O2C(CH2)4CO2 dianion

Formula: C₆H₈O₄^-2
Molecular weight: 144.1264
CAS Registry Number: 764-65-8
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Other data available:
- Gas phase ion energetics data
- Ion clustering data
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Reaction thermochemistry data

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

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Individual Reactions

(C₆H₈O₄^-2 • 2) + = (C₆H₈O₄^-2 • 3)

By formula: (C₆H₈O₄^-2 • 2H₂O) + H₂O = (C₆H₈O₄^-2 • 3H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	35.1 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; B,M

(C₆H₈O₄^-2 • 3) + = (C₆H₈O₄^-2 • 4)

By formula: (C₆H₈O₄^-2 • 3H₂O) + H₂O = (C₆H₈O₄^-2 • 4H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	31.4 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; B,M

(C₆H₈O₄^-2 • 4) + = (C₆H₈O₄^-2 • 5)

By formula: (C₆H₈O₄^-2 • 4H₂O) + H₂O = (C₆H₈O₄^-2 • 5H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	26.8 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; B,M

(C₆H₈O₄^-2 • 5) + = (C₆H₈O₄^-2 • 6)

By formula: (C₆H₈O₄^-2 • 5H₂O) + H₂O = (C₆H₈O₄^-2 • 6H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	24.3 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; B,M

(C₆H₈O₄^-2 • ) + = (C₆H₈O₄^-2 • 2)

By formula: (C₆H₈O₄^-2 • H₂O) + H₂O = (C₆H₈O₄^-2 • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	56. ± 18.	kJ/mol	N/A	Ding, Wang, et al., 1998	gas phase; Affinity is EA difference from next lower solvated ion.; B

C₆H₈O₄^-2 + = (C₆H₈O₄^-2 • )

By formula: C₆H₈O₄^-2 + H₂O = (C₆H₈O₄^-2 • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	30. ± 18.	kJ/mol	N/A	Ding, Wang, et al., 1998	gas phase; Affinity is EA difference from next lower solvated ion.; B

C₆H₈O₄^-2 + = C₆H₉O₄^-2

By formula: C₆H₈O₄^-2 + H⁺ = C₆H₉O₄^-2

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1687. ± 15.	kJ/mol	D-EA	Ding, Wang, et al., 1998	gas phase; B

References

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Blades, Klassen, et al., 1995
Blades, A.T.; Klassen, J.S.; Kebarle, P., Free Energies of Hydration in the Gas Phase on the Anions of Some Oxo Acids of C, N, S, P, Cl and I, J. Am. Chem. Soc., 1995, 117, 42, 10563, https://doi.org/10.1021/ja00147a019 . [all data]

Ding, Wang, et al., 1998
Ding, C.F.; Wang, X.B.; Wang, L.S., Photoelectron spectroscopy of doubly charged anions: Intramolecular Coulomb repulsion and solvent stabilization, J. Phys. Chem. A, 1998, 102, 45, 8633-8636, https://doi.org/10.1021/jp982698x . [all data]

Notes

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Symbols used in this document:

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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Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions