Oxygen

Formula: O₂
Molecular weight: 31.9988
IUPAC Standard InChI: InChI=1S/O2/c1-2
IUPAC Standard InChIKey: MYMOFIZGZYHOMD-UHFFFAOYSA-N
CAS Registry Number: 7782-44-7
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript.
Other names: Molecular oxygen; Oxygen molecule; Pure oxygen; O2; Liquid oxygen; UN 1072; UN 1073; Dioxygen
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Information on this page:
Other data available:
- Gas phase thermochemistry data
- Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 70
- Henry's Law data
- Ion clustering data
- Mass spectrum (electron ionization)
- Constants of diatomic molecules
- Fluid Properties
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Phase change data

Go To: Top, Gas phase ion energetics data, References, Notes

Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director

Quantity	Value	Units	Method	Reference	Comment
T_boil	90.2	K	N/A	Streng, 1971	Uncertainty assigned by TRC = 0.2 K; TRC
Quantity	Value	Units	Method	Reference	Comment
T_fus	54.8	K	N/A	Streng, 1971	Uncertainty assigned by TRC = 0.2 K; TRC
Quantity	Value	Units	Method	Reference	Comment
T_triple	54.33	K	N/A	Henning and Otto, 1936	Uncertainty assigned by TRC = 0.06 K; temperature measured with He gas thermometer; TRC
Quantity	Value	Units	Method	Reference	Comment
T_c	154.58	K	N/A	Pentermann and Wagner, 1978	Uncertainty assigned by TRC = 0.0015 K; TRC
T_c	154.58	K	N/A	Wagner, Ewers, et al., 1976	Uncertainty assigned by TRC = 0.0015 K; TRC
T_c	155.15	K	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.3 K; 4 determinations with same result; TRC
Quantity	Value	Units	Method	Reference	Comment
P_c	50.43	bar	N/A	Wagner, Ewers, et al., 1976	Uncertainty assigned by TRC = 0.005 bar; Vapour-pressure measurements give pc=5.04332 MPa at Tc from L.A.Weber, 1970 PRT, IPTS-68, PP+ differential pressure transducer.; TRC
P_c	50.0343	bar	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.3039 bar; TRC
P_c	49.9228	bar	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.3039 bar; TRC
P_c	49.8519	bar	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.3039 bar; TRC
Quantity	Value	Units	Method	Reference	Comment
ρ_c	13.60	mol/l	N/A	Pentermann and Wagner, 1978	Uncertainty assigned by TRC = 0.014 mol/l; from density measurements 65 to 300 K, Tc from Weber, 1970; TRC

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
P = vapor pressure (bar)
T = temperature (K)

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Temperature (K)	A	B	C	Reference	Comment
54.36 to 100.16	3.85845	325.675	-5.667	Brower and Thodos, 1968	Coefficents calculated by NIST from author's data.
54.36 to 154.33	3.9523	340.024	-4.144	Brower and Thodos, 1968	Coefficents calculated by NIST from author's data.

In addition to the Thermodynamics Research Center (TRC) data available from this site, much more physical and chemical property data is available from the following TRC products:

Gas phase ion energetics data

Go To: Top, Phase change data, References, Notes

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
MM - Michael M. Meot-Ner (Mautner)
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

View reactions leading to O₂⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	12.0697 ± 0.0002	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	421.	kJ/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	396.3	kJ/mol	N/A	Hunter and Lias, 1998	HL

Electron affinity determinations

EA (eV)	Method	Reference	Comment
0.4480 ± 0.0060	LPES	Ervin, Anusiewicz, et al., 2003	B
0.4510 ± 0.0070	LPES	Travers, Cowles, et al., 1989	B
0.4400 ± 0.0080	LPES	Celotta, Bennett, et al., 1972	89SAW puts DH(H-O2.) at 59 kcal/mol, implying ΔHacid=362.5; B
0.451 ± 0.052	ECD	Chen and Wentworth, 1983	B
0.44 ± 0.10	CIDT	Tiernan and Wu, 1978	From O₂^-; B
0.40 ± 0.10	NBIE	Durup, Parlant, et al., 1977	B
0.450 ± 0.024	ETS	Burrow, 1974	B
0.50 ± 0.10	NBIE	Baeda, 1972	B
0.430 ± 0.030	LPES	Celotta, Bennett, et al., 1971	B
0.460 ± 0.050	NBIE	Nalley and Compton, 1971	B
>0.45 ± 0.10	Endo	Tiernan, Hughes, et al., 1971	B
0.50 ± 0.20	NBIE	Lacmann and Herschbach, 1970	B
0.430 ± 0.020	Kine	Pack and Phelps, 1966	B
>0.479998	Endo	Berkowitz, Chupka, et al., 1971	B
>0.56 ± 0.10	Endo	Chantry, 1971	B
0.725005	ECD	Chen and Chen, 2003	B
>1.27 ± 0.20	Endo	Bailey and Mahadevan, 1970	B
1.119 ± 0.069	IMRB	Vogt, Hauffle, et al., 1970	B
>1.10 ± 0.10	EIAE	Stockdale, Compton, et al., 1969	From NO₂; B
0.150 ± 0.050	PD	Burch, Smith, et al., 1958	B

Proton affinity at 298K

Proton affinity (kJ/mol)	Reference	Comment
421. ± 3.	Litorja and Ruscic, 1998	T = 298K; MM

Ionization energy determinations

IE (eV)	Method	Reference	Comment
12.0697 ± 0.0002	S	Tonkyn, Winniczek, et al., 1989	LL
12.1 ± 0.1	EI	Grade, Wienecke, et al., 1983	LBLHLM
12.8 ± 0.5	EI	Gomez, Chatillon, et al., 1982	LBLHLM
12.0 ± 1.0	S	Farber, Srivastava, et al., 1982	LBLHLM
12.076 ± 0.002	PE	MacNeil and Dixon, 1977	LLK
12.071	PE	Kronebusch and Berkowitz, 1976	LLK
12.071 ± 0.001	PE	Samson and Gardner, 1975	LLK
12.0 ± 0.5	EI	Hildenbrand, 1975	LLK
12.2 ± 0.2	EI	Bennett, Lin, et al., 1974	LLK
12.07 ± 0.01	PI	Tanaka and Tanaka, 1973	LLK
12.08	PE	Natalis, 1973	LLK
12.077	PE	Dromey, Morrison, et al., 1973	LLK
12.127	PE	Vilesov and Lopatin, 1972	LLK
12.072 ± 0.008	PI	Dibeler and Walker, 1967	RDSH
12.059 ± 0.001	S	Samson and Cairns, 1966	RDSH
12.078 ± 0.005	PI	Brehm, 1966	RDSH
12.065 ± 0.003	PI	Nicholson, 1963	RDSH
12.08 ± 0.01	PI	Watanabe, 1957	RDSH
12.30	PE	Kimura, Katsumata, et al., 1981	Vertical value; LLK
12.33 ± 0.01	PE	Banna and Shirley, 1976	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
O⁺	18.734	O	PIPECO	Blyth, Powis, et al., 1981	LLK
O⁺	17.28	O^-	PI	Oertel, Schenk, et al., 1980	LLK
O⁺	18.69 ± 0.04	O	EI	Locht and Schopman, 1974	LLK
O⁺	17.3 ± 0.2	O^-	EI	Locht and Momigny, 1971	LLK
O⁺	17.25 ± 0.01	O^-	PI	Dibeler and Walker, 1967	RDSH
O⁺	17.272 ± 0.024	O^-	PI	Elder, Villarejo, et al., 1965	RDSH
O⁺	18.8 ± 0.4	O	PI	Weissler, Samson, et al., 1959	RDSH
O⁺	18.99 ± 0.05	O	EI	Frost and McDowell, 1959	RDSH

Anion protonation reactions

+ =

By formula: O₂^- + H⁺ = HO₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1476.9 ± 3.0	kJ/mol	D-EA	Travers, Cowles, et al., 1989	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1450.5 ± 3.4	kJ/mol	H-TS	Travers, Cowles, et al., 1989	gas phase; B

References

Go To: Top, Phase change data, Gas phase ion energetics data, Notes

Streng, 1971
Streng, A.G., Miscibility and Compatibility of Some Liquid and Solidified Gases at Low Temperature, J. Chem. Eng. Data, 1971, 16, 357. [all data]

Henning and Otto, 1936
Henning, F.; Otto, J., Vapor pressure curves and triple points in the temperature region from 14 to 90 k, Phys. Z., 1936, 37, 633-8. [all data]

Pentermann and Wagner, 1978
Pentermann, W.; Wagner, W., New pressure-density-temperature measurements and new rational equations for the saturated liquid and vapor densities of oxygen, J. Chem. Thermodyn., 1978, 10, 1161-1172. [all data]

Wagner, Ewers, et al., 1976
Wagner, W.; Ewers, J.; Pentermann, W., A New Vapor-Pressure Measurement and a New Rational Vapor-Pressure Equation for Oxygen, J. Chem. Thermodyn., 1976, 8, 1049. [all data]

Cardoso, 1915
Cardoso, E., Study of the Critical Point of Several Difficultly LIquifiable Gases: Nitrogen, Carbon Monoxide, Oxygen and Methane, J. Chim. Phys. Phys.-Chim. Biol., 1915, 13, 312. [all data]

Brower and Thodos, 1968
Brower, G.T.; Thodos, G., Vapor Pressures of Liquid Oxygen Between the Triple Point and Critical Point, J. Chem. Eng. Data, 1968, 13, 2, 262-264, https://doi.org/10.1021/je60037a038 . [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Ervin, Anusiewicz, et al., 2003
Ervin, K.M.; Anusiewicz, W.; Skurski, P.; Simons, J.; Lineberger, W.C., The only stable state of O-2(-) is the X (2)Pi(g) ground state and it (still!) has an adiabatic electron detachment energy of, J. Phys. Chem. A, 2003, 107, 41, 8521-8529, https://doi.org/10.1021/jp0357323 . [all data]

Travers, Cowles, et al., 1989
Travers, M.J.; Cowles, D.C.; Ellison, G.B., Reinvestigation of the Electron Affinities of O2 and NO, Chem. Phys. Lett., 1989, 164, 5, 449, https://doi.org/10.1016/0009-2614(89)85237-6 . [all data]

Celotta, Bennett, et al., 1972
Celotta, R.J.; Bennett, R.A.; Hall, J.L.; Siegel, M.W.; Levine, J., Molecular photodetachment spectrometry. II. The electron affinity of O₂ and the structure of O₂-, Phys. Rev. A:, 1972, 6, 631. [all data]

Chen and Wentworth, 1983
Chen, E.C.M.; Wentworth, W.E., Determination of molecular electron affinities using the electron capture detector in the pulse sampling mode at steady state, J. Phys. Chem., 1983, 87, 45. [all data]

Tiernan and Wu, 1978
Tiernan, T.O.; Wu, R.L.C., Thermochemical Data for Molecular Negative Ions from Collisional Dissociation Thresholds, Adv. Mass Spectrom., 1978, 7A, 136. [all data]

Durup, Parlant, et al., 1977
Durup, M.; Parlant, G.; Appell, J.; Durup, J.; Ozenne, J.-B., Translational spectroscopy of neutralization-reionization double collision processes of Ar⁺ ions at keV energies, Chem. Phys., 1977, 25, 245. [all data]

Burrow, 1974
Burrow, P.D., Temporary negative ion formation in NO and O₂, Chem. Phys. Lett., 1974, 26, 265. [all data]

Baeda, 1972
Baeda, A.P.M., The adiabatic electron affinities of Cl₂, Br₂, I₂, IBr, NO₂, and O₂, Physica, 1972, 59, 541. [all data]

Celotta, Bennett, et al., 1971
Celotta, R.J.; Bennett, R.A.; Hall, J.L.; Levine, J.; Siegel, M.W., Electron affinity of O₂ by laser photodetachment, Bull. Am. Phys. Soc., 1971, 16, 212. [all data]

Nalley and Compton, 1971
Nalley, S.J.; Compton, R.N., Collisional ionization of cesium by oxygen: The electron affinity of O₂, Chem. Phys. Lett., 1971, 9, 529. [all data]

Tiernan, Hughes, et al., 1971
Tiernan, T.O.; Hughes, B.M.; Lifschitz, C., Electron affinities from endothermic negative ion charge transfer reactions. II. O₂, J. Chem. Phys., 1971, 55, 5692. [all data]

Lacmann and Herschbach, 1970
Lacmann, K.; Herschbach, D.R., Collisional Excitation and Ionization of K Atoms by Diatomic Molecules: Role of Ion-pair States, Chem. Phys. Lett., 1970, 6, 2, 106, https://doi.org/10.1016/0009-2614(70)80144-0 . [all data]

Pack and Phelps, 1966
Pack, J.L.; Phelps, A.V., Electron Attachment and Detachment. I. Pure O₂ at Low Energy, J. Chem. Phys., 1966, 44, 5, 1870, https://doi.org/10.1063/1.1726956 . [all data]

Berkowitz, Chupka, et al., 1971
Berkowitz, J.; Chupka, W.A.; Gutman, D., Electron Affinities of O₂, O₃, NO, NO₂, and NO₃ by Endothermic Charge Transfer, J. Chem. Phys., 1971, 55, 6, 2733, https://doi.org/10.1063/1.1676488 . [all data]

Chantry, 1971
Chantry, P.J., Doppler broadening in beam experiments, J. Chem. Phys., 1971, 55, 2746. [all data]

Chen and Chen, 2003
Chen, E.S.; Chen, E.C.M., Semiempirical characterization of homonuclear diatomic ions: 6. Group VI and VII anions, J. Phys. Chem. A, 2003, 107, 1, 169-177, https://doi.org/10.1021/jp0268922 . [all data]

Bailey and Mahadevan, 1970
Bailey, T.L.; Mahadevan, P., Electron Transfer and Detachment in Collisions of Low Energy Negative Ions with O₂, J. Chem. Phys., 1970, 52, 1, 179, https://doi.org/10.1063/1.1672663 . [all data]

Vogt, Hauffle, et al., 1970
Vogt, D.; Hauffle, B.; Neuert, H., Ladungsaustausch-Reaktionen Einiger Negativer Ionen mit O₂ und die Elektronenaffinitat des O₂, Z. Phys., 1970, 232, 5, 439, https://doi.org/10.1007/BF01395674 . [all data]

Stockdale, Compton, et al., 1969
Stockdale, J.A.D.; Compton, R.N.; Hurst, G.S.; Reinhardt, P.W., Collisions of Monoenergetic Electrons with NO₂: Possible Lower Limits to the Electron Affinities of O₂ and NO, J. Chem. Phys., 1969, 50, 5, 2176, https://doi.org/10.1063/1.1671347 . [all data]

Burch, Smith, et al., 1958
Burch, D.S.; Smith, S.J.; Branscomb, L.M., Photodetachment of O₂^-., Phys. Rev., 1958, 112, 1, 171, https://doi.org/10.1103/PhysRev.112.171 . [all data]

Litorja and Ruscic, 1998
Litorja, M.; Ruscic, B., A photoionization study of the hydroperoxyl radical, HO2, and hydrogen peroxide, H2O2, J. Electron Spectroscopy and Related Phenomena, 1998, 97, 131. [all data]

Tonkyn, Winniczek, et al., 1989
Tonkyn, R.G.; Winniczek, J.W.; White, M.G., Rotationally resolved photoionization of O₂ near threshold, Chem. Phys. Lett., 1989, 164, 137. [all data]

Grade, Wienecke, et al., 1983
Grade, M.; Wienecke, J.; Rosinger, W.; Hirschwald, W., Electron impact investigation of the molecules SeS(g) and TeSe(g) under high-temperature equilibrium conditions, Ber. Bunsen-Ges. Phys. Chem., 1983, 87, 355. [all data]

Gomez, Chatillon, et al., 1982
Gomez, M.; Chatillon, C.; Allibert, M., Thermodynamics of gaseous and condensed indium oxides by mass spectrometry with controlled oxygen oressure, J. Chem. Thermodyn., 1982, 14, 447. [all data]

Farber, Srivastava, et al., 1982
Farber, M.; Srivastava, R.D.; Moyer, J.W., Mass spectrometric determination of the thermodynamics of potassium hydroxide and minor potassium-containing species required in magnetohydrodynamic power systems, J. Chem. Thermodyn., 1982, 14, 1103. [all data]

MacNeil and Dixon, 1977
MacNeil, K.A.G.; Dixon, R.N., High-resolution photoelectron spectroscopy of methanol and its deuterated derivatives: Internal rotation in the ground ionic state, J. Electron Spectrosc. Relat. Phenom., 1977, 11, 315. [all data]

Kronebusch and Berkowitz, 1976
Kronebusch, P.L.; Berkowitz, J., Photodissociative ionization in the 21-41 eV region: O₂, N₂, CO, NO, CO₂, H₂O, NH₃ and CH₄, Int. J. Mass Spectrom. Ion Phys., 1976, 22, 283. [all data]

Samson and Gardner, 1975
Samson, J.A.R.; Gardner, J.L., On the ionization potential of molecular oxygen, Can. J. Phys., 1975, 53, 1948. [all data]

Hildenbrand, 1975
Hildenbrand, D.L., Vertical ionization potential of the CF₂ radical, Chem. Phys. Lett., 1975, 32, 30. [all data]

Bennett, Lin, et al., 1974
Bennett, S.L.; Lin, S.-S.; Gilles, P.W., High-temperature vaporization of ternary systems. I. Mass spectrometry of oxygen-rich vanadium-tungsten-oxygen species, J. Phys. Chem., 1974, 78, 266. [all data]

Tanaka and Tanaka, 1973
Tanaka, K.; Tanaka, I., Photoelectron spectra from some autoionizing state of O₂ near the ionization threshold, J. Chem. Phys., 1973, 59, 5042. [all data]

Natalis, 1973
Natalis, P., Contribution a la spectroscopie photoelectronique. Effets de l'autoionisation dans less spectres photoelectroniques de molecules diatomiques et triatomiques, Acad. R. Belg. Mem. Cl. Sci. Collect. 8, 1973, 41, 1. [all data]

Dromey, Morrison, et al., 1973
Dromey, R.G.; Morrison, J.D.; Peel, J.B., Time-averaged and deconvoluted photoelectron spectrum of the first band of O₂, Chem. Phys. Lett., 1973, 23, 30. [all data]

Vilesov and Lopatin, 1972
Vilesov, F.I.; Lopatin, S.N., Photoelectron spectrometer, Zh. Tekh. Fiz., 1972, 42, 176. [all data]

Dibeler and Walker, 1967
Dibeler, V.H.; Walker, J.A., Mass spectrometric study of the photoionization of small polyatomic molecules, Advan. Mass Spectrom., 1967, 4, 767. [all data]

Samson and Cairns, 1966
Samson, J.A.R.; Cairns, R.B., Ionization potential of O₂, J. Opt. Soc. Am., 1966, 56, 769. [all data]

Brehm, 1966
Brehm, B., Massenspektrometrische Untersuchung der Photoionisation von Molekulen, Z. Naturforsch., 1966, 21a, 196. [all data]

Nicholson, 1963
Nicholson, A.J.C., Photo-ionization efficiency curves. Measurement of ionization potentials and interpretation of fine structure, J. Chem. Phys., 1963, 39, 954. [all data]

Watanabe, 1957
Watanabe, K., Ionization potentials of some molecules, J. Chem. Phys., 1957, 26, 542. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Banna and Shirley, 1976
Banna, M.S.; Shirley, D.A., Molecular photoelectron spectroscopy at 132.3 eV: N₂, CO, C₂H₄ and O₂, J. Electron Spectrosc. Relat. Phenom., 1976, 8, 255. [all data]

Blyth, Powis, et al., 1981
Blyth, R.C.G.; Powis, I.; Danby, C.J., Competing pre-dissociations of O₂⁺(B ²Σ_g^-), Chem. Phys. Lett., 1981, 84, 272. [all data]

Oertel, Schenk, et al., 1980
Oertel, H.; Schenk, H.; Baumgartel, H., Ion pair formation from photon irradiation of O₂, NO and CO in 17-30 eV, Chem. Phys., 1980, 46, 251. [all data]

Locht and Schopman, 1974
Locht, R.; Schopman, J., The dissociative ionization in oxygen, Int. J. Mass Spectrom. Ion Phys., 1974, 15, 361. [all data]

Locht and Momigny, 1971
Locht, R.; Momigny, J., Mass spectrometric study of ion-pair processes in diatomic molecules: H₂, CO, NO and O₂, Int. J. Mass Spectrom. Ion Phys., 1971, 7, 121. [all data]

Elder, Villarejo, et al., 1965
Elder, F.A.; Villarejo, D.; Inghram, M.G., Electron affinity of oxygen, J. Chem. Phys., 1965, 43, 758. [all data]

Weissler, Samson, et al., 1959
Weissler, G.L.; Samson, J.A.R.; Ogawa, M.; Cook, G.R., Photoionization analysis by mass spectroscopy, J. Opt. Soc. Am., 1959, 49, 338. [all data]

Frost and McDowell, 1959
Frost, D.C.; McDowell, C.A., Recent electron impact studies on simple molecules (O₂, Cl₂, I₂), Advan. Mass Spectrom., 1959, 1, 413. [all data]

Notes

Go To: Top, Phase change data, Gas phase ion energetics data, References

Symbols used in this document:

AE	Appearance energy
EA	Electron affinity
IE (evaluated)	Recommended ionization energy
P_c	Critical pressure
T_boil	Boiling point
T_c	Critical temperature
T_fus	Fusion (melting) point
T_triple	Triple point temperature
Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions
ρ_c	Critical density

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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