The Heterolytic Dissociation of Neutral and Protonated Nitrous Acid
Abstract
Structures, energies, and vibrational properties of HONO and H2ONO+ and of their dissociation products NO+, HO-, and water were studied with the DFT methods B3LYP and MPW1PW91 and with the configurational methods MP2, QCISD, QCISD(T), CCSD, and CCSD(T) in conjunction with the basis sets 6-31G**, 6-31++G**, 6-311G**, 6-311++G**, 6-311++G(2d,p), and 6-311++G(2df,2p). The multilevel methods G1, G2, G2(MP2), G3, and CBS-Q also were employed. The experimental trans-preference energy ΔE0pref = 1.555 ± 0.167 kJ/mol of HONO is reproduced well at all levels with good basis sets. On the basis of the CCSD(T)/6-311++G(2df,2p) energies and the thermochemical data, our best computed estimate is ΔE0pref = 1.83 kJ/mol. The experimental heterolytic bond dissociation energy of ΔE0 = 917.80 kJ/mol for HONO and of ΔH298 = 77.3 kJ/mol for H2ONO+ are more difficult to reproduce. At the CCSD(T)/6-311++G-(2df,2p) level, we found ΔE0 = 925.5 kJ/mol and ΔH298 = 81.6 kJ/mol. The MP2, QCISD, and CCSD methods yield reasonable results when used with larger basis sets. The G2 method as well as the G2-mimics G2(MP2) and G3 also yield reasonable results. The density functional methods performed significantly worse than the MP2(full), QCISD, and CCSD methods. The structures of E- and Z-HONO, of the electrostatic complex H2ONO+, and of the dissociation products also are discussed. Effects of aqueous solvation were examined with the IPCM method at DFT, MP2, and QCISD levels with the 6-311++G(2df,2p) basis set. Only the proton-catalyzed heterolysis plays a role at ambient temperatures, and our results suggests different mechanisms for NO+ formation in gas-phase and in solution.
Recommended Citation
H. Wu and R. Glaser, "The Heterolytic Dissociation of Neutral and Protonated Nitrous Acid," Journal of Physical Chemistry A, vol. 107, no. 50, pp. 11112 - 11119, American Chemical Society (ACS), Nov 2003.
The definitive version is available at https://doi.org/10.1021/jp035149m
Department(s)
Chemistry
Keywords and Phrases
Catalysis; Chemical bonds; Dissociation; Electrostatics; Ionization; Molecular vibrations; Probability density function; Protons; Electron affinity; Heterolysis; Thermochemical reactions; Organic acids
International Standard Serial Number (ISSN)
1089-5639; 1520-5215
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2003 American Chemical Society (ACS), All rights reserved.
Publication Date
01 Nov 2003
