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]

Methyliumyl

Formula: [CH2]+ (g)

CAS RN: 15091-72-2

ATcT ID: 15091-72-2*0

SMILES: [CH2+]

InChI: InChI=1S/CH2/h1H2/q+1

InChIKey: CCOXZMOGYFFTRT-UHFFFAOYSA-N

Hills Formula: C1H2+

2D Image:

Aliases: [CH2]+; Methyliumyl; Methyliumyl ion; Methyliumyl cation; Methyliumyl ion (1+); Methylene cation; Methylen ion (1+); Carbene cation; Carbene ion (1+); Carbon dihydride cation; Carbon dihydride ion (1+); Methaniumyl; CH2+

Relative Molecular Mass: 14.02603 ± 0.00081

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
1393.19	1394.05	± 0.11	kJ/mol

3D Image of [CH2]+ (g)

spin ON spin OFF

Top contributors to the provenance of Δ_fH° of [CH2]+ (g)

The 20 contributors listed below account only for 56.6% of the provenance of Δ_fH° of [CH2]+ (g).
A total of 240 contributors would be needed to account for 90% of the provenance.

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
11.3	2284.1	CH2 (g, triplet) → [CH2]+ (g)	Δ_rH°(0 K) = 83772 ± 3 cm-1	Willitsch 2002, Willitsch 2003
8.7	2281.9	CH2 (g, triplet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 179.80 ± 0.06 kcal/mol	Feller 2016, note unc2
5.8	2281.8	CH2 (g, triplet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 179.76 ± 0.07 (×1.044) kcal/mol	Feller 2014
5.3	2299.1	CH3 (g) → CH2 (g, triplet) + H (g)	Δ_rH°(0 K) = 109.26 ± 0.08 kcal/mol	Feller 2016, est unc, note unc2
2.7	2245.1	2 H2 (g) + C (graphite) → CH4 (g)	Δ_rG°(1165 K) = 37.521 ± 0.068 kJ/mol	Smith 1946, note COf, 3rd Law
2.5	2323.8	CH2 (g, triplet) → CH (g) + H (g)	Δ_rH°(0 K) = 417.85 ± 0.35 kJ/mol	Csaszar 2003
2.3	2296.1	CH3 (g) → [CH2]+ (g) + H (g)	Δ_rH°(0 K) = 15.120 ± 0.006 eV	Litorja 1998
1.8	2298.8	CH3 (g) → CH2 (g, triplet) + H (g)	Δ_rH°(0 K) = 457.05 ± 0.56 kJ/mol	Harding 2008
1.7	2280.9	CH2 (g, triplet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 752.45 ± 0.56 kJ/mol	Harding 2008
1.5	2298.4	CH3 (g) → CH2 (g, triplet) + H (g)	Δ_rH°(0 K) = 109.22 ± 0.15 kcal/mol	Karton 2008
1.4	2323.12	CH2 (g, triplet) → CH (g) + H (g)	Δ_rH°(0 K) = 99.75 ± 0.08 (×1.384) kcal/mol	Feller 2014
1.4	2281.1	CH2 (g, triplet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 753.03 ± 0.62 kJ/mol	Csaszar 2003
1.3	2280.5	CH2 (g, triplet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 179.86 ± 0.15 kcal/mol	Karton 2008
1.3	2303.1	[CH2]- (g) → C- (g) + 2 H (g)	Δ_rH°(0 K) = 165.69 ± 0.12 kcal/mol	Feller 2016, note unc2
1.2	2283.9	CH2 (g, singlet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 170.98 ± 0.11 (×1.354) kcal/mol	Feller 2014
1.2	2309.12	CH (g) → C (g) + H (g)	Δ_rH°(0 K) = 80.01 ± 0.04 kcal/mol	Feller 2014
1.2	2298.6	CH3 (g) → CH2 (g, triplet) + H (g)	Δ_rH°(0 K) = 457.05 ± 0.70 kJ/mol	Harding 2008
1.1	2280.7	CH2 (g, triplet) → C (g) + 2 H (g)	Δ_rH°(0 K) = 752.43 ± 0.70 kJ/mol	Harding 2008
1.1	2827.1	CH3OH (g) → CH2 (g, triplet) + H2O (g)	Δ_rH°(0 K) = 81.77 ± 0.17 kcal/mol	Nguyen 2015a
1.0	2298.7	CH3 (g) → CH2 (g, triplet) + H (g)	Δ_rH°(0 K) = 457.04 ± 0.74 kJ/mol	Harding 2008

Top 10 species with enthalpies of formation correlated to the Δ_fH° of [CH2]+ (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
93.7	Methylene	CH2 (g, triplet)	391.054	391.600	± 0.096	kJ/mol	14.02658 ± 0.00081	2465-56-7*1
93.7	Methylene	CH2 (g)	391.054	391.600	± 0.096	kJ/mol	14.02658 ± 0.00081	2465-56-7*0
81.7	Methylene	CH2 (g, singlet)	428.71	429.13	± 0.11	kJ/mol	14.02658 ± 0.00081	2465-56-7*2
79.8	Ketene	CH2CO (g, ortho singlet)	-45.24	-48.42	± 0.11	kJ/mol	42.0367 ± 0.0016	463-51-4*22
79.8	Ketene	CH2CO (g, para singlet)	-45.36	-48.42	± 0.11	kJ/mol	42.0367 ± 0.0016	463-51-4*21
79.8	Ketene	CH2CO (g)	-45.36	-48.42	± 0.11	kJ/mol	42.0367 ± 0.0016	463-51-4*0
79.8	Ketene	CH2CO (g, singlet)	-45.36	-48.42	± 0.11	kJ/mol	42.0367 ± 0.0016	463-51-4*2
79.6	Ketene cation	[CH2CO]+ (g)	882.21	879.04	± 0.11	kJ/mol	42.0361 ± 0.0016	64999-16-2*0
41.8	Methylene anion	[CH2]- (g)	328.16	328.59	± 0.18	kJ/mol	14.02713 ± 0.00081	50928-07-9*0
36.2	Carbon	C (g)	711.404	716.889	± 0.044	kJ/mol	12.01070 ± 0.00080	7440-44-0*0

Most Influential reactions involving [CH2]+ (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
0.984	2284.1	CH2 (g, triplet) → [CH2]+ (g)	Δ_rH°(0 K) = 83772 ± 3 cm-1	Willitsch 2002, Willitsch 2003
0.353	3159.5	CH3CCH3 (g, singlet) + [CH2]+ (g) → [CH3CCH3]+ (g) + CH2 (g, singlet)	Δ_rH°(0 K) = -2.295 ± 0.027 eV	Ruscic W1RO
0.107	3159.2	CH3CCH3 (g, singlet) + [CH2]+ (g) → [CH3CCH3]+ (g) + CH2 (g, singlet)	Δ_rH°(0 K) = -2.315 ± 0.049 eV	Ruscic G4
0.102	3159.4	CH3CCH3 (g, singlet) + [CH2]+ (g) → [CH3CCH3]+ (g) + CH2 (g, singlet)	Δ_rH°(0 K) = -2.318 ± 0.050 eV	Ruscic CBS-n
0.067	3159.1	CH3CCH3 (g, singlet) + [CH2]+ (g) → [CH3CCH3]+ (g) + CH2 (g, singlet)	Δ_rH°(0 K) = -2.282 ± 0.062 eV	Ruscic G3X
0.059	3159.3	CH3CCH3 (g, singlet) + [CH2]+ (g) → [CH3CCH3]+ (g) + CH2 (g, singlet)	Δ_rH°(0 K) = -2.289 ± 0.066 eV	Ruscic CBS-n
0.031	2296.1	CH3 (g) → [CH2]+ (g) + H (g)	Δ_rH°(0 K) = 15.120 ± 0.006 eV	Litorja 1998
0.006	4098.2	CH2CO (g) → [CH2]+ (g) + CO (g)	Δ_rH°(0 K) = 13.729 ± 0.008 eV	McCulloh 1976a
0.003	2284.2	CH2 (g, triplet) → [CH2]+ (g)	Δ_rH°(0 K) = 10.385 ± 0.006 eV	Coudert 2018
0.002	4098.1	CH2CO (g) → [CH2]+ (g) + CO (g)	Δ_rH°(0 K) = 13.743 ± 0.005 (×2.65) eV	Ruscic 1999
0.001	2284.4	CH2 (g, triplet) → [CH2]+ (g)	Δ_rH°(0 K) = 10.396 ± 0.003 (×3.221) eV	Herzberg 1959, Herzberg 1961a, Herzberg 1971
0.001	2285.11	CH2 (g, triplet) → [CH2]+ (g)	Δ_rH°(0 K) = 10.382 ± 0.010 eV	Lau 2005
0.001	2284.3	CH2 (g, triplet) → [CH2]+ (g)	Δ_rH°(0 K) = 10.393 ± 0.011 eV	Litorja 1998
0.000	2296.2	CH3 (g) → [CH2]+ (g) + H (g)	Δ_rH°(0 K) = 15.09 ± 0.03 (×1.189) eV	Chupka 1968a
0.000	2296.3	CH3 (g) → [CH2]+ (g) + H (g)	Δ_rH°(0 K) = 15.121 ± 0.040 eV	Ruscic W1RO
0.000	2288.8	[CH2]+ (g) → C (g) + 2 H (g)	Δ_rH°(0 K) = -59.60 ± 1 kcal/mol	Matus 2006
0.000	4098.10	CH2CO (g) → [CH2]+ (g) + CO (g)	Δ_rH°(0 K) = 13.720 ± 0.040 eV	Ruscic W1RO
0.000	2288.9	[CH2]+ (g) → C (g) + 2 H (g)	Δ_rH°(0 K) = -59.17 ± 1.50 kcal/mol	Ruscic W1RO
0.000	2288.7	[CH2]+ (g) → C (g) + 2 H (g)	Δ_rH°(0 K) = -59.73 ± 1.60 kcal/mol	Ruscic CBS-n
0.000	2288.4	[CH2]+ (g) → C (g) + 2 H (g)	Δ_rH°(0 K) = -59.07 ± 1.60 kcal/mol	Ruscic G4

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.