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]

Isocyanic acid

Formula: HNCO (g)

CAS RN: 75-13-8

ATcT ID: 75-13-8*0

SMILES: N=C=O

InChI: InChI=1S/CHNO/c2-1-3/h2H

InChIKey: OWIKHYCFFJSOEH-UHFFFAOYSA-N

Hills Formula: C1H1N1O1

2D Image:

Aliases: Isocyanic acid; Carbimide; Hydrogen isocyanate; Methenamide; HNCO; OCNH; HN=C=O

Relative Molecular Mass: 43.02478 ± 0.00086

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
-115.96	-118.95	± 0.28	kJ/mol

3D Image of HNCO (g)

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

The 20 contributors listed below account only for 68.4% of the provenance of Δ_fH° of HNCO (g).
A total of 106 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
11.4	4531.7	HNCO (g) → NH (g) + CO (g)	Δ_rH°(0 K) = 30150 ± 60 cm-1	Zyrianov 1996
6.1	4567.4	NCO (g) → N (g) + CO (g)	Δ_rH°(0 K) = 55.0 ± 0.2 kcal/mol	Cyr 1992, est unc
4.8	4533.8	HNCO (g) + H2O (g) → CO2 (g) + NH3 (g)	Δ_rH°(0 K) = -18.46 ± 0.3 kcal/mol	Schuurman 2004, est unc
4.8	6799.1	NH2C(O)NH2 (g) → [NH3]+ (g) + HNCO (g)	Δ_rH°(0 K) = 10.838 ± 0.010 eV	Bodi 2013
4.7	4525.11	HNCO (g) → H (g) + N (g) + C (g) + O (g)	Δ_rH°(0 K) = 420.73 ± 0.30 kcal/mol	Karton 2011
4.6	4531.8	HNCO (g) → NH (g) + CO (g)	Δ_rH°(0 K) = 30075 ± 25 (×3.748) cm-1	Sanov 1997
3.7	4534.6	HNCO (g) + O (g) → NH (g) + CO2 (g)	Δ_rH°(0 K) = -39.33 ± 0.3 kcal/mol	Schuurman 2004, est unc
3.6	4574.1	HNCO (g) → NCO (g) + H (g)	Δ_rH°(0 K) = 38370 ± 30 cm-1	Zyrianov 1996
3.4	4531.9	HNCO (g) → NH (g) + CO (g)	Δ_rH°(0 K) = 30060 ± 25 (×4.362) cm-1	Zyrianov 1999
3.3	4530.1	NH3 (g) + CH4 (g) + H2O (g) → HNCO (g) + 4 H2 (g)	Δ_rH°(0 K) = 228.35 ± 1.50 kJ/mol	Klippenstein 2017
2.7	4572.1	NCO (g) + O (g) → CO2 (g) + N (g)	Δ_rH°(0 K) = -70.89 ± 0.3 kcal/mol	Schuurman 2004, est unc
1.9	4536.11	HOCN (g) → H (g) + N (g) + C (g) + O (g)	Δ_rH°(0 K) = 395.98 ± 0.30 kcal/mol	Karton 2011
1.9	4573.1	NCO (g) + OH (g) → CO2 (g) + NH (g)	Δ_rH°(0 K) = -47.42 ± 0.3 kcal/mol	Schuurman 2004, est unc
1.9	4550.11	HONC (g) → H (g) + N (g) + C (g) + O (g)	Δ_rH°(0 K) = 336.83 ± 0.30 kcal/mol	Karton 2011
1.8	4531.6	HNCO (g) → NH (g) + CO (g)	Δ_rH°(0 K) = 30022 ± 100 (×1.477) cm-1	Brown 1996, Brazier 1986
1.8	4543.11	HCNO (g) → H (g) + N (g) + C (g) + O (g)	Δ_rH°(0 K) = 352.25 ± 0.30 kcal/mol	Karton 2011
1.3	4541.1	NH3 (g) + CH4 (g) + H2O (g) → HOCN (g) + 4 H2 (g)	Δ_rH°(0 K) = 331.66 ± 1.50 kJ/mol	Klippenstein 2017
1.3	4553.1	NH3 (g) + CH4 (g) + H2O (g) → HONC (g) + 4 H2 (g)	Δ_rH°(0 K) = 579.20 ± 1.50 kJ/mol	Klippenstein 2017
1.3	4525.10	HNCO (g) → H (g) + N (g) + C (g) + O (g)	Δ_rH°(0 K) = 420.71 ± 0.56 kcal/mol	Karton 2011
1.0	6801.3	NH2C(O)NH2 (cr,l) → NH2C(O)NH2 (g)	Δ_rH°(351.3 K) = 96.9 ± 0.6 kJ/mol	de Wit 1983a, est unc

Top 10 species with enthalpies of formation correlated to the Δ_fH° of HNCO (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
64.1	Cyanooxidanyl	NCO (g)	126.94	127.41	± 0.33	kJ/mol	42.01684 ± 0.00086	22400-26-6*0
55.8	Isocyanic acid cation	[HNCO]+ (g)	1002.99	1000.32	± 0.49	kJ/mol	43.02423 ± 0.00086	444010-28-0*0
42.4	Isofulminic acid	HONC (g)	235.24	233.53	± 0.43	kJ/mol	43.02478 ± 0.00086	506-85-4*0
42.1	Cyanic acid	HOCN (g)	-12.33	-15.04	± 0.43	kJ/mol	43.02478 ± 0.00086	420-05-3*0
41.0	Cyanate	[NCO]- (g)	-221.18	-221.40	± 0.53	kJ/mol	42.01739 ± 0.00086	661-20-1*0
40.3	Fulminic acid	HCNO (g)	170.71	169.26	± 0.44	kJ/mol	43.02478 ± 0.00086	51060-05-0*0
35.3	Cyanato cation	[NCO]+ (g)	1261.50	1262.00	± 0.58	kJ/mol	42.01629 ± 0.00086	17247-99-3*0
21.4	Imidogen	NH (g)	358.74	358.79	± 0.16	kJ/mol	15.014680 ± 0.000099	13774-92-0*0
21.4	Imidogen	NH (g, triplet)	358.74	358.79	± 0.16	kJ/mol	15.014680 ± 0.000099	13774-92-0*1
21.4	Imidogen anion	[NH]- (g)	322.62	322.67	± 0.16	kJ/mol	15.015229 ± 0.000099	23841-33-0*0

Most Influential reactions involving HNCO (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
0.694	4526.1	HNCO (g) → [HNCO]+ (g)	Δ_rH°(0 K) = 11.595 ± 0.005 eV	Ruscic 1994b
0.525	4574.1	HNCO (g) → NCO (g) + H (g)	Δ_rH°(0 K) = 38370 ± 30 cm-1	Zyrianov 1996
0.381	4527.5	[HNCO]- (g) → HNCO (g)	Δ_rH°(0 K) = -0.646 ± 0.050 eV	Ruscic W1RO
0.256	4527.2	[HNCO]- (g) → HNCO (g)	Δ_rH°(0 K) = -0.605 ± 0.061 eV	Ruscic G4
0.228	6799.1	NH2C(O)NH2 (g) → [NH3]+ (g) + HNCO (g)	Δ_rH°(0 K) = 10.838 ± 0.010 eV	Bodi 2013
0.173	4526.3	HNCO (g) → [HNCO]+ (g)	Δ_rH°(0 K) = 11.60 ± 0.01 eV	Rowland 1968, est unc
0.162	4531.7	HNCO (g) → NH (g) + CO (g)	Δ_rH°(0 K) = 30150 ± 60 cm-1	Zyrianov 1996
0.155	4547.11	HCNO (g) → HNCO (g)	Δ_rH°(0 K) = -68.48 ± 0.25 kcal/mol	Karton 2011
0.146	4576.8	HNCO (g) → [NCO]- (g) + H+ (g)	Δ_rH°(0 K) = 340.17 ± 0.3 kcal/mol	Schuurman 2004, est unc
0.146	4542.11	HOCN (g) → HNCO (g)	Δ_rH°(0 K) = -24.75 ± 0.25 kcal/mol	Karton 2011
0.143	4554.11	HONC (g) → HNCO (g)	Δ_rH°(0 K) = -83.90 ± 0.25 kcal/mol	Karton 2011
0.132	4527.1	[HNCO]- (g) → HNCO (g)	Δ_rH°(0 K) = -0.667 ± 0.085 eV	Ruscic G3X
0.117	4527.4	[HNCO]- (g) → HNCO (g)	Δ_rH°(0 K) = -0.667 ± 0.090 eV	Ruscic CBS-n
0.112	4527.3	[HNCO]- (g) → HNCO (g)	Δ_rH°(0 K) = -0.634 ± 0.092 eV	Ruscic CBS-n
0.101	4542.13	HOCN (g) → HNCO (g)	Δ_rH°(0 K) = -24.58 ± 0.3 kcal/mol	Schuurman 2004, est unc
0.099	4554.13	HONC (g) → HNCO (g)	Δ_rH°(0 K) = -83.97 ± 0.3 kcal/mol	Schuurman 2004, est unc
0.071	4542.14	HOCN (g) → HNCO (g)	Δ_rH°(0 K) = -103.31 ± 1.50 kJ/mol	Klippenstein 2017
0.070	6836.5	[NH2CO]+ (g) + NH3 (g) → HNCO (g) + [NH4]+ (g)	Δ_rH°(0 K) = -30.92 ± 0.8 kcal/mol	Ruscic W1RO
0.070	6837.5	[NH2CO]+ (g) + H2O (g) → HNCO (g) + [H3O]+ (g)	Δ_rH°(0 K) = 8.16 ± 0.8 kcal/mol	Ruscic W1RO
0.069	4554.14	HONC (g) → HNCO (g)	Δ_rH°(0 K) = -350.85 ± 1.50 kJ/mol	Klippenstein 2017

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.