An AM1 MO study of bond dissociation energies in substituted benzene and toluene derivatives relative to the principle of maximum hardness
✍ Scribed by Gerritt P. Bean
- Book ID
- 104208972
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- French
- Weight
- 723 KB
- Volume
- 54
- Category
- Article
- ISSN
- 0040-4020
No coin nor oath required. For personal study only.
✦ Synopsis
The heats of formation of a series of m-and p-substituted benzene and toluene derivatives, Ar-Y and ArCH,.Y, and their phenyi or benzyl cations, anions, and radicals were calculated by the semiempirical AM1 MO method. Using this data and either the experimental values for the Y species or those obtained by the ab initio CBS-4 method, the haterolytic and homolytic bond dissociation energies ('BDEs) were calculated along with the electron transfer energies for the ions. While the values of the homolytic BDEs were essentially indeptmdent of the ring substituents, a plot of the heterolytic BDEs versus the electron tranffer energies gave a straight line of unit slope with an intercept at ~ thus confirming that AI-Im = AHE~ + ~. Likewise, a plot of the appropriate HOMO or LUMO energies of the phenyl, benzyl, or Y ions versus AI-Im gave a linear plot in agreement with the principle of maximum hardness. A positive charge adjacent to the bond being broken increases the ~ value while a negative charge decreases AHhm..