Dioxygen

Athanor · official

O₂ · 31.999 g/mol

IUPAC name: molecular oxygen

Also called oxygen, molecular oxygen, O2

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerMay cause or intensify fire; oxidizer

Names and identifiers

IUPAC name: molecular oxygen
Synonyms: oxygen, molecular oxygen, O2
+ 37 more
Molecular oxygen, oxygen molecule, Pure oxygen, Oxygenium, Liquid oxygen, Oxygen, liquified, Oxygen-16, Compressed oxygen, Oxygen, compressed, INS NO.948, DTXSID2037681, INS-948, E-948, S88TT14065, E948, RNS60 COMPONENT OXYGEN, RNS-60 COMPONENT OXYGEN, CHEBI:15379, Oxygen 16, OXYGEN GAS, oxidanone, Air Compressed, reconstituted Air, Oxygen Compressed, Nitrogen, Oxygen, Oxygen Size B, Oxygen Size C, Oxygen Size D, Oxygen Size E, Oxygen Size F, Oxygen Size H, Oxygen Size M, Oxygen Size T, Helium/Oxygen Mix, Oxygen, USP, G02 Therapy, Ez-OX Plus
Molecular formula: O₂
Empirical formula: O
Molecular weight: 31.999 g/mol
Exact mass: 31.98983
CAS number: 7782-44-7
PubChem CID: 977
Canonical SMILES: O=O
Isomeric SMILES: O=O
InChI: InChI=1S/O2/c1-2
InChIKey: MYMOFIZGZYHOMD-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Slightly bluish liquid at -183 °C[5]
7 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Oxygen is a colorless, odorless and tasteless gas. It will support life. It is noncombustible, but will actively support the burning of combustible materials. Some materials that will not burn in air will burn in oxygen. Materials that burn in air will burn more vigorously in oxygen. As a non-liquid gas it is shipped at pressures of 2000 psig or above. Pure oxygen is nonflammable. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Oxygen is used in the production of synthesis gas from coal, for resuscitation and as an inhalant. [1] CAMEO Chemicals
– Oxygen is a colorless, odorless and tasteless gas. It will support life. It is noncombustible, but will actively support the burning of combustible materials. Some materials that will not burn in air will burn in oxygen. Materials that burn in air will burn more vigorously in oxygen. As a non-liquid gas it is shipped at pressures of 2000 psig or above. Pure oxygen is nonflammable. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Oxygen is used in the production of synthesis gas from coal, for resuscitation and as an inhalant. [1] CAMEO Chemicals
– Dry Powder; Wet Solid; Other Solid; Gas Vapor; Liquid [2] EPA Chemical Data Reporting (CDR)
– ODOURLESS COMPRESSED GAS. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– LIQUEFIED GAS. COLOURLESS-TO-BLUE EXTREMELY COLD LIQUID. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Colorless, odorless and tasteless gas. [4] Occupational Safety and Health Administration (OSHA)
–shown Slightly bluish liquid at -183 °C [5] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 13th ed. New York, NY: John Wiley & Sons, Inc. 1997., p. 830
Melting point: -218.4 °C[3]
4 values
3 of 3 sources agree on it (most common value).
Value As written Source
−218 °C -361 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−218.4 °Cshown -218.4 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−218.4 °C -218.4 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−218 °C -361 °F [4] Occupational Safety and Health Administration (OSHA)
3 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Boiling point: -182.9 °C (-297.3 °F) at 760 mmHg (USCG, 1999)[1]
4 values
3 of 3 sources agree on it (most common value).
Value As written Source
−182.9 °Cshown -297.3 °F at 760 mmHg (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−183 °C -183 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−183 °C -183 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−182.9 °C -297.3 °F [4] Occupational Safety and Health Administration (OSHA)
Density: 1.14 at -183.0 °C (-297.4 °F) (USCG, 1999) - Denser than water[1]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
–shown 1.14 at -297.4 °F (USCG, 1999) - Denser than water [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
– 1.14 at -297.4 °F [4] Occupational Safety and Health Administration (OSHA)
Solubility in water: Solubility in water, ml/100ml at 20 °C: 3.1[3]
2 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
–shown Solubility in water, ml/100ml at 20 °C: 3.1 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Solubility in water, ml/100ml at 20 °C: 3.1 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
log P: 0.65[3]
3 values
2 of 2 sources agree on it (most common value).
Value As written Source
– log Kow = 0.65 [5] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 3
–shown 0.65 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 0.65 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Vapor pressure: Vapor pressure, kPa at -118 °C: 5080[3]
Viscosity: Reported, but no value passed the checks.
The 2 values and why
Gas: 101.325 kPa at 25 °C (0.020 75 cP) (could not be read; source [5])
Liquid: 99.70 K (0.156 cP) (could not be read; source [5])

Value	As written	Source
–	Oxygen is a colorless, odorless and tasteless gas. It will support life. It is noncombustible, but will actively support the burning of combustible materials. Some materials that will not burn in air will burn in oxygen. Materials that burn in air will burn more vigorously in oxygen. As a non-liquid gas it is shipped at pressures of 2000 psig or above. Pure oxygen is nonflammable. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Oxygen is used in the production of synthesis gas from coal, for resuscitation and as an inhalant.	[1] CAMEO Chemicals
–	Oxygen is a colorless, odorless and tasteless gas. It will support life. It is noncombustible, but will actively support the burning of combustible materials. Some materials that will not burn in air will burn in oxygen. Materials that burn in air will burn more vigorously in oxygen. As a non-liquid gas it is shipped at pressures of 2000 psig or above. Pure oxygen is nonflammable. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Oxygen is used in the production of synthesis gas from coal, for resuscitation and as an inhalant.	[1] CAMEO Chemicals
–	Dry Powder; Wet Solid; Other Solid; Gas Vapor; Liquid	[2] EPA Chemical Data Reporting (CDR)
–	ODOURLESS COMPRESSED GAS.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	LIQUEFIED GAS. COLOURLESS-TO-BLUE EXTREMELY COLD LIQUID.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Colorless, odorless and tasteless gas.	[4] Occupational Safety and Health Administration (OSHA)
–shown	Slightly bluish liquid at -183 °C	[5] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 13th ed. New York, NY: John Wiley & Sons, Inc. 1997., p. 830

Value	As written	Source
−218 °C	-361 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−218.4 °Cshown	-218.4 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−218.4 °C	-218.4 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−218 °C	-361 °F	[4] Occupational Safety and Health Administration (OSHA)

Value	As written	Source
−182.9 °Cshown	-297.3 °F at 760 mmHg (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
−183 °C	-183 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−183 °C	-183 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−182.9 °C	-297.3 °F	[4] Occupational Safety and Health Administration (OSHA)

Value	As written	Source
–shown	1.14 at -297.4 °F (USCG, 1999) - Denser than water	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–	1.14 at -297.4 °F	[4] Occupational Safety and Health Administration (OSHA)

Value	As written	Source
–shown	Solubility in water, ml/100ml at 20 °C: 3.1	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Solubility in water, ml/100ml at 20 °C: 3.1	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
–	log Kow = 0.65	[5] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 3
–shown	0.65	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	0.65	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 2
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 2
Rotatable bonds: 0
TPSA (Å²): 34.1
Formal charge: 0
XLogP3: -1.1 PubChem
Complexity: 0 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: D∞h of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

O100.00%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 0.07 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.08 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 3.37 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 32
log P ≤ 5 (Crippen): 0.07
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 2

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Harmonized EU classification (CLP Annex VI). Source [6].

Oxidizer
Compressed gas

NFPA 704[5]

H270May cause or intensify fire; oxidizer

Precautionary statements: P220, P244, P370+P376, P403

View all classifications (3)

[6] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH270
[7] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 1% (13 of 1351) of reports.
[7] European Chemicals Agency (ECHA) · 1,351 reports · DangerH270, H280, H281

First aid

Inhalation: In all but the most severe cases (pneumonia), recovery is rapid after reduction of oxygen pressure; supportive treatment should include immediate sedation, anticonvulsive therapy if needed, and rest. Eyes: Treat frostbite burns. Skin: Treat frostbite; soak in lukewarm water. (USCG, 1999)[1]
Excerpt from ERG Guide 122 [Gases - Oxidizing (Including Refrigerated Liquids)]: Refer to the "General First Aid" section. Specific First Aid: Clothing frozen to the skin should be thawed before being removed. In case of contact with liquefied gas, only medical personnel should attempt thawing frosted parts. (ERG, 2024)[1]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[8]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[8]

Storage

Fireproof. Separated from combustible substances and reducing agents. Cool.[3]
GAS & liq: Gaseous oxygen IS stored ... IN cylinders AT A pressure OF 150-160 ATM, & insulated tanks ARE USED FOR liquid oxygen; small quantities OF liquid oxygen (2-50 L) CAN BE stored IN dewar flasks.[5]
Oxygen should be stored in an area that is at least 20 ft away from any flammable or combustible materials (especially oil & grease) or separated from them by a noncombustible barrier at least 5 ft high & having a fire-resistant rating of at least 1/2 hr.[5]
Liq: Protect against physical damage. Isolate from combustible gas installations and combustible materials by adequate distance or by gas-tight fire-resistive barriers. Protect against overheating. Outside storage of liq oxygen tanks is recommended.[5]

Incompatibilities

Liq: Heat of water will vigorously vaporize liquid oxygen.[5]
Oxygen leaked into the free space in an acetaldehyde storage tank normally purged with nitrogen. Accelerating exothermic oxidation led to detonation. The self-ignition temperature of acetaldehyde-oxygen mixtures depends on dimensions of the reactor and the partial pressure of peracetic acid accumulated on the walls. Spontaneous ignition temperatures of 71 to 73 °C were observed.[5]
Oxygen reacts explosively with phosphine, hydrazine, hydrogen sulfide ...[5]
Synthesis gas (CO + H2) at 40 bar containing a low level of hydrogen sulfide was to be freed of the latter impurity by adding the theoretical quantity of oxygen and passing the mixture over a catalyst. Introducing of oxygen (from a supply at 60 bar) via a simple T-piece (instead of through the recommended small bore coaxial injection nozzle to ensure thorough mixing with the gas stream) caused development of an intense inverse flame in the locally very high oxygen concn which burned through the reactor side wall opposite the oxygen inlet and ejected a meter-long flame-jet.[5]

Safety data sheets on the supplier’s page: Sigma-Aldrich, Yuhao Chemical, AA BLOCKS.

Always read the supplier’s safety data sheet before working with it.

Spectra

GC-MSNIST Mass Spectrometry Data Center · SpectraBase

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[4]Occupational Safety and Health Administration (OSHA) · Public domain (US DOL) · via PubChem · retrieved 2026-10-14
[5]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[6]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[7]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[8]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[9]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[10]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.