A comparative quantum mechanical study of bond separation energies as a measure of cyclic conjugation
✍ Scribed by D. B. Chesnut
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 907 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0192-8651
No coin nor oath required. For personal study only.
✦ Synopsis
Restricted Hartree-Fock (RHF), second-order Mdler-Plesset (MP2), and density functional calculations [using the Becke/Lee-Yang-Parr (B-LYP) exchange/correlation gradient-corrected functionals] employing the 6-311G(d, p ) and 6-311 + + G(d, p ) basis sets have been carried out to calculate isodesmic bond separation energies for reactions involving a number of representative five-and six-membered ring organic compounds. The MP2 and density functional approaches yield reasonably good energies; the density functional method agrees particularly well with experiment, exhibiting a root-mean-square error of only 2.5 kcal/mol. Ring geometries are calculated satisfactorily in all approaches but are given particularly accurately by the MP2 approach. A comparison of the B-LYP bond separation energies with several other definitions of resonance energy shows that these different approaches correlate with each other in a reasonable fashion. 0 1995 by John Wiley & Sons, Inc. interest, although there is no general agreement on a unique definiti0n.2,~ It is, as Bird states: a "tenet of faith' whose quantification has proven remarkably elusive. Many references to discussions on this issue may be found in these and in the recent book by Minkin, Glukhovtsev, and Simkin.5 Properties other than energy have been invoked to measure aromaticity. and Julg and Francois' have suggested the use of bond alternation (or lack thereof) as a measure, and Palmer