A Theoretical Study of the Bifurcation Reaction of Formic Acid : Dynamics around the Intrinsic Reaction Coordinate

Takahashi Osamu

Itoh Kuniharu

Kawano Akio

Saito Ko

Journal of Molecular Structure : THEOCHEM

Transition state structures, activation energies, and the intrinsic reaction coordinate (IRC) for the two decomposition paths of formic acid are studied using Hartree-Fock and density functional theory (DFT). Formic acid decomposes via the following competing paths; to: (1) H2O+CO and to (2) H2+CO2. Experimental results which were obtained by Saito et al. have shown that the rate constant of path (2) is smaller than that of path (1) by about forty times over the experimental temperature range. On the other hand, calculated results using high level ab initio calculations such as MP4/cc-pVQZ//B3LYP/cc-pVTZ show that the activation energies of paths (1) and (2) are comparable. Detailed examinations of the mode coupling between the vibrational modes and the IRC's suggest that the large difference in the rate constants between the two reaction paths is attributable to the difference in curvature of the potential energy surfaces for the reaction paths around the IRC.

formic acid

thermal decomposition

bifurcation reaction

IRC

reaction-path Hamiltonian

Chemistry [ 430 ]

eng

Elsevier

Copyright (c) 2001 Elsevier Ltd.

[ISSN] 0166-1280

[DOI] 10.1016/S0166-1280(01)00406-7

[NCID] AA11533429

[DOI] http://dx.doi.org/10.1016/S0166-1280(01)00406-7 isVersionOf