Selected ATcT [1, 2] enthalpy of formation based on version 1.176 of the Thermochemical Network [3]

This version of ATcT results[3] was generated by additional expansion of version 1.172 to include species related to Criegee intermediates that are involved in several ongoing studies[4].

Hydrogen cyanide

Formula: HCN (g)

CAS RN: 74-90-8

ATcT ID: 74-90-8*0

SMILES: C#N

SMILES: [CH]#N

InChI: InChI=1S/CHN/c1-2/h1H

InChIKey: LELOWRISYMNNSU-UHFFFAOYSA-N

SMILES: [H+].[C-]#N

InChI: InChI=1S/CN/c1-2/q-1/p+1

InChIKey: XFXPMWWXUTWYJX-UHFFFAOYSA-O

Hills Formula: C1H1N1

2D Image:

Aliases: HCN; Hydrogen cyanide; Hydrocyanic acid; Carbon hydride nitride; Formic anammonide; Formonitrile; Nitrilomethane; Prussic Acid; Zootic acid; AC; Cyclon; Cyclon B; Evercyn; NA 1051; RCRA P063; UN 1051; UN 1613; UN 1614; NCH

Relative Molecular Mass: 27.02538 ± 0.00081

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
129.677	129.292	± 0.087	kJ/mol

3D Image of HCN (g)

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Top contributors to the provenance of Δ_fH° of HCN (g)

The 20 contributors listed below account only for 37.6% of the provenance of Δ_fH° of HCN (g).
A total of 296 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
4.5	2766.11	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -30.43 ± 0.56 kJ/mol	Harding 2008
2.9	2766.9	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -30.29 ± 0.70 kJ/mol	Harding 2008
2.9	2766.8	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -30.73 ± 0.70 kJ/mol	Tajti 2004, est unc
2.6	2766.10	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -30.47 ± 0.74 kJ/mol	Harding 2008
2.1	2772.10	CO (g) + NH3 (g) → HCN (g) + H2O (g)	Δ_rH°(0 K) = 42.67 ± 0.56 kJ/mol	Harding 2008
2.0	2766.12	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -30.22 ± 0.84 kJ/mol	Harding 2008
2.0	2766.14	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -30.37 ± 0.84 kJ/mol	Harding 2008
1.8	2764.10	2 CO (g) + NH3 (g) → HCN (g) + CO2 (g) + H2 (g)	Δ_rH°(0 K) = 2.37 ± 0.56 kJ/mol	Harding 2008
1.7	2770.10	HCN (g) + N (g) → N2 (g) + H (g) + C (g)	Δ_rH°(0 K) = 327.05 ± 0.56 kJ/mol	Harding 2008
1.7	2286.9	C (graphite) + CO2 (g) → 2 CO (g)	Δ_rG°(1165 K) = -33.545 ± 0.058 kJ/mol	Smith 1946, note COf, 3rd Law
1.6	2754.4	HCN (g) → H (g) + C (g) + N (g)	Δ_rH°(0 K) = 1268.59 ± 0.56 kJ/mol	Harding 2008
1.3	2772.8	CO (g) + NH3 (g) → HCN (g) + H2O (g)	Δ_rH°(0 K) = 42.74 ± 0.70 kJ/mol	Harding 2008
1.3	2772.7	CO (g) + NH3 (g) → HCN (g) + H2O (g)	Δ_rH°(0 K) = 42.89 ± 0.70 kJ/mol	Tajti 2004, est unc
1.3	2766.7	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -7.42 ± 0.25 kcal/mol	Martin 2006, Karton 2006
1.3	2766.5	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -7.43 ± 0.25 kcal/mol	Martin 2006, Karton 2006
1.3	2766.6	2 HCN (g) → HCCH (g) + N2 (g)	Δ_rH°(0 K) = -7.41 ± 0.25 kcal/mol	Martin 2006
1.2	2772.9	CO (g) + NH3 (g) → HCN (g) + H2O (g)	Δ_rH°(0 K) = 42.94 ± 0.74 kJ/mol	Harding 2008
1.1	2764.7	2 CO (g) + NH3 (g) → HCN (g) + CO2 (g) + H2 (g)	Δ_rH°(0 K) = 2.39 ± 0.70 kJ/mol	Tajti 2004, est unc
1.1	2764.8	2 CO (g) + NH3 (g) → HCN (g) + CO2 (g) + H2 (g)	Δ_rH°(0 K) = 2.05 ± 0.70 kJ/mol	Harding 2008
1.1	2770.8	HCN (g) + N (g) → N2 (g) + H (g) + C (g)	Δ_rH°(0 K) = 327.03 ± 0.70 kJ/mol	Harding 2008

Top 10 species with enthalpies of formation correlated to the Δ_fH° of HCN (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
99.8	Hydrogen cyanide anion	[HCN]- (g)	129.525	129.047	± 0.087	kJ/mol	27.02593 ± 0.00081	12334-27-9*0
94.9	Cyanide	[CN]- (g)	63.972	67.258	± 0.091	kJ/mol	26.01799 ± 0.00080	57-12-5*0
47.9	Nitrilomethyl	CN (g)	436.72	440.01	± 0.14	kJ/mol	26.01744 ± 0.00080	2074-87-5*0
46.2	Acetylene	HCCH (g)	228.86	228.30	± 0.12	kJ/mol	26.0373 ± 0.0016	74-86-2*0
46.2	Acetylene cation	[HCCH]+ (g)	1328.88	1328.21	± 0.12	kJ/mol	26.0367 ± 0.0016	25641-79-6*0
43.7	Hydrogen cyanide cation	[HCN]+ (g)	1442.53	1442.06	± 0.20	kJ/mol	27.02483 ± 0.00081	12601-62-6*0
36.4	Ethynylium	[CCH]+ (g)	1687.62	1690.95	± 0.15	kJ/mol	25.0288 ± 0.0016	16456-59-0*0
33.1	Carbon	C (g)	711.381	716.866	± 0.039	kJ/mol	12.01070 ± 0.00080	7440-44-0*0
33.1	Carbon	C (g, triplet)	711.381	716.866	± 0.039	kJ/mol	12.01070 ± 0.00080	7440-44-0*1
33.1	Carbon cation	C+ (g)	1797.834	1803.432	± 0.039	kJ/mol	12.01015 ± 0.00080	14067-05-1*0

Most Influential reactions involving HCN (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
0.844	2755.4	HCN (g) → [HCN]+ (g)	Δ_rH°(0 K) = 13.607 ± 0.002 eV	Fridh 1975
0.731	2756.2	[HCN]- (g) → HCN (g)	Δ_rH°(0 K) = 0.001565 ± 0.00005 eV	Ard 2009, est unc
0.632	2864.3	HCN (g) → H+ (g) + [CN]- (g)	Δ_rH°(0 K) = 122246 ± 3 cm-1	Suits 2006, Hu 2005
0.405	2763.1	HCN (g) + [CH2OH]+ (g) → [HCNH]+ (g) + CH2O (g)	Δ_rG°(300 K) = 0.5 ± 0.5 kcal/mol	Wolf 1977, est unc
0.355	2864.2	HCN (g) → H+ (g) + [CN]- (g)	Δ_rH°(0 K) = 122244 ± 4 cm-1	Hu 2006
0.258	2782.10	HCN (g) → HNC (g)	Δ_rH°(0 K) = 5236 ± 50 cm-1	Nguyen 2015c
0.191	8606.1	SiH4 (g) + CN (g) → SiH3 (g) + HCN (g)	Δ_rH°(0 K) = -34.60 ± 0.30 kcal/mol	Burke 2021
0.182	2756.4	[HCN]- (g) → HCN (g)	Δ_rH°(0 K) = 0.0015601 ± 0.0001 eV	Garrett 2010, est unc
0.179	8422.6	NCNNN (g) + H2 (g) → HNNN (g) + HCN (g)	Δ_rH°(0 K) = -18.3 ± 1.0 kcal/mol	Pfeifle 2017, est unc
0.162	2893.5	ClCN (g) + H (g) → HCN (g) + Cl (g)	Δ_rH°(0 K) = -24.36 ± 0.25 kcal/mol	Karton 2011
0.160	5687.4	NCN (g) + H (g) → HCN (g) + N (g)	Δ_rH°(0 K) = -67.10 ± 1.0 kJ/mol	Harding 2018
0.124	8422.5	NCNNN (g) + H2 (g) → HNNN (g) + HCN (g)	Δ_rH°(0 K) = -18.88 ± 1.2 kcal/mol	Ruscic W1RO
0.113	5750.2	HCNN (g, doublet) → HCN (g) + N (g, quartet)	Δ_rH°(0 K) = 133.10 ± 2.0 kJ/mol	Klippenstein 2017
0.106	8422.4	NCNNN (g) + H2 (g) → HNNN (g) + HCN (g)	Δ_rH°(0 K) = -17.87 ± 1.3 kcal/mol	Ruscic CBS-n
0.106	8422.2	NCNNN (g) + H2 (g) → HNNN (g) + HCN (g)	Δ_rH°(0 K) = -17.78 ± 1.3 kcal/mol	Ruscic G4
0.101	7417.9	N(CHCHCHCHCH) (g) → [CH2C(CHCH)]+ (g) + HCN (g)	Δ_rH°(0 K) = 11.973 ± 0.040 eV	Ruscic W1RO
0.099	2823.8	CH3NC (g) + HCN (g) → CH3CN (g) + HNC (g)	Δ_rH°(0 K) = -40.97 ± 1.5 kJ/mol	Klippenstein 2017
0.099	5717.2	HNCN (g, doublet) → HCN (g) + N (g, quartet)	Δ_rH°(0 K) = 277.37 ± 2.0 kJ/mol	Klippenstein 2017
0.098	2774.12	2 HCN (g) → NCCN (g) + H2 (g)	Δ_rH°(0 K) = 11.51 ± 0.30 kcal/mol	Martin 2006, Karton 2006
0.098	2919.4	BrCN (g) + CH4 (g) → HCN (g) + CH3Br (g)	Δ_rH°(0 K) = -1.87 ± 1.0 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. 1.176 of the Thermochemical Network (2024); available at ATcT.anl.gov
4		T. L. Nguyen et al, ongoing studies (2024)
5		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]
6		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 [5] and Ruscic and Bross[6]).
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.