Acetylene

Formula: C₂H₂
Molecular weight: 26.0373
IUPAC Standard InChI: InChI=1S/C2H2/c1-2/h1-2H
IUPAC Standard InChIKey: HSFWRNGVRCDJHI-UHFFFAOYSA-N
CAS Registry Number: 74-86-2
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript.
Other names: Ethyne; Ethine; Narcylen; C2H2; Acetylen; UN 1001; Vinylene
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Gas phase thermochemistry data

Go To: Top, Gas phase ion energetics data, Mass spectrum (electron ionization), References, Notes

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

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	226.73	kJ/mol	Review	Chase, 1998	Data last reviewed in March, 1961
Δ_fH°_gas	227.4 ± 0.8	kJ/mol	Review	Manion, 2002	adopted recommendation of Gurvich, Veyts, et al., 1991; DRB
Δ_fH°_gas	226.7 ± 0.79	kJ/mol	Ccb	Wagman, Kilpatrick, et al., 1945	Unpublished work of E. J. Prosen; ALS
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	200.93	J/mol*K	Review	Chase, 1998	Data last reviewed in March, 1961

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
29.35	100.	Gurvich, Veyts, et al., 1989	p=1 bar.; GT
35.57	200.
44.04	298.15
44.17	300.
50.39	400.
54.75	500.
58.12	600.
60.97	700.
63.51	800.
65.83	900.
67.96	1000.
69.91	1100.
71.69	1200.
73.30	1300.
74.76	1400.
76.08	1500.
77.27	1600.
78.35	1700.
79.32	1800.
80.21	1900.
81.01	2000.
81.74	2100.
82.41	2200.
83.03	2300.
83.60	2400.
84.12	2500.
84.61	2600.
85.06	2700.
85.49	2800.
85.89	2900.
86.26	3000.

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 (J/mol*K)
H° = standard enthalpy (kJ/mol)
S° = standard entropy (J/mol*K)
t = temperature (K) / 1000.

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Temperature (K)	298. to 1100.	1100. to 6000.
A	40.68697	67.47244
B	40.73279	11.75110
C	-16.17840	-2.021470
D	3.669741	0.136195
E	-0.658411	-9.806418
F	210.7067	185.4550
G	235.0052	253.5337
H	226.7314	226.7314
Reference	Chase, 1998	Chase, 1998
Comment	Data last reviewed in March, 1961	Data last reviewed in March, 1961

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Mass spectrum (electron ionization), References, Notes

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

View reactions leading to C₂H₂⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	11.400 ± 0.002	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	641.4	kJ/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	616.7	kJ/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
11.41 ± 0.01	EI	Plessis and Marmet, 1986	LBLHLM
11.40	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
11.4	EVAL	Rosmus, Botschwina, et al., 1981	LLK
11.40	PE	Kimura, Katsumata, et al., 1981	LLK
11.40	PE	Bieri, Schmelzer, et al., 1980	LLK
11.4 ± 0.1	EI	Suzuki and Maeda, 1978	LLK
11.4 ± 0.1	EI	Suzuki and Maeda, 1977	LLK
11.40 ± 0.02	PE	Bieri, Burger, et al., 1977	LLK
~11.3	EI	Van Veen and Plantenga, 1976	LLK
11.37 ± 0.05	EI	Reeher, Flesch, et al., 1976	LLK
11.403 ± 0.0003	PE	Carlier, Dubois, et al., 1975	LLK
11.394 ± 0.005	PI	Parr and Taylor, 1973	LLK
11.398 ± 0.005	PI	Dibeler and Walker, 1973	LLK
11.40	PE	Brogli, Heilbronner, et al., 1973	LLK
11.39 ± 0.02	EI	Lossing, 1970	RDSH
11.395 ± 0.015	PI	Omura, Kaneko, et al., 1969	RDSH
11.39 ± 0.05	EI	Williams and Hamill, 1968	RDSH
11.41 ± 0.01	EI	Collins, Winters, et al., 1968	RDSH
11.40 ± 0.01	PE	Baker and Turner, 1968	RDSH
11.400 ± 0.005	PI	Brehm, 1966	RDSH
11.396 ± 0.003	PI	Nicholson, 1965	RDSH
11.40 ± 0.02	EI	Melton and Hamill, 1964	RDSH
11.406 ± 0.006	PI	Dibeler and Reese, 1964	RDSH
11.41 ± 0.01	PI	Watanabe and Namioka, 1956	RDSH
11.2 ± 0.1	EI	Kusch, Hustrulid, et al., 1937	RDSH
11.41	S	Price, 1935	RDSH
11.49	PE	Bieri and Asbrink, 1980	Vertical value; LLK
11.43	PE	Cavell and Allison, 1978	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C⁺	21.20 ± 0.05	CH₂	EI	Locht and Davister, 1995	LL
C⁺	24. ± 1.	?	PI	Cooper, Ibuki, et al., 1988	LL
C⁺	20.43 ± 0.05	CH₂	EI	Plessis and Marmet, 1986	LBLHLM
C⁺	22.5 ± 0.3	C⁺²H	EI	Suzuki and Maeda, 1977	LLK
C⁺	23.6	?	EI	Bloch, 1963	RDSH
C⁺	24.5 ± 1.0	C⁺²H	EI	Kusch, Hustrulid, et al., 1937	RDSH
CH⁺	20.85 ± 0.05	CH	EI	Davister and Locht, 1995	LL
CH⁺	20.54 ± 0.05	CH	EI	Plessis and Marmet, 1986	LBLHLM
CH⁺	23.9 ± 0.2	C+H	EI	Plessis and Marmet, 1986	LBLHLM
CH⁺	24.1	C+H	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
CH⁺	20.7 ± 0.1	CH	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
CH⁺	20.9 ± 0.2	CH	EI	Suzuki and Maeda, 1977	LLK
CH⁺	21.5 ± 0.2	CH	EI	Kloster-Jensen, Pascual, et al., 1970	RDSH
CH⁺	21.9	CH	EI	Haney and Franklin, 1968	RDSH
CH⁺	22.2 ± 0.5	CH	EI	Kusch, Hustrulid, et al., 1937	RDSH
CH₂⁺	19.74 ± 0.20	C	EI	Locht and Davister, 1995	LL
CH₂⁺	18.17 ± 0.09	C^-	EI	Plessis and Marmet, 1986	LBLHLM
CH₂⁺	19.40 ± 0.12	C	EI	Plessis and Marmet, 1986	LBLHLM
CH₂⁺	19.4 ± 0.1	C	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
CH₂⁺	20.5 ± 0.2	?	EI	Suzuki and Maeda, 1977	LLK
CH₂⁺	21.	C	EI	Franklin and Munson, 1965	RDSH
C₂⁺	19. ± 1.	H₂	CIEL	Reid, Ballantine, et al., 1995	LL
C₂⁺	18.44 ± 0.07	H₂	EI	Locht and Davister, 1995	LL
C₂⁺	22.60 ± 0.12	2H	EI	Plessis and Marmet, 1986	LBLHLM
C₂⁺	18.16 ± 0.05	H₂	EI	Plessis and Marmet, 1986	LBLHLM
C₂⁺	18.1 ± 0.1	H₂	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
C₂⁺	22.7 ± 0.1	2H	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
C₂⁺	19.2 ± 0.2	?	EI	Suzuki and Maeda, 1977	LLK
C₂⁺	23.6	2H?	EI	Momigny and Derouane, 1968	RDSH
C₂⁺	19.5	H₂	EI	Bloch, 1963	RDSH
C₂⁺	23.8	2H?	EI	Bloch, 1963	RDSH
C₂⁺	22.7	2H?	EI	Field, Franklin, et al., 1957	RDSH
C₂⁺	18.2	H₂	EI	Field, Franklin, et al., 1957	RDSH
C₂⁺	23.3 ± 0.5	2H?	EI	Coats and Anderson, 1957	RDSH
C₂⁺	23.8 ± 0.3	2H	EI	Kusch, Hustrulid, et al., 1937	RDSH
C₂H⁺	17.35 ± 0.04	H	PIPECO	Servais and Locht, 1995	LL
C₂H⁺	17.360	H	PIPECO	Weitzel, Mahnert, et al., 1994	LL
C₂H⁺	17.30 ± 0.08	H	EI	Davister and Locht, 1994	LL
C₂H⁺	17.33 ± 0.05	H	PIPECO	Norwood and Ng, 1989	LL
C₂H⁺	16.70 ± 0.10	H	EI	Plessis and Marmet, 1986	LBLHLM
C₂H⁺	16.8 ± 0.1	H	PI	Hayaishi, Iwata, et al., 1982	LBLHLM
C₂H⁺	16.79 ± 0.03	H	PI	Ono and Ng, 1981	LLK
C₂H⁺	17.3	H	PIPECO	Eland, 1979	LLK
C₂H⁺	17.5 ± 0.1	H	EI	Suzuki and Maeda, 1977	LLK
C₂H⁺	17.36 ± 0.01	H	PI	Dibeler, Walker, et al., 1973	LLK
C₂H⁺	17.22	H	PI	Botter, Dibeler, et al., 1966	RDSH
C₂H⁺	17.3	H	EI	Field, Franklin, et al., 1957	RDSH
C₂H⁺	17.8 ± 0.2	H	EI	Kusch, Hustrulid, et al., 1937	RDSH
H⁺	18.83 ± 0.23	C₂H	EI	Davister and Locht, 1994	LL
H⁺	23. ± 1.	?	PI	Cooper, Ibuki, et al., 1988	LL
H⁺	19.35 ± 0.05	C₂H	PI	Shiromaru, Achiba, et al., 1987	LBLHLM
H⁺	20.6 ± 0.3	?	EI	Suzuki and Maeda, 1977	LLK
H⁺	21.7 ± 1.0	C₂+H	EI	Kusch, Hustrulid, et al., 1937	RDSH
H⁺	25.6 ± 1.0	CH+C	EI	Kusch, Hustrulid, et al., 1937	RDSH

De-protonation reactions

C₂H^- + = Acetylene

By formula: C₂H^- + H⁺ = C₂H₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1580. ± 20.	kJ/mol	AVG	N/A	Average of 8 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1550. ± 20.	kJ/mol	AVG	N/A	Average of 7 values; Individual data points

Mass spectrum (electron ionization)

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

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

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NIST MS number	18810

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References

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), Notes

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Manion, 2002
Manion, J.A., Evaluated Enthalpies of Formation of the Stable Closed Shell C1 and C2 Chlorinated Hydrocarbons, J. Phys. Chem. Ref. Data, 2002, 31, 1, 123-172, https://doi.org/10.1063/1.1420703 . [all data]

Gurvich, Veyts, et al., 1991
Thermodynamic Properties of Individual Substances, 4th edition, Volume 2, Gurvich, L.V.; Veyts, I.V.; Alcock, C.B.;, ed(s)., Hemisphere, New York, 1991. [all data]

Wagman, Kilpatrick, et al., 1945
Wagman, D.D.; Kilpatrick, J.E.; Pitzer, K.S.; Rossini, F.D., Heats, equilibrium constants, and free energies of formation of the acetylene hydrocarbons through the pentynes, to 1,500° K, J. Res. NBS, 1945, 35, 467-496. [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]

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]

Plessis and Marmet, 1986
Plessis, P.; Marmet, P., Electroionization study of acetylene and fragment ions, Int. J. Mass Spectrom. Ion Processes, 1986, 70, 23. [all data]

Hayaishi, Iwata, et al., 1982
Hayaishi, T.; Iwata, S.; Sasanuma, M.; Ishiguro, E.; Morioka, Y.; Iida, Y.; Nakamura, M., Photoionisation mass spectrometric study of acetylene in the VUV region, J. Phys. B:, 1982, 15, 79. [all data]

Rosmus, Botschwina, et al., 1981
Rosmus, P.; Botschwina, P.; Maier, J.P., On the ionic states of vinylidene and acetylene, Chem. Phys. Lett., 1981, 84, 71. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Bieri, Schmelzer, et al., 1980
Bieri, G.; Schmelzer, A.; Asbrink, L.; Jonsson, M., Fluorine and the fluoroderivatives of acetylene and diacetylene studied by 30.4 nm He(II) photoelectron spectroscopy, Chem. Phys., 1980, 49, 213. [all data]

Suzuki and Maeda, 1978
Suzuki, I.H.; Maeda, K., Ionization efficiency curves of acetylene by mono-energetic electron impact, Adv. Mass Spectrom., 1978, 7, 182. [all data]

Suzuki and Maeda, 1977
Suzuki, I.H.; Maeda, K., Ionization efficiency curves of acetylene by electron impact, Mass Spectrosc. (Tokyo), 1977, 25, 223. [all data]

Bieri, Burger, et al., 1977
Bieri, G.; Burger, F.; Heilbronner, E.; Maier, J.P., Valence ionization enrgies of hydrocarbons, Helv. Chim. Acta, 1977, 60, 2213. [all data]

Van Veen and Plantenga, 1976
Van Veen, E.H.; Plantenga, F.L., Low-energy electron-impact excitation spectra of acetylene, Chem. Phys. Lett., 1976, 38, 493. [all data]

Reeher, Flesch, et al., 1976
Reeher, J.R.; Flesch, G.D.; Svec, H.J., The mass spectra and ionization potentials of the neutral fragments produced during the electron bombardment of aromatic compounds, Org. Mass Spectrom., 1976, 11, 154. [all data]

Carlier, Dubois, et al., 1975
Carlier, P.; Dubois, J.E.; Masclet, P.; Mouvier, G., Spectres de photoelectrons des alcynes, J. Electron Spectrosc. Relat. Phenom., 1975, 7, 55. [all data]

Parr and Taylor, 1973
Parr, G.R.; Taylor, J.W., A photoionization mass spectrometer utilizing a high intensity molecular beam sampling system and synchrotron radiation, Rev. Sci. Instrum., 1973, 44, 1578. [all data]

Dibeler and Walker, 1973
Dibeler, V.H.; Walker, J.A., Photoionization of acetylene near threshold, Int. J. Mass Spectrom. Ion Phys., 1973, 11, 49. [all data]

Brogli, Heilbronner, et al., 1973
Brogli, F.; Heilbronner, E.; Hornung, V.; Kloster-Jensen, E., 230. Die photoelektronen-spektren methyl-substituierter Acetylene, Helv. Chim. Acta, 1973, 56, 2171. [all data]

Lossing, 1970
Lossing, F.P., Threshold ionization of acetylene by monoenergetic electron impact, Intern. J. Mass Spectrom. Ion Phys., 1970, 5, 190. [all data]

Omura, Kaneko, et al., 1969
Omura, I.; Kaneko, T.; Yamada, Y.; Tanaka, K., Mass spectrometric studies of photoionization. IV. Acetylene and propyne, J. Phys. Soc. Japan, 1969, 27, 178. [all data]

Williams and Hamill, 1968
Williams, J.M.; Hamill, W.H., Ionization potentials of molecules and free radicals and appearance potentials by electron impact in the mass spectrometer, J. Chem. Phys., 1968, 49, 4467. [all data]

Collins, Winters, et al., 1968
Collins, J.H.; Winters, R.E.; Engerholm, G.G., Fine structure in energy-distribution-difference ionizationefficiency curves, J. Chem. Phys., 1968, 49, 2469. [all data]

Baker and Turner, 1968
Baker, C.; Turner, D.W., High resolution molecular photoelectron spectroscopy. III.Acetylenes and azaacetylenes, Proc. Roy. Soc. (London), 1968, A308, 19. [all data]

Brehm, 1966
Brehm, B., Massenspektrometrische Untersuchung der Photoionisation von Molekulen, Z. Naturforsch., 1966, 21a, 196. [all data]

Nicholson, 1965
Nicholson, A.J.C., Photoionization-efficiency curves. II. False and genuine structure, J. Chem. Phys., 1965, 43, 1171. [all data]

Melton and Hamill, 1964
Melton, C.E.; Hamill, W.H., Appearance potentials by the retarding potential-difference method for secondary ions produced by excited-neutral, excited ion-neutral, and ion-neutral reactions, J. Chem. Phys., 1964, 41, 1469. [all data]

Dibeler and Reese, 1964
Dibeler, V.H.; Reese, R.M., Mass spectrometric study of photoionization. I. Apparatus and initial observations on acetylene, acetylene-d₂, benzene, and benzene-d₆, J. Res. NBS, 1964, 68A, 409. [all data]

Watanabe and Namioka, 1956
Watanabe, K.; Namioka, T., Ionization potential of propyne, J. Chem. Phys., 1956, 24, 915. [all data]

Kusch, Hustrulid, et al., 1937
Kusch, P.; Hustrulid, A.; Tate, J.T., The dissociation of HCN, C₂H₂, C₂N₂ and C₂H₄ by electron impact, Phys. Rev., 1937, 52, 843. [all data]

Price, 1935
Price, W.C., The absorption spectra of acetylene, ethylene, and ethane in the far ultraviolet, Phys. Rev., 1935, 47, 444. [all data]

Bieri and Asbrink, 1980
Bieri, G.; Asbrink, L., 30.4-nm He(II) photoelectron spectra of organic molecules, J. Electron Spectrosc. Relat. Phenom., 1980, 20, 149. [all data]

Cavell and Allison, 1978
Cavell, R.G.; Allison, D.A., Photoelectron spectra of acetylene with He(I), He(II) , Zr M175»_{zeta}, MgK»α radiation sources, J. Chem. Phys., 1978, 69, 159. [all data]

Locht and Davister, 1995
Locht, R.; Davister, M., The dissociative ionization of C₂H₂. The C⁺, C₂⁺, and CH₂⁺ dissociation channels. The vinylidene ion as a transient?, Chem. Phys., 1995, 195, 443. [all data]

Cooper, Ibuki, et al., 1988
Cooper, G.; Ibuki, T.; Iida, Y.; Brion, C.E., Absolute dipole oscillator strengths for photoabsorption and the molecular and dissociative photoionization of acetylene, Chem. Phys., 1988, 125, 307. [all data]

Bloch, 1963
Bloch, A., Mass spectra of acetylene under high pressure in the ion source, Advan. Mass Spectrom., 1963, 2, 48. [all data]

Davister and Locht, 1995
Davister, M.; Locht, R., The dissociative ionization of C₂H₂ and C₂D₂. The [CH(CD)]⁺ dissociation channel. The H(D)C≡C(D)H binding energy, Chem. Phys., 1995, 191, 333. [all data]

Kloster-Jensen, Pascual, et al., 1970
Kloster-Jensen, E.; Pascual, C.; Vogt, J., Mass spectrometric studies of mono- and di-haloacetylenes,, Helv. Chim. Acta, 1970, 53, 2109. [all data]

Haney and Franklin, 1968
Haney, M.A.; Franklin, J.L., Correlation of excess energies of electron-impact dissociations with the translational energies of the products, J.Chem. Phys., 1968, 48, 4093. [all data]

Franklin and Munson, 1965
Franklin, J.L.; Munson, M.S.B., Ion-molecule reactions in methane-oxygen and acetylene-oxygen systems, Symp. Combust., 10th, Univ. Cambridge, Cambridge, Engl.,, 1965, 1964, 561. [all data]

Reid, Ballantine, et al., 1995
Reid, C.J.; Ballantine, J.A.; Andrews, S.R.; Harris, F.M., Charge inversion of ground-state and metastable-state C₂⁺ cations formed from electroionised C₂H₂ and C₂N₂, and a re-evaluation of the carbon dimer's ionisation energy, Chem. Phys., 1995, 190, 113. [all data]

Momigny and Derouane, 1968
Momigny, J.; Derouane, E., Fine structure in the first derivative of ionization curves obtained under electron impact, Advan. Mass Spectrom., 1968, 4, 607. [all data]

Field, Franklin, et al., 1957
Field, F.H.; Franklin, J.L.; Lampe, F.W., Reactions of gaseous ions. II. Acetylene, J. Am. Chem. Soc., 1957, 79, 2665. [all data]

Coats and Anderson, 1957
Coats, F.H.; Anderson, R.C., Thermodynamic data from electron-impact measurements on acetylene and substituted acetylenes, J. Am. Chem. Soc., 1957, 79, 1340. [all data]

Servais and Locht, 1995
Servais, C.; Locht, R., The appearance energy of C₂H⁺ from C₂H₂ revisited. A photoion-photoelectron coincidence spectroscopic determination, Chem. Phys. Lett., 1995, 236, 96. [all data]

Weitzel, Mahnert, et al., 1994
Weitzel, K.-M.; Mahnert, J.; Penno, M., ZEKE-PEPICO investigations of dissociation energies in ionic reactions, Chem. Phys. Lett., 1994, 224, 371. [all data]

Davister and Locht, 1994
Davister, M.; Locht, R., The dissociative electroionization of C₂H₂, C₂D₂ and C₂HD. Investigation of the [C₂H(D)]⁺ and [H(D)]⁺ dissociation channels. The (D)H-C₂H(D) binding energy, Chem. Phys., 1994, 189, 805. [all data]

Norwood and Ng, 1989
Norwood, K.; Ng, C.Y., A state-selected study of the unimolecular decompoisition of C₂H₂⁺(A,B) using the photoion photoelectron coincidence method, J. Chem. Phys., 1989, 91, 2898. [all data]

Ono and Ng, 1981
Ono, Y.; Ng, C.Y., The heat of formation of C₂H⁺, J. Chem. Phys., 1981, 74, 6985. [all data]

Eland, 1979
Eland, J.H.D., Dissociations of state-selected C₂H₂⁺, H₂S⁺ and D₂S⁺ ions studied by photoelectron-photoion coincidence spectroscopy, Int. J. Mass Spectrom. Ion Phys., 1979, 31, 161. [all data]

Dibeler, Walker, et al., 1973
Dibeler, V.H.; Walker, J.A.; McCulloh, K.E., Observations on hot bands in the molecular and dissociative photoionization of acetylene and the heat of formation of the ethynyl ion, J. Chem. Phys., 1973, 59, 2264. [all data]

Botter, Dibeler, et al., 1966
Botter, R.; Dibeler, V.H.; Walker, J.A.; Rosenstock, H.M., Experimental and theoretical studies of photoionization-efficiency curves for C₂H₂ and C₂D₂, J. Chem. Phys., 1966, 44, 1271. [all data]

Shiromaru, Achiba, et al., 1987
Shiromaru, H.; Achiba, Y.; Kimura, K.; Lee, Y.T., Determination of the C-H bond dissociation energies of ethylene and acetylene by observation of the threshold energies of H⁺ formation by synchrotron radiation, J. Phys. Chem., 1987, 91, 17. [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
C_p,gas	Constant pressure heat capacity of gas
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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NIST Chemistry WebBook, SRD 69