthane Teflurane Toluene Trichloroethane (methyl chloroform) Trichloroethylene Vinyl ether
Others/unsorted	3-Hydroxybutanal Avermectins (e.g., ivermectin) Bromide compounds (e.g., lithium bromide, potassium bromide, sodium bromide) Carbamazepine Chloralose Chlormezanone Clomethiazole DEABL Dihydroergolines (e.g., dihydroergocryptine, , dihydroergotamine, ergoloid (dihydroergotoxine)) Efavirenz Etazepine Etifoxine Fenamates (e.g., flufenamic acid, mefenamic acid, niflumic acid, tolfenamic acid) Fluoxetine Flupirtine Hopantenic acid Lanthanum Lavender oil Lignans (e.g., 4-O-methylhonokiol, honokiol, magnolol, obovatol) Loreclezole Menthyl isovalerate (validolum) Monastrol Niacin Niacinamide Org 25,435 Phenytoin Propanidid Retigabine (ezogabine) Safranal Seproxetine Stiripentol (e.g., sulfonmethane (sulfonal), tetronal, trional) Terpenoids (e.g., borneol) Topiramate Valerian constituents (e.g., isovaleric acid, isovaleramide, valerenic acid, ) Unsorted benzodiazepine site positive modulators: α-Pinene
See also: Receptor/signaling modulators • GABA receptor modulators • GABA metabolism/transport modulators

show v t Other respiratory system products (R07)
Lung surfactants	Colfosceril palmitate Dipalmitoylphosphatidylcholine
Respiratory stimulants	Almitrine Amiphenazole Bemegride Dimefline Doxapram Etamivan GAL-021 Mepixanox Nikethamide Pentetrazol Prethcamide
5-HT4 receptor agonists	BIMU-8 Zacopride
Other agents for treating respiratory depression	Ivacaftor (+ lumacaftor, + elexacaftor/tezacaftor) Nitric oxide BW373U86 CX-546 CX-717

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Nitric oxide

Contents

Reactions[]

With di- and triatomic molecules[]

Organic chemistry[]

Coordination complexes[]

Production and preparation[]

Laboratory methods[]

Detection and assay[]

Environmental effects[]

Acid rain deposition[]

Ozone depletion[]

Precursor to NO₂[]

Biological functions[]

Occupational safety and health[]

References[]

Further reading[]

External links[]

Nitric oxide

Reactions[]

With di- and triatomic molecules[]

Organic chemistry[]

Coordination complexes[]

Production and preparation[]

Laboratory methods[]

Detection and assay[]

Environmental effects[]

Acid rain deposition[]

Ozone depletion[]

Precursor to NO2[]

Biological functions[]

Occupational safety and health[]

References[]

Further reading[]

External links[]

Precursor to NO₂[]