Sulfur dimer

Formula: S₂
Molecular weight: 64.130
IUPAC Standard InChI: InChI=1S/S2/c1-2
IUPAC Standard InChIKey: MAHNFPMIPQKPPI-UHFFFAOYSA-N
CAS Registry Number: 23550-45-0
Chemical structure:
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Gas phase thermochemistry data

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Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	30.736 ± 0.072	kcal/mol	Review	Cox, Wagman, et al., 1984	CODATA Review value
Δ_fH°_gas	30.736	kcal/mol	Review	Chase, 1998	Data last reviewed in September, 1977
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	54.5332 ± 0.0024	cal/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
S°_{gas,1 bar}	54.539	cal/mol*K	Review	Chase, 1998	Data last reviewed in September, 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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Temperature (K)	298. to 6000.
A	8.009831
B	1.210651
C	-0.253267
D	0.021488
E	-0.050648
F	28.12751
G	63.59749
H	30.73621
Reference	Chase, 1998
Comment	Data last reviewed in September, 1977

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, References, Notes

Data evaluated as indicated in comments:
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
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 S₂⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	9.356 ± 0.002	eV	N/A	N/A	L

Electron affinity determinations

EA (eV)	Method	Reference	Comment
1.670 ± 0.015	LPES	Moran and Ellison, 1988	B
1.663 ± 0.040	LPES	Celotta, Bennett, et al., 1974	B
1.565 ± 0.050	LPD	Hunsicker, Jones, et al., 1995	B
>0.86 ± 0.10	R-A	Dillard and Franklin, 1968	S^- + COS -> S₂^- + CO. Also S₂^- + COS -> S₃^- + CO, etc. to n=6; B
>2.50 ± 0.80	EIAE	Thynne, 1972	From CS₂; B

Ionization energy determinations

IE (eV)	Method	Reference	Comment
9.4	PE	Bender, Carnovale, et al., 1988	LL
9.356 ± 0.002	PI	Liao and Ng, 1986	LBLHLM
9.6 ± 0.2	EI	Rosinger, Grade, et al., 1983	LBLHLM
9.5 ± 0.2	EI	Grade, Wienecke, et al., 1983	LBLHLM
9.5 ± 0.3	EI	Lau, Brittain, et al., 1982	LBLHLM
9.38 ± 0.03	DER	Coppens, Reynaert, et al., 1979	LLK
9.36 ± 0.02	EI	Tal'roze, Butkovskaya, et al., 1978	LLK
9.8 ± 0.3	EI	Smoes, Drowart, et al., 1977	LLK
10.1 ± 0.3	EI	Piacente, Bardi, et al., 1976	LLK
9.4 ± 0.1	EI	Hildenbrand, 1975	LLK
9.38 ± 0.01	PE	Golob, Jonathan, et al., 1975	LLK
9.30	PE	Berkowitz, 1975	LLK
9.8 ± 0.5	EI	Muenow and Margrave, 1972	LLK
9.42 ± 0.10	EI	Hildenbrand, 1972	LLK
9.40 ± 0.05	S	Donovan, Husain, et al., 1970	RDSH
9.32	S	Barrow, duParcq, et al., 1969	RDSH
9.36 ± 0.02	PI	Berkowitz and Lifshitz, 1968	RDSH
9.55	PE	Wu and Fehlner, 1976	Vertical value; LLK
9.56	PE	Berkowitz, 1975	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
S⁺	14.732 ± 0.005	S	PI	Liao and Ng, 1986	LBLHLM
S⁺	13.5 ± 0.5	S	EI	Piacente, Bardi, et al., 1976	LLK
S⁺	14.74 ± 0.01	S	PI	Berkowitz and Chupka, 1969	RDSH

Anion protonation reactions

S₂^- + = HS₂

By formula: S₂^- + H⁺ = HS₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	329.9 ± 3.7	kcal/mol	D-EA	Moran and Ellison, 1988	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	>344.60	kcal/mol	IMRB	Goodings, Bohme, et al., 1986	gas phase; S- deprotonates H2S, Sn- for n≥2, does not.; 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]

Moran and Ellison, 1988
Moran, S.; Ellison, G.B., Photoelectron Spectroscopy of Sulfur Ions, J. Phys. Chem., 1988, 92, 7, 1794, https://doi.org/10.1021/j100318a021 . [all data]

Celotta, Bennett, et al., 1974
Celotta, R.S.; Bennett, R.A.; Hall, J.L., Laser Photodetachment Determination of the Electron Affinities of OH, NH₂, NH, SO₂, and S₂, J. Chem. Phys., 1974, 60, 5, 1740, https://doi.org/10.1063/1.1681268 . [all data]

Hunsicker, Jones, et al., 1995
Hunsicker, S.; Jones, R.O.; Gantefor, G., Rings and chains in sulfur cluster anions S- to S-9(-): Theory (simulated annealing) and experiment (photoelectron detachment), J. Chem. Phys., 1995, 102, 15, 5917, https://doi.org/10.1063/1.469326 . [all data]

Dillard and Franklin, 1968
Dillard, J.G.; Franklin, J.L., Ion-Molecule Reactions of Negative Ions. I. Negative Ions of Sulfur, J. Chem. Phys., 1968, 48, 5, 2349, https://doi.org/10.1063/1.1669435 . [all data]

Thynne, 1972
Thynne, J.C.J., Negative Ion Studies with a Time-of-Flight Mass Spectrometer., Dyn. Mass Spectrom., 1972, 3, 67. [all data]

Bender, Carnovale, et al., 1988
Bender, H.; Carnovale, F.; Peel, J.B.; Wentrup, C., Dinitrogen sulfide, N₂S, revealed by photoelectron spectroscopy, J. Am. Chem. Soc., 1988, 110, 3458. [all data]

Liao and Ng, 1986
Liao, C.; Ng, C., Molecular beam photoionization study of S₂, J. Chem. Phys., 1986, 84, 788. [all data]

Rosinger, Grade, et al., 1983
Rosinger, W.; Grade, M.; Hirschwald, W., Detection of ion states of S₂ to S₈ by electron impact, Int. J. Mass Spectrom. Ion Processes, 1983, 47, 239. [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]

Lau, Brittain, et al., 1982
Lau, K.H.; Brittain, R.D.; Hildenbrand, D.L., Vaporization of As₂S₃ and the dissociation energy of AsS, J. Phys. Chem., 1982, 86, 4429. [all data]

Coppens, Reynaert, et al., 1979
Coppens, P.; Reynaert, J.C.; Drowart, J., Mass spectrometric study of the photoionization of carbon disulphide in the wavelength interval 125-60nm, J. Chem. Soc. Faraday Trans. 2, 1979, 75, 292. [all data]

Tal'roze, Butkovskaya, et al., 1978
Tal'roze, V.L.; Butkovskaya, N.I.; Larichev, M.N.; Leipunskii, I.O.; Morozov, I.I.; Dodonov, A.F.; Kudrov, B.V.; Zelenov, V.V.; Raznikov, V.V., Advances in the mass spectrometry of free radicals, Adv. Mass Spectrom., 1978, 7, 693. [all data]

Smoes, Drowart, et al., 1977
Smoes, S.; Drowart, J.; Welter, J.M., Thermodynamic study of the vaporization of europium monosulfide by Knudsen-cell mass spectrometry atomization energies of EuS(g), Eu₂S(g), EuS₂(g), Eu₂O(g), Eu₂O₂(g), Eu₂OS(g), and Eu₂S₂(g), J. Chem. Thermodyn., 1977, 9, 275. [all data]

Piacente, Bardi, et al., 1976
Piacente, V.; Bardi, G.; di Paolo, V.; Ferro, D., The vapour pressure over Ga₂S₂ and Ga₂Se₂, J. Chem. Thermodyn., 1976, 8, 391. [all data]

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

Golob, Jonathan, et al., 1975
Golob, L.; Jonathan, N.; Morris, A.; Okuda, M.; Ross, K.J.; Smith, D.J., Vacuum ultraviolet photoelectron spectroscopy of transient species, J. Chem. Soc. Faraday Trans. 2, 1975, 71, 1026. [all data]

Berkowitz, 1975
Berkowitz, J., PES of high temperature vapors. VII. S₂ and Te₂, J. Chem. Phys., 1975, 62, 4074. [all data]

Muenow and Margrave, 1972
Muenow, D.W.; Margrave, J.L., Mass spectrometric observations of gaseous phosphorus sulfides and oxysulfides, J. Inorg. Nucl. Chem., 1972, 34, 89. [all data]

Hildenbrand, 1972
Hildenbrand, D.L., Thermochemistry of the molecules CS and CS⁺, Chem. Phys. Lett., 1972, 15, 379. [all data]

Donovan, Husain, et al., 1970
Donovan, R.J.; Husain, D.; Stevenson, C.D., Vacuum ultra-violet spectra of transient molecules and radicals. Part 1. CS and S₂, J. Chem. Soc. Faraday Trans., 1970, 66, 1. [all data]

Barrow, duParcq, et al., 1969
Barrow, R.F.; duParcq, R.P.; Ricks, J.M., Rotational analysis of the C 3Σ_u--X 3g- system of ³²S₂, J. Phys. B:, 1969, 2, 413. [all data]

Berkowitz and Lifshitz, 1968
Berkowitz, J.; Lifshitz, C., Photoionization of high temperature vapors. II. Sulfur molecular species, J. Chem. Phys., 1968, 48, 4346. [all data]

Wu and Fehlner, 1976
Wu, M.; Fehlner, T.P., Valence level photoelectron spectra of some heavy group 4-6 diatomic molecules, J. Am. Chem. Soc., 1976, 98, 7578. [all data]

Berkowitz and Chupka, 1969
Berkowitz, J.; Chupka, W.A., Photoionization of high-temperature vapors. VI. S₂, Se₂, and Te₂, J. Chem. Phys., 1969, 50, 4245. [all data]

Goodings, Bohme, et al., 1986
Goodings, J.M.; Bohme, D.K.; Elguindi, K.; Fox, A., Sulphur Anion Chemistry in Hydrocarbon Flames with H₂S, OCS, and SO₂ Additives, Can. J. Chem., 1986, 64, 4, 689, https://doi.org/10.1139/v86-110 . [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_fH°_gas	Enthalpy of formation of gas at standard conditions
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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