Formic acid

Formula: CH₂O₂
Molecular weight: 46.0254
IUPAC Standard InChI: InChI=1S/CH2O2/c2-1-3/h1H,(H,2,3)
IUPAC Standard InChIKey: BDAGIHXWWSANSR-UHFFFAOYSA-N
CAS Registry Number: 64-18-6
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
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Other names: Methanoic acid; Aminic acid; Bilorin; Collo-Bueglatt; Collo-Didax; Formisoton; Formylic acid; Hydrogen carboxylic acid; Myrmicyl; HCOOH; Acide formique; Acido formico; Ameisensaeure; Kwas metaniowy; Kyselina mravenci; Mierenzuur; Rcra waste number U123; UN 1779; Formira; Add-F; Amasil
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Gas phase thermochemistry data

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Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DRB - Donald R. Burgess, Jr.
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-90.49	kcal/mol	Cm	Guthrie, 1974	Heat of hydrolysis; ALS
Δ_fH°_gas	-90.58	kcal/mol	N/A	Lebedeva, 1964	Value computed using Δ_fH_liquid° value of -425.5±0.3 kj/mol from Lebedeva, 1964 and Δ_vapH° value of 46.5 kj/mol from Guthrie, 1974.; DRB
Δ_fH°_gas	-90.6 ± 0.1	kcal/mol	Ccb	Lebedeva, 1964	Value computed using Δ_fH_liquid° from Lebedeva, 1964 and Δ_vapH° value of 11.1 kcal/mol from Konicek and Wadso, 1970.; DRB
Δ_fH°_gas	-90.42	kcal/mol	N/A	Sinke, 1959	Value computed using Δ_fH_liquid° value of -424.8±0.3 kj/mol from Sinke, 1959 and Δ_vapH° value of 46.5 kj/mol from Guthrie, 1974.; DRB
Δ_fH°_gas	-90.5 ± 0.1	kcal/mol	Ccb	Sinke, 1959	Value computed using Δ_fH_liquid° from Sinke, 1959 and Δ_vapH° value of 11.1 kcal/mol from Konicek and Wadso, 1970.; DRB
Quantity	Value	Units	Method	Reference	Comment
S°_gas	59.44 ± 0.10	cal/mol*K	N/A	Millikan R.C., 1957	Other third-law S(298.15 K) value is 248.11(1.26) J/mol*K [ Halford J.O., 1942, Millikan R.C., 1957]. Please also see Waring W., 1952.; GT

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
7.949	50.	Chao J., 1986	p=1 bar. Selected entropies and heat capacities are in close agreement with statistically calculated values [ Fukushima K., 1971] and value of S(298.15 K) calculated by ab initio method [ East A.L.L., 1997]. Maximum discrepancies with other statistical calculations [ Waring W., 1952, Green J.H.S., 1961, Gurvich, Veyts, et al., 1989] amount to 1.1-3.9 J/molK for S(T) and 3.0-5.9 J/molK for Cp(T). Please also see Chao J., 1978.; GT
7.992	100.
8.344	150.
9.042	200.
10.41	273.15
10.92 ± 0.02	298.15
10.96	300.
13.03	400.
14.97	500.
16.68	600.
18.17	700.
19.44	800.
20.50	900.
21.37	1000.
22.07	1100.
22.62	1200.
23.06	1300.
23.40	1400.
23.67	1500.

Gas phase ion energetics data

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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
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
LL - Sharon G. Lias and Joel F. Liebman

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	11.33 ± 0.01	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	177.3	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	169.8	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
11.31	PI	Traeger, 1985	LBLHLM
11.329 ± 0.002	S	Bell, Ng, et al., 1975	LLK
11.16 ± 0.03	PI	Warneck, 1974	LLK
11.314 ± 0.002	PI	Knowles and Nicholson, 1974	LLK
11.3	PE	Watanabe, Yokoyama, et al., 1973	LLK
11.33	PE	Watanabe, Yokoyama, et al., 1973, 2	LLK
11.35 ± 0.03	PE	Thomas, 1972	LLK
11.16 ± 0.03	PI	Matthews and Warneck, 1969	RDSH
11.33	PE	Brundle, Turner, et al., 1969	RDSH
11.05 ± 0.03	PI	Vilesov, 1960	RDSH
11.05 ± 0.01	PI	Watanabe, 1957	RDSH
11.33	S	Price and Evans, 1937	RDSH
11.5	PE	Von Niessen, Bieri, et al., 1980	Vertical value; LLK
11.34	PE	Benoit and Harrison, 1977	Vertical value; LLK
10.7	PE	Rao, 1975	Vertical value; LLK
11.51	PE	Kimura, Katsumata, et al., 1975	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C⁺	22.7 ± 0.5	O+H₂O	EI	Stepanov, Perov, et al., 1988	LL
CHO⁺	12.76	OH	PI	Traeger, 1985	LBLHLM
CHO⁺	13.0 ± 0.1	OH	PI	Golovin, Akopyan, et al., 1979	LLK
CHO⁺	12.79 ± 0.03	OH	PI	Warneck, 1974	LLK
CHO⁺	12.79 ± 0.03	OH	PI	Matthews and Warneck, 1969	RDSH
CHO₂⁺	12.4 ± 0.1	H	PI	Golovin, Akopyan, et al., 1979	LLK
CHO₂⁺	12.26	H	PI	Akopyan and Villem, 1976	LLK
CHO₂⁺	12.29 ± 0.03	H	PI	Warneck, 1974	LLK
HO⁺	17.97 ± 0.06	HCO	PI	Warneck, 1974	LLK
O⁺	20.0 ± 0.5	CO+H₂	EI	Stepanov, Perov, et al., 1988	LL

De-protonation reactions

+ = Formic acid

By formula: CHO₂^- + H⁺ = CH₂O₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	346.2 ± 1.2	kcal/mol	D-EA	Kim, Bradforth, et al., 1995	gas phase; dHacid(0K) = 344.67±0.62 kcal/mol; B
Δ_rH°	345.3 ± 2.2	kcal/mol	G+TS	Caldwell, Renneboog, et al., 1989	gas phase; B
Δ_rH°	345.4 ± 2.2	kcal/mol	G+TS	Fujio, McIver, et al., 1981	gas phase; value altered from reference due to change in acidity scale; B
Δ_rH°	345.2 ± 2.9	kcal/mol	G+TS	Cumming and Kebarle, 1978	gas phase; B
Δ_rH°	340.1 ± 4.6	kcal/mol	EIAE	Muftakhov, Vasil'ev, et al., 1999	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	339.2 ± 1.5	kcal/mol	H-TS	Kim, Bradforth, et al., 1995	gas phase; dHacid(0K) = 344.67±0.62 kcal/mol; B
Δ_rG°	338.3 ± 2.0	kcal/mol	IMRE	Caldwell, Renneboog, et al., 1989	gas phase; B
Δ_rG°	338.4 ± 2.0	kcal/mol	IMRE	Fujio, McIver, et al., 1981	gas phase; value altered from reference due to change in acidity scale; B
Δ_rG°	338.2 ± 2.0	kcal/mol	IMRE	Cumming and Kebarle, 1978	gas phase; B

IR Spectrum

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Data compiled by: Coblentz Society, Inc.

GAS (20 mmHg, N2 ADDED, TOTAL PRESSURE 600 mmHg); DOW KBr FOREPRISM-GRATING; DIGITIZED BY NIST FROM HARD COPY (FROM TWO SEGMENTS); 2 cm^-1 resolution

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Vibrational and/or electronic energy levels

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, IR Spectrum, References, Notes

Data compiled by: Takehiko Shimanouchi

Symmetry: C_s Symmetry Number σ = 1

Sym.	No	Approximate	Selected Freq.		Infrared		Raman

Species		type of mode	Value	Rating	Value	Phase	Value	Phase

a'	1	OH str	3570	D	3570 M	gas
a'	2	CH str	2943	C	2942.8 M	gas
a'	3	C=O str	1770	C	1770 VS	gas
a'	4	CH bend	1387	C	1387 VW	gas
a'	5	OH bend	1229	C	1229 W	gas
a'	6	C-O str	1105	C	1105.3 S	gas
a'	7	OCO deform	625	C	625 M	gas
a	8	CH bend	1033	C	1033 W	gas
a	9	Torsion	638	C	638 S	gas

Source: Shimanouchi, 1972

Notes

Very strong

Strong

Medium

Weak

Very weak

3~6 cm^-1 uncertainty

6~15 cm^-1 uncertainty

References

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, IR Spectrum, Vibrational and/or electronic energy levels, Notes

Guthrie, 1974
Guthrie, J.P., Hydration of carboxamides. Evaluation of the free energy change for addition of water to acetamide and formamide derivatives, J. Am. Chem. Soc., 1974, 96, 3608-3615. [all data]

Lebedeva, 1964
Lebedeva, N.D., Heats of combustion of monocarboxylic acids, Russ. J. Phys. Chem. (Engl. Transl.), 1964, 38, 1435-1437. [all data]

Konicek and Wadso, 1970
Konicek, J.; Wadso, I., Enthalpies of vaporization of organic compounds. VII. Some carboxylic acids, Acta Chem. Scand., 1970, 24, 2612-26. [all data]

Sinke, 1959
Sinke, G.C., The heat of formation of formic acid, J. Phys. Chem., 1959, 63, 2063. [all data]

Millikan R.C., 1957
Millikan R.C., Infrared spectra and vibrational assignment of monomeric formic acid, J. Chem. Phys., 1957, 27, 1305-1308. [all data]

Halford J.O., 1942
Halford J.O., Entropy of the monomeric forms of formic acid and acetic acid, J. Chem. Phys., 1942, 10, 582-584. [all data]

Waring W., 1952
Waring W., Some thermodynamic properties of formic acid, Chem. Rev., 1952, 51, 171-183. [all data]

Chao J., 1986
Chao J., Thermodynamic properties of key organic oxygen compounds in the carbon range C1 to C4. Part 2. Ideal gas properties, J. Phys. Chem. Ref. Data, 1986, 15, 1369-1436. [all data]

Fukushima K., 1971
Fukushima K., Normal coordinate treatment and thermodynamic properties of the cis-trans isomers of formic acid and its deutero-analog, J. Chem. Thermodyn., 1971, 3, 553-562. [all data]

East A.L.L., 1997
East A.L.L., Ab initio statistical thermodynamical models for the computation of third-law entropies, J. Chem. Phys., 1997, 106, 6655-6674. [all data]

Green J.H.S., 1961
Green J.H.S., Thermodynamic properties of organic oxygen compounds. Part III. Formic acid, J. Chem. Soc., 1961, 2241-2242. [all data]

Gurvich, Veyts, et al., 1989
Gurvich, L.V.; Veyts, I.V.; Alcock, C.B., Thermodynamic Properties of Individual Substances, 4th ed.; Vols. 1 and 2, Hemisphere, New York, 1989. [all data]

Chao J., 1978
Chao J., Ideal gas thermodynamic properties of methanoic and ethanoic acids, J. Phys. Chem. Ref. Data, 1978, 7, 363-377. [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Traeger, 1985
Traeger, J.C., Heat of formation for the formyl cation by photoionization mass spectrometry, Int. J. Mass Spectrom. Ion Processes, 1985, 66, 271. [all data]

Bell, Ng, et al., 1975
Bell, S.; Ng, T.L.; Walsh, A.D., Vacuum ultraviolet spectra of formic and acetic acids, J. Chem. Soc. Faraday Trans. 2, 1975, 71, 393. [all data]

Warneck, 1974
Warneck, P., Heat of formation of the HCO radical, Z. Naturforsch. A:, 1974, 29, 350. [all data]

Knowles and Nicholson, 1974
Knowles, D.J.; Nicholson, A.J.C., Ionization energies of formic and acetic acid monomers, J. Chem. Phys., 1974, 60, 1180. [all data]

Watanabe, Yokoyama, et al., 1973
Watanabe, I.; Yokoyama, Y.; Ikeda, S., Vibrational structures in the photoelectron spectrum of formic acid, Chem. Phys. Lett., 1973, 19, 406. [all data]

Watanabe, Yokoyama, et al., 1973, 2
Watanabe, I.; Yokoyama, Y.; Ikeda, S., Lone pair ionization potentials of carboxylic acids determined by He(I) photoelectron spectroscopy, Bull. Chem. Soc. Jpn., 1973, 46, 1959. [all data]

Thomas, 1972
Thomas, R.K., Photoelectron spectroscopy of hydrogen-bonded systems: spectra of monomers, dimers and mixed complexes of carboxylic acides, Proc. R. Soc. London A:, 1972, 331, 249. [all data]

Matthews and Warneck, 1969
Matthews, C.S.; Warneck, P., Heats of formation of CHO⁺ and C₃H₃⁺ by photoionization, J. Chem. Phys. 5, 1969, 1, 854. [all data]

Brundle, Turner, et al., 1969
Brundle, C.R.; Turner, D.W.; Robin, M.B.; Basch, H., Photoelectron spectroscopy of simple amides and carboxylic acids, Chem. Phys. Lett., 1969, 3, 292. [all data]

Vilesov, 1960
Vilesov, F.I., The photoionization of vapors of compounds whose molecules contain carbonyl groups, Dokl. Phys. Chem., 1960, 132, 521, In original 1332. [all data]

Watanabe, 1957
Watanabe, K., Ionization potentials of some molecules, J. Chem. Phys., 1957, 26, 542. [all data]

Price and Evans, 1937
Price, W.C.; Evans, W.M., The absorption spectrum of formic acid in the vacuum ultra-violet, Proc. Roy. Soc. (London), 1937, A162, 110. [all data]

Von Niessen, Bieri, et al., 1980
Von Niessen, W.; Bieri, G.; Asbrink, L., 30.4 nm He(II) photoelectron spectra of organic molecules. Part III. Oxo-compounds (C,H,O), J. Electron Spectrosc. Relat. Phenom., 1980, 21, 175. [all data]

Benoit and Harrison, 1977
Benoit, F.M.; Harrison, A.G., Predictive value of proton affinity. Ionization energy correlations involving oxygenated molecules, J. Am. Chem. Soc., 1977, 99, 3980. [all data]

Rao, 1975
Rao, C.N.R., Lone-pair ionization bands of chromophores in the photoelectron spectra of organic molecules, Indian J. Chem., 1975, 13, 950. [all data]

Kimura, Katsumata, et al., 1975
Kimura, K.; Katsumata, S.; Yamazaki, T.; Wakabayashi, H., UV photoelectron spectra and sum rule consideration; out-of-plane orbitals of unsaturated compounds with planar-skeleton structure, J. Electron Spectrosc. Relat. Phenom., 1975, 6, 41. [all data]

Stepanov, Perov, et al., 1988
Stepanov, A.N.; Perov, A.A.; Kabanov, S.P.; Simonov, A.P., Formation of long-lived, highly excited atoms during dissociative excitation of CH₃CN, CH₃CH₂OH, CH₃COOH, HCOOH, and C₄H₄S molecules on electron impact, Russ. J. Phys. Chem., 1988, 22, 81. [all data]

Golovin, Akopyan, et al., 1979
Golovin, A.V.; Akopyan, M.E.; Vilesov, F.I.; Sergeev, Y.L., Ion-electron coincidence study of the photoionization of formic and acetic acids, Khim. Vys. Energ., 1979, 13, 200. [all data]

Akopyan and Villem, 1976
Akopyan, M.E.; Villem, Ya.Ya., Ion-molecule reactions in the photoionization of formic and acetic acid vapors, High Energy Chem., 1976, 10, 24. [all data]

Kim, Bradforth, et al., 1995
Kim, E.H.; Bradforth, S.E.; Arnold, D.W.; Metz, R.B.; Neumark, D.M., Study of HCO2 and DCO2 by Negative Ion Photoelectron Spectroscopy, J. Chem. Phys., 1995, 103, 18, 7801, https://doi.org/10.1063/1.470196 . [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]

Fujio, McIver, et al., 1981
Fujio, M.; McIver, R.T., Jr.; Taft, R.W., Effects on the acidities of phenols from specific substituent-solvent interactions. Inherent substituent parameters from gas phase acidities, J. Am. Chem. Soc., 1981, 103, 4017. [all data]

Cumming and Kebarle, 1978
Cumming, J.B.; Kebarle, P., Summary of gas phase measurements involving acids AH. Entropy changes in proton transfer reactions involving negative ions. Bond dissociation energies D(A-H) and electron affinities EA(A), Can. J. Chem., 1978, 56, 1. [all data]

Muftakhov, Vasil'ev, et al., 1999
Muftakhov, M.V.; Vasil'ev, Y.V.; Mazunov, V.A., Determination of electron affinity of carbonyl radicals by means of negative ion mass spectrometry, Rapid Commun. Mass Spectrom., 1999, 13, 12, 1104-1108, https://doi.org/10.1002/(SICI)1097-0231(19990630)13:12<1104::AID-RCM619>3.0.CO;2-C . [all data]

Shimanouchi, 1972
Shimanouchi, T., Tables of Molecular Vibrational Frequencies Consolidated Volume I, National Bureau of Standards, 1972, 1-160. [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, IR Spectrum, Vibrational and/or electronic energy levels, References

Symbols used in this document:

AE	Appearance energy
C_p,gas	Constant pressure heat capacity of gas
IE (evaluated)	Recommended ionization energy
S°_gas	Entropy of gas at standard conditions
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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Formic acid

Data at NIST subscription sites:

Gas phase thermochemistry data

Constant pressure heat capacity of gas

Gas phase ion energetics data

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

IR Spectrum

Vibrational and/or electronic energy levels

Symmetry: Cs Symmetry Number σ = 1

Notes

References

Notes

Symmetry: C_s Symmetry Number σ = 1