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:
- Phase change 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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Gas phase thermochemistry data

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

Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	49.033 ± 0.001	cal/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
S°_{gas,1 bar}	49.032	cal/mol*K	Review	Chase, 1998	Data last reviewed in March, 1977

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
C_p = heat capacity (cal/mol*K)
H° = standard enthalpy (kcal/mol)
S° = standard entropy (cal/mol*K)
t = temperature (K) / 1000.

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View table.

Temperature (K)	100. to 700.	700. to 2000.	2000. to 6000.
A	7.486219	7.177904	4.997876
B	-4.836356	2.096791	2.562312
C	13.83041	-0.953187	-0.482910
D	-8.725201	0.188411	0.035002
E	-0.001762	-0.177246	2.209781
F	-2.127981	-2.706664	1.275730
G	58.98530	56.44510	56.79219
H	0.0	0.0	0.0
Reference	Chase, 1998	Chase, 1998	Chase, 1998
Comment	Data last reviewed in March, 1977; New parameter fit January 2009	Data last reviewed in March, 1977; New parameter fit January 2009	Data last reviewed in March, 1977; New parameter fit January 2009

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry 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)	101.	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	94.72	kcal/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 (kcal/mol)	Reference	Comment
100.6 ± 0.8	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°	352.99 ± 0.72	kcal/mol	D-EA	Travers, Cowles, et al., 1989	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	346.67 ± 0.82	kcal/mol	H-TS	Travers, Cowles, et al., 1989	gas phase; B

References

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

Cox, Wagman, et al., 1984
Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [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, Gas phase thermochemistry data, Gas phase ion energetics data, References

Symbols used in this document:

AE	Appearance energy
EA	Electron affinity
IE (evaluated)	Recommended ionization energy
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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