S2 anion

• Formula: S₂^-
• Molecular weight: 64.131
• CAS Registry Number: 12185-15-8
• Information on this page:
  • Gas phase thermochemistry data
  • Reaction thermochemistry data
  • References
  • Notes
• Other data available:
  • Gas phase ion energetics data
  • Ion clustering data
  • Constants of diatomic molecules
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Gas phase thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: John E. Bartmess

Quantity	Value	Units	Method	Reference	Comment
fH°gas	-33. ± 22.	kJ/mol	Acid	Moran and Ellison, 1988
fH°gas	<46.0 ± 9.6	kJ/mol	IMRB	Dillard and Franklin, 1968	S- + COS -> S2- + CO. Also S2- + COS -> S3- + CO, etc. to n=6

Reaction thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

(S₂^-  ) +  = (S₂^-  2)

By formula: (S₂^-  CS₂) + CS₂ = (S₂^-  2CS₂)

Quantity	Value	Units	Method	Reference	Comment
rH°	26.	kJ/mol	PHPMS	Hiraoka, Fujimaki, et al., 1994	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
rS°	84.	J/mol*K	N/A	Hiraoka, Fujimaki, et al., 1994	gas phase; Entropy change calculated or estimated; M

S₂^- +  = HS₂

By formula: S₂^- + H⁺ = HS₂

Quantity	Value	Units	Method	Reference	Comment
rH°	1380. ± 15.	kJ/mol	D-EA	Moran and Ellison, 1988	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
rG°	>1441.8	kJ/mol	IMRB	Goodings, Bohme, et al., 1986	gas phase; S- deprotonates H2S, Sn- for n>=2, does not.; B

S₂^- +  = (S₂^-  )

By formula: S₂^- + CS₂ = (S₂^-  CS₂)

Quantity	Value	Units	Method	Reference	Comment
rH°	79.9	kJ/mol	PHPMS	Hiraoka, Fujimaki, et al., 1994	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	120.	J/mol*K	PHPMS	Hiraoka, Fujimaki, et al., 1994	gas phase; M

(S₂^-  4294967295) +  = S₂^-

By formula: (S₂^-  4294967295S) + S = S₂^-

Quantity	Value	Units	Method	Reference	Comment
rH°	388. ± 22.	kJ/mol	N/A	Moran and Ellison, 1988	gas phase; B

S₂^- = CS₄^-

By formula: S₂^- = CS₄^-

Quantity	Value	Units	Method	Reference	Comment
rH°	79.9 ± 6.3	kJ/mol	TDAs	Hiraoka, Fujimaki, et al., 1994, 2	gas phase; B

References

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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]

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]

Hiraoka, Fujimaki, et al., 1994
Hiraoka, K.; Fujimaki, S.; Aruga, K.; Yamabe, S., Frontier-Controlled Structures of the Gas-Phase A+-(CS2)n Clusters ,A+- = S2+, CS2+, S2-, and CS2-, J. Phys. Chem., 1994, 98, 7, 1802, https://doi.org/10.1021/j100058a014 . [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]

Hiraoka, Fujimaki, et al., 1994, 2
Hiraoka, K.; Fujimaki, S.; Aruga, K., Frontier-controlled Structures of the Gas Phas Clusters A+/-(CS2)n, A+/- = S2+, CS2+, S2-, and CS2-, J. Phys. Chem. (1994), 1994, 98, 7, 1802-1809, https://doi.org/10.1021/j100058a014 . [all data]

Notes

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• Symbols used in this document:
  

  fH°gas	Enthalpy of formation of gas at standard conditions
  rG°	Free energy of reaction at standard conditions
  rH°	Enthalpy of reaction at standard conditions
  rS°	Entropy of reaction at standard conditions

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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