Selected ATcT [1, 2] enthalpy of formation based on version 1.124 of the Thermochemical Network [3]

This version of ATcT results was generated by additional expansion of version 1.122x [4] to include additional information relevant to the study of thermophysical and thermochemical properties of CH2 and CH3 using nonrigid rotor anharmonic oscillator (NRRAO) partition functions [5], the development and benchmarking of a state-of-the-art computational approach that aims to reproduce total atomization energies of small molecules within 10–15 cm^-1 [6], as well as the study of the reversible reaction C₂H₃ + H₂ ⇌ C₂H₄ + H ⇌ C₂H₅ [7]

Ethynylene cation

Formula: [C2]+ (g)

CAS RN: 12595-79-8

ATcT ID: 12595-79-8*0

SMILES: [C]=[C+]

InChI: InChI=1S/C2/c1-2/q+1

InChIKey: ADIRGMFQWJHVBM-UHFFFAOYSA-N

Hills Formula: C2+

2D Image:

Aliases: [C2]+; Ethynylene cation; Ethynylene ion (1+); Ethynyliumyl; 2-Ethynylium-1-yl; 1,2-Ethynediyl cation; 1,2-Ethynediyl ion (1+); Carbon dimer cation; Carbon dimer ion (1+); Diatomic carbon cation; Diatomic carbon ion (1+); Dicarbon cation; Dicarbon ion (1+); Carbon molecule cation; Carbon molecule ion (1+); Carbon cluster cation; Carbon cluster ion (1+)

Relative Molecular Mass: 24.0209 ± 0.0016

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
1964.94	1971.53	± 0.40	kJ/mol

3D Image of [C2]+ (g)

spin ON spin OFF

Top contributors to the provenance of Δ_fH° of [C2]+ (g)

The 3 contributors listed below account for 91.3% of the provenance of Δ_fH° of [C2]+ (g).

Please note: The list is limited to 20 most important contributors or, if less, a number sufficient to account for 90% of the provenance. The Reference acts as a further link to the relevant references and notes for the measurement. The Measured Quantity is normaly given in the original units; in cases where we have reinterpreted the original measurement, the listed value may differ from that given by the authors. The quoted uncertainty is the a priori uncertainty used as input when constructing the initial Thermochemical Network, and corresponds either to the value proposed by the original authors or to our estimate; if an additional multiplier is given in parentheses immediately after the prior uncertainty, it corresponds to the factor by which the prior uncertainty needed to be multiplied during the ATcT analysis in order to make that particular measurement consistent with the prevailing knowledge contained in the Thermochemical Network.

Contribution (%)	TN ID	Reaction	Measured Quantity	Reference
60.8	2177.1	C2 (g, triplet) → [C2]+ (g)	Δ_rH°(0 K) = 11.791 ± 0.005 eV	Krechkivska 2016
15.2	2177.2	C2 (g, triplet) → [C2]+ (g)	Δ_rH°(0 K) = 11.795 ± 0.010 eV	Harper 2020
15.2	2177.3	C2 (g, triplet) → [C2]+ (g)	Δ_rH°(0 K) = 11.788 ± 0.010 eV	Krechkivska 2016

Top 10 species with enthalpies of formation correlated to the Δ_fH° of [C2]+ (g)

Please note: The correlation coefficients are obtained by renormalizing the off-diagonal elements of the covariance matrix by the corresponding variances.
The correlation coefficient is a number from -1 to 1, with 1 representing perfectly correlated species, -1 representing perfectly anti-correlated species, and 0 representing perfectly uncorrelated species.

Correlation Coefficent (%)	Species Name	Formula	Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units	Relative Molecular Mass	ATcT ID
23.1	Ethynylene	C2 (g, triplet)	827.228	833.933	± 0.092	kJ/mol	24.0214 ± 0.0016	12070-15-4*1
23.1	Ethynylene	C2 (g, singlet)	820.005	826.577	± 0.092	kJ/mol	24.0214 ± 0.0016	12070-15-4*2
23.1	Ethynylene	C2 (g)	820.005	828.470	± 0.092	kJ/mol	24.0214 ± 0.0016	12070-15-4*0
22.0	Carbon cation	C+ (g)	1797.857	1803.455	± 0.044	kJ/mol	12.01015 ± 0.00080	14067-05-1*0
22.0	Carbon	C (g, quintuplet)	1114.967	1120.114	± 0.044	kJ/mol	12.01070 ± 0.00080	7440-44-0*3
22.0	Carbon	C (g, singlet)	833.335	838.482	± 0.044	kJ/mol	12.01070 ± 0.00080	7440-44-0*2
22.0	Carbon	C (g, triplet)	711.404	716.889	± 0.044	kJ/mol	12.01070 ± 0.00080	7440-44-0*1
22.0	Carbon	C (g)	711.404	716.889	± 0.044	kJ/mol	12.01070 ± 0.00080	7440-44-0*0
22.0	Carbon dication	[C]+2 (g)	4150.474	4155.620	± 0.044	kJ/mol	12.00960 ± 0.00080	16092-61-8*0
22.0	Carbon anion	C- (g)	589.628	594.774	± 0.044	kJ/mol	12.01125 ± 0.00080	14337-00-9*0

Most Influential reactions involving [C2]+ (g)

Please note: The list, which is based on a hat (projection) matrix analysis, is limited to no more than 20 largest influences.

Influence Coefficient	TN ID	Reaction	Measured Quantity	Reference
0.643	2177.1	C2 (g, triplet) → [C2]+ (g)	Δ_rH°(0 K) = 11.791 ± 0.005 eV	Krechkivska 2016
0.160	2177.3	C2 (g, triplet) → [C2]+ (g)	Δ_rH°(0 K) = 11.788 ± 0.010 eV	Krechkivska 2016
0.160	2177.2	C2 (g, triplet) → [C2]+ (g)	Δ_rH°(0 K) = 11.795 ± 0.010 eV	Harper 2020
0.010	2164.11	C2 (g) → [C2]+ (g)	Δ_rH°(0 K) = 11.880 ± 0.040 eV	Ruscic W1RO
0.006	2171.1	[C2]+ (g) → C (g) + C+ (g)	Δ_rH°(0 K) = 5.634 ± 0.050 eV	Shi 2013a, est unc
0.003	2168.8	[C2]+ (g) → 2 C (g)	Δ_rH°(0 K) = -130.55 ± 1.50 kcal/mol	Ruscic W1RO
0.003	2168.7	[C2]+ (g) → 2 C (g)	Δ_rH°(0 K) = -130.86 ± 1.60 kcal/mol	Ruscic CBS-n
0.003	2168.4	[C2]+ (g) → 2 C (g)	Δ_rH°(0 K) = -129.24 ± 1.60 kcal/mol	Ruscic G4
0.002	2168.3	[C2]+ (g) → 2 C (g)	Δ_rH°(0 K) = -128.41 ± 1.72 kcal/mol	Ruscic G3X
0.001	2168.6	[C2]+ (g) → 2 C (g)	Δ_rH°(0 K) = -130.91 ± 2.16 kcal/mol	Ruscic CBS-n
0.001	2182.1	HCCH (g) → [C2]+ (g) + H2 (g)	Δ_rH°(0 K) = 18.1 ± 0.1 (×1.091) eV	Hayaishi 1982
0.000	2164.13	C2 (g) → [C2]+ (g)	Δ_rH°(0 K) = 11.771 ± 0.15 eV	Harper 2020, est unc
0.000	2164.12	C2 (g) → [C2]+ (g)	Δ_rH°(0 K) = 11.80 ± 0.15 eV	Fura 2002
0.000	2164.3	C2 (g) → [C2]+ (g)	Δ_rH°(0 K) = 11.6 ± 0.4 eV	Gingerich 1994
0.000	2164.2	C2 (g) → [C2]+ (g)	Δ_rH°(0 K) = 11.4 ± 0.3 (×1.576) eV	Reid 1995

References

1		B. Ruscic, R. E. Pinzon, M. L. Morton, G. von Laszewski, S. Bittner, S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner, Introduction to Active Thermochemical Tables: Several "Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 108, 9979-9997 (2004) [DOI: 10.1021/jp047912y]
2		B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, and A. F. Wagner, Active Thermochemical Tables: Thermochemistry for the 21^st Century. J. Phys. Conf. Ser. 16, 561-570 (2005) [DOI: 10.1088/1742-6596/16/1/078]
3		B. Ruscic and D. H. Bross, Active Thermochemical Tables (ATcT) values based on ver. 1.124 of the Thermochemical Network, Argonne National Laboratory, Lemont, Illinois 2022; available at ATcT.anl.gov [DOI: 10.17038/CSE/1885923]
4		Y. Ren, L. Zhou, A. Mellouki, V. Daële, M. Idir, S. S. Brown, B. Ruscic, Robert S. Paton, M. R. McGillen, and A. R. Ravishankara, Reactions of NO3 with Aromatic Aldehydes: Gas-Phase Kinetics and Insights into the Mechanism of the Reaction. Atmos. Chem. Phys. 21, 13537-13551 (2021) [DOI: 10.5194/acp2021-228]
5		B. Ruscic and D. H. Bross, Active Thermochemical Tables: The Thermophysical and Thermochemical Properties of Methyl, CH3, and Methylene, CH2, Corrected for Nonrigid Rotor and Anharmonic Oscillator Effects. Mol. Phys. e1969046 (2021) [DOI: 10.1080/00268976.2021.1969046]
6		J. H. Thorpe, J. L. Kilburn, D. Feller, P. B. Changala, D. H. Bross, B. Ruscic, and J. F. Stanton, Elaborated Thermochemical Treatment of HF, CO, N2, and H2O: Insight into HEAT and Its Extensions J. Chem. Phys. 155, 184109 (2021) [DOI: 10.1063/5.0069322]
7		T. L. Nguyen, D. H. Bross, B. Ruscic, G. B. Ellison, and J. F. Stanton, Mechanism, Thermochemistry, and Kinetics of the Reversible Reactions: C2H3 + H2 ⇌ C2H4 + H ⇌ C2H5. Faraday Discuss. , (Advance Article) (2022) [DOI: 10.1039/D1FD00124H]
8		B. Ruscic, Uncertainty Quantification in Thermochemistry, Benchmarking Electronic Structure Computations, and Active Thermochemical Tables. Int. J. Quantum Chem. 114, 1097-1101 (2014) [DOI: 10.1002/qua.24605]
9		B. Ruscic and D. H. Bross, Thermochemistry Computer Aided Chem. Eng. 45, 3-114 (2019) [DOI: 10.1016/B978-0-444-64087-1.00001-2]

Formula

The aggregate state is given in parentheses following the formula, such as: g - gas-phase, cr - crystal, l - liquid, etc.

Uncertainties

The listed uncertainties correspond to estimated 95% confidence limits, as customary in thermochemistry (see, for example, Ruscic [8,9]).
Note that an uncertainty of ± 0.000 kJ/mol indicates that the estimated uncertainty is < ± 0.000₅ kJ/mol.

Website Functionality Credits

The reorganization of the website was developed and implemented by David H. Bross (ANL).
The find function is based on the complete Species Dictionary entries for the appropriate version of the ATcT TN.
The molecule images are rendered by Indigo-depict.
The XYZ renderings are based on Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/.

Acknowledgement

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Contract No. DE-AC02-06CH11357.