(E)-1,2-Difluoroethylene

Formula: C₂H₂F₂
Molecular weight: 64.0341
CAS Registry Number: 1630-78-0
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Data at other public NIST sites:
- Gas Phase Kinetics Database
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Reaction thermochemistry data

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Data compiled by: Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

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Individual Reactions

C₂H₂F₂ =

By formula: C₂H₂F₂ = C₂H₂F₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-1.08 ± 0.12	kcal/mol	Eqk	Craig, Piper, et al., 1971	gas phase

= C₂H₂F₂

By formula: C₂H₂F₂ = C₂H₂F₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	0.93	kcal/mol	Eqk	Craig and Entemann, 1961	gas phase

Gas phase ion energetics data

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Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias

Data compiled as indicated in comments:
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

View reactions leading to C₂H₂F₂⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	164.6	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	157.2	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
10.15	PI	Frenking, Koch, et al., 1984	LBLHLM
10.21 ± 0.02	PE	Bieri, Niessen, et al., 1981	LLK
10.15 ± 0.02	PI	Jochims, Lohr, et al., 1979	LLK
10.21	PE	Sell, Mintz, et al., 1978	LLK
10.63 ± 0.02	PE	Bieri, Niessen, et al., 1981	Vertical value; LLK
10.38 ± 0.02	PE	Sell and Kuppermann, 1979	Vertical value; LLK
10.39 ± 0.02	PE	Jochims, Lohr, et al., 1979	Vertical value; LLK
10.38	PE	Brundle, Robin, et al., 1972	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
CF⁺	14.45	CH₂F	PI	Frenking, Koch, et al., 1984	LBLHLM
CF⁺	14.5 ± 0.1	?	PI	Stadelmann and Vogt, 1980	LLK
CF⁺	14.45 ± 0.03	CH₂F	PI	Jochims, Lohr, et al., 1979	LLK
CHF⁺	18.1 ± 0.2	CHF	PI	Stadelmann and Vogt, 1980	LLK
CH₂F⁺	14.35	CF	PI	Frenking, Koch, et al., 1984	LBLHLM
CH₂F⁺	14.3 ± 0.1	CF	PI	Stadelmann and Vogt, 1980	LLK
CH₂F⁺	14.35 ± 0.03	CF	PI	Jochims, Lohr, et al., 1979	LLK
C₂HF⁺	13.70	HF	PI	Frenking, Koch, et al., 1984	LBLHLM
C₂HF⁺	13.7 ± 0.1	HF	PI	Stadelmann and Vogt, 1980	LLK
C₂HF⁺	13.70 ± 0.03	HF	PI	Jochims, Lohr, et al., 1979	LLK
C₂HF₂⁺	15.4 ± 0.2	H	PI	Stadelmann and Vogt, 1980	LLK
C₂H₂⁺	18.3 ± 0.2	?	PI	Stadelmann and Vogt, 1980	LLK
C₂H₂F⁺	13.97	F	PI	Frenking, Koch, et al., 1984	LBLHLM
C₂H₂F⁺	13.9 ± 0.1	F	PI	Stadelmann and Vogt, 1980	LLK
C₂H₂F⁺	13.95 ± 0.03	F	PI	Jochims, Lohr, et al., 1979	LLK

References

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Craig, Piper, et al., 1971
Craig, N.C.; Piper, L.G.; Wheeler, V.L., Thermodynamics of cis-trans isomerizations. II. The 1-chloro-2-fluoroethylenes, 1,2-difluorocyclopropanes, and related molecules, J. Phys. Chem., 1971, 75, 1453-1460. [all data]

Craig and Entemann, 1961
Craig, N.C.; Entemann, E.A., Thermodynamics of cis-trans isomerizations. The 1,2-difluoroethylenes, J. Am. Chem. Soc., 1961, 83, 3047-3050. [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]

Frenking, Koch, et al., 1984
Frenking, G.; Koch, W.; Schaale, M.; Baumgartel, H., The unimolecular decay of difluoroethene cations. An experimental and quantum-chemical study, Int. J. Mass Spectrom. Ion Phys., 1984, 61, 305. [all data]

Bieri, Niessen, et al., 1981
Bieri, G.; Niessen, W.V.; Asbrink, L.; Svensson, A., The He(II) photoelectron spectra of the fluorosubstituted ethylenes and their analysis by the green's function method, Chem. Phys., 1981, 60, 61. [all data]

Jochims, Lohr, et al., 1979
Jochims, H.-W.; Lohr, W.; Baumgartel, H., Photoreactions of small organic molecules. VI. Photoionization processes of difluoroethylenes, Nouv. J. Chim., 1979, 3, 109. [all data]

Sell, Mintz, et al., 1978
Sell, J.A.; Mintz, D.M.; Kupperman, A., Photoelectron angular distributions of carbon-carbon π electrons in ethylene, benzene, and their fluorinated derivatives, Chem. Phys. Lett., 1978, 58, 601. [all data]

Sell and Kuppermann, 1979
Sell, J.A.; Kuppermann, A., Variable angle photoelectron spectroscopy of the fluoroethylenes, J. Chem. Phys., 1979, 71, 4703. [all data]

Brundle, Robin, et al., 1972
Brundle, C.R.; Robin, M.B.; Kuebler, N.A.; Basch, H., Perfluoro effect in photoelectron spectroscopy. I. Nonaromatic molecules, J. Am. Chem. Soc., 1972, 94, 1451. [all data]

Stadelmann and Vogt, 1980
Stadelmann, J.P.; Vogt, J., A photoelectron-photoion coincidence study of cis- and trans- difluoroethene, Int. J. Mass Spectrom. Ion Phys., 1980, 35, 83. [all data]

Notes

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Symbols used in this document:

AE Appearance energy

Δ_rH° Enthalpy of reaction at standard conditions
Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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AE	Appearance energy
Δ_rH°	Enthalpy of reaction at standard conditions