A Model Investigation of Ab Initio Geometries for Identity and Nonidentity Substitution with Three-Center Four- and Three-Electron Transition States

作者：Buck Henk M^*

来源：International Journal of Quantum Chemistry, 2011, 111(10): 2242-2250.

DOI：10.1002/qua.22529

• S(N)2 carbon transfer
• proton transfer
• hydrogen transfer
• frozen-core approximation
• ab initio
• van't Hoff modeling

With the van't Hoff model derived from the dynamics of a regular tetrahedron in which the interstitial carbon changes its position from tetrahedral into a trigonal (bi) pyramidal configuration, the introduction of dimensionless ratio numbers (R) can serve to localize significant points on the principal reaction coordinate. These numbers are expressed as R(d) and R(n) based on transition state geometries and the number of electrons involved in the three-center bonding, respectively. Using this concept, we obtain a model for the evaluation of different ab initio calculations based on identity and nonidentity substitution reactions for three-center four-and three-electron bonding transition states. Similar ratio numbers have been derived for proton exchange reactions. The reactions under investigation show clearly that in spite of the differences in chemical outcome the transition steps reduced to the first principles of chemical bonding are similar.

• 出版日期2011-8-15