On the Model Dependence of Kinetic Shifts in Unimolecular Reactions: The Dissociation of the Cations of Benzene and n-Butylbenzene
Abstract
Statistical adiabatic channel model/classical trajectory (SACM/CT) calculations have been performed for transitional mode dynamics in the simple bond fission reactions of C6H6+ --> C6H5+ + H and n-C6H5C4H9+ --> C7H7+ + n-C3H7. Reduced-dimensionality model potentials have been designed that take advantage of ab initio results as far as available. Average anisotropy amplitudes of the potentials were fitted by comparison of calculated specific rate constants k(E,J) with measured values. The kinetic shifts of the calculated k(E) curves and the corresponding bond energies E0(J=0), derived as 3.90 +or- 0.05 eV for C6H6+ and 1.78 +or- 0.05 eV for n-C6H5C4H9+, were in good agreement with literature values from thermochemical studies. Kinetic shifts from fixed tight activated complex Rice-Ramsperger-Kassel-Marcus (RRKM) theory, which also reproduces the measured k(E), were larger than the present SACM/CT results as well as earlier results from variational transition state theory (for C6H6+). The approach using RRKM theory was found to underestimate E0(J=0) by about 0.2-0.3 eV. A simplified SACM/CT-based method is also proposed which circumvents the trajectory calculations and allows derivation of E0(J=0) on the basis of measured k(E) and which provides similar accuracy as the full SACM/CT treatment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2006
- Accession Number
- ADA449280
Entities
People
- Albert A Viggiano
- J. Troe
- V. G. Ushakov
Organizations
- Air Force Research Laboratory