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Thermokinetic study of the isomerization of isocyanic acid

Nguyen Huu Tho

Abstract


In this work, the detailed study on the mechanism, kinetics and thermochemistry of the isomerization of isocyanic is described. Theoretical study was carried out by ab initio molecular orbital theory based on the CCSD(T) and B3LYP/6-311++G(3df,2p) methods in conjunction with statistical theoretical kinetic Rice-Ramsperger-Kassel-Marcus (RRKM) Master equation calculations. The potential energy surface (PES) for the isomeric reactions was also examined. At 760 Torr pressure, temperature dependent rate constants of the isomeric reactions HNCO ® HOCN (a), HNCO  ® H(CNO) (b) and HNCO ® H(NCO) (c) were: k(T) (a) = 10-37.70.T13.09.e-93.30kcal/mol/RT, k(T) (b)  = 103.46.T1.76.e-93.98kcal/mol/RT, k(T) (c) = 10-28.50.T10.61.e-91.16kcal/mol/RT respectively. Calculated results show that the isomerization of isocyanic acid may take place via three mechanisms and have very high barriers; all rate constants of them are very small in the temperature range from 300 to 2000 K.

Keywords. Potential energy surface, isocyanic acid, density function theory, isomerization.

Keywords


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

References


M. Mladenovic, M. Elhiyani, M. Lewerenz, Marius. Electric and magnetic properties of the four most stable CHNO isomers from ab initio CCSD(T) studies, J. Chem. Phys., 131, 034302 (2009).

J.S. Zhang, M. Dulligan, C. Wittig. HNCO + h.nu.(193.3 nm).fwdarw. H + NCO: Center-of-Mass Translational Energy Distribution, Reaction Dynamics, and D0(H-NCO), J. Phys. Chem., 99, 7446-7452 (1995).

J. M. Roberts, P. R. Veres, A. K. Cochran, C. Warneke, I. R. Burling, R. J. Yokelson, B. Lerner, J. B. Gilman, W. C. Kuster, R. Fall and Joost de Gouw. Isocyanic acid in the atmosphere and its possible link to smoke-related health effects, Proceedings of the National Academy of Sciences of the United States of American, 108(22), 8966-8971 (2011).

A. Bodi, P. Hemberger, T. Gerber, A robust link between the thermochemistry of urea and isocyanic acid by dissociative photoionization, J. Chem. Thermodynamics, 58, 292-299 (2013).

A. L. East, C. S. Johnson and W. D. Allen,

Characterization of the X 1A’ state of isocyanic acid, J. Chem. Phys., 98(2), 1299-1328 (1993).

Yan Li, Hui-ling Liu, Yan-bo Sun, Zhuo Li, Xu-ri Huang, Chia-chung Sun. Radical reaction HCNO + 3NH: a mechanistic study, Theor. Chem. Acc., 124, 123-137 (2009).

D. Poppinger, L. Radom, and J. A. Pople. Theoretical Study of the CHNO Isomers, J. Am. Chem. Soc., 99(24), 7806-7816 (1977).

M. Mladenovic, M. Lewerenz, M. C. McCarthy, P. Thaddeus. Isofulminic acid, HONC: Ab initio theory and microwave spectroscopy, J. Chem. Phys., 131, 174308 (2009).

Donghui Quan, Eric Herbst, Yoshihiro Osamura, and Evelyne Roueff. Gas-grain Modeling of Isocyanic Acid (HNCO), Cyanic Acid (HOCN), Fulminic Acid (HCNO), and Isofulminic Acid (HONC) in Assorted Interstellar Environments, The Astrophysical Journal, 725, 2101-2109 (2010).

M. Mladenovic and M. Lewerenz. Equilibrium structure and energetics of CHNO isomers: steps towards ab initio rovibrational spectra of quasi-linear molecules, Chemical Physics, 343, 129-140 (2008).

J. L. Collister, H. O. Pritchard. The Thermal Isomerisation of Methyl Isocyanide in the Temperature Range 120-320 oC, Can. J. Chem., 54, 2380-2384 (1976).

F. W. Schneider, B. S. Rabinovitch. The thermal unimolecular isomerization of methyl isocyanide. Fall-off behavior, J. Am. Chem. Soc., 20, 4215-4230 (1962).

M. E. Clarkson, H. O. Pritchard. Partial state-to-state calculation of the infinite-pressure rate constant for the isomerisation of methyl isocyanide, J. Chem. Phys., 117, 29-37 (1987).

M. C. Lin, Y. He, F. Melius. Communication: implications of the HCN → HNC process to high-temperature nitrogen-containing fuel chemistry, Int. J. Chem. Kinet., 24, 1103-1107 (1992).

M. J. Frisch et al. Gaussian 03, revision E.01, Gaussian Inc.: Wallingford, CT (2004).

C. J. Cramer. Essentials of Computational Chemistry: Theories and Models, John Wiley & Sons Ltd, (2004).

T. Baer, W. L. Hase. Unimolecular Reaction Dynamics: Theory and Experiments, Oxford, New York (1996).

V. Mokrushin, V. Bedanov, W. Tsang, M. R. Zachariah, V. D. Knyazev, W. S. McGivern. ChemRate, version 1.5.8, in: Technology, N.I.o.S.a. (Ed.), Gaithersburg, MD (2011).

L. V. Moskaleva and M. C. Lin. The Spin-Conserved Reaction CH + N2 → H + NCN: A Major Pathway to Prompt NO Studied by Quantum-Statistical Theory Calculations and Kinetic Modeling of Rate Constant, Proc. Combust. Inst., 28, 2393-2401 (2000).

M. S. Schuurman, S. R. Muir, W. D. Allen, and H. F. Schaefer. Toward subchemical accuracy in computational thermochemistry: focal point analysis of the heat of formation of NCO and [H,N,C,O] isomers, J. Chem. Phys., 120, 11586-11599 (2004).

J. K. Yu, S. Wang, H. Zhang, H. X. Zhang, D. J. Ding, C. C. Sun. Theoretical study on the decomposition mechanism of the HCNO molecules, Acta Chim. Sin., 66, 597-602 (2008).

S. S. Brown, H. L. Berghout, and F. F. Crim. The HNCO heat of formation and the N–H and C–N bond enthalpies from initial state selected photodissociation, J. Chem. Phys., 105, 8103-8110 (1996).

M. Zyrianov, T. Droz-Georget, A. Sanov, and H. Reisler. Competitive photodissociation channels in jet-cooled HNCO: Thermochemistry and near-threshold predissociation, J. Chem. Phys., 105(18), 8111-8116 (1996).

B. Ruscic. Updated Active Thermochemical Tables (ATcT) values based on ver. 1.112 of the Thermochemical Network (2012); available at ATcT.anl.gov; Last update

/Mar/(2015).


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