Portable Models for Entropy Effects on Kinetic Selectivity

Abstract

Differences in entropies of competing transition states can direct kinetic selectivity. Understanding and modeling such entropy differences at the molecular level is complicated by the fact that entropy is statistical in nature; i.e., it depends on multiple vibrational states of transition structures, the existence of multiple dynamically accessible pathways past these transition structures, and contributions from multiple transition structures differing in conformation/configuration. The difficulties associated with modeling each of these contributors are discussed here, along with possible solutions, all with an eye toward the development of portable qualitative models of use to experimentalists aiming to design reactions that make use of entropy to control kinetic selectivity.

Why Woodward and Hoffmann? And Why 1965?**

“…[186] Here we refer to the portability of new chemical theories. [188][189][190] Regarding the use of pictorial representations of orbitals, Fukui made the same type of transition as did Hoffmannand also only after the publication of the first WÀ H publications. This can easily be seen by the transformation of Fukui's publications, pre-and post-1965.…”

Mechanism and Origins of Site‐Selectivity of Template‐Directed C−H Insertion of Quinolines

“…Note, however, that the method used for correcting free energies matters (Figure 9b). [45] Figure 9a highlights the geometry change between the lowest-energy intermediate structure and the lowest-energy transition structure. The intermediate structure prefers the DG to come from behind to direct the Pd-catalyst to the π-orbital of quinoline while also distorting the linearity of the PdÀ N�C array (2.02 Å) to 160.6°and pointing the other DG away from the reaction site.…”

Computational Strategies for Entropy Modeling in Chemical Processes

“…50 This approach can be potentially used to understand the entropic origin behind the selectivity of organic reaction dynamics. 51 However, the configurational entropy cannot characterize the entropy of the many-body system, where the solvent-mediated interaction entropy remains uncertain. Configurational entropy calculation can address the entropy of condensation by calculating the entropy difference of the target molecule between gas phase and condensed phase simulations.…”