HCO2 anion

Formula: CHO₂^-
Molecular weight: 45.0180
IUPAC Standard InChI: InChI=1S/CH2O2/c2-1-3/h1H,(H,2,3)/p-1
IUPAC Standard InChIKey: BDAGIHXWWSANSR-UHFFFAOYSA-M
CAS Registry Number: 71-47-6
Chemical structure:
This structure is also available as a 2d Mol file
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Other data available:
- Reaction thermochemistry data
- Gas phase ion energetics data
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Ion clustering data

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

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Clustering reactions

HCO2 anion + = ( • )

By formula: CHO₂^- + CHN = (CHO₂^- • CHN)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	92.0	kJ/mol	PHPMS	Meot-ner, 1988	gas phase; M,B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	92.	J/mol*K	N/A	Meot-ner, Cybulski, et al., 1988	gas phase; Entropy change calculated or estimated; M
Δ_rS°	89.5	J/mol*K	PHPMS	Meot-ner, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	65.3 ± 6.7	kJ/mol	TDAs	Meot-ner, Cybulski, et al., 1988	gas phase; Entropy of 22.0 eu assumed.; B

Free energy of reaction

Δ_rG° (kJ/mol)	T (K)	Method	Reference	Comment
49.4	473.	PHPMS	Meot-ner, Cybulski, et al., 1988	gas phase; Entropy change calculated or estimated; M

( HCO2 anion • ) + = ( • 2)

By formula: (CHO₂^- • CHN) + CHN = (CHO₂^- • 2CHN)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	74.5	kJ/mol	PHPMS	Meot-ner, 1988	gas phase; M,B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	92.	J/mol*K	N/A	Meot-ner, Cybulski, et al., 1988	gas phase; Entropy change calculated or estimated; M
Δ_rS°	98.7	J/mol*K	PHPMS	Meot-ner, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	44.77	kJ/mol	TDAs	Meot-ner, Cybulski, et al., 1988	gas phase; Entropy estimated; B

Free energy of reaction

Δ_rG° (kJ/mol)	T (K)	Method	Reference	Comment
40.	350.	PHPMS	Meot-ner, Cybulski, et al., 1988	gas phase; Entropy change calculated or estimated; M

HCO2 anion + = ( • )

By formula: CHO₂^- + CH₂O₂ = (CHO₂^- • CH₂O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	154. ± 4.2	kJ/mol	N/A	Meot-Ner and Sieck, 1986	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	164.	J/mol*K	PHPMS	Meot-Ner and Sieck, 1986	gas phase; large Δ_rH, Δ_rS,; cyclic structure? pyrolysis?; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	105. ± 6.7	kJ/mol	TDAs	Meot-Ner and Sieck, 1986	gas phase; B

( HCO2 anion • ) + = ( • 2)

By formula: (CHO₂^- • CH₂O₂) + CH₂O₂ = (CHO₂^- • 2CH₂O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	109. ± 13.	kJ/mol	N/A	Luczynski, Wlodek, et al., 1978	gas phase; Buffer gas H2. There may be appreciable fractionation of neutral gases: Williamson, Knighton, et al., 1996; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	140.	J/mol*K	HPMS	Luczynski, Wlodek, et al., 1978	gas phase; M

( HCO2 anion • 2) + = ( • 3)

By formula: (CHO₂^- • 2CH₂O₂) + CH₂O₂ = (CHO₂^- • 3CH₂O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	84. ± 11.	kJ/mol	N/A	Luczynski, Wlodek, et al., 1978	gas phase; Buffer gas H2. There may be appreciable fractionation of neutral gases: Williamson, Knighton, et al., 1996; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	130.	J/mol*K	HPMS	Luczynski, Wlodek, et al., 1978	gas phase; M

( HCO2 anion • 3) + = ( • 4)

By formula: (CHO₂^- • 3CH₂O₂) + CH₂O₂ = (CHO₂^- • 4CH₂O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	59.4 ± 8.8	kJ/mol	N/A	Luczynski, Wlodek, et al., 1978	gas phase; Buffer gas H2. There may be appreciable fractionation of neutral gases: Williamson, Knighton, et al., 1996; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	90.0	J/mol*K	HPMS	Luczynski, Wlodek, et al., 1978	gas phase; M

( HCO2 anion • 4) + = ( • 5)

By formula: (CHO₂^- • 4CH₂O₂) + CH₂O₂ = (CHO₂^- • 5CH₂O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	42.3 ± 8.4	kJ/mol	N/A	Luczynski, Wlodek, et al., 1978	gas phase; Buffer gas H2. There may be appreciable fractionation of neutral gases: Williamson, Knighton, et al., 1996; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	50.	J/mol*K	HPMS	Luczynski, Wlodek, et al., 1978	gas phase; Entropy change is questionable; M

HCO2 anion + = ( • )

By formula: CHO₂^- + CH₄O = (CHO₂^- • CH₄O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	73.6 ± 4.2	kJ/mol	N/A	Meot-Ner and Sieck, 1986	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	98.7	J/mol*K	PHPMS	Meot-Ner and Sieck, 1986	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	43.9 ± 6.7	kJ/mol	TDAs	Meot-Ner and Sieck, 1986	gas phase; B

( HCO2 anion • 4294967295) + =

By formula: (CHO₂^- • 4294967295CO₂) + CO₂ = CHO₂^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	216. ± 9.6	kJ/mol	N/A	Caldwell, Renneboog, et al., 1989	gas phase; B

HCO2 anion + = ( • )

By formula: CHO₂^- + H₂O = (CHO₂^- • H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	66.9 ± 4.2	kJ/mol	TDAs	Meot-Ner and Sieck, 1986	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	96.2	J/mol*K	PHPMS	Meot-Ner and Sieck, 1986	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	38. ± 6.7	kJ/mol	TDAs	Meot-Ner and Sieck, 1986	gas phase; B
Δ_rG°	35.1 ± 0.84	kJ/mol	N/A	Viidanoja, Reiner, et al., 2000	gas phase; B
Δ_rG°	38.5 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; T: 293 K. ΔSaff approx. 24 cal/mol-K; B,M

( HCO2 anion • ) + = ( • 2)

By formula: (CHO₂^- • H₂O) + H₂O = (CHO₂^- • 2H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	57.7 ± 6.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; T: 293 K. ΔSaff approx. 24 cal/mol-K; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	28.5 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; T: 293 K. ΔSaff approx. 24 cal/mol-K; B,M
Δ_rG°	28.9 ± 0.84	kJ/mol	N/A	Viidanoja, Reiner, et al., 2000	gas phase; B

( HCO2 anion • 2) + = ( • 3)

By formula: (CHO₂^- • 2H₂O) + H₂O = (CHO₂^- • 3H₂O)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	50.6 ± 6.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; T: 293 K. ΔSaff approx. 24 cal/mol-K; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	21.3 ± 1.3	kJ/mol	TDAs	Blades, Klassen, et al., 1995	gas phase; T: 293 K. ΔSaff approx. 24 cal/mol-K; B,M
Δ_rG°	21.8 ± 0.84	kJ/mol	N/A	Viidanoja, Reiner, et al., 2000	gas phase; B

References

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Meot-ner, 1988
Meot-ner, M., Ionic Hydrogen Bond and Ion Solvation. ₆. Interaction Energies of the Acetate Ion with Organic Molecules. Comparison of CH₃COO^- with Cl^-, CN^-, and SH^-, J. Am. Chem. Soc., 1988, 110, 12, 3854, https://doi.org/10.1021/ja00220a022 . [all data]

Meot-ner, Cybulski, et al., 1988
Meot-ner, M.; Cybulski, S.M.; Scheiner, S.; Liebman, J.F., Is CN^- Significantly Anisotropic? Comparison of CN^- vs. Cl^-: Clustering with HCN and Condensed Phase Thermochemistry, J. Phys. Chem., 1988, 92, 10, 2738, https://doi.org/10.1021/j100321a009 . [all data]

Meot-Ner and Sieck, 1986
Meot-Ner, M.; Sieck, L.W., The ionic hydrogen bond and ion solvation. 5. OH...O^- bonds. Gas phase solvation and clustering of alkoxide and carboxylate anions, J. Am. Chem. Soc., 1986, 108, 7525. [all data]

Luczynski, Wlodek, et al., 1978
Luczynski, Z.; Wlodek, S.; Wincel, H., Stabilities of HCOO-.(HCOOH)n and Cl-.(HCOOH)n clusters, Int. J. Mass Spectrom. Ion Phys., 1978, 26, 103. [all data]

Williamson, Knighton, et al., 1996
Williamson, D.H.; Knighton, W.B.; Grimsrud, E.P., Pulsed High Pressure Mass Spectrometry with Near-Viscous Flow Ion Sampling, Int. J. Mass Spectrom. Ion Proc., 1996, 154, 1-2, 15, https://doi.org/10.1016/0168-1176(96)04372-8 . [all data]

Caldwell, Renneboog, et al., 1989
Caldwell, G.; Renneboog, R.; Kebarle, P., Gas Phase Acidities of Aliphatic Carboxylic Acids, Based on Measurements of Proton Transfer Equilibria, Can. J. Chem., 1989, 67, 4, 661, https://doi.org/10.1139/v89-092 . [all data]

Viidanoja, Reiner, et al., 2000
Viidanoja, J.; Reiner, T.; Kiendler, A.; Grimm, F.; Arnold, F., Laboratory investigations of negative ion molecule reactions of propionic, butyric, glyoxylic, pyruvic, and pinonic acids, Int. J. Mass Spectrom., 2000, 194, 1, 53-68, https://doi.org/10.1016/S1387-3806(99)00172-4 . [all data]

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]

Notes

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Symbols used in this document:

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