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
Permanent link for this species. Use this link for bookmarking this species for future reference.
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
- Mass spectrum (electron ionization)
- Constants of diatomic molecules
- Fluid Properties
Data at other public NIST sites:
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Phase change data

Go To: Top, Gas phase ion energetics data, Ion clustering 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	49.77	atm	N/A	Wagner, Ewers, et al., 1976	Uncertainty assigned by TRC = 0.005 atm; 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	49.3800	atm	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.2999 atm; TRC
P_c	49.2700	atm	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.2999 atm; TRC
P_c	49.2000	atm	N/A	Cardoso, 1915	Uncertainty assigned by TRC = 0.2999 atm; 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 (atm)
T = temperature (K)

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Temperature (K)	A	B	C	Reference	Comment
54.36 to 100.16	3.85274	325.675	-5.667	Brower and Thodos, 1968	Coefficents calculated by NIST from author's data.
54.36 to 154.33	3.9466	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, Ion clustering 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

Ion clustering data

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

Data compiled as indicated in comments:
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
B - John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

+ Oxygen = ( • Oxygen )

By formula: Ca⁺ + O₂ = (Ca⁺ • O₂)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
6.0	296.	FA	Spears and Fehsenfeld, 1972	gas phase; M

HO₂⁺ + Oxygen = (HO₂⁺ • Oxygen )

By formula: HO₂⁺ + O₂ = (HO₂⁺ • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	20.0	kcal/mol	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	27.	cal/mol*K	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; M

(HO₂⁺ • Oxygen ) + Oxygen = (HO₂⁺ • 2 Oxygen )

By formula: (HO₂⁺ • O₂) + O₂ = (HO₂⁺ • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.9 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rH°	6.6	kcal/mol	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.1	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rS°	22.	cal/mol*K	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; M

(HO₂⁺ • 2 Oxygen ) + Oxygen = (HO₂⁺ • 3 Oxygen )

By formula: (HO₂⁺ • 2O₂) + O₂ = (HO₂⁺ • 3O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.7 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rH°	3.2	kcal/mol	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.3	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rS°	20.	cal/mol*K	N/A	Hiraoka, Saluja, et al., 1979	gas phase; Entropy change calculated or estimated; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
1.1	105.	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; Entropy change calculated or estimated; M

(HO₂⁺ • 3 Oxygen ) + Oxygen = (HO₂⁺ • 4 Oxygen )

By formula: (HO₂⁺ • 3O₂) + O₂ = (HO₂⁺ • 4O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.5 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.1	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(HO₂⁺ • 4 Oxygen ) + Oxygen = (HO₂⁺ • 5 Oxygen )

By formula: (HO₂⁺ • 4O₂) + O₂ = (HO₂⁺ • 5O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.2 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.9	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(HO₂⁺ • 5 Oxygen ) + Oxygen = (HO₂⁺ • 6 Oxygen )

By formula: (HO₂⁺ • 5O₂) + O₂ = (HO₂⁺ • 6O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.0 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.3	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(HO₂⁺ • 6 Oxygen ) + Oxygen = (HO₂⁺ • 7 Oxygen )

By formula: (HO₂⁺ • 6O₂) + O₂ = (HO₂⁺ • 7O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.0 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.5	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(HO₂⁺ • 7 Oxygen ) + Oxygen = (HO₂⁺ • 8 Oxygen )

By formula: (HO₂⁺ • 7O₂) + O₂ = (HO₂⁺ • 8O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.8 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.1	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(HO₂⁺ • 8 Oxygen ) + Oxygen = (HO₂⁺ • 9 Oxygen )

By formula: (HO₂⁺ • 8O₂) + O₂ = (HO₂⁺ • 9O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.7 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.6	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

H₃⁺ + Oxygen = (H₃⁺ • Oxygen )

By formula: H₃⁺ + O₂ = (H₃⁺ • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.5	kcal/mol	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; From thermochemical cycle(O2H+)O2; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.6	cal/mol*K	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; From thermochemical cycle(O2H+)O2; M

(H₃⁺ • Oxygen ) + Oxygen = (H₃⁺ • 2 Oxygen )

By formula: (H₃⁺ • O₂) + O₂ = (H₃⁺ • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.5	kcal/mol	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; From thermochemical cycle(O2H+)O2; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.	cal/mol*K	PHPMS	Hiraoka, Saluja, et al., 1979	gas phase; From thermochemical cycle(O2H+)O2; M

+ Oxygen = ( • Oxygen )

By formula: Li⁺ + O₂ = (Li⁺ • O₂)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
4.2	319.	DT	Colonna-Romano and Keller, 1976	gas phase; low E/N; M

+ Oxygen = ( • Oxygen )

By formula: NO^- + O₂ = (NO^- • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.9 ± 0.2	kcal/mol	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	14.5	cal/mol*K	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
-0.4	200.	FA	Dunkin, Fehsenfeld, et al., 1971	gas phase; DG>; M

( • Oxygen ) + Oxygen = ( • 2 Oxygen )

By formula: (NO^- • O₂) + O₂ = (NO^- • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.9 ± 0.2	kcal/mol	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	15.7	cal/mol*K	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M

( • 2 Oxygen ) + Oxygen = ( • 3 Oxygen )

By formula: (NO^- • 2O₂) + O₂ = (NO^- • 3O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.8 ± 0.2	kcal/mol	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	15.7	cal/mol*K	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M

( • 3 Oxygen ) + Oxygen = ( • 4 Oxygen )

By formula: (NO^- • 3O₂) + O₂ = (NO^- • 4O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.4 ± 0.2	kcal/mol	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.1	cal/mol*K	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M

( • 4 Oxygen ) + Oxygen = ( • 5 Oxygen )

By formula: (NO^- • 4O₂) + O₂ = (NO^- • 5O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.4 ± 0.2	kcal/mol	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.2	cal/mol*K	PHPMS	Hiraoka and Yamabe, 1991	gas phase; M

+ Oxygen = ( • Oxygen )

By formula: Na⁺ + O₂ = (Na⁺ • O₂)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
0.2	310.	DT	Keller and Beyer, 1971	gas phase; low E/N; M

+ Oxygen = ( • Oxygen )

By formula: O⁺ + O₂ = (O⁺ • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	42.9	kcal/mol	PDiss	Hiller and Vestal, 1982	gas phase; M
Δ_rH°	48.	kcal/mol	PI	Linn, Ono, et al., 1981	gas phase; M
Δ_rH°	49.9	kcal/mol	PDiss	Mosely, Ozenne, et al., 1981	gas phase; M

( • Oxygen ) + Oxygen = ( • 2 Oxygen )

By formula: (O⁺ • O₂) + O₂ = (O⁺ • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.9	kcal/mol	PI	Linn, Ono, et al., 1981	gas phase; M

( • 2 Oxygen ) + Oxygen = ( • 3 Oxygen )

By formula: (O⁺ • 2O₂) + O₂ = (O⁺ • 3O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	0.9	kcal/mol	PI	Linn, Ono, et al., 1981	gas phase; M

O^- + Oxygen = (O^- • Oxygen )

By formula: O^- + O₂ = (O^- • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	32.	kcal/mol	PDiss	Hiller and Vestal, 1981	gas phase; From thermochemical cycle, Δ_rH<; M
Δ_rH°	39.0	kcal/mol	PES	Novich, Engelking, et al., 1979	gas phase; From thermochemical cycle, from EA(O3), D(O-O2) AND EA(O); M
Δ_rH°	38.	kcal/mol	PDiss	Cosby, Moseley, et al., 1978	gas phase; M
Δ_rH°	42.	kcal/mol	CID	Lifschitz, Wu, et al., 1978	gas phase; M

+ Oxygen = ( • Oxygen )

By formula: O₂⁺ + O₂ = (O₂⁺ • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10. ± 1.	kcal/mol	AVG	N/A	Average of 5 out of 6 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.8	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rS°	25.02	cal/mol*K	PHPMS	Conway and Janik, 1970	gas phase; M
Δ_rS°	20.	cal/mol*K	PHPMS	Durden, Kebarle, et al., 1969	gas phase; M
Δ_rS°	20.6	cal/mol*K	PHPMS	Yang and Conway, 1964	gas phase; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.8	300.	DT	Rakshit and Warneck, 1981	gas phase; M
3.3	300.	DT	Rakshit and Warneck, 1980	gas phase; M
3.4	296.	FA	Howard, Bierbaum, et al., 1972	gas phase; M
5.9	200.	FA	Adams and Bohme, 1970	gas phase; M

( • Oxygen ) + Oxygen = ( • 2 Oxygen )

By formula: (O₂⁺ • O₂) + O₂ = (O₂⁺ • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.9 ± 0.3	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rH°	6.87 ± 0.06	kcal/mol	PHPMS	Conway and Janik, 1970	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.3	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rS°	31.78	cal/mol*K	PHPMS	Conway and Janik, 1970	gas phase; M

( • 2 Oxygen ) + Oxygen = ( • 3 Oxygen )

By formula: (O₂⁺ • 2O₂) + O₂ = (O₂⁺ • 3O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.5 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rH°	2.5 ± 0.1	kcal/mol	PHPMS	Conway and Janik, 1970	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.7	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rS°	19.8	cal/mol*K	PHPMS	Conway and Janik, 1970	gas phase; M

( • 3 Oxygen ) + Oxygen = ( • 4 Oxygen )

By formula: (O₂⁺ • 3O₂) + O₂ = (O₂⁺ • 4O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.1 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rH°	2.46 ± 0.18	kcal/mol	PHPMS	Conway and Janik, 1970	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.2	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rS°	23.9	cal/mol*K	PHPMS	Conway and Janik, 1970	gas phase; M

( • 4 Oxygen ) + Oxygen = ( • 5 Oxygen )

By formula: (O₂⁺ • 4O₂) + O₂ = (O₂⁺ • 5O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.9 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rH°	1.8 ± 0.7	kcal/mol	PHPMS	Conway and Janik, 1970	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.4	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rS°	17.0	cal/mol*K	PHPMS	Conway and Janik, 1970	gas phase; M

( • 5 Oxygen ) + Oxygen = ( • 6 Oxygen )

By formula: (O₂⁺ • 5O₂) + O₂ = (O₂⁺ • 6O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.9 ± 0.3	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.7	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 6 Oxygen ) + Oxygen = ( • 7 Oxygen )

By formula: (O₂⁺ • 6O₂) + O₂ = (O₂⁺ • 7O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.9 ± 0.4	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.9	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 7 Oxygen ) + Oxygen = ( • 8 Oxygen )

By formula: (O₂⁺ • 7O₂) + O₂ = (O₂⁺ • 8O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.82	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.	cal/mol*K	N/A	Hiraoka, 1988	gas phase; Entropy change calculated or estimated; M

+ Oxygen = ( • Oxygen )

By formula: O₂^- + O₂ = (O₂^- • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12. ± 4.	kcal/mol	AVG	N/A	Average of 5 out of 7 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.4	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M
Δ_rS°	32.	cal/mol*K	PHPMS	Conway and Nesbit, 1968	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.2 ± 1.1	kcal/mol	TDAs	Hiraoka, 1888	gas phase; see also Sherwood, Hanold, et al., 1996. Aquino, Taylor, et al., 2001 calns indicate rectangular anion; B
Δ_rG°	5.4 ± 1.0	kcal/mol	IMRE	Payzant J.D. and Kebarle, 1972	gas phase; B
Δ_rG°	3.2 ± 1.0	kcal/mol	IMRE	Pack and Phelps, 1971	gas phase; B
Δ_rG°	4.00 ± 0.50	kcal/mol	IMRE	Parkes, 1971	gas phase; B
Δ_rG°	3.8 ± 1.0	kcal/mol	TDAs	Conway and Nesbit, 1968	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.5	300.	DT	Pack and Phelps, 1971	gas phase; M

( • Oxygen ) + Oxygen = ( • 2 Oxygen )

By formula: (O₂^- • O₂) + O₂ = (O₂^- • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.5 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.9	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 2 Oxygen ) + Oxygen = ( • 3 Oxygen )

By formula: (O₂^- • 2O₂) + O₂ = (O₂^- • 3O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.4 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.3	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 3 Oxygen ) + Oxygen = ( • 4 Oxygen )

By formula: (O₂^- • 3O₂) + O₂ = (O₂^- • 4O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.8 ± 0.3	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	15.4	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 4 Oxygen ) + Oxygen = ( • 5 Oxygen )

By formula: (O₂^- • 4O₂) + O₂ = (O₂^- • 5O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.5 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	15.4	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 5 Oxygen ) + Oxygen = ( • 6 Oxygen )

By formula: (O₂^- • 5O₂) + O₂ = (O₂^- • 6O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.5 ± 0.3	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.2	cal/mol*K	PHPMS	Hiraoka, 1988	gas phase; M

( • 6 Oxygen ) + Oxygen = ( • 7 Oxygen )

By formula: (O₂^- • 6O₂) + O₂ = (O₂^- • 7O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.40	kcal/mol	PHPMS	Hiraoka, 1988	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.	cal/mol*K	N/A	Hiraoka, 1988	gas phase; Entropy change calculated or estimated; M

O₃^- + Oxygen = (O₃^- • Oxygen )

By formula: O₃^- + O₂ = (O₃^- • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.10 ± 0.20	kcal/mol	TDAs	Hiraoka, 1988, 2	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.0	cal/mol*K	PHPMS	Hiraoka, 1988, 2	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-3.60 ± 0.50	kcal/mol	TDAs	Hiraoka, 1988, 2	gas phase; B

(O₃^- • Oxygen ) + Oxygen = (O₃^- • 2 Oxygen )

By formula: (O₃^- • O₂) + O₂ = (O₃^- • 2O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.0 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1988, 2	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	PHPMS	Hiraoka, 1988, 2	gas phase; M

(O₃^- • 2 Oxygen ) + Oxygen = (O₃^- • 3 Oxygen )

By formula: (O₃^- • 2O₂) + O₂ = (O₃^- • 3O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.0 ± 0.3	kcal/mol	PHPMS	Hiraoka, 1988, 2	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.0	cal/mol*K	PHPMS	Hiraoka, 1988, 2	gas phase; M

(O₃^- • 3 Oxygen ) + Oxygen = (O₃^- • 4 Oxygen )

By formula: (O₃^- • 3O₂) + O₂ = (O₃^- • 4O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.6 ± 0.3	kcal/mol	PHPMS	Hiraoka, 1988, 2	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	15.4	cal/mol*K	PHPMS	Hiraoka, 1988, 2	gas phase; M

(O₃^- • 4 Oxygen ) + Oxygen = (O₃^- • 5 Oxygen )

By formula: (O₃^- • 4O₂) + O₂ = (O₃^- • 5O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.54	kcal/mol	PHPMS	Hiraoka, 1988, 2	gas phase; Δ_rH, Δ_rS approximate; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.4	cal/mol*K	PHPMS	Hiraoka, 1988, 2	gas phase; Δ_rH, Δ_rS approximate; M

O₄^- + + Oxygen = N₂O₄^-

By formula: O₄^- + N₂ + O₂ = N₂O₄^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.90 ± 0.20	kcal/mol	TDAs	Hiraoka, 1988, 2	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.10 ± 0.50	kcal/mol	TDAs	Hiraoka, 1988, 2	gas phase; B

References

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

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Rakshit, A.B.; Warneck, P., Formation and Reactions of O2+.CO2, O2+.H2O and O2+(CO2)2 Ions, Int. J. Mass Spectrom Ion Phys., 1981, 40, 2, 135, https://doi.org/10.1016/0020-7381(81)80037-X . [all data]

Rakshit and Warneck, 1980
Rakshit, A.B.; Warneck, P., A Drift Chamber Study of the Formation of Water Cluster Ions in Oxygen, J. Chem. Phys., 1980, 73, 10, 5074, https://doi.org/10.1063/1.439985 . [all data]

Howard, Bierbaum, et al., 1972
Howard, C.J.; Bierbaum, V.M.; Rundle, H.W.; Kaufman, F., Kinetics and Mechanism of Formation of Water Cluster Ions from O2+ and H2O+, J. Chem. Phys., 1972, 57, 8, 3491, https://doi.org/10.1063/1.1678783 . [all data]

Adams and Bohme, 1970
Adams, N.G.; Bohme, D., Flowing Afterglow Studies of Formation and Reactions of Cluster Ions of O₂⁺, O₂^-, and O^-, J. Chem. Phys., 1970, 52, 6, 3133, https://doi.org/10.1063/1.1673449 . [all data]

Conway and Nesbit, 1968
Conway, D.C.; Nesbit, L.E., Stability of O₄^-, J. Chem. Phys., 1968, 48, 1, 509, https://doi.org/10.1063/1.1667956 . [all data]

Hiraoka, 1888
Hiraoka, K., A Determination of the Stability of O₂⁺(O₂)n and O₂^-(O₂)n with n=1-8 from Measurements of the Gas Phase Ion Equilibria, J. Chem. Phys., 1888, 89, 5, 3190, https://doi.org/10.1063/1.454976 . [all data]

Sherwood, Hanold, et al., 1996
Sherwood, C.R.; Hanold, K.A.; Garner, M.C.; Strong, K.M.; Continetti, R.E., Translational Spectroscopy Studies of the Photodissociation Dynamics of O4-, J. Chem. Phys., 1996, 105, 24, 10803, https://doi.org/10.1063/1.472888 . [all data]

Aquino, Taylor, et al., 2001
Aquino, A.J.A.; Taylor, P.R.; Walch, S.P., Structure, properties, and photodissociation of O-4(-), J. Chem. Phys., 2001, 114, 7, 3010-3017, https://doi.org/10.1063/1.1288379 . [all data]

Payzant J.D. and Kebarle, 1972
Payzant J.D.; Kebarle, P., Kinetics and Reactions Leading to O2-(H2O)n in Moist Oxygen, J. Chem. Phys., 1972, 56, 7, 3482, https://doi.org/10.1063/1.1677723 . [all data]

Pack and Phelps, 1971
Pack, J.L.; Phelps, A.V., Hydration of Oxygen Negative Ions, Bull. Am. Phys. Soc., 1971, 16, 214. [all data]

Parkes, 1971
Parkes, D.A., Electron Attachment and Negative Ion-Molecule Reactions in Pure O₂, Trans. Farad. Soc., 1971, 97, 711, https://doi.org/10.1039/tf9716700711 . [all data]

Hiraoka, 1988, 2
Hiraoka, K., Determination of the Stabilities of O₃^-(N₂)n, O₃^-(O₂)n, and O₄^-(N₂)n from Measurements of the Gas Phase Equilibria, Chem. Phys., 1988, 125, 2-3, 439, https://doi.org/10.1016/0301-0104(88)87096-4 . [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
EA	Electron affinity
IE (evaluated)	Recommended ionization energy
P_c	Critical pressure
T	Temperature
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
Δ_rS°	Entropy of reaction at standard conditions
ρ_c	Critical density

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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