Thermokinetic study of the formation of carbon monoxide in the dimerization of isocyanic acid

Nguyen Huu Tho, Nguyen Huu Tri



The mechanism of the dimerization of HNCO was investigated using the ab initio method. The barrier heights, reaction energies and geometrical parameters of the reactants, products, intermediates and transition state were studied. It was found that there are possibly three reaction channels. The B3LYP 6-311++G(3df,2p)//CCSD(T) 6-311++G(d,p) calculated barriers show that reaction of  formation of four-membered ring O=CNHNHC=O is more favorable than formations of CO2 or CO. The reaction pathway of the formation of carbon monoxide from the dimerization of isocyanic acid is a new pathway. Its rate constant is very small, k = 2.62´ 10-19 cm3/molecule/s at 2500K, 1atm, which  is about 2000 times as small as rate constant of formation CO from a bimolecular mechanism of HNCO with Ar.


Potential energy surface, isocyanic acid, density function theory, dimerization


Brown, Steven S., Berghout, H. Laine, and Crim, F. Fleming (1997), "Raman spectroscopy of the N–C–O symmetric (ν3) and antisymmetric (ν2) stretch fundamentals in HNCO", The Journal of Chemical Physics. 107(23), pp. 9764-9771.

Canneaux, Sébastien, Bohr, Frédéric, and Henon, Eric (2014), "KiSThelP: A program to predict thermodynamic properties and rate constants from quantum chemistry results", Journal of Computational Chemistry. 35(1), pp. 82-93.

East, Allan L. L., Johnson, Christopher S., and Allen, Wesley D. (1993), "Characterization of the X̃ 1A’ state of isocyanic acid", The Journal of Chemical Physics. 98(2), pp. 1299-1328.

Eckart, Carl (1930), "The Penetration of a Potential Barrier by Electrons", Physical Review. 35(11), pp. 1303-1309.

Fedoseev, G., et al. (2015), "Low-temperature surface formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues", Monthly Notices of the Royal Astronomical Society. 446(1), pp. 439-448.

Feng, Wen-Lin, Wang, Yan, and Zhang, Shao-Wen (1995), "Theoretical study of the mechanism and rate constant of the dimerization of isocyanic acid", Journal of Molecular Structure: THEOCHEM. 342, pp. 147-151.

Frisch, M. J. and Trucks, G. W. (2004), "Gaussian 03, Revision C.02", Gaussian, Inc., Wallingford CT.

G. Fischer, J. Geith, T. M. Klapötke, and B. Krumm (2002), "Synthesis, Properties and Dimerization Study of Isocyanic Acid", Z. Naturforsch. 57 b.

He, Y., et al. (1991), "The thermal reaction of HNCO at moderate temperatures", International Journal of Chemical Kinetics. 23(12), pp. 1129-1149.

Lowry, D., et al. (2016), "Marked long-term decline in ambient CO mixing ratio in SE England, 1997–2014: evidence of policy success in improving air quality", Scientific Reports. 6, p. 25661.

Lu, Lilin, et al. (2013), "An improved B3LYP method in the calculation of organic thermochemistry and reactivity", Computational and Theoretical Chemistry. 1015, pp. 64-71.

Mertens, J. D., Chang, A. Y., Hanson, R. K. and Bowman, C. T. (1989), "Reaction kinetics of NH in the shock tube pyrolysis of HNCO", Int. J. Chem. Kinet. 21, p. 19.

Miller, James A. and Bowman, Craig T. (1989), "Mechanism and modeling of nitrogen chemistry in combustion", Progress in Energy and Combustion Science. 15(4), pp. 287-338.

Okitsugu, Kajimoto, et al. (1985), "Kinetic Study of the Thermal Decomposition of Isocyanic Acid in Shock Waves", Bulletin of the Chemical Society of Japan. 58(12), pp. 3469-3474.

Omaye, Stanley T. (2002), "Metabolic modulation of carbon monoxide toxicity", Toxicology. 180(2), pp. 139-150.

Perry, R. A. and Siebers, D. L. (1986), "Rapid reduction of nitrogen oxides in exhaust gas streams", Nature. 324(6098), pp. 657-658.

Robson Wright, Margaret (2005), "Theories of Chemical Reactions", An Introduction to Chemical Kinetics, John Wiley & Sons, Ltd, pp. 99-164.

Teles, Joaquim Henrique, et al. (1989), "The CHNO Isomers", Chemische Berichte. 122(4), pp. 753-766.

Tsang, W. (1992), "Chemical Kinetic Data Base for Propellant Combustion. II. Reactions Involving CN, NCO, and HNCO", Journal of Physical and Chemical Reference Data. 21(4), pp. 753-791.

Wu, C. H., et al. (1990), "Kinetics of carbon monoxide and hydrogen-atom production from the decomposition of cyanic acid in shock waves", The Journal of Physical Chemistry. 94(8), pp. 3344-3347.

Wu, Lingyun and Wang, Rui (2005), "Carbon Monoxide: Endogenous Production, Physiological Functions, and Pharmacological Applications", Pharmacological Reviews. 57(4), p. 585.

Xiao-Hong, Li, Xiang-Ru, Liu, and Xian-Zhou, Zhang (2011), "Calculation of vibrational spectroscopic and NMR parameters of 2-Dicyanovinyl-5-(4-N,N-dimethylaminophenyl) thiophene by ab initio HF and density functional methods", Computational and Theoretical Chemistry. 969(1–3), pp. 27-34.

Young, David C. (2002), "Molecular Vibrations", Computational Chemistry, John Wiley & Sons, Inc., pp. 92-98.