DFT and CASPT2 study of two thermal reactions of nitromethane: C–N bond cleavage and nitro-to-nitrite isomerization. An example of the inverse symmetry breaking deficiency in density functional calculations of an homolytic dissociation |
| |
Authors: | J. F. Arenas, S. P. Centeno, I. L pez-Toc n, D. Pel ez,J. Soto |
| |
Affiliation: | Department of Physical Chemistry, Faculty of Sciences, University of Málaga, E-29071-, Málaga, Spain |
| |
Abstract: | The reaction paths of nitromethane leading to the dissociation products or isomerization to methyl nitrite have been computationally investigated at the CAS-SCF and DFT levels of theory. Additionally, the CAS-SCF wave functions were used as reference in a second-order perturbation treatment, CASPT2, in order to obtain a good estimate for the activation energy of each reaction path. Both methods predict the isomerization as a concerted reaction. However, the behavior of the two approximations with respect to dissociation is rather different; while CASPT2 predicts a barrier height of (≈59 kcal/mol) in good accordance with the experimental activation energy (59.0 kcal/mol), B3-LYP/6-31G* calculations overestimate the barrier for more than 30 kcal/mol. The DFT prediction of the dissociation channel exhibits inverse symmetry breaking, dissociating to the unphysical absurd CH3δ+ plus NO2δ−. |
| |
Keywords: | Nitromethane Methyl nitrite CAS-SCF CASPT2 Density functional theory |
本文献已被 ScienceDirect 等数据库收录! |
|