An ab initio study of the Cl(2P)+C2H6→C2H5+HCl abstraction reaction

Electronic energies, geometries, and harmonic vibration frequencies for the reactants, products, and transition state for the Cl(P-3) + C2H6 --> C2H5 + HCl abstraction reaction were evaluated at the HF and MP2 levels using several correlation consistent polarized-valence basis sets. Single-point calculations at PMP2, MP4, QCISD(T), and CCSD(T) levels were also carried out. The values of the forward activation energies obtained at the MP4/cc-pVTZ, QCISD(T)/cc-pVTZ, and CCSD(T)/cc-pVTZ levels using the MP2/cc-pVTZ structures are equal to -0.1, -0.4, and -0.3 kcal/mol, respectively. The experimental value is equal to 0.3 +/- 0.2 kcal/mol. We found that the MP2/aug-cc-pVTZ adiabatic vibration energy for the reaction (-2.4 kcal/mol) agrees well with the experimental value -(2.2-2.6) kcal/mol. Rate constants calculated with the zeroth-order interpolated variational transition state (IVTST-0) method are in good agreement with experiment. In general, the theoretical rate constants differ from experiment by, at most, a factor of 2.6. (C) 2002 Elsevier Science B.V. All rights reserved.